Methods for gas separation

Abstract

A method of separating acetylene from a gas mixture comprising acetylene is provided. The method involves the use of a hybrid porous material with an affinity for acetylene adsorption. The hybrid porous material comprises a three-dimensional structure of metal species (M) and first and second linker groups (L.sup.1 and L.sup.2), wherein the metal species (M) are linked together in a first and second direction by first linker groups (L.sup.1) and are linked together in a third direction by second linker groups (L.sup.2) to form the three-dimensional structure. The hybrid porous materials may have a high selectivity for acetylene and/or a high capacity for acetylene adsorption. The method may be particularly useful for the purification of ethylene gas contaminated with acetylene during an ethylene production/purification process. The method may be particularly useful for the large scale separation of acetylene from other gases such as ethylene and carbon dioxide, during an acetylene production/purification process.

Claims

1. A method of separating acetylene from a gas mixture comprising acetylene, the method comprising contacting the gas mixture with a hybrid porous material; wherein the hybrid porous material comprises a three-dimensional lattice of metal species (M) and linker groups; wherein the metal species (M) are linked together in a first dimension and a second dimension by first linker groups (L.sup.1) and are linked together in a third dimension by a second linker groups (L.sup.2) to form the three-dimensional lattice; wherein one of L.sup.1 and L.sup.2 is an organic linker group and the other of L.sup.1 and L.sup.2 is an inorganic linker group; and wherein the gas mixture is selected from a gas mixture comprising acetylene and ethylene, a gas mixture comprising acetylene and carbon dioxide, and a gas mixture comprising acetylene, ethylene, and carbon dioxide.

2. The method according to claim 1, wherein the hybrid porous material has the chemical formula: M(L.sup.1).sub.2(L.sup.2).

3. The method according to claim 1, wherein the three-dimensional lattice of metal species (M) and linker groups (L.sup.1 and L.sup.2) comprises the repeating structural unit (I): ##STR00006##

4. The method according to claim 1, wherein the metal species (M) are selected from atoms or ions of Cu, Zn and Ni.

5. The method according to claim 1, wherein the first linker groups (L.sup.1) are organic linkers.

6. The method according to claim 5, wherein the first linker groups (L.sup.1) are two-connected nitrogen ligands.

7. The method according to claim 6, wherein the first linker groups (L.sup.1) are two-connected nitrogen ligands selected from pyrazine, 4,4-bipyridine and 4,4-bipyridylacetylene.

8. The method according to claim 1, wherein the second linker groups (L.sup.2) comprise at least one fluorine atom.

9. The method according to claim 1, wherein the second linker groups (L.sup.2) are compounds of formula AX.sub.n.sup.y, wherein X is selected from F or Cl, n is an integer from 2 to 6, y is an integer from 0 to 2 and A is selected from Si, Ti, Sn, Zr or Ge.

10. The method according to claim 1, wherein the metal species (M) are selected from Cu.sup.2+, Ni.sup.2+ and Zn.sup.2+ ions, the first linker groups (L.sup.1) are selected from 4,4-bipyridylacetylene, 4,4-bipyridine and pyrazine and the second liker groups (L.sup.2) are selected from SiF.sub.6.sup.2, TiF.sub.6.sup.2 and SnF.sub.6.sup.2 ions.

11. The method according to claim 1, wherein the hybrid porous material comprises pores with an effective pore size of from 3.5 to 12 .

12. The method according to claim 1, wherein the gas mixture comprises a ratio of acetylene:ethylene of from 0.1:99.9 to 10:90.

13. The method according to claim 1, wherein the gas mixture comprises a ratio of acetylene:ethylene of from 4:6 to 9:1.

14. The method according to claim 1, wherein the contacting of the gas mixture with the hybrid porous material is carried out at a temperature of from 20 C. to 60 C.

15. The method according to claim 1, wherein the contacting of the gas mixture with the hybrid porous material is carried out at a pressure of from 0.5 to 2 bar.

Description

EXAMPLE 1: SIFSIX-2-Cu-i

(1) Synthesis of SIFSIX-2-Cu-i

(2) A methanol solution (4.0 ml) of 4,4-bipyridylacetylene (0.286 mmol) was mixed with an aqueous solution (4.0 ml) of Cu(BF.sub.4).sub.2.xH.sub.2O (0.26 mmol) and (NH.sub.4).sub.2SiF.sub.6 (0.26 mmol) and then heated at 85 C. for 12 h. The resulting green microcrystalline solid, SIFSIX-2-Cu-i, was harvested by filtration.

