Metal-organic frameworks (MOF) for gas capture

Abstract

The present invention relates to a metal organic framework comprising of a metal ion (M) and an organic ligand wherein more than one hydroxy ligand are present about the metal ion. Also provided is a method for synthesizing the metal-organic frameworks and their application in areas including scrubbing exhaust gas streams of acidic gases, scrubbing natural gas of acidic gases by separation or sequestration and separating C.sub.2H.sub.a or other VOC gases from other gas mixtures.

Claims

1. A metal organic framework comprising metal ions (M) and an organic ligand wherein more than one hydroxy ligand are present, wherein the metal ions are octahedrally coordinated as MO.sub.4(OH).sub.2 units, wherein four of the oxygen atoms are from the organic ligands and a coordination sphere is completed by hydroxy ligands, wherein bridging OH groups are linked to each other in a cis-configuration.

2. The metal organic framework of claim 1 wherein hydroxy ligands point into the channels of the framework.

3. The metal organic framework of claim 1, wherein the metal ion is a metal (III) ion.

4. The metal organic framework of claim 1, wherein the metal ion is selected from the group consisting of Al(III), Cr(III), Sb(III), In(III), Ga(III), and Fe(III).

5. The metal organic framework of claim 1 wherein the metal organic framework is synthesised using a metal (III) ion.

6. The metal organic framework of claim 5 wherein the metal organic framework is synthesised using one metal (III) ion selected from the group consisting of Al(III), In(III), Sb(III), Ga(III), Cr(III), Fe(III) and Co(III).

7. The metal organic framework of claim 1 comprising two or more different types of metal(III) ions.

8. The metal organic framework of claim 1, wherein the metal organic framework comprises a polycarboxylate ligand.

9. The metal organic framework of claim 8, wherein the polycarboxylate ligand is a tetracarboxylate ligand.

10. The metal organic framework of claim 9 wherein the tetracarboxylate ligand is a phenyltetracarboxylate ligand.

11. The metal organic framework of claim 10 wherein the phenyltetracarboxylate ligand has the formula: ##STR00007## wherein R is one of ##STR00008## wherein A, B, C, D, E, F, G, H, I, and J are selected from the group consisting of H, F, Cl, Br, I, CH.sub.3, CH.sub.2CH.sub.3, CH(CH.sub.3).sub.2, C(CH.sub.3).sub.3, NH.sub.2, NHR, NRR, OH, OR, CO2H, CO.sub.2R, CF.sub.3, NHCOR, NHCONHR, NHSO.sub.2R, SO.sub.3H; and wherein S, T, U and V are selected from the group consisting of H, F, Cl, Br, I, CH.sub.3, CH.sub.2CH.sub.3, CH(CH.sub.3).sub.2, C(CH.sub.3).sub.3, NH.sub.2, NHR, NRR, OH, OR, CO.sub.2H, CO.sub.2R, CF.sub.3, NHCOR, NHCONHR, NHSO.sub.2R, SO.sub.3H and ##STR00009## wherein R and R are each independently a C.sub.1 to C.sub.5 alkyl.

12. The metal organic framework of claim 11 wherein, two of A,B,C,D, or E are COOH and two of F,G,H,I or J are COOH.

13. The metal organic framework of claim 11 wherein one of A,B,C,D, or E is COOH and one of F,G,H,I or J is COOH, and two of T, S, U and V are COOH or ##STR00010##

14. The metal organic framework of claim 1 wherein the organic ligand is selected from the group consisting of: ##STR00011## ##STR00012##

15. The metal organic framework of claim 1, wherein the metal organic framework has the formula:
M.sub.2(OH).sub.2(C.sub.16O.sub.8H.sub.6); where M=Al, In, Sb, Ga, or Cr.

16. The metal organic framework of claim 15, wherein the metal organic framework comprises a biphenyl-3, 3,5,5 tetracarboxylate ligand.

17. The metal organic framework of claim 1, wherein the metal organic framework contains two or more different types of metal (III) ion and wherein said two or more different types of metal (III) ion are selected from the group consisting of Al(III), Cr(III), Sb(III), In(III), Ga(III), and Fe(III).

18. The metal organic framework of claim 17, wherein the metal organic framework comprises both gallium and iron and has the formula (Ga.sub.2-x Fe.sub.x)(OH).sub.2(C.sub.16O.sub.8H.sub.6) wherein x is greater than zero.

19. A metal organic framework comprising a metal ion (M) and an organic ligand wherein more than one hydroxy ligand are present, wherein the metal organic framework comprises a polycarboxylate ligand which is a tetracarboxylate ligand.

20. A metal organic framework comprising a metal ion (M) and an organic ligand wherein more than one hydroxy ligand are present, wherein the metal organic framework has the formula: M.sub.2(OH).sub.2(C.sub.16O.sub.8H.sub.6);where M=Al, In, Sb, Ga, or Cr.

Description

DESCRIPTION OF THE FIGURES

(1) The above-mentioned and other features and objects of this invention, and the manner of obtaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

(2) FIGS. 1(a)-1(d) show a schematic view comparing gas binding interactions in amine-functionalised materials and in hydroxyl-functionalised materials;

(3) FIG. 1(a) illustrates the bonds formed between carbon dioxide molecules and an amine group as would be present in known amine functionalised systems. In such systems the first CO.sub.2 molecule interacts with the NH.sub.2 group through a side-on mode and the second CO.sub.2 molecules interacts with the first CO.sub.2 molecule through an end-on mode. Such interactions result in high isosteric heats of adsorption particularly when there is direct bond formation between the N-centre of the amine group and the electro-positive C-carbon centre of CO.sub.2 (i.e. chemisorption);

(4) FIG. 1(b) illustrates the hydrogen bonds present between a hydroxyl functionalised material and CO.sub.2 molecules;

(5) FIG. 1(c) illustrates the hydrogen bonds present between a hydroxyl functionalised material and SO.sub.2 molecules;

(6) FIG. 1(d) shows the anticipated interactions believed to be the rationale behind the high NO.sub.2 adsorption capacities observed;

(7) FIG. 2 provides views of the structure for NOTT-solvate. The structure was solved from high resolution PXRD data by ab initio methods for NOTT Al-solvate and has been found to be correct for equivalent compounds using other metal (III) ions. FIG. 2(a) illustrates the coordination environment for ligand L.sup.4 and M(III) centre. FIG. 2(b) illustrates a corner-sharing extended octahedral chain of [MO.sub.4(OH).sub.2].sub.. The .sub.2-(OH) groups are highlighted as a space-filling model, and linked to each other in a cis-configuration. FIG. 2(c) illustrates the 3D framework structure with channel formed along the c-axis. The free water molecules in the channel are omitted for clarity. FIG. 2(d) is a schematic view of the square-shaped channel. The .sub.2-(OH) groups protrude into the centre of the channel from four directions. [MO.sub.4(OH).sub.2] groups are illustrated as octahedral. A .sub.2-OH group is an OH group that is coordinated to two metal centres, i.e. it is a bridging OH group;

(8) FIG. 3 (a) is a graph comparison of the gas adsorption isotherms for NOTT-300 (Al) at 273 K and 1.0 bar for a selection of gases;

(9) FIG. 3 (b) is a graph illustrating the variation of isosteric enthalpy (Q.sub.st) and entropy (S) of CO.sub.2 adsorption;

(10) FIGS. 4(a)-4(d) show in situ inelastic neutron scattering (INS) spectra and simulated CO.sub.2 positions in the pore channel of NOTT-300 (Al);

(11) FIG. 4 (a) shows in situ inelastic neutron scattering (INS) spectra and simulated CO.sub.2 positions in the pore channel. This diagram shows a comparison of the experimental (top) and DFT simulated (bottom) INS spectra for bare and CO.sub.2-loaded NOTT-300 (Al).

(12) FIG. 4 (b) is a difference plot for experimental INS spectra of bare and CO.sub.2-loaded NOTT-300 (Al). Two distinct energy transfer peaks are labelled as I and II.

(13) FIG. 4 (c) is a view of the structure of NOTT-300 (Al).3.2CO.sub.2 obtained from PXRD analysis. The adsorbed CO.sub.2 molecules in the pore channel are highlighted by the use of ball-and-stick mode. The carbon atom of second site of CO.sub.2 is shown. The dipole interaction between CO.sub.2 (I, II) molecules are shown [OCO . . . CO.sub.2=3.920 ].

(14) FIG. 4 (d) is a detailed view of the role of the OH and CH groups in binding CO.sub.2 molecules in a pocket-like cavity. The model was obtained from DFT simulation. The modest hydrogen bond between O() of CO.sub.2 and H(+) from the AlOH moiety is shown, [O . . . H=2.335 ]. The weak cooperative hydrogen bond interactions between O() of CO.sub.2 and H(+) from CH is shown, [O . . . H=3.029, 3.190 , each occurring twice]. Each O() centre therefore interacts with five different H(+) centres.

(15) FIGS. 5(a)-5(c) show in-situ synchrotron X-ray powder diffraction patterns and refined SO.sub.2 positions in the pore channel of NOTT-300 (Al);

(16) FIG. 5 (a) is a comparison of the powder diffraction patterns for original, evacuated, SO.sub.2-loaded, and final desolvated samples at 273 K.

(17) FIG. 5 (b) illustrates the crystal structure of NOTT-300 (Al).4.0SO.sub.2 obtained from Rietveld refinement of data on SO.sub.2-loaded material at 1.0 bar. The adsorbed SO.sub.2 molecules in the pore channel are highlighted by the use of ball-and-stick mode. The sulphur atom of second site of SO.sub.2 is labelled with an asterisk.

(18) FIG. 5 (c) provides a detailed view of the role of the OH and CH groups in binding SO.sub.2 molecules into a distorted pocket-like cavity. The moderate hydrogen bond between O() of SO.sub.2(I) and H(+) from OH is shown as the a vertical dashed line, [O . . . H=2.376(13) ]. The weak cooperative hydrogen interaction between O() of SO.sub.2 and H(+) from CH is shown, [O . . . H=2.806(14), 2.841(17), 3.111(16), 3.725(18) ]. Therefore, each O() centre is interacting with five different H(+) centres simultaneously. The bond distance between S(+) of SO.sub.2(I) and O() of SO.sub.2(II) is 3.34(7) .

(19) FIGS. 6(a)-6(c) show in situ inelastic neutron scattering (INS) spectra and simulated SO.sub.2 positions in the pore channel of NOTT-300 (Al);

(20) FIG. 6 (a) provides a comparison of the experimental (top) and DFT simulated (bottom) INS spectra for bare and SO.sub.2-loaded NOTT-300;

(21) FIG. 6 (b) is a difference plot for experimental INS spectra of bare and SO.sub.2-loaded NOTT-300. Two distinct energy transfer peaks are labelled as I and II;

(22) FIG. 6 (c) is a detailed view of the role of the OH and CH groups in binding SO.sub.2 molecules in a pocket-like cavity. Model was obtained from DFT simulation. The adsorbed SO.sub.2 molecules in the pore channel are highlighted by the use of ball-and-stick mode. The modest hydrogen bond between O() of SO.sub.2 and H(+) from the AlOH moiety is shown as the vertical dashed line, [O . . . H=2.338 ]. The weak cooperative hydrogen bond interactions between O() of CO.sub.2 and H(+) from CH is shown, [O . . . H=2.965-3.238 ]. Each O() centre therefore interacts with five different H(+) centres;

(23) FIG. 7 is a three dimensional representation of the pore structure of a MOF according to an embodiment of the invention;

(24) FIG. 8 is a graph comparing the gas adsorption isotherms of various hydrocarbons with NOTT-300 (Al). The corresponding desorption isotherms exhibit full reversibility without hysteresis demonstrating the stability of the MOF in the hydrocarbon environments.