(3) Structure of SIFSIX-2-Cu-i

(4) SIFSIX-2-Cu-i is a two-fold interpenetrated network comprising two SIFSIX-2-Cu hybrid porous material. In each of the two SIFSIX-2-Cu metal-organic frameworks, the copper cations and 4,4-bipyridylacetylene ligands form a two dimensional (2D) layer which forms a three dimensional (3D) hybrid porous material of primitive cubic topology pillared by SiF.sub.6.sup.2 anions. By pillared we mean that the SiF.sub.6.sup.2 anions provides a link between the 2D layers of copper cations and 4,4-bipyridylacetylene ligands to provide the 3D metal-organic framework. The independent hybrid porous materials interpenetrate in a staggered fashion, affording one dimensional (1D) channels with pores having an effective pore size of from 5 to 6 . The inorganic pillars, SiF.sub.6.sup.2, are exposed on the inner surface of the pore and facilitate strong interactions with C.sub.2H.sub.2. FIG. 1A shows a single hybrid porous material of SIFSIX-2-Cu which when formed as an interpenetrated structure according to the above experimental procedure forms SIFSIX-2-Cu-i which is shown in FIG. 1B.

(5) Pure Gas Sorption Studies of SIFSIX-2-Cu-i

(6) C.sub.2H.sub.2 and C.sub.2H.sub.4 sorption isotherms for SIFSIX-2-Cu-i were collected at 273 and 298 K. As seen in FIG. 2A, SIFSIX-2-Cu-i exhibits more uptake for C.sub.2H.sub.2 than C.sub.2H.sub.4, especially in the low pressure region. At 298 K, uptakes for C.sub.2H.sub.2 of 2.1 and 3.9 mmol/g were measured at 0.025 and 1 bar, respectively. Under the same conditions, C.sub.2H.sub.4 uptakes of only 0.15 and 2.0 mmol/g were measured. By using the Clausius-Clapeyron equation, isosteric heat (adsorption energyQst) for C.sub.2H.sub.2 was calculated as 52.7 kJ/mol, much higher than the 35.1 kJ/mol for C.sub.2H.sub.4, as shown in FIG. 2B.

(7) Powder X-Ray Diffraction (PXRD) and Stability Data

(8) Stability to humidity of SIFSIX-2-Cu-i prepared according to the procedure above was tested by exposing the SIFSIX-2-Cu-i to 75% humidity and 40 C. for 1 day and 14 days. PXRD patterns of the samples after humidity testing (see FIG. 3A) were equivalent to those obtained for the pristine sample (before humidity testing). C.sub.2H.sub.2 isotherms for the exposed and pristine samples (FIG. 3B) show that SIFSIX-2-Cu-i is stable to humidity and that its sorption behaviour is not affected by exposure to humidity.

EXAMPLE 2: TIFSIX-2-Cu-i

(9) Synthesis of TIFSIX-2-Cu-i

(10) A methanol solution (4.0 ml) of 4,4-bipyridylacetylene (0.286 mmol) was mixed with an aqueous solution (4.0 ml) of Cu(BF.sub.4).sub.2.xH.sub.2O (0.26 mmol) and (NH.sub.4).sub.2TiF.sub.6 (0.26 mmol) and then heated at 85 C. for 12 h. The resulting green microcrystalline solid, TIFSIX-2-Cu-i, was harvested by filtration.

(11) Structure of TIFSIX-2-Cu-i

(12) TIFSIX-2-Cu-i is a two-fold interpenetrated network comprising two TIFSIX-2-Cu metal-organic frameworks. In each of the two TIFSIX-2-Cu metal-organic frameworks, the copper cations and 4,4-bipyridylacetylene ligands form a 2D layer which forms a 3D hybrid porous material of primitive cubic topology pillared by SiF.sub.6.sup.2 anions. The independent hybrid porous materials interpenetrate in a staggered fashion, affording 1D channels with pores having an effective pore size of from 5 to 6 . The inorganic pillars, TiF.sub.6.sup.2, are exposed on the inner surface of the pore and facilitate strong interactions with C.sub.2H.sub.2. FIG. 4A shows a single hybrid porous material of TIFSIX-2-Cu which when formed as an interpenetrated structure according to the above experimental procedure forms TIFSIX-2-Cu-i which is shown in FIG. 4B.