(25) FIG. 9 shows graphs of the gas selectivity ratio for C.sub.2H.sub.2/C.sub.2H.sub.4 with NOTT-300 (Al) as a function of gas pressure at various temperatures. Also see Table A provides derived values of extreme selectivity ratios for C.sub.2H.sub.2/C.sub.2H.sub.4 at 0 mbar.

(26) FIGS. 10(a)-10(d) show INS spectra for adsorbed C.sub.2H.sub.2 and C.sub.2H.sub.4 in NOTT-300(Al). FIG. 10(a) is a plot of the experimental INS spectra for bare and C.sub.2H.sub.2-loaded NOTT-300. FIG. 10(b) is a difference plot for the experimental INS spectra of bare and C.sub.2H.sub.2-loaded NOTT-300. FIG. 10(c) is a plot of the experimental INS spectra for bare and C.sub.2H.sub.4-loaded NOTT-300. FIG. 10(d) is a difference plot for the experimental INS spectra of bare and C.sub.2H.sub.4-loaded NOTT-300.

(27) FIGS. 11(a)-11(b) show INS spectra for condensed phase C.sub.2H.sub.2. FIG. 11(a) is a plot of the experimental INS spectra for solid C.sub.2H.sub.2. FIG. 11(b) is a plot for the experimental INS spectra of solid C.sub.2H.sub.2, showing backward scattering and forward scattering results.

(28) FIG. 12 shows in situ diamond powder diffraction patterns for C.sub.2H.sub.2-loaded NOTT-300.

(29) FIGS. 13(a)-13(b) show an illustration of the structure of NOTT-300 (Al).3C.sub.2H.sub.2.

(30) FIG. 13(a) is a view from above. FIG. 13(b) is a side view;

(31) FIGS. 14(a)-14(b) show an illustration of the structure of NOTT-300 (Al).1C.sub.2H.sub.4. FIG. 14(a) is a view from above. FIG. 14(b) is a side view;

(32) FIGS. 15(a)-15(b) show an illustration of the structure of NOTT-300 (Al).1C.sub.2H.sub.6. FIG. 15(a) is a view from above. FIG. 15(b) is a side view;

(33) FIG. 16 illustrates INS spectra for C.sub.2H.sub.2,4;

(34) FIG. 17 is an illustration of the structure of NOTT-300 (Al).2.4C.sub.2H.sub.2.0.7C.sub.2H.sub.4;

(35) FIG. 18 is an illustration of some structures of NOTT-300 (Al) with adsorbed acetylene and/or ethylene;

(36) FIG. 19 provides graphs of enthalpy and entropy versus gas pressure for the adsorption of C.sub.2H.sub.2 and C.sub.2H.sub.4;

(37) FIG. 20 illustrates a gas adsorption isotherm of NO.sub.2 with NOTT-300 (Al) at 295K.

(38) FIGS. 21(a)-21(c) illustrate X-ray diffraction data for NOTT-300 (In). FIG. 21(a) is a broad 2Th degree spectrum whereas FIG. 21(b) is a scaled up spectrum and FIG. 21 (c) is an even further scaled up spectrum.

(39) FIG. 22(a) illustrates the gas adsorption isotherms of NOTT-300 (Cr) for CO.sub.2 at various temperatures. It can be seen that there is a high uptake of CO.sub.2;

(40) FIG. 22(b) shows the CO.sub.2 gas adsorption isotherm for NOTT-300 (Cr) at 198K to more clearly show a high degree of hysteresis between adsorption and desorption thereby indicating the stability of the complex in carbon dioxide gas;

(41) FIG. 22(c) shows the N.sub.2 gas adsorption isotherm for NOTT-300 (Cr). It can be seen that the uptake of N.sub.2 here is higher than for NOTT-300 (Al);

(42) FIG. 22(d) shows the CH.sub.4 gas adsorption isotherm for NOTT-300 (Cr);

(43) FIG. 22(e) shows the H.sub.2 gas adsorption isotherm for NOTT-300 (Cr). It can be seen that the uptake of these gases is very low compared to CO.sub.2 and SO.sub.2. All the isotherms show good hysteresis of between adsorption and desorption of the gases demonstrating the stability of the compound in the gases.

(44) FIG. 23 is a packing diagram for NOTT-300 (Cr) illustrating that this MOF is isostructural with NOTT-300 (Al) with 1-dimensional square pore channels.

(45) FIG. 24 illustrates the powder X-ray diffraction data (PXRD) patterns for (Ga.sub.2-xFe.sub.x)MOF(x=0, 0.13, 0.21, 0.45). The patterns confirm that the parent MOF NOTT-300 (Ga)-solvated is iso-structural to NOTT-300(Al)-solvated.

(46) FIG. 25 shows the CO.sub.2 adsorption isotherms for NOTT3-00(Ga.sub.2-xFe.sub.x) (x=0, 0.13, 0.21, 0.45) at 195 K at pressures up to 1 bar. It can be seen that the degree of CO.sub.2 uptake is dependent on the molar ratio of Ga and Fe used in the MOF.

(47) FIG. 26 shows the CO.sub.2 adsorption isotherms for NOTT-300(Ga.sub.2-xFe.sub.x) (x=0, 0.13, 0.21, 0.45) at 293 K at pressures up to 20 bar.

(48) FIG. 27 is a schematic illustration of an apparatus for gas storage.

(49) FIG. 28(a) illustrates a cartridge placed within a gas stream. FIG. 28(b) illustrates a cartridge at the end of a flue or exhaust pipe.

(50) FIG. 29 is a graph showing the potential energy surface along the first vibrational eigenvector of the hydrogen bond between CO.sub.2 and an OH group of NOTT-300 (Al);

(51) FIG. 30(a) illustrates PXRD patterns for the Rietveld refinement of the as-synthesized NOTT-300 (Al)-solvate [=0.826949(2) ].

(52) FIG. 30(b) illustrates PXRD patterns for higher angle data (2=22.5-55) scaled up to show the quality of the fit between the observed and the calculated patterns.

(53) FIG. 31(a) illustrates PXRD patterns for the Rietveld refinement of the CO.sub.2-loaded NOTT-300 (Al).3.2CO.sub.2 [=0.826126(2) ].

(54) FIG. 31(b) illustrates PXRD patterns for higher angle data (2=22.5-60) scaled up to show the quality of fit between the observed and the calculated patterns.

(55) FIG. 32(a) illustrates PXRD patterns for the Rietveld refinement of the SO.sub.2-loaded NOTT-300 (Al).4SO.sub.2 [=0.826126(2) ].

(56) FIG. 32(b) illustrates PXRD patterns for higher angle data (2=22.5-55) scaled up to show the quality of fit between the observed and the calculated patterns.

(57) FIG. 33(a) provides a comparison of the powder diffraction patterns for original, evacuated, SO.sub.2-loaded, and final desolvated samples at 273 K.

(58) FIG. 33(b) shows the powder diffraction patterns for higher angle data (2=4.5-250) has been scaled up to show the changes upon SO.sub.2 inclusion. NOTT-300 (Al) retains crystallinity after removal of SO.sub.2.

(59) FIG. 34(a) shows powder X-ray diffraction patterns for original, evacuated, CO.sub.2-loaded, and final desolvated samples at 273 K.

(60) FIG. 34(b) shows powder X-ray diffraction patterns for higher angle data (2=4.5-25) has been scaled up confirming that NOTT-300 (Al) retains crystallinity on removal of CO.sub.2.

(61) FIG. 35 are TEM images for NOTT-300 (Al)-solvate. TEM images confirm that the crystals have uniform morphology (1 m plates)

(62) FIG. 36 provides a view of the structure of NOTT-300 (Al)-solvate along the a-axis.

(63) FIGS. 37(a)-37(b) provide a view of the structure of NOTT-300 (Al).1.0CO.sub.2 along the c-axis (FIG. 37a) and a-axis (FIG. 37b). The structure was obtained by DFT simulation. The adsorbed CO.sub.2 molecules in the pore channel are highlighted by the use of spacing filling style.

(64) FIGS. 38(a)-38(c) provide detailed views of OH and CH groups binding CO.sub.2 in the pocket cavity of NOTT-300 (Al).1.0CO.sub.2. Views along (FIG. 38a) the a-axis, (FIG. 38b), the b-axis and (FIG. 38c) the c-axis. The moderate hydrogen bond between O() of CO.sub.2 and H(+) of OH is shown, [O . . . H=2.335 ]. The weak cooperative hydrogen bond between O() of CO.sub.2 and H(+) from CH is shown, [O . . . H=3.029, 3.190 with each occurring twice]. Therefore, each O() centre interacts with five different H(+) centres.

(65) FIGS. 39(a)-39(b) provide a view of the structure of NOTT-300 (Al).4.0SO.sub.2 along the c-axis (FIG. 39a) and a-axis (FIG. 39b). The structure was obtained by Rietveld refinement of high resolution powder diffraction data collected for NOTT-300 (Al).4.0SO.sub.2. The adsorbed SO.sub.2 molecules in the pore channel are highlighted by the use of spacing filling style

(66) FIGS. 40(a)-40(c) provide detailed views of OH and CH groups binding SO.sub.2 in the pocket cavity of NOTT-300 (Al).4.0SO.sub.2. Views along (FIG. 40a) the a-axis, (FIG. 40b), the b-axis and (FIG. 40c) the c-axis. The modest hydrogen bond between O() of SO.sub.2(I) and H(+) from OH is shown, [O . . . H=2.376(13) ]. The weak cooperative hydrogen bond between O() of SO.sub.2 and H(+) from CH is shown, [O . . . H=2.806(14), 2.841(17), 3.111(16), 3.725(18) ]. Therefore, each O() centre is interacting with five different H(+) centres. The bond distance between S(+) of SO.sub.2(I) and O() of SO.sub.2(II) is 3.34(7) is shown. The SO bond distances are 1.481(4) and 1.500(8) for SO.sub.2(I) and SO.sub.2(II), respectively. The <OSO angles are 117.5(11) and 109.1(9) for SO.sub.2(I) and SO.sub.2(II), respectively.

(67) FIG. 41 is a Thermo Gravimetric Analysis (TGA) plot shows that the as-synthesised sample NOTT-300 (Al)-solvate loses solvent rapidly between 30 and 100 C., with a plateau observed from 100-200 C. indicating no further weight loss to give NOTT-300 (Al). The weight loss of 20.0% from NOTT-300 (Al)-solvate between 20 and 200 C. corresponds to a loss of three water molecules per aluminium (calc. 20.6 wt. %). Above 400 C. NOTT-300 (Al) starts to decompose rapidly.

(68) FIG. 42 illustrates PXRD spectra for NOTT-300(Al) under different chemical environments [=0.826134(2) ];

(69) FIG. 43 shows graphs comparing of unit cell parameters of NOTT-300(Al) under different chemical environments and;

(70) FIG. 44 illustrates variable temperature PXRD spectra for NOTT-300(Al)-solvate (=1.54056 );

(71) FIG. 45 is a graph comparing of unit cell parameters for NOTT-300(Al)-solvate as a function of temperature;

(72) FIG. 46 illustrates H.sub.2, N.sub.2 and Ar sorption isotherms at 77 or 87 K for NOTT-300 (Al). No significant uptake was observed for these adsorption isotherms.

(73) FIGS. 47(a)-47(d) illustrate CO.sub.2 adsorption and desorption isotherms for NOTT-300 (Al) at (FIG. 47a) 273 K, (FIG. 47b) 283 K, (FIG. 47c) 293 K and (FIG. 47d) 303 K.

(74) FIG. 48 illustrates high pressure CO.sub.2 adsorption and desorption isotherms at 273 K for NOTT-300 (Al).