(13) Pure Gas Sorption Studies of TIFSIX-2-Cu-i

(14) C.sub.2H.sub.2 and C.sub.2H.sub.4 sorption isotherms for TIFSIX-2-Cu-i were obtained at 273 and 298 K. As seen in FIG. 5A, TIFSIX-2-Cu-i exhibits more uptake for C.sub.2H.sub.2 than C.sub.2H.sub.4, especially in the low pressure region. At 298 K, uptakes for C.sub.2H.sub.2 of 2.2 and 4.1 mmol/g were measured at 0.025 and 1 bar, respectively. Under the same conditions, C.sub.2H.sub.4 uptakes of only 0.22 and 2.5 mmol/g were measured. By using the Clausius-Clapeyron equation, isosteric heat (adsorption energyQst) for C.sub.2H.sub.2 was calculated as 46.3 kJ/mol, much higher than the 35.9 kJ/mol for C.sub.2H.sub.4, as shown in FIG. 5B.

(15) Powder X-Ray Diffraction (PXRD) and Stability Data

(16) Stability to humidity of TIFSIX-2-Cu-i prepared according to the procedure above was tested by exposing TIFSIX-2-Cu-i to 75% humidity and 40 C. for 14 days. PXRD patterns of samples after humidity testing (see FIG. 6A) were equivalent to those obtained for the pristine sample (before humidity testing). C.sub.2H.sub.2 isotherms for the exposed and pristine samples (FIG. 6B) show that TIFSIX-2-Cu-i is stable to humidity and that its sorption behaviour is not affected by exposure to humidity.

EXAMPLE 3: SNFSIX-2-Cu-i

(17) Synthesis of SNFSIX-2-Cu-i

(18) A methanol solution (4.0 ml) of 4,4-bipyridylacetylene (0.286 mmol) was mixed with an aqueous solution (4.0 ml) of Cu(BF.sub.4).sub.2.xH.sub.2O (0.26 mmol) and (NH.sub.4).sub.2SnF.sub.6 (0.26 mmol) and then heated at 85 C. for 12 h. The resulting green microcrystalline solid, SNFSIX-2-Cu-i, was harvested by filtration.

(19) Structure of SNFSIX-2-Cu-i

(20) SNFSIX-2-Cu-i is a two-fold interpenetrated network comprising two SNFSIX-2-Cu metal-organic frameworks. In each of the two SNFSIX-2-Cu metal-organic frameworks, the copper cations and 4,4-bipyridylacetylene ligands form a two dimensional (2D) layer which forms a three dimensional (3D) hybrid porous material of primitive cubic topology pillared by SiF.sub.6.sup.2 anions. The independent hybrid porous materials interpenetrate in a staggered fashion, affording 1D channels with pores having an effective pore size of from 5 to 6 . The inorganic pillars, SnF.sub.6.sup.2, are exposed to the pore surface and facilitate strong interactions with C.sub.2H.sub.2. FIG. 7A shows a single hybrid porous material of SNFSIX-2-Cu which when formed as an interpenetrated structure according to the above experimental procedure forms SNFSIX-2-Cu-i which is shown in FIG. 7B.

(21) Pure Gas Sorption Studies of SNFSIX-2-Cu-i

(22) C.sub.2H.sub.2 and C.sub.2H.sub.4 sorption isotherms for SNFSIX-2-Cu-i were collected at 273 and 298 K. As seen in FIG. 8A, SNFSIX-2-Cu-i exhibits more uptake for C.sub.2H.sub.2 than C.sub.2H.sub.4, especially in the low pressure region. At 298 K, uptakes for C.sub.2H.sub.2 of 2.1 and 3.8 mmol/g were measured at 0.025 and 1 bar, respectively. Under the same conditions, C.sub.2H.sub.4 uptakes of only 0.17 and 2.1 mmol/g were measured. By using the Clausius-Clapeyron equation, isosteric heat (adsorption energyQst) for C.sub.2H.sub.2 was calculated as 49.2 kJ/mol, much higher than the 34.2 kJ/mol for C.sub.2H.sub.4, as shown in FIG. 8B.