(75) FIG. 49 is a pore size distribution (PSD) plot and cumulative pore volume for NOTT-300 (Al). Data were calculated the CO.sub.2 adsorption isotherm at 273 K using DFT/Monte Carlo methods.

(76) FIG. 50 is a comparison of the gas adsorption isotherms for NOTT-300 (Al) at 273 K and 0.15 bar. NOTT-300 (Al) exhibits highly selective uptake for CO.sub.2 and SO.sub.2 compared with CH.sub.4, CO, N.sub.2, H.sub.2, 02 and Ar. The CO.sub.2 selectivities, calculated from the ratio of isotherm uptakes at 0.15 bar, are 88, 99, 148, 197, 85, and 160 for CH.sub.4, CO, N.sub.2, H.sub.2, O.sub.2, and Ar, respectively. The SO.sub.2 selectivities, calculated from the ratio of isotherm uptakes at 0.15 bar, are 250, 278, 418, 557, 239, and 451 for CH.sub.4, CO, N.sub.2, H.sub.2, 02 and Ar, respectively.

(77) FIGS. 51(a)-51(d) illustrate SO.sub.2 adsorption and desorption isotherms for NOTT-300 (Al) at (FIG. 51a) 273 K, (FIG. 51b) 283 K, (FIG. 51c) 293 K and (FIG. 51d) 303 K.

(78) FIGS. 52(a)-52(c) show a comparison of the gas adsorption isotherms for NOTT-300 (Al) at 283 K (FIG. 52a), 293 K (FIG. 52b), 303 K (FIG. 52c) and 1.0 bar. NOTT-300 (Al) exhibits highly selective uptake for CO.sub.2 and SO.sub.2 compared with CH.sub.4, CO, N.sub.2, H.sub.2, O.sub.2, and Ar.

(79) FIG. 53 illustrates CO.sub.2 adsorption isotherms at 273 K for NOTT-300(Al) upon cyclic hydration and desolvation process;

(80) FIG. 54 is a comparison of INS spectra for bare NOTT-300 (Al), 0.25 H.sub.2/Al and 0.5 H.sub.2/Al loaded-NOTT-300 (Al).

(81) FIG. 55(a) is a difference INS spectra plot for forward and back scattering between bare and 0.25H.sub.2/Al-loaded NOTT-300 (Al). The broad hump shows recoil of hydrogen; a very small and poorly defined peak at 10 meV suggests a very weak interaction. FIG. 55(b) shows a detailed view of where the low energy transfer has been scaled up.

(82) FIG. 56(a) is a difference INS spectra plot for forward and back scattering between bare and 0.5 H.sub.2/Al-loaded NOTT-300 (Al). The broad hump shows recoil of hydrogen. The peak at 10 meV is still broad and very weak, but can be seen to have increased in intensity slightly. Furthermore, an additional peak at 15 meV can be observed. This peak is very close to the rotational line of hydrogen (14.7 meV), further indicating that the interactions between the hydrogen and the NOTT-300 (Al) framework are very weak. FIG. 56(b) shows a detailed view of where the low energy transfer has been scaled up.

(83) FIGS. 57(a)-57(d) provide linear fitting of Vant Hoff plots for the CO.sub.2 adsorption isotherms at (FIG. 57a) 0.5, (FIG. 57b) 1.0, (FIG. 57c) 1.5 and (FIG. 57d) 2.0 mmol g.sup.1 loadings;

(84) FIGS. 58(a)-58(b) provide linear virial fitting plots for the adsorption isotherms for (FIG. 58a) CO.sub.2 and (FIG. 58b) SO.sub.2 for NOTT-300(Al) at 273 K;

(85) FIGS. 59(a)-59(e) provide non-linear virial fitting plots for the adsorption isotherms for (FIG. 59a) CO, (FIG. 59b) CH.sub.4, (FIG. 59c) O.sub.2, (FIG. 59d) N.sub.2 and (FIG. 59e) Ar for NOTT-300(Al) at 273 K;

(86) FIGS. 60(a)-60(b) provide linear virial fitting plots for the adsorption isotherms for (FIG. 60a) CO.sub.2 and (FIG. 60b) SO.sub.2 for NOTT-300(Al) at 283 K;

(87) FIGS. 61(a)-61(e) provide non-linear virial fitting plots for the adsorption isotherms for (FIG. 61a) CO, (FIG. 61b) CH.sub.4, (FIG. 61c) O.sub.2, (FIG. 61d) N.sub.2 and (FIG. 61e) Ar for NOTT-300(Al) at 283 K;

(88) FIGS. 62(a)-62(b) provide linear virial fitting plots for the adsorption isotherms for (FIG. 62a) CO.sub.2 and (FIG. 62b) SO.sub.2 for NOTT-300(Al) at 293 K;

(89) FIGS. 63(a)-63(e) provide non-linear virial fitting plots for the adsorption isotherms for (FIG. 63a) CO, (FIG. 63b) CH.sub.4, (FIG. 63c) O.sub.2, (FIG. 63d) N.sub.2 and (FIG. 63e) Ar for NOTT-300 at 293 K;

(90) FIGS. 64(a)-64(b) provide linear virial fitting plots for the adsorption isotherms for (FIG. 64a) CO.sub.2 and (FIG. 64b) SO.sub.2 for NOTT-300(Al) at 303 K; and

(91) FIGS. 65(a)-65(e) provide non-linear virial fitting plots for the adsorption isotherms for (FIG. 65a) CO, (FIG. 65b) CH.sub.4, (FIG. 65c) O.sub.2, (FIG. 65d) N.sub.2 and (FIG. 65e) Ar for NOTT-300(Al) at 303 K.

LIST OF EXAMPLES

(92) For the purposes of this description the term NOTT-300 is used to denote complexes M.sub.2(OH).sub.2(C.sub.16O.sub.8H.sub.6) (M=Al, Cr, Sb, In, Ga, and Fe) whereas the term NOTT-300-solvate is used to denote the solvated form of the complex. The organic ligand C.sub.16O.sub.8H.sub.6 takes the form of biphenyl-3, 3,5,5 tetracarboxylate. Such structures are discussed in detail herein-below.

Example 1

Synthesis of NOTT-300 (Al)

(93) Biphenyl-3,3,5,5-tetracarboxylic acid (0.06 g, 0.182 mmol), Al(NO.sub.3).sub.3.9H.sub.2O (0.34 g, 0.906 mmol), and piperazine (0.10 g, 1.26 mmol) were mixed and dispersed in a water (10.0 ml) and HNO.sub.3 (2.8M, 2.0 ml) was then added to the resulting white slurry. The slurry was transferred into a 23 ml autoclave which was sealed and heated to 210 C. for 3 days. After cooling over 12 h to room temperature, the resulting white microcrystalline product was separated by filtration, washed with water and dried in air. Yield: 0.095 g (75%). Elemental analysis (% calc/found): Al.sub.2O.sub.16C.sub.16H.sub.20 (C, 36.8/36.3; H, 3.8/4.0; N, 0.0/0.0). Selected IR: /cm.sup.1: 3574 (m), 3425 (m), 2926 (w), 1623 (vs), 1570 (vs), 1475 (s), 1442 (s), 1346 (m), 1324 (m), 1265 (m), 1108 (m), 1003 (m), 914 (w), 807 (w), 742 (m), 702 (s), 668 (m).

(94) Compared to traditional methods for the production of MOF materials, the synthetic conditions developed here for NOTT-300-(Al) can be viewed as constituting a green synthesis, not only because no organic solvent (e.g., DMF) is involved, but also because the ligand can be prepared from a simple oxidation reaction without using the toxic Pd(0) catalysts typically applied in Suzuki-coupling reactions to synthesise such polycarboxylate ligands..sup.18,19 Thus, this synthesis offers potential for inexpensive, feasible and environmentally-friendly scale-up.

(95) PXRD Studies of NOTT-300 (Al)

(96) The structure of NOTT-300 (Al)-solvate was solved from high resolution synchrotron PXRD data by ab initio methods in the chiral tetragonal space group I4.sub.122. NOTT-300 (Al)-solvate exhibits an open structure comprising chains of [AlO.sub.4(OH).sub.2] moieties bridged by tetracarboxylate ligands L.sup.4. The Al(III) ion in NOTT-300 (Al)-solvate is bound to six O-donors, four from carboxylates [AlO=1.935(1) and 1.929(2) ] and two from bridging hydroxyl groups .sub.2-OH [AlO=1.930(1) ]. Bond valence sum calculations give a valence of approximately 0.87 for this bridging oxygen atom, confirming its protonation to form a dangling .sub.2-OH group. This overall connectivity affords a porous 3D framework structure with 1D channels (FIG. 2) formed by corner-sharing [AlO.sub.4(OH).sub.2] octahedra linked via two mutually cis-.sub.2-OH groups. Thus, the observed cis-configuration of .sub.2-OH groups is responsible for the observed chirality and rigidity of the framework in NOTT-300 (Al). The rigidity of the framework structure of NOTT-300 (Al) has been confirmed by in situ variable temperature (100-483 K) PXRD data (FIG. 44). Another important consequence of the cis-configuration is the formation of square-shaped channels with hydroxyl groups protruding into them, endowing the pore environment with free hydroxyl groups over four different directions (FIG. 2d). The approximate diameter of the channel window, taking into account the van der Waals radii of the surface atoms, is 6.56.5 , and these channels are filled by crystallographically-disordered water molecules which are not bound to Al(III). The total free solvent (water) volume in NOTT-300 (Al)-solvate was estimated by PLATON/SOLV* to be 42% (*Spek, A. L. Structure validation in chemical crystallography. Acta Crystallogr., Sect. D 65, 148-155 (2009)). The water molecules can be readily removed by heating, giving the desolvated and activated material NOTT-300 (Al), the PXRD of which confirms retention of the original porous structure. Thermogravimetric analysis (TGA) confirms NOTT-300 (Al) to have high thermal stability with a decomposition temperature at 400 C. (FIG. 41). NOTT-300 (Al) also shows good chemical stability towards air, moisture and common organic solvents, and can be re-hydrated with retention of the framework structure (FIG. 42). Significantly, the framework porosity and surface area of NOTT-300 (Al) is retained upon multiple hydration-dehydration cycles (FIG. 53), thereby confirming the stability of this material to water.

(97) Gas Adsorption Properties of of NOTT-300 (Al)

(98) Al-NOTT-300 (Al) exhibits highly selective uptake for CO.sub.2 and SO.sub.2 compared with CH.sub.4, CO, N.sub.2, H.sub.2, O.sub.2, and Ar. The CO.sub.2 selectivities, calculated from the ratio of initial slopes of the isotherm are 100, 86, 180, >10.sup.5, 70, and 137 for CH.sub.4, CO, N.sub.2, H.sub.2, O.sub.2, and Ar, respectively. The SO.sub.2 selectivities, calculated from the ratio of the initial slopes of the isotherms are 3620, 3105, 6522, >10.sup.5, 2518, and 4974 for CH.sub.4, CO, N.sub.2, H.sub.2, O.sub.2, and Ar, respectively. The thermodynamic parameters Q.sub.st and S were calculated using the van't Hoff isochore on CO.sub.2 adsorption isotherms measured at 273-303 K. The Q.sub.st values lie in the range 27.5-28 kJ mol.sup.1 for CO.sub.2 uptakes of 1-2 mmol g.sup.1 and increase continuously thereafter to 30 kJ mol.sup.1 at 4.5 mmol g.sup.1. The error in Q.sub.st is estimated as 0.05-0.5 kJ mol.sup.1 as shown by the error bars. Overall, S decreases continuously with increasing surface coverage over the whole loading range. The error in S is estimated as 0.2-1.6 J Kmol.sup.1 as shown by the error bars.

(99) H.sub.2 and N.sub.2 isotherms at 77 K and the Ar isotherm at 87 K for NOTT-300 (Al) show, surprisingly, no apparent adsorption uptakes (FIG. 46). This is probably due to diffusion effects at low temperatures caused by the narrow pore channels. In contrast, low pressure CO.sub.2 isotherms at ambient temperatures (273-303 K) show very high uptake capacities, with a maximum value of 7.0 mmol g.sup.1 at 273 K and 1.0 bar, representing one of the highest value observed for a MOF under these conditions (FIG. 3a)..sup.9 The CO.sub.2 uptake at 0.15 bar, which is relevant to the CO.sub.2 partial pressure in flue gas, is 2.64 mmol g.sup.1 (FIG. 50). This uptake is higher than the value (0.682 mmol g.sup.1 at 0.15 bar and 298 K) observed by other workers for H.sub.3[(Cu.sub.4Cl).sub.3(BTTri).sub.8]-en (H.sub.3BTTri=1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene),.sup.22 but lower than the value observed by other workers for Mg.sub.2(dobpdc)(mmen).sub.1.6(H.sub.2O).sub.0.4 (dobpdc.sup.4=4,4-dioxido-3,3-biphenyldicarboxylate;mmen=N,Ndimethylethylenediamine) (3.14 mmol g.sup.1 at 0.15 bar and 313 K). Analysis of the CO.sub.2 adsorption isotherm at 273 K by DFT/Monte-Carlo methods gives a surface area of 1370 m.sup.2 g.sup.1, a pore size distribution centred at 5.7 , and a cumulative pore volume of 0.375 cm.sup.3 g.sup.1 (FIG. 49), confirming the microporous nature of this material. Saturated CO.sub.2 uptake at 273 K and 7.0 bar was found to be 8.7 mmol g.sup.1 (FIG. 48). These data are entirely consistent with the crystallographically-determined extra-framework pore volume of 0.433 cm.sup.3 g.sup.1 and the channel window diameter of 6.5 .

(100) Interestingly, compared with the isotherm for CO.sub.2, (kinetic diameter 3.30 ), the isotherm for SO.sub.2 (kinetic diameter 4.11 ) exhibits higher uptakes with a maximum capacity of 8.1 mmol g.sup.1 at 273 K and 1.0 bar, representing the highest value observed in the current literature. The SO.sub.2 uptake increases sharply at low pressure (below 50 mbar) and reaches saturation at around 0.10 bar, giving a typical type-I isotherm. The very rapid uptake observed at low pressure indicates the presence of stronger interactions in NOTT-300 (Al)SO.sub.2 compared with NOTT-300 (Al)CO.sub.2. This is probably due to the high dipole moment of SO.sub.2 (1.62 D compared with 0 D for CO.sub.2) which results in stronger interactions of SO.sub.2 with the pore surface of NOTT-300 (Al). The density of adsorbed CO.sub.2 and SO.sub.2 in NOTT-300 (Al) is unknown. By using a density of 1.032 g cm.sup.3 of liquid CO.sub.2 at 253 K or a density of 1.458 g cm.sup.3 of liquid SO.sub.2 at its boiling point of 263 K, it can be deduced that the volumes of CO.sub.2 and SO.sub.2 adsorbed in NOTT-300 (Al) at 1.0 bar and 273 K are 0.298 and 0.356 cm.sup.3 g.sup.1, respectively. This corresponds to fillings of 69% and 82%, respectively, of the total crystallographically-determined pore volume of 0.433 cm.sup.3 g.sup.1. At 7.0 bar, up to 89% of the total pore volume in NOTT-300 (Al) is filled by CO.sub.2 molecules. These values are entirely reasonable considering that in each case the adsorption temperature lies above the relevant boiling point; moreover, in an isotherm experiment not all the void space within a porous material is necessarily accessible to the gaseous substrate. In contrast, under the same conditions the isotherms for CH.sub.4, CO, N.sub.2, H.sub.2, O.sub.2, and Ar show only surface adsorption by NOTT-300 (Al), with very low uptake of gas (0.04-0.25 mmol g.sup.1). Significantly, comparison of the gas adsorption isotherms (FIG. 3a) clearly shows ultra-high selectivities for CO.sub.2 and SO.sub.2 (e.g., CO.sub.2/CH.sub.4: 100; CO.sub.2/N.sub.2: 180; CO.sub.2/H.sub.2: >10.sup.5; SO.sub.2/CH.sub.4: 3620; SO.sub.2/N.sub.2: 6522; SO.sub.2/H.sub.2: >10.sup.5), indicating the potential of NOTT-300 (Al) for the selective capture of these harmful gases.

(101) Gas adsorption isotherms (CO.sub.2, SO.sub.2, CH.sub.4, N.sub.2, CO, O.sub.2, Ar, H.sub.2) for NOTT-300 (Al) have also been measured at more ambient temperatures (i.e., 283, 293 and 303 K), where highly selective uptakes for CO.sub.2 and SO.sub.2 are confirmed (FIGS. 52(a)-52(c)), and the corresponding desorption isotherms exhibit full reversibility without hysteresis. This suggests that the adsorbed CO.sub.2 and SO.sub.2 gases can be readily released and that NOTT-300 (Al) can be re-generated at ambient temperatures without the need for heating, a factor which reduces the energy efficiency of traditional amine-based carbon capture systems.

(102) In Situ Inelastic Neutron Scattering and Powder Diffraction Studies of of NOTT-300 (Al)

(103) Direct visualisation of the interaction between CO.sub.2 molecules and the NOTT-300 (Al) host is crucial to understanding the detailed binding mechanism and hence the observed high selectivities. Inelastic neutron scattering (INS) is a powerful neutron spectroscopy technique which has been used widely to investigate the H.sub.2 binding interactions within various storage systems by exploiting the high neutron scattering cross-section of hydrogen (82.02 barns). However, this technique cannot directly detect the CO.sub.2 binding interaction within a carbon capture system because the scattering cross-sections for carbon (5.551 barns) and oxygen (4.232 barns) are too small to obtain a clear neutron scattering signal. In this study, INS and DFT been successfully combined to visualise captured CO.sub.2 molecules within NOTT-300 (Al) by investigating the change in the dynamics of the hydrogen atoms of the local MOF structure, including those of the hydroxyl groups and benzene rings of the ligand (FIG. 4). Calculation of the INS spectra from DFT vibrational analysis can be readily achieved, and the DFT calculations relate directly to the INS spectra, and, in the case of solid state calculations, there are no approximations other than the use of DFT eigenvectors and eigenvalues to determine the spectral intensities..sup.24 Comparison of INS spectra, measured at temperatures below 5 K to minimise the thermal motion of the adsorbed CO.sub.2 and the framework host, reveals two major increases in peak intensity on going from bare NOTT-300 (Al) to NOTT-300 (Al).1.0CO.sub.2: peak I occurs at low energy transfer (30 meV) and peak II at high energy transfer (125 meV). Moreover, the peaks in the range 100-160 meV are slightly shifted to higher energies in NOTT-300 (Al).1.0CO.sub.2 (FIG. 4b), indicating a stiffening of the motion of the NOTT-300 (Al) host upon CO.sub.2 adsorption. To understand these changes, DFT calculations have been used to simulate the INS spectra and optimise the structures for NOTT-300 (Al) and NOTT-300 (Al).1.0CO.sub.2. The INS spectra derived from these calculations show good agreement with experimental spectra and confirm that the adsorbed CO.sub.2 molecules interact end-on to the hydroxyl groups. The O . . . H distance between the CO.sub.2 molecule and the hydroxyl group is 2.335 , indicating a moderate-to-weak hydrogen bond (See Table S13 in the supplementary section of this specification). The optimised CO bond distances in CO.sub.2 are 1.183 (hydrogen-bonded end) and 1.178 (free end), and the <OCO bond angle is 180. Each adsorbed CO.sub.2 molecule is also surrounded by four aromatic CH groups, forming weak cooperative supramolecular interactions between O() of CO.sub.2 and H(+) from CH [O . . . H=3.029, 3.190 , each occurring twice]. Specifically, peak I can be assigned to the OH groups wagging perpendicular to the AlOAl direction, attributed to the presence of the CO.sub.2, and peak II to the wagging of the four aromatic CH groups on four benzene rings adjacent to each CO.sub.2 molecule in conjunction with the wagging of the OH group along the AlOAl direction (FIG. 4d and film in SI). Thus, a total of five hydrogen atoms H(+) interact cooperatively with the O() charge centres of CO.sub.2 molecules in the channel via moderate-to-weak hydrogen bonds and supramolecular interactions.

(104) The preferred binding sites for CO.sub.2 molecules within NOTT-300 (Al) have also been determined by in situ PXRD analysis which also confirms end-on binding of CO.sub.2 molecules to the hydroxyl group [O . . . H=2.298(10) ]. The weaker supramolecular contacts from surrounding CH groups to the O() charged centres of CO.sub.2 molecules in the channel [O . . . H=3.021(31), 3.171(22) , each occurring twice] are also observed. This PXRD analysis is in excellent agreement with the INS model obtained independently from DFT modelling with regard to both hydrogen-bonding and the combination of supramolecular binding interactions. Additionally, a second CO.sub.2(II) site has been identified in NOTT-300 (Al).3.2CO.sub.2 studied by PXRD. This second site interacts principally with the first CO.sub.2 via dipole interaction [O(I) . . . C(II)=3.920 ], forming an edge-on intermolecular CO.sub.2 network [O(I) . . . O(II)=2.713(28) ] along the pore channel that is reminiscent of solid CO.sub.2 (FIG. 4c).

(105) In order to understand why low uptakes are observed for some gases while high selectivity for CO.sub.2 is achieved, the interactions between H.sub.2 and NOTT-300 (Al) were probed The INS spectra of NOTT-300 (Al).1.0H.sub.2 show an overall increase in signal upon H.sub.2 loading, indicating adsorption of H.sub.2 by NOTT-300 (Al) at below 40 K (FIG. 54). The difference INS spectra, measured at below 5 K, between bare NOTT-300 (Al) and NOTT-300 (Al).1.0H.sub.2 show a series of features that resemble the signal of liquid molecular H.sub.2. Significantly, the sharp rotational peak usually observed around 14.7 meV as a prominent feature in the INS of molecular H.sub.2 in the solid state or adsorbed on surface is not observed here. This suggests a 1D fluid-like recoil motion of the H.sub.2 along the channel.sup.25,26 consistent with extremely weak interactions and low uptake of H.sub.2 in NOTT-300 (Al) (FIGS. 55(a), 55(b), 56(a), and 56(b)).

(106) In order to determine the reasons for the high selectivity and high uptake capacity, the preferred binding sites for SO.sub.2 molecules within NOTT-300 (Al) have been determined by in situ PXRD. The in situ PXRD confirms the retention of the structure of NOTT-300 (Al) upon inclusion and subsequent removal of SO.sub.2 (FIG. 5a), thereby confirming the high stability of NOTT-300 (Al) in the presence of corrosive SO.sub.2. Indeed, the uptake of SO.sub.2 in NOTT-300 (Al) is entirely reversible with no apparent loss of capacity on recycling. For NOTT-300 (Al).4SO.sub.2 (at 1.0 bar), two distinct, equally-occupied binding sites (I and II) were located within the channel (FIG. 5b): SO.sub.2(I) occupies the same position as CO.sub.2 and interacts with OH groups via its O() charged centre [OSO . . . HOAl=2.376(13) ], which also forms weak interactions with four CH groups from neighbouring benzene rings [OSO . . . HC=2.806(14), 2.841(17), 3.111(16), 3.725(18) ]. Thus, as for CO.sub.2, a total of five cooperative hydrogen bonds accommodate SO.sub.2(I) in a pocket-like cavity. A second site, identified as SO.sub.2(II), was observed between two SO.sub.2(I) molecules. However, no hydrogen bonding between the SO.sub.2(II) and OH or CH groups are apparent; rather, the O() centre of SO.sub.2(II) interacts with the S(+) charge centre of SO.sub.2(I), thus stabilising an SO.sub.2(I,II) intermolecular chain via O() . . . S(+) dipole interactions [O(I) . . . S(II)=3.34(7) ](FIG. 5b) within the channel. The SO bond distances for SO.sub.2(I) and SO.sub.2(II) are 1.481(4) and 1.500(8) , respectively, with corresponding <OSO angles of 117.5(11) and 109.1(9). The structural investigation of NOTT-300 (Al).4SO.sub.2 represents a distinct crystallographic study of a SO.sub.2-loaded MOF and gives important insights into the SO.sub.2 adsorption mechanism.