(23) Powder X-Ray Diffraction (PXRD) and Stability Data

(24) Stability to humidity of SNFSIX-2-Cu-i prepared according to the procedure above was tested by exposing the SNFSIX-2-Cu-i to 75% humidity and 40 C. for 14 days. PXRD patterns of samples after humidity testing (see FIG. 9A) were equivalent to those obtained for the pristine sample (before humidity testing). C.sub.2H.sub.2 isotherms for the exposed and pristine samples (see FIG. 9B) show that SNFSIX-2-Cu-i is stable to humidity and that its sorption behaviour is not affected by exposure to humidity.

EXAMPLE 4: SIFSIX-3-Ni

(25) Synthesis of SIFSIX-3-Ni

(26) 0.32 g of pyrazine (4 mmol) and 0.62 g of NiSiF.sub.6.6H.sub.2O (2 mmol) were added to 3 ml H.sub.2O, and the suspension was stirred for days. The resulting purple microcrystalline solid, SIFSIX-3-Ni, was harvested by filtration.

(27) Structure of SIFSIX-3-Ni

(28) SIFSIX-3-Ni is a 3D hybrid porous material of primitive cubic topology. In this structure, the metal cations and pyrazine ligands generate a 2D layer pillared by SiF.sub.6.sup.2 anions (see FIGS. 10A and 10B). This structure comprises 1D channels pores having an effective pore size of approximately 3.7 . The inorganic pillars, SiF.sub.6.sup.2, are exposed to the inner surface of the pores and facilitate strong interactions with C.sub.2H.sub.2.

(29) Pure Gas Sorption Studies of SIFSIX-3-Ni

(30) C.sub.2H.sub.2 and C.sub.2H.sub.4 sorption isotherms for SIFSIX-3-Ni were collected at 273 and 298 K. As seen in FIG. 11A, SIFSIX-3-Ni exhibits more uptake for C.sub.2H.sub.2 than C.sub.2H.sub.4, especially in the low pressure region. At 298 K, uptakes for C.sub.2H.sub.2 of 0.77 and 3.3 mmol/g were measured at 0.025 and 1 bar, respectively. Under the same conditions, C.sub.2H.sub.4 uptakes of only 0.05 and 1.75 mmol/g were measured. By using the Clausius-Clapeyron equation, isosteric heat (adsorption energyQst) for C.sub.2H.sub.2 was calculated as 36.7 kJ/mol, much higher than the 31.6 kJ/mol for C.sub.2H.sub.4, as shown in FIG. 11B.

(31) Powder X-Ray Diffraction (PXRD) and Stability Data

(32) Stability to humidity of SIFSIX-3-Ni prepared according to the procedure above was tested by exposing the SIFSIX-3-Ni to 75% humidity and 40 C. for 1, 7 and 14 days. PXRD patterns of samples after humidity testing (see FIG. 12A) were equivalent to those obtained for the pristine sample (before humidity testing). C.sub.2H.sub.2 isotherms for the exposed and pristine samples (see FIG. 12B) show that SIFSIX-3-Ni is stable to humidity and that its sorption behaviour is not affected by exposure to humidity.

EXAMPLE 5: SIFSIX-1-Cu

(33) Synthesis of SIFSIX-1-Cu

(34) 0.35 g 4,4-bipyridine was dissolved in 40 ml ethylene glycol at 65 C. An aqueous solution (20 ml) of Cu(BF.sub.4).sub.2.xH.sub.2O (266 mg, 1.12 mmol) and (NH.sub.4).sub.2SiF.sub.6 (199 mg, 1.12 mmol) was added to the above solution before the mixture was heated at 65 C. for 3 h under stirring. The obtained purple powder was filtered, washed with methanol, and exchanged with methanol for 3 days.

(35) Structure of SIFSIX-1-Cu

(36) SIFSIX-1-Cu is a 3D hybrid porous material wherein the metal cation and 4,4-bipyridine ligands generate a 2D square grid network which forms a 3D primitive cubic network pillared by SiF.sub.6.sup.2 anions (see FIG. 13). The 3D hybrid porous material provides channels with pores having an effective pore size of approximately 8 and a pore repeat distance along the c axis (defined by the CuSiF.sub.6Cu bonds, i.e. the M-L.sup.2-M bonds) of from 7 to 8 . The inorganic pillars, SiF.sub.6.sup.2, are exposed to the pore inner surface and facilitate strong interactions with C.sub.2H.sub.2.

(37) Pure Gas Sorption Studies of SIFSIX-1-Cu

(38) C.sub.2H.sub.2 and C.sub.2H.sub.4 sorption isotherms for SIFSIX-1-Cu were collected between 283 and 313 K. As seen in FIG. 14A, SIFSIX-1-Cu exhibits a high uptake of acetylene (8.5 mmol/g) at 298 K and 1.0 bar. The C.sub.2H.sub.2 uptake of SIFSIX-1-Cu is among the highest yet reported with MOFs and other porous adsorbents. Under the same conditions, only 4.1 mmol/g of C.sub.2H.sub.4 was adsorbed on SIFSIX-1-Cu (see FIG. 14B). By using the Clausius-Clapeyron equation, the isosteric heat for C.sub.2H.sub.2 and C.sub.2H.sub.4 were calculated and are shown in FIG. 15. The Qst of C.sub.2H.sub.2 (37 kJ/mol) for SIFSIX-1-Cu is much higher than the Qst for C.sub.2H.sub.4 (19.7 kJ/mol).

(39) Powder X-Ray Diffraction (PXRD)

(40) FIG. 16 shows PXRD patterns for SIFSIX-1-Cu.

EXAMPLE 6: SIFSIX-2-Cu

(41) Synthesis of SIFSIX-2-Cu

(42) An ethanol solution (2.0 ml) of 4,4-bipyridylacetylene (0.115 mmol) was carefully layered onto an ethylene glycol solution (2.0 ml) of CuSiF.sub.6.xH.sub.2O (0.149 mmol). Crystals of SIFSIX-2-Cu were obtained after two weeks. The obtained sample was exchanged with ethanol for 4 days.

(43) Structure of SIFSIX-2-Cu

(44) SIFSIX-2-Cu is a 3D hybrid porous material having a primitive-cubic coordination network with square channels (pores), as shown in FIG. 17. The metal cation and 4,4-bipyridylacetylene ligands generate a 2D square grid network which forms a 3D network of primitive cubic topology pillared by SiF.sub.6.sup.2 anions. The channels comprise pores having an effective pore size of approximately 10.5 and a pore repeat distance along the c axis (defined by the CuSiF.sub.6Cu bonds, i.e. the M-L.sup.2-M bonds) of approximately 10.5 . The inorganic pillars, SiF.sub.6.sup.2, are exposed to the pore inner surface and facilitate interactions with C.sub.2H.sub.2.

(45) Pure Gas Sorption Studies of SIFSIX-2-Cu

(46) C.sub.2H.sub.2 and C.sub.2H.sub.4 sorption isotherms for SIFSIX-2-Cu were collected between 283 K and 303 K. As seen in FIGS. 18A and 18B, SIFSIX-2-Cu exhibits type-II isotherm for both C.sub.2H.sub.2 and C.sub.2H.sub.4 with a C.sub.2H.sub.2 uptake of 5.38 mmol/g at 298 K and 1.0 bar. Under the same conditions, SIFSIX-2-Cu uptakes only 2.02 mmol/g of C.sub.2H.sub.4.

(47) FIG. 19 shows C.sub.2H.sub.2 and C.sub.2H.sub.4 adsorption energy (Qst) of SIFSIX-2-Cu.

(48) Powder X-Ray Diffraction (PXRD)

(49) FIG. 20 shows PXRD patterns of SIFSIX-2-Cu.

EXAMPLE 7: SIFSIX-3-Zn

(50) Synthesis of SIFSIX-3-Zn

(51) A methanol solution (2.0 ml) of pyrazine (1.3 mmol) was carefully layered onto a methanol solution (2.0 ml) of ZnSiF.sub.6.xH.sub.2O (0.13 mmol). Colourless crystals of SIFSIX-3-Zn were obtained after two days. The obtained sample was exchanged with ethanol for 1 day.

(52) Structure of SIFSIX-3-Zn

(53) SIFSIX-3-Zn is a 3D hybrid porous material having a primitive-cubic coordination network with square channels (pores) as shown in FIG. 21. The metal cation and pyrazine ligands generate a 2D square grid network which forms a 3D network of primitive cubic topology pillared by SiF.sub.6.sup.2 anions. The channels have pores having an effective pore size of approximately 4.2 and a pore repeat distance along the c axis (defined by the ZnSiF.sub.6Zn bonds, i.e. the M-L.sup.2-M bonds) of 4.2 . The inorganic pillars, SiF.sub.6.sup.2, are exposed to the pore surface and facilitate strong interactions with C.sub.2H.sub.2.