(107) Despite the small total bound scattering cross section of sulphur (1.026 barns), comparison of the INS spectra below 5 K reveals two major increases in peak intensity on going from bare NOTT-300 (Al) to NOTT-300 (Al).2SO.sub.2 (or NOTT-300 (Al).3SO.sub.2): peak I occurs at low energy transfer (30-50 meV) and peak II at high energy transfer (125 meV), similar to that observed in the INS spectra for CO.sub.2-loaded NOTT-300 (Al) (FIG. 6b). Moreover, immediate stiffening of the motion of the NOTT-300 (Al) host was observed upon SO.sub.2 inclusion, as evidenced by the slight shift in INS peak to higher energies in NOTT-300 (Al).2SO.sub.2 and NOTT-300 (Al).3SO.sub.2 (FIG. 6a). DFT simulation has also been performed to optimise the structures of both NOTT-300 (Al) and NOTT-300 (Al).2SO.sub.2 materials. The simulated INS spectra show good agreement with the experimental spectra and are consistent with the adsorbed SO.sub.2 molecules interacting end-on to the hydroxyl groups via the hydrogen bond interactions [O . . . H=2.338 ] with additional supramolecular contacts with the adjacent aromatic CH groups [O . . . H=2.965-3.238 ] (FIG. 6c). The INS/DFT results are entirely consistent with the PXRD analysis and provide key insights into the dynamics of the NOTT-300 (Al) host upon SO.sub.2 inclusion.

(108) Selective Hydrocarbon Uptake of NOTT-300 (Al)

(109) TABLE-US-00001 TABLE A Selectivity 273K 283K 293K 303K C.sub.2H.sub.2/C.sub.2H.sub.4 4.20 2.52 2.06 1.56
Structure Determination and Refinement for NOTT-300 (Al)-Solvate, NOTT-300 (Al).3.2CO.sub.2 and NOTT-300 (Al).4SO.sub.2

(110) High resolution powder diffraction data were collected on Beamline I11 at Diamond Light Source by using multi-analysing-crystal detectors (MACs).sup.28 and an in-situ gas cell system. The powder pattern was firstly indexed on a body-centred tetragonal lattice and the independent unit cell parameters were refined using TOPAS..sup.29 The body centring and the reflection condition 00l:l=4n indicates that the space group is one of the enantiomeric pair I4.sub.122 and I4.sub.322. In the absence of any component capable of directing chirality, the product is expected to be a 1:1 racemic mixture. The structure solution was initially established in space group I4.sub.122 by charge flipping using the program Superflip,.sup.30 and further developed from subsequent difference Fourier analysis using TOPAS. The final structure refinement was carried out using the Rietveld method.sup.29 with isotropic displacement parameters for all atoms. A total of 40 disordered water molecules per unit cell were found within the pore channel and included in the final structure refinement for NOTT-300 (Al)-solvate. Upon desolvation and SO.sub.2 loading, we observe neither major changes to cell parameters nor extra features in the patterns, suggesting that there is no structural phase change during the experiment. However, upon SO.sub.2 loading, there are significant increases in the peak intensities at 6.2, 10.2, 12 and 14 2, indicating that the SO.sub.2 molecules are adsorbed into the material, and that the overall microscopic ordering of the SO.sub.2/host system is increasing. A Monte-Carlo-based simulated annealing technique in which the guest SO.sub.2 molecules were treated as rigid bodies was used to locate their positions in NOTT-300 (Al).4SO.sub.2. Two independent SO.sub.2 sites were found each with half occupancy. The SO.sub.2 content was refined giving a stoichiometry of 1.98(2) molecules of SO.sub.2 per Al, slightly higher than the experimental value of 1.7 SO.sub.2 per Al. The occupancy of the first CO.sub.2 site was determined to be 0.865(9) and the second CO.sub.2 site 0.727(7), leading to a total refined CO.sub.2 stoichiometry of 1.592(12) in excellent agreement with the experimental value of 1.6 CO.sub.2 per Al. The final stage of the Rietveld refinement involved soft restraints to the CC bond lengths within the benzene rings. Rigid body refinement was applied to the CO.sub.2 and SO.sub.2 molecules in the pore.

(111) Crystal Data for NOTT-300 (Al)-Solvate

(112) [Al.sub.2(OH).sub.2(C.sub.16H.sub.6O)](H.sub.2O).sub.6. White powder. Tetragonal, space group I4.sub.122, a=b=14.82958(6), c=11.77317(5) , V=2589.11(3) .sup.3, M=522.29, T=293(2) K, Z=4. The final Rietveld plot corresponds to satisfactory crystal structure model (R.sub.Bragg=0.056) and profile (R.sub.p=0.052 and R.sub.wp=0.072) indicators with a goodness-of-fit parameter of 1.345. Final fractional coordinates for NOTT-300 (Al)-solvate are listed in Table S1.

(113) TABLE-US-00002 TABLE S1 Atomic positions for non-hydrogen atoms in NOTT-300 (Al)-solvate x y z B.sub.iso (.sup.2) Al1 0.69426(5) 0.30574(5) 0.5 0.72(13) O1 0.75744(13) 0.25 0.625 0.51(12) O2 0.89782(9) 0.28675(9) 0.99869(15) 0.51(12) O3 0.62165(10) 0.37371(10) 0.39436(12) 0.51(12) C1 0.59280(35) 0.36039(14) 0.69453(19) 0.70(13) C2 0.54498(10) 0.43181(7) 0.75722(10) 0.70(13) C3 0.5 0.5 0.69649(14) 0.70(13) C4 0.54071(10) 0.428618(71) 0.87716(8) 0.70(13) C5 0.5 0.5 0.93474(11) 0.70(13) O1w 0.91080(23) 0.80489(16) 0.94077(28) 21.6(2) O2w 0.45734(19) 0.73953(30) 0.06123(32) 11.9(3) O3w 0.13041(22) 0.29586(24) 0.53782(37) 35.7(3)
Crystal Data for NOTT-300 (Al).3.2CO.sub.2

(114) [Al.sub.2(OH).sub.2(C.sub.16H.sub.6O.sub.8)](CO.sub.2).sub.3.2. White powder. Tetragonal, space group I4.sub.122, a=b=14.82432(6), c=11.80570(5), V=2594.43(3) .sup.3, M=550.03, T=273(2) K, Z=4. The final Rietveld plot corresponds to satisfactory crystal structure model (R.sub.Bragg=0.025) and profile (R.sub.p=0.043 and R.sub.wp=0.059) indicators with a goodness-of-fit parameter of 1.531. Final fractional coordinates for NOTT-300 (Al).3.2CO.sub.2 are listed in Table S2.

(115) TABLE-US-00003 TABLE S2 Atomic positions for NOTT-300 (Al)3.2CO.sub.2 X y z B.sub.iso (.sup.2) Al1 0.30694(4) 0.30694(4) 0.5 0.93(40) O1 0.75117(13) 0.25 6.625 0.82(40) H1 0.8123(17) 0.25 0.625 0.75(40) O2 0.62152(22) 0.37975(22) 0.60276(28) 0.82(40) O3 0.60511(22) 0.28380(22) 0.75032(28) 0.82(40) C1 0.59215(19) 0.36044(15) 0.70222(15) 1.37(40) C2 0.54078(8) 0.43003(6) 0.76456(13) 1.37(40) C3 0.5 0.5 0.70584(14) 1.37(40) H3 0.5 0.5 0.6125(7) 1.37(40) C4 0.54078(8) 0.43003(6) 0.88199(13) 1.37(40) H4 0.5675(4) 0.3842(6) 0.9205(6) 1.37(40) C5 0.5 0.5 0.94071(14) 1.37(40) C1_1 1.0335(25) 0.25 0.6676(12) 15.1(2) O1_1 0.9673(23) 0.25 0.625 18.7(5) O2_1 1.0998(22) 0.25 0.7102(24) 39.4(8) C1_2 0.25 0.35535 0.375 18.3(2) O1_2 0.32821 0.35535 0.375 38.4(8)
Crystal Data for NOTT-300 (Al).4SO.sub.2

(116) [Al.sub.2(OH).sub.2(C.sub.16H.sub.6O.sub.8)](SO.sub.2).sub.4. White powder. Tetragonal, space group I4.sub.122, a=b=14.84740(10), c=11.80564(8), V=2602.50(4) .sup.3, M=670.46, T=273(2) K, Z=4. The final Rietveld plot corresponds to satisfactory crystal structure model (R.sub.Bragg=0.024) and profile (R.sub.p=0.044 and R.sub.wp=0.057) indicators with a goodness-of-fit parameter of 1.293. Final fractional coordinates for NOTT-300 (Al).4SO.sub.2 are listed in Table S3.

(117) TABLE-US-00004 TABLE S3 Atomic positions for NOTT-300 (Al)4SO.sub.2 X y z B.sub.iso (.sup.2) Al1 0.30668(4) 0.30668(4) 0.5 0.83(11) O1 0.75093(11) 0.25 0.625 0.50(11) H1 0.8094(7) 0.2737(13) 0.6182(19) 0.75(17) 02 0.87680(8) 0.12169(8) 0.10281(9) 0.50(11) O3 0.89634(7) 0.21365(7) 0.25360(13) 0.50(11) C1 0.85735(12) 0.09466(13) 0.79858(16) 0.90(12) C2 0.53958(11) 0.43084(7) 0.75958(9) 0.90(12) C3 0.5 0.5 0.69441(10) 0.90(12) H3 0.5 0.5 0.6125(7) 1.09(14) C4 0.54005(7) 0.42960(5) 0.87811(9) 0.90(12) H4 0.57318 0.38162 0.90735 1.09(14) C5 0.5 0.5 0.93693(9) 0.90(12) S1 0.062518 0.257889 0.415951 15.1(2) O1s 0.036130 0.243180 0.416293 5.8(2) O2s 0.110299 0.250886 0.525706 39.4(8) S2 0.103150 0.184862 0.037573 18.3(2) O3s 0.117697 0.239213 0.143103 38.4(8) O4s 0.123069 0.242537 0.063692 24.4(4)

(118) A detailed description has been given above for an aluminium hydroxyl metal organic framework complex. Analogues to this complex have also been synthesised based on indium, antimony, chromium and gallium. A metal organic framework has also be synthesised that contains both aluminium and iron functional groups. These analogue complexes also exhibit the same high uptake and selectivity for XO.sub.2 gases (X=C, S, O).

(119) Transmission Electron Microscopic (TEM) Study on NOTT-300 (Al).

(120) A TEM image shows the crystals to have uniform morphology of 1 m plates (Fig. S7a,b), and a high resolution (HRTEM) image confirms the presence of extended crystalline planes (Fig. S7c).