(54) Pure Gas Sorption Studies of SIFSIX-3-Zn

(55) C.sub.2H.sub.2 and C.sub.2H.sub.4 sorption isotherms for SIFSIX-3-Zn were collected at 283 K and 398 K. As seen in FIG. 22A, SIFSIX-3-Zn uptakes 1.56 mmol/g and 3.6 mmol/g C.sub.2H.sub.2 at 0.025 and 1 bar, respectively. Under the same conditions, C.sub.2H.sub.4 uptakes of only 0.196 and 2.24 mmol/g were measured.

(56) FIG. 22B shows C.sub.2H.sub.2 adsorption energy (Qst) of SIFSIX-3-Zn.

(57) Powder X-Ray Diffraction (PXRD)

(58) FIG. 23 shows PXRD patterns for SIFSIX-3-Zn.

EXAMPLE 8: BREAKTHROUGH TESTING ON GAS MIXTURES

(59) Gases were purchased as certified mixtures of C.sub.2H.sub.2 and C.sub.2H.sub.4. For the purposes of this example, the term GAS I is used to denote a gas mixture composed of 1% C.sub.2H.sub.2 and 99% C.sub.2H.sub.4, whereas the term GAS II is used to denote a gas mixture composed of 50% C.sub.2H.sub.2 and 50% C.sub.2H.sub.4. Flow rate was monitored using a mass flow controller and held at 1.25 ml/min. Experiments were carried out at 25 C. Outlet from the column was monitored using gas chromatography (GC-8A, SHIMADZU) with an flame ionization detector (FID). The concentration of the certified mixtures was used to calibrate the concentration of the outlet gas.

(60) All experiments were conducted using a stainless steel column (4.6 mm inner diameter50 mm). According to the different particle size and density of the sample powder, the weight packed in the column was as follows: 0.23 g SIFSIX-1-Cu powder, 0.19 g SIFSIX-2-Cu-i and 0.78 g SIFSIX-3-Zn, respectively. The sample was first purged with He flow (15 ml/min) for 12 h at room temperature (25 C.). The gas mixture (GAS II) flow was then introduced at 1.25 ml/min. After the breakthrough experiment, the sample was regenerated with He flow (15 ml/min) for about 20 hours. The breakthrough tests of GAS I were then conducted on the packed bed of SIFSIX-1-Cu, SIFSIX-2-Cu-i or SIFSIX-3-Zn at 25 C. The recorded breakthrough curves are shown in FIG. 24A and FIG. 24B. The x-axis is the ratio of acetylene in the gas eluted from the column to the fraction of acetylene in the starting gas (GAS I or GAS II) and the y-axis is time. These breakthrough tests measure how long it takes for ethylene and acetylene to pass through a column containing each porous material. The longer it takes for acetylene to pass through compared to ethylene, the better the separation.

(61) FIG. 24A shows breakthrough curves of GAS I (1% C.sub.2H.sub.2 99% C.sub.2H.sub.4) for SIFSIX-1-Cu, SIFSIX-2-Cu-i and SIFSIX-3-Zn. FIG. 24B shows breakthrough curves of GAS II (50% C.sub.2H.sub.2 50% C.sub.2H.sub.4) for SIFSIX-1-Cu, SIFSIX-2-Cu-i and SIFSIX-3-Zn.

(62) The breakthrough curves FIG. 24A and FIG. 24B show highly efficient separations were achieved for both 1/99 and 50/50 C.sub.2H.sub.2/C.sub.2H.sub.4. The hierarchy of breakthrough time for 1/99 mixture is SIFSIX-2-Cu-i>SIFSIX-1-Cu>SIFSIX-3-Zn, and for 50/50 mixture is SIFSIX-1-Cu>SIFSIX-3-Zn>SIFSIX-2-Cu-i. The amounts of C.sub.2H.sub.2 captured by SIFSIX-1-Cu, SIFSIX-2-Cu-i, and SIFSIX-3-Zn from the 50/50 C.sub.2H.sub.2/C.sub.2H.sub.4. (GAS II) mixture during the dynamic breakthrough process are 6.37, 2.88 and 1.52 mmol/g, respectively. These results demonstrate that the methods of the present invention using the hybrid porous materials described herein can provide a highly efficient and selective separation of acetylene from a gas mixture under ambient conditions.

EXAMPLE 9: BREAKTHROUGH TESTING ON GAS MIXTURES

(63) Breakthrough measurements were also carried out to compare the hybrid porous materials of the present invention with known benchmark materials (Fe-MOF-74 and UTSA-100a). As shown in FIG. 25A, SIFSIX-3-Zn, SIFSIX-1-Cu and SIFSIX-2-Cu-i are unexpectedly superior to all other materials.

(64) FIG. 25B is a plot of uptake vs. selectivity at low pressures of acetylene (0.01 atm). These conditions are relevant for trapping acetylene when acetylene is a minor component of a gas mixture (as is the case for purification of ethylene). The higher to the top right of the graph, the better the material. Three of the hybrid porous materials of the present invention demonstrate much higher selectivity than previously seen and they exhibit outstanding uptake. For example, Fe-MOF-74 has essentially no selectivity even though it has high uptake. This is because Fe-MOF-74 chemically bonds both ethylene and acetylene strongly (chemisorption) whereas our materials trap acetylene using physical forces (physisorption). To see such strong selectivity for physical forces is unprecedented and unexpected.

EXAMPLE 10: C.SUB.2.H.SUB.2./CO.SUB.2 .SEPARATION

(65) Remove CO.sub.2 impurities from equimolar C.sub.2H.sub.2/CO.sub.2 gas mixtures is an important industrial process for obtaining highly pure C.sub.2H.sub.2 as the starting material for many chemical products. Considering that the strict process pressure limit (below 2 bar) of pure C.sub.2H.sub.2 and the very similar chemical-physical properties of C.sub.2H.sub.2 and CO.sub.2, this separation is considered to be more challenging than other separations such as C.sub.2H.sub.2/C.sub.2H.sub.4, CO.sub.2/CH.sub.4 and CO.sub.2/N.sub.2. FIGS. 26A, 26B, 26C show pure gas C.sub.2H.sub.2 and CO.sub.2 sorption data of SIFSIX-2-Cu-i, TIFSIX-2-Cu-i and SNFSIX-2-Cu-i respectively. FIG. 27 shows adsorption energy (Qst) of SIFSIX-2-Cu-i, TIFSIX-2-Cu-i and SNFSIX-2-Cu-i and FIG. 28 shows IAST selectivity of SIFSIX-2-Cu-i, TIFSIX-2-Cu-i and SNFSIX-2-Cu-i.

(66) C.sub.2H.sub.2 and CO.sub.2 sorption isotherms for SIFSIX-2-Cu-i, TIFSIX-2-Cu-i and SNFSIX-2-Cu-i were collected at 273 and 298 K. As seen in FIGS. 26A-C, all three of these materials exhibit more uptake for C.sub.2H.sub.2 than CO.sub.2 in the lower pressure region. At 273 K, uptakes for C.sub.2H.sub.2 of 2.9, 3.0 and 2.9 mmol/g were measured at 0.025 bar, for SIFSIX-2-Cu-i, TIFSIX-2-Cu-i and SNFSIX-2-Cu-i, respectively. Under the same conditions, CO.sub.2 uptakes of only 1.4, 1.7 and 1.1 mmol/g were measured. By using the Clausius-Clapeyron equation, C.sub.2H.sub.2 isosteric heat at low loading of 52.7, 46.3 and 49.2 kJ/mol were obtained for SIFSIX-2-Cu-i, TIFSIX-2-Cu-i and SNFSIX-2-Cu-i, respectively, higher than the 40.5, 42.2 and 42.1 kJ/mol for CO.sub.2. Based on the ideal adsorbed solution theory (IAST) calculation, the selectivity of SIFSIX-2-Cu-i for the equimolar mixture is c.a. 3 at 1 bar and 293 K, showing selective adsorption of C.sub.2H.sub.2 over CO.sub.2.

(67) In summary, the present invention provides a method of separating acetylene from a gas mixture comprising acetylene. The method involves the use of a hybrid porous material with an affinity for acetylene adsorption. The hybrid porous material comprises a three-dimensional structure of metal species (M) and first and second linker groups (L.sup.1 and L.sup.2), wherein the metal species (M) are linked together in a first and second direction by first linker groups (L.sup.1) and are linked together in a third direction by second linker groups (L.sup.2) to form the three-dimensional structure. The hybrid porous materials may have a high selectivity for acetylene and/or a high capacity for acetylene adsorption. The method may be particularly useful for the purification of ethylene gas contaminated with acetylene, for example during an ethylene production/purification process. The method may be particularly useful for the separation of acetylene from other gases such as ethylene and carbon dioxide, on a relatively large scale, for example during an acetylene production/purification process.