(121) Synchrotron Powder Diffraction Studies of Solvated NOTT-300

(122) To investigate the chemical stability of desolvated NOTT-300, an important feature for a capture material, PXRD patterns were collected for a range of NOTT-300 samples under variable chemical environments. Some of these are illustrated in FIG. 42. After the collection of an original pattern for the as-synthesised sample, NOTT-300 solvate was degassed at 150 C. to generate desolvated NOTT-300. The desolvated material was then separated into ten portions, each of which was exposed to air for one month, or immersed in water, methanol, ethanol, CHCl.sub.3, CH.sub.3CN, DMF, THF, benzene or toluene for one week. Comparison of the resultant PXRD patterns confirms the excellent stability of the desolvated NOTT-300 material under air, water and common organic solvents. FIG. 43 provides an illustration comparing of unit cell parameters of NOTT-300 under different chemical environments.

(123) Variable Temperature Powder Diffraction of NOTT-300 (Al)

(124) To investigate the possible framework phase change of NOTT-300 (Al)-solvate as a function of temperature, variable temperature PXRD patterns were collected at 100-483 K for NOTT-300 (Al)-solvate (FIG. 44). Comparison of the PXRD patterns confirms that there is no framework phase transition over this temperature range and the framework of NOTT-300 (Al) remains intact after removal of the water molecules in the channels. The lattice parameters were refined via Le Bail methods, and results are summarised in Table S3. The overall change in the unit cell volume is less than 1.0%, confirming the rigidity of the framework. FIG. 44 provides variable temperature PXRD patterns for NOTT-300 (Al)-solvate (=1.54056 ). FIG. 45. Unit cell parameters for NOTT-300 (Al)-solvate as a function of temperature.

(125) Table S4 provides a summary of Le Bail refinement results and unit cell parameters for NOTT-300 (Al)-solvate.

(126) TABLE-US-00005 TABLE S4 Unit cell a, b () c () V (.sup.3) change (%) 100 K 14.78200(30) 11.76100(35) 2569.87(13) 0.000 140 K 14.78821(29) 11.76287(33) 2572.44(12) 0.100 180 K 14.79348(30) 11.76458(34) 2574.64(13) 0.186 220 K 14.80187(30) 11.76717(34) 2578.13(13) 0.321 260 K 14.81512(30) 11.77028(35) 2583.43(13) 0.527 273 K 14.82847(31) 11.77667(37) 2589.50(13) 0.764 303 K 14.83686(30) 11.77726(36) 2592.56(13) 0.883 333 K 14.83822(31) 11.77750(38) 2593.09(14) 0.904 363 K 14.83625(48) 11.78236(61) 2593.46(21) 0.918 383 K 14.83288(42) 11.78464(54) 2592.79(19) 0.892 403 K 14.82777(38) 11.78762(47) 2591.66(17) 0.848 423 K 14.81612(45) 11.81073(51) 2592.66(19) 0.887 443 K 14.81299(54) 11.81873(59) 2593.32(23) 0.912 463 K 14.81193(51) 11.82149(60) 2593.55(22) 0.921 483 K 14.8186(13) 11.8244(15) 2596.54(56) 1.04
Exposure of NOTT-300 (Al) to Water.

(127) The NOTT-300 (Al)-solvate material was loaded into an IGA and degassed at 120 C. and 10.sup.10 bar for 24 h to give the fully desolvated NOTT-300 (Al) material. A CO.sub.2 adsorption isotherm was then measured at 273 K and up to 1.0 bar (noted as first cycle). The desolvated sample was then exposed to high temperature (90-100 C.) water vapour for 1 h as a humidity treatment. The hydrated sample was then loaded into IGA and degassed again at 120 C. and 10.sup.10 bar for 24 h to give desolvated NOTT-300 (Al) material. A second CO.sub.2 adsorption isotherm was then measured at 273 K and up to 1.0 bar (noted as the second cycle). The same humidity treatment (hydration), degassing (de-hydration), and CO.sub.2 adsorption were repeated twice more (noted as third and fourth cycles). Comparisons of these four CO.sub.2 adsorption isotherms confirm that there is no apparent loss of uptake capacity and that the pore surface can be fully regenerated, showing that the framework has good stability upon exposure to the above humidity cycle. FIG. 53 illustrates the CO.sub.2 adsorption isotherms at 273 K for NOTT-300 (Al) upon cyclic hydration and desolvation process.

(128) DFT Modelling and Simulations on NOTT-300

(129) The vibrational properties of the NOTT-300 (Al) were calculated using a combination of density functional theory (DFT) and plane-wave pseudopotential methods as implemented in the CASTEP code,.sup.2 using ultra-soft pseudopotentials with a plane-wave energy cutoff of 380 eV. Calculations were performed under the PBE approximation.sup.3 for exchange and correlation. The unit cell used has a volume of 2589.2 .sup.3 and contains 144 and 156 atoms for the bare and CO.sub.2-loaded materials, respectively. The wave functions were sampled according to the Monkhorst-Pack scheme with a k-points mesh of spacing 0.05 .sup.1. The normal modes of the solid were determined from dynamical matrices calculated using finite displacements, by numerical differentiation. The INS spectra was the calculated using the a Climax software..sup.4

(130) The calculation of the bare material is computationally stable, in the calculation of the vibrational frequencies, all the frequencies are positive. FIG. 29 illustrates the potential energy surface along the first vibrational eigenvector of the hydrogen bond between CO.sub.2 and the OH moieties. At the centre it is clear that the potential would give an unstable configuration from a classical point of view. The calculated solution of the Schrdinger equation gives the energy levels at 14.2 and 81 cm.sup.1. The zero point energy is higher than the local maximum so that from a quantum point of view, the system is in a stable equilibrium. In the calculation of the MOF material loaded with four CO.sub.2 molecules per unit cell (FIG. 29), corresponding to NOTT-300 (Al).1.0CO.sub.2, 8 imaginary frequency modes were found. Following the methodology previously used in MOF modelling,.sup.5 we calculated the potential energy surface (PES) along each of the negative frequency modes (corresponding to the rocking motion of the CO.sub.2 unit). FIG. 29 shows the potential energy surface (PES) for the hydrogen bond between CO2 and OH group of the NOTT-300 (Al).1.0CO.sub.2. The obtained PES confirms that the zero-point energy (ZPE) level (the ground state) lies at an energy above the local minimum calculated by DFT. This means that these PES, although corresponding to an unstable structure from a static classical point of view, are indeed stable structures from the quantum mechanical view.

(131) The location of SO.sub.2 molecules in NOTT-300 has been optimised by DFT modelling based on the measured INS spectra. The DFT calculation was performed using the same settings as in the case of CO.sub.2. Notably, a high symmetry configuration, which does not take into account the disorder of SO.sub.2 molecules in the channel, was used.

(132) Analysis and Derivation of the Isosteric Heat of Adsorption for CO.sub.2 in NOTT-300 (Al).

(133) To estimate the isosteric enthalpies (AH) for CO.sub.2 adsorption, all isotherms at 273-303 K were fitted to the van't Hoff equation (1):

(134) $\begin{array}{cc}\frac{\ln \left(p\right)}{\left(1/T\right)}=-\frac{H}{R}& \left(1\right)\end{array}$
where p is pressure, T is the temperature, R is the real gas constant. Selected linear fitting plots at 0.5, 1.0, 1.5 and 2.0 mmol g.sup.1 are shown in FIG. 53. All linear fittings show R.sup.2 above 0.999, indicating consistency of the isotherm data.

(135) FIGS. 57(a)-57(d) provide linear fitting of Vant Hoff plots for the CO.sub.2 adsorption isotherms at 0.5, 1.0, 1.5 and 2.0 mmol g.sup.1 loadings.

(136) Calculation of Henry's Law Selectivity for Gas Adsorption in NOTT-300.

(137) To estimate the selectivity of CO.sub.2 and SO.sub.2 over other gases at zero surface coverage, all low pressure isotherm data at 273 K were fitted using a linear virial-type expression (2) employed previously to model gas sorption in MOFs. For the isotherms with overall low uptakes, where a good linear fitting cannot be obtained at low pressure, the non-linear virial type expression (3) was employed to achieve reasonable virial fitting with inclusion of data at relatively high pressure..sup.6
ln(n/p)=A.sub.0+A.sub.1n(2)
ln(n/p)=A.sub.0+A.sub.1n+A.sub.2n.sup.2+(3)
where p is the pressure expressed, n is the amount adsorbed, A, are virial coefficients, and i represent the number of coefficients required to adequately describe the isotherms with low uptakes. The results of the fitting for all isotherms give R.sup.2 greater than 0.99 and the Henry constants for each component were extracted from the virial coefficients (Tables S5).

(138) The Henry's constant (K.sub.H) can be extracted from the values of the virial coefficients A.sub.0 using expression (4).
K.sub.H=exp(A.sub.0)(4)

(139) The Henry's Law selectivity for component i(CO.sub.2 or SO.sub.2) over other gas component j(CO, CH.sub.4, N.sub.2, O.sub.2, Ar or H.sub.2) was estimated based on the ratio of their Henry's constants (equation 5). The results are listed in Table S6. The selectivity data from virial fittings and Henry's Law analysis are confined to the zero surface coverage situations.
S.sub.ij=K.sub.Hi/K.sub.Hj(5)

(140) Table S5 provides virial fitting results and Henry's constants K.sub.H for CO.sub.2, SO.sub.2, CH.sub.4, N.sub.2, H.sub.2, O.sub.2 and Ar in NOTT-300 (Al) from isotherm data at 273 K.

(141) TABLE-US-00006 TABLE S5 CO.sub.2 SO.sub.2 CO CH.sub.4 N.sub.2 H.sub.2 O.sub.2 Ar A.sub.0/ln(mol g.sup.1 14.11(8) 6.22(40) 20.27(3) 20.34(3) 20.81(1) n.a. * 20.04(2) 20.57(2) Pa.sup.1) K.sub.H/mol g.sup.1 7.45(57) 508(167) 1.57(5) 1.46(4) 9.14(10) 1.98(2) 1.16(2) Pa.sup.1 10.sup.7 10.sup.9 10.sup.9 10.sup.10 10.sup.9 10.sup.9 Fitting R.sup.2 0.990 0.996 >0.999 >0.999 >0.999 >0.999 >0.999 Residual 0.00075 0.034 0.022 0.022 0.016 0.011 0.030 error * The uptake of H.sub.2 isotherm at 273 K (below 0.01 wt %) is too low to obtain a reasonable virial fitting curve, and the Henry constant is therefore considered to be approximately zero.

(142) Table S6 provides virial fitting results and Henry's constants K.sub.H for CO.sub.2, SO.sub.2, CH.sub.4, N.sub.2, H.sub.2, O.sub.2 and Ar in NOTT-300 (Al) from isotherm data at 283 K.

(143) TABLE-US-00007 TABLE S6 CO.sub.2 SO.sub.2 CO CH.sub.4 N.sub.2 H.sub.2 O.sub.2 Ar A.sub.0/ln(mol g.sup.1 14.57(5) 5.75(50) 20.38(2) 20.29(2) 20.84(1) n.a.* 20.11(2) 20.70(3) Pa.sup.1) K.sub.H/mol g.sup.1 4.70(24) 314(123) 1.41(3) 1.54(3) 8.88(9) 1.85(4) 1.03(4) Pa.sup.1 10.sup.7 10.sup.9 10.sup.9 10.sup.10 10.sup.9 10.sup.9 Fitting R.sup.2 0.994 0.991 >0.999 >0.999 >0.999 >0.999 >0.999 Residual error 0.00050 0.141 0.021 0.013 0.024 0.023 0.012 *The uptake of H.sub.2 isotherm at 283 K (below 0.01 wt %) is too low to obtain a reasonable virial fitting curve, and the Henry constant is therefore considered to be approximately zero.

(144) Table S7. Virial fitting results and Henry's constants K.sub.H for CO.sub.2, SO.sub.2, CH.sub.4, N.sub.2, H.sub.2, O.sub.2 and Ar in NOTT-300 (Al) from isotherm data at 293 K.

(145) TABLE-US-00008 TABLE S7 CO.sub.2 SO.sub.2 CO CH.sub.4 N.sub.2 H.sub.2 O.sub.2 Ar A.sub.0/ln(mol g.sup.1 15.52(3) 5.46(126) 20.37(2) 20.23(3) 20.78(3) n.a.* 19.98(2) 20.69(2) Pa.sup.1) K.sub.H/mol g.sup.1 1.82(6) 235(168) 1.42(2) 1.63(4) 9.42(22) 2.10(5) 1.03(2) Pa.sup.1 10.sup.7 10.sup.9 10.sup.9 10.sup.10 10.sup.9 10.sup.9 Fitting R.sup.2 0.997 0.977 >0.999 >0.999 >0.999 >0.999 >0.999 Residual error 0.000030 0.024 0.020 0.013 0.011 0.017 0.015 *The uptake of H.sub.2 isotherm at 283 K (below 0.01 wt %) is too low to obtain a reasonable virial fitting curve, and the Henry constant is therefore considered to be approximately zero.

(146) Table S8 provides virial fitting results and Henry's constants K.sub.H for CO.sub.2, SO.sub.2, CH.sub.4, N.sub.2, H.sub.2, O.sub.2 and Ar in NOTT-300 (Al) from isotherm data at 303 K.

(147) TABLE-US-00009 TABLE S8 CO.sub.2 SO.sub.2 CO CH.sub.4 N.sub.2 H.sub.2 O.sub.2 Ar A.sub.0/ln(mol g.sup.1 16.44(1) 4.30(100) 20.27(2) 20.15(2) 20.73(1) n.a.* 20.03(1) 20.42(2) Pa.sup.1) K.sub.H/mol g.sup.1 7.25(8) 73.7(465) 1.57(2) 1.77(4) 9.89(10) 2.04(1) 1.35(2) Pa.sup.1 10.sup.8 10.sup.9 10.sup.9 10.sup.10 10.sup.9 10.sup.9 Fitting R.sup.2 0.994 0.976 >0.999 >0.999 >0.999 >0.999 >0.999 Residual error 0.000072 0.050 0.016 0.016 0.0048 0.022 0.013 *The uptake of H.sub.2 isotherm at 283 K (below 0.01 wt %) is too low to obtain a reasonable virial fitting curve, and the Henry constant is therefore considered to be approximately zero.

(148) Table S9 provides a summary of gas adsorption selectivity data obtained by two methods: (i).sup.a the ratio of slopes of initial adsorption isotherm plot; (ii).sup.b Henry's Law analysis at 273 K.

(149) TABLE-US-00010 TABLE S9 Selectivity ratio Isotherm plot slop Henry's Law analysis CO.sub.2/CO 86 475.sup. CO.sub.2/CH.sub.4 100 510.sup. CO.sub.2/N.sub.2 180 815.sup. CO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 CO.sub.2/O.sub.2 70 376.sup. CO.sub.2/Ar 137 642.sup. SO.sub.2/CO 3105 >10.sup.5 SO.sub.2/CH.sub.4 3620 >10.sup.5 SO.sub.2/N.sub.2 6522 >10.sup.5 SO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 SO.sub.2/O.sub.2 2518 >10.sup.5 SO.sub.2/Ar 4974 >10.sup.5 .sup.aThis method represents the selectivity at low pressure region (50-350 mbar) and is close to the situation from the direct comparison of gas uptakes. .sup.bThis method represents the extreme selectivity at zero surface coverage of a given material, and therefore is higher than the values from method (i). Selectivity data obtained from method (i) are reported in the main text.

(150) Table S10. Summary of gas adsorption selectivity data obtained by two methods: (i).sup.a the ratio of slopes of initial adsorption isotherm plot; (ii).sup.b Henry's Law analysis at 283 K.

(151) TABLE-US-00011 TABLE S10 Selectivity ratio Isotherm plot slop Henry's Law analysis CO.sub.2/CO 67 333.sup. CO.sub.2/CH.sub.4 57 305.sup. CO.sub.2/N.sub.2 110 529.sup. CO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 CO.sub.2/O.sub.2 54 254.sup. CO.sub.2/Ar 90 456.sup. SO.sub.2/CO 3586 >10.sup.5 SO.sub.2/CH.sub.4 3061 >10.sup.5 SO.sub.2/N.sub.2 5864 >10.sup.5 SO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 SO.sub.2/O.sub.2 2880 >10.sup.5 SO.sub.2/Ar 4831 >10.sup.5 .sup.aThis method represents the selectivity at low pressure region (50-350 mbar) and is close to the situation from the direct comparison of gas uptakes. .sup.bThis method represents the extreme selectivity at zero surface coverage of a given material, and therefore is higher than the values from method (i).

(152) Table S11. Summary of gas adsorption selectivity data obtained by two methods: (i).sup.a the ratio of slopes of initial adsorption isotherm plot; (ii).sup.b Henry's Law analysis at 293 K.

(153) TABLE-US-00012 TABLE S11 Selectivity ratio Isotherm plot slop Henry's Law analysis CO.sub.2/CO 45 128.sup. CO.sub.2/CH.sub.4 39 112.sup. CO.sub.2/N.sub.2 72 193.sup. CO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 CO.sub.2/O.sub.2 39 .sup.87 CO.sub.2/Ar 64 177.sup. SO.sub.2/CO 2854 >10.sup.5 SO.sub.2/CH.sub.4 2464 >10.sup.5 SO.sub.2/N.sub.2 4545 >10.sup.5 SO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 SO.sub.2/O.sub.2 2490 >10.sup.5 SO.sub.2/Ar 4070 >10.sup.5 .sup.aThis method represents the selectivity at low pressure region (50-350 mbar) and is close to the situation from the direct comparison of gas uptakes. .sup.bThis method represents the extreme selectivity at zero surface coverage of a given material, and therefore is higher than the values from method (i).

(154) Table S12 provides a summary of gas adsorption selectivity data obtained by two methods: (i).sup.a the ratio of slopes of initial adsorption isotherm plot; (ii).sup.b Henry's Law analysis at 303 K.

(155) TABLE-US-00013 TABLE S12 Selectivity ratio Isotherm plot slop Henry's Law analysis CO.sub.2/CO 32 .sup.46 CO.sub.2/CH.sub.4 31 .sup.41 CO.sub.2/N.sub.2 46 .sup.73 CO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 CO.sub.2/O.sub.2 30 .sup.36 CO.sub.2/Ar 41 .sup.54 SO.sub.2/CO 1586 >10.sup.5 SO.sub.2/CH.sub.4 1510 >10.sup.5 SO.sub.2/N.sub.2 2252 >10.sup.5 SO.sub.2/H.sub.2 .sup.>10.sup.5 >10.sup.5 SO.sub.2/O.sub.2 1458 >10.sup.5 SO.sub.2/Ar 2002 >10.sup.5 aThis method represents the selectivity at low pressure region (50-350 mbar) and is close to the situation from the direct comparison of gas uptakes. .sup.bThis method represents the extreme selectivity at zero surface coverage of a given material, and therefore is higher than the values from method (i).
Summary of the Hydrogen Bond Interactions in NOTT-300 (Al).

(156) A hydrogen bond system is conventionally represented as a linear A-H . . . B arrangement of a hydrogen donor (A-H) and an acceptor (B). Relevant properties of the different strengths of hydrogen bonds are given in Table C1. In this system, the hydrogen bond length H . . . O is around 2.3 (FIG. 4d), and therefore it can be classed as a moderate-to-weak hydrogen bond. The four CH supramolecular contacts are likely to be of lower energies. Based on this analysis, we view the observed value of Q.sub.st as entirely reasonable and consistent with the likely hydrogen bond energies. In addition, there is the possibility of electrostatic Al(III)/XO.sub.2 interactions. The high CO.sub.2 uptakes also reflect the relatively narrow pore size of the host which provides strong overlap potentials.

(157) Table S13 provides properties of strong, moderate and weak H-bonds.

(158) TABLE-US-00014 Properties Strong H-bonds Moderate H-bonds Weak H-bonds Bond energy 4-10 1-3 <1 (kJ mol.sup.1) Bond nature mostly mostly electrostatic covalent electrostatic Bond linearity, always mostly sometimes A-H . . . B linear linear linear Bond length 1.2 to 1.5 ca 1.0 ca 1.0 A-H () Bond length 1.2 to 1.5 1.5 to 2.2 2.2 to 3.2 H . . . B () Bond length 2.2 to 2.5 2.5 to 3.2 3.2 to 4.0 A . . . B ()

Example 2

Synthesis of NOTT-300 (In)

(159) Biphenyl-3,3,5,5-tetracarboxylic acid (0.015 g, 0.045 mmol), In(NO.sub.3).(H.sub.2O).sub.5 (0.014 mg, 0.045 mmol) and piperazine (7.0 mg, 0.081 mmol) were mixed and dispersed in DMF/MeCN mixture (1.3 mL, 1:0.3 v/v). The white slurry was acidified with dilute nitric acid (5%, 0.3 mL) and heated to 100 C. Upon reaching 60 C. the white slurry was observed to fully dissolve resulting in a colourless solution followed by precipitation of a white crystalline powder which was washed sequentially with DMF and dried briefly in air. Powder diffraction data (PXRD) confirm that the parent MOF NOTT-300 (In)-solv is iso-structural to NOTT-300(Al)-solv. Yield: 20 mg (75%). Elemental analysis (% calc/found): [In.sub.2(C.sub.16H.sub.6O.sub.8).sub.2 (DMF).sub.0.75(H.sub.2O).sub.1.75 (C, 33.02/33.02; H, 2.20/2.53; N, 1.58/1.58). Selected IR(ATR): /cm.sup.1=1705 (s), 1669 (s), 1652 (s), 1612 (m), 1549 (s), 1423 (s), 1367 (s), 1311 (w), 1253 (w), 1226 (w), 974 (m), 799 (s), 709 (s).

Example 3

Synthesis of NOTT-300(Sb)

(160) Biphenyl-3,3,5,5-tetracarboxylic acid (0.015 g, 0.045 mmol) and SbCl.sub.3 (0.010 mg, 0.045 mmol) were mixed and dispersed in DMF/MeCN mixture (1.3 mL, 1:0.3 v/v). The white slurry was acidified with dilute nitric acid (5%, 0.3 mL) and heated to 100 C. Upon reaching 60 C. the white slurry was observed to fully dissolve resulting in a colourless solution followed by precipitation of a white crystalline powder which was washed sequentially with DMF and dried briefly in air. [Sb.sub.2(C.sub.16H.sub.6O.sub.8)-.sub.2.(DMF).sub.x.(H.sub.2O).sub.y. Colourless block (0.030.020.01 mm) I4.sub.122, a=15.4500(5) c=12.2908(6) , V=2933.9(2) .sup.3, Z=4, D.sub.calc=1.362 g cm.sup.3, =14.927 mm.sup.1, F(000)=1136. A total of 1473 reflections was collected, of which 1392 were unique, with R.sub.int=0.0606. Final R.sub.1 (wR.sub.2)=0.0643 (0.2060) with GOF=1.880. The final difference Fourier extrema were 3.32 and 0.88 e/.sup.3.

Example 4

Synthesis of NOTT 300 (Cr)

(161) Chromium nitrate, Cr(NO.sub.3).sub.3.9H.sub.2O, (0.36 g, 0.9 mmol) was dissolved in water (10 mL), biphenyl-3,3,5,5-tetracarboxylic acid (0.06 g, 0.18 mmol) was then added. Piperazine (0.1 g) was added followed by addition of 2.8 M nitric acid (2 mL). The reaction mixture was transferred to a 2 mL autoclave which was sealed and heated to 210 C. for 72-96 h. The resulting powder product was separated by filtration and washed with water.

Example 5

Synthesis of NOTT-300(Ga)

(162) NOTT-300(Ga.sub.2) {[Ga.sub.2(OH).sub.2(C.sub.16H.sub.6O.sub.8)]} was synthesised under solvothermal conditions by reacting biphenyl-3,3,5,5-tetracarboxylic acid (0.02 g, 0.06 mmol) and gallium nitrate, Ga(NO.sub.3).sub.3.xH.sub.2O, (0.1 g, 0.36 mmol), in a mixture of DMF, THF and water (8 mL, 2:5:1, v/v) which was then acidified with 5-15 drops of hydrochloric acid and heated at 75 C. for 72 h.

Crystal Structure of NOTT-300(Ga)

(163) NOTT-301(Ga.sub.2)-solv crystallises in a chiral space group I4.sub.122 and shows a 3D open framework structure constructed from 1D helical [Ga(OH).sub.2O.sub.4].sub. chains bridged by tetracarboxylate ligand. The Ga(III) ion is octahedrally coordinated via six O-donors: four from carboxylate groups and two from bridging hydroxyl groups .sub.2-OH which are aligned in cis confirmation.

(164) TABLE-US-00015 TABLE 1 Summary of unit cell parameters for (Ga.sub.2)-solvated, (Ga.sub.2)-desolvated and (Ga.sub.2)-CO2 loaded (In situ single crystal) Single Parameter cell Parameter cell Cell volume, Crystal (a = b), (c), .sup.3 M (Ga.sub.2)-solv 15.1675(9) 11.9197(15) 2742.2(4) 688.68 (Ga.sub.2) 15.0174(7) 11.9111(11) 2686.2(3) 499.66 CO.sub.2-loaded 15.0535(6) 11.8737(10) 2690.7(3) 596.49

(165) TABLE-US-00016 TABLE 2 Summary of unit cell parameters for (Ga.sub.2xFe.sub.x)MOF (x = 0, 0.13, 0.21, 0.45) Parameter Parameter Cell cell (a = b), cell (c), volume, .sup.3 R.sub.Bragg Rp Rwp GOF Ga.sub.2 15.0071(1) 11.8814(9) 2675.9(4) 0.045 0.068 0.01 4.512 Ga.sub.1.87Fe.sub.0.13 15.0439(7) 11.8767(6) 2687.9(3) 0.036 0.068 0.090 2.673 Ga.sub.1.79Fe.sub.0.21 14.9980(1) 11.8938(1) 2675.4(5) 0.02 0.059 0.076 1.293 Ga.sub.1.55Fe.sub.0.45 15.0684(8) 11.9111(8) 2704.5(4) 0.06 0.050 0.066 1.877

Example 6

Synthesis of NOTT-300(GaFe)

(166) A mixed GaFe material was obtained using a similar procedure but incorporating stoichiometric mixtures of gallium nitrate Ga(NO.sub.3).sub.3.xH.sub.2O and iron nitrate Fe(NO.sub.3).sub.3. 9H.sub.2O in the following ratios: [Ga.sub.1.87Fe.sub.0.13(OH).sub.2(C.sub.16H.sub.6O.sub.8)]: (0.09 g, 0.34 mmol), (0.007 g, 0.18 mmol); [Ga.sub.1.79Fe.sub.0.21(OH).sub.2(C.sub.16H.sub.6O.sub.8)]: (0.083 g, 0.32 mmol), (0.015 g, 0.036 mmol); [Ga.sub.1.55Fe.sub.0.45(OH).sub.2(C.sub.16H.sub.6O.sub.8)]: (0.078 g, 0.31 mmol), (0.022 g, 0.054 mmol), respectively.

(167) Conclusions

(168) In situ INS and PXRD studies on the non-amine-containing capture material NOTT-300 have led to the same conclusions, for all of the metal (III) complexes, namely that the M-OH groups (M=Al, Cr, Sb, In, Ga, Fe) in the pore cavity can participate in moderate interactions with XO.sub.2 (X=C, S, N) and C.sub.2H.sub.x (x=2,4,6), and that these can be supplemented by cooperative interactions with adjacent CH groups of benzene rings. The binding energy of these moderate-to-weak hydrogen bonds (Table S13) can be viewed as soft binding interactions, quite distinct from the direct bond formation between the N-centre of amine groups and the electro-positive C-carbon centre of CO.sub.2. The latter, seen in amine systems, lead to very high isosteric heats of adsorption (40-90 kJ mol.sup.1 for physisorption; 85-105 kJ mol.sup.1 for chemisorption) and result in a substantial energy penalty to release adsorbed CO.sub.2. The moderate isosteric heat of adsorption in NOTT-300 [eg 27-30 kJ mol.sup.1 for NOTT-300-(Al) (FIG. 3b)] confirms that the relatively weak hydrogen bonding interactions within this OH decorated system are sufficiently strong to selectively bind CO.sub.2 and SO.sub.2. The weak interaction is also evidenced by the fully reversible desorption isotherms observed for these gases. This offers great promise not only for the efficient capture of CO.sub.2 SO.sub.2, and NO.sub.2 but also for their facile, low-energy and therefore economic release subsequently; moreover this easy-on/easy-off soft binding model is achieved without any reduction in either selectivity or capacity.

(169) Gas Capture Apparatus

(170) FIG. 27 illustrates a gas capture apparatus comprising a container 10 in which the MOF 40 is contained. The container 10 may have one or more inlets 20 in which gases may enter the container 10. The gases may be flue gases produced be a power station or from some other combustion or industrial processes for example in the production of iron, steel, ammonia and cement. In such applications the MOF 40 may be regenerated. In this case the MOF 40 in container 10 may be heated using a heater 80 so as drive-off adsorbed gases and regenerate the MOF 40 for its re-use. Alternatively desorption of gasses from the MOF 40 may proceed through the application of vacuum to the vessel containing the MOF. In such applications the container 10 may be in fluid connection with a vacuum pump 50 configured to draw off the gases (eg. XO.sub.2 (X=C, S, N) or hydrocarbons such as C.sub.2H.sub.2, C.sub.2H.sub.4, C.sub.2H.sub.6), that have been trapped and subsequently released by the MOF, for subsequent storage, handling and/or transportation, for example the gases may be compressed or liquefied before subsequent handling or transportation. An inlet valve 60 may be closed and an outlet valve 70 may be opened whilst the MOF 40 is being heated so that the captured are not released back into the flue. Or a vacuum may be applied through valve 70 to desorb the gas from MOF 40 where heating is not used. Whilst the apparatus is being used to capture gases the inlet valve 60 will be open and the outlet valve 60 may be closed.

(171) The MOF may also be used as part of a cartridge system in which a cartridge 90 (or other container/mechanism to support or hold the MOF) is placed in the gas stream to be processed. The cartridge 90 may then be removed from the gas stream so as to be regenerated off-line from the gas stream. FIG. 28(a) illustrates such a cartridge 90 placed within a gas stream. The cartridge 90 may cover the majority of the cross section of a conduit 100 carrying the gas stream or may be adapted to cover substantially all of the conduit cross section as illustrated in FIG. 28(a). When the cartridge 90 is in the conduit 100, the conduit 100 may form both the inlet 20 and the outlet 30 (as illustrated in FIG. 28(a)). Such a cartridge system may be useful for anaesthetic systems and exhausts systems from combustion. FIG. 28(b) illustrates a cartridge at the end of a flue or exhaust pipe. In this case the side or sides of the cartridge distal from the flue may act as the outlet 30.

(172) Experimental InformationPhysical Characterisation

(173) All reagents were used as received from commercial suppliers without further purification. Analyses for C, H and N were carried out on a CE-440 elemental analyzer (EAI Company). Thermal gravimetric analyses (TGA) were performed under N.sub.2 flow (100 ml/min) with a heating rate of 2 C./min using a TA SDT-600 thermogravimetric analyzer (TA Company). IR spectra were recorded using a Nicolet Avatar 360 FT-IR spectrophotometer. High-resolution transmission electron microscopy (TEM) imaging was performed using a Jeol 2100F transmission electron microscope using an accelerating voltage of 100 kV. TEM samples were prepared by casting several drops of a suspension of the NOTT-300 solvate complex in water onto copper-grid mounted lacy carbon film before drying under a stream of nitrogen. Variable temperature powder X-ray diffraction data (PXRD) were collected over the 2 range 4-50 on a Bruker Advance D8 diffractometer using Cu-K.sub.1 radiation (=1.54056 , 40 kV/40 mA), and the temperature was controlled by an Oxford Cryosystems open-flow cryostat operating at 100-483 K.

(174) CO.sub.2, SO.sub.2, CH.sub.4, CO, N.sub.2, O.sub.2, H.sub.2 and Ar sorption isotherms were recorded at 77 K (liquid nitrogen), 87 K (liquid argon) or 273-303 K (temperature-programmed water bath from Hiden Company) on an IGA-003 system at the University of Nottingham under ultra-high vacuum from a diaphragm and turbo pumping system. All gases used were ultra-pure research grade (99.999%) purchased from BOC or AIRLIQUIDE. The density of the desolvated NOTT-300 sample used in buoyancy corrections was 1.80 g cm.sup.3 and was estimated from the crystallographic density of the desolvated sample derived from the PLATON/SOLV.sup.1 results. In a typical gas adsorption experiment, 100 mg of NOTT-300 (Al)-solvate was loaded into the IGA, and degassed at 120 C. and high vacuum (10-10 bar) for 1 day to give fully desolvated NOTT-300 (Al).

(175) INS spectra were recorded on the TOSCA spectrometer at the ISIS Facility at the Rutherford Appleton Laboratory (UK) for energy transfers between 2 and 500 meV. In this region TOSCA has a resolution of 1% AE/E. The desolvated NOTT-300 (Al) sample was loaded into a cylindrical vanadium sample container with an annealed copper vacuum seal and connected to a gas handling system. The sample was degassed at 10.sup.7 mbar and 140 C. for 1 day to remove any remaining trace guest water molecules. The temperature during data collection was controlled using a helium cryostat (70.2 K). The loading of CO.sub.2 was performed at room temperature in order to ensure that CO.sub.2 was present in the gas phase when not adsorbed and also to ensure sufficient mobility of CO.sub.2 inside the crystalline structure of NOTT-300 (Al). The loading of H.sub.2 was performed at 40-50 K in order ensure that H.sub.2 was adsorbed into NOTT-300 (Al). Subsequently, the temperature was reduced to below 10 K in order to perform the scattering measurements with the minimum achievable thermal motion for CO.sub.2 or H.sub.2. Background spectra (sample can plus NOTT-300 (Al)) were subtracted to obtain the difference spectra. INS was used to study the binding interaction and structure dynamics in this case, because it has several unique advantages: INS spectroscopy is ultra-sensitive to the vibrations of hydrogen atoms, and hydrogen is ten times more visible than other elements due to its high neutron cross-section. The technique is not subject to any optical selection rules. All vibrations are active and, in principle, measurable. INS observations are not restricted to the centre of the Brillouin zone (gamma point) as is the case for optical techniques. INS spectra can be readily and accurately modelled: the intensities are proportional to the concentration of elements in the sample and their cross-sections, and the measured INS intensities relate straightforwardly to the associated displacements of the scattering atom. Treatment of background correction is also straightforward. Neutrons penetrate deeply into materials and pass readily through the walls of metal containers making neutrons ideal to measure bulk properties of this material. INS spectrometers cover the whole range of the molecular vibrational spectrum, 0-500 meV (0-4000 cm.sup.1) INS data can be collected at below 10 K, where the thermal motion of the MOF material and adsorbed CO.sub.2 molecules can be significantly reduced.