Amine-based porous polymer for selective carbon dioxide capture

Abstract

An amine-functionalized, crosslinked porous copolymer can be synthesized by linking 1,4-benzenediamine and pyrrole with p-formaldehyde in the presence of concentrated hydrochloric acid catalyst. The polymer is permanently microporous, with a BET surface area of 250 to 350 m.sup.2/g. Due to the high concentration of polar amines within its backbone, the polymer exhibits a CO.sub.2 uptake of 17.5 to 30 cm3/g at 298 K and 1 bar, but demonstrated a remarkably high selectivity for CO.sub.2 over N.sub.2 at 298 K. Dynamic breakthrough experiments indicate that this material is an effective adsorbent for selectively separating CO.sub.2 from a dry and wet gas mixture containing N.sub.2 for over 45 cycles without significant loss of performance. Furthermore, the polymer can be regenerated at room temperature after each cycle by a simple N.sub.2 flow.

Claims

1. A polymer, comprising, in polymerized form: 10 to 20 mol. % of one or more C5 to C10 aryl diamines; 50 to 65 mol. % of a mono-aldehyde; and 20 to 35 mol. % of one or more 5-membered heteroaromatic rings, wherein mol % is relative to the total moles of the C5 to C10 aryl diamine monomer units, the mono-aldehyde monomer units and the 5-membered heteroaromatic ring monomer units, and the polymer is cross-linked and is porous in bulk form.

2. The polymer of claim 1, wherein the heteroaromatic ring comprises a pyrrole group, an imidazole group, a pyrazole group, a thiazole group, an oxazole group, a furan group, a thiophene group, or a mixture of two or more of any of these groups.

3. The polymer of claim 1, wherein the heteroaromatic ring comprises a pyrrole group.

4. The polymer of claim 1, wherein the heteroaromatic ring comprises an unsubstituted pyrrole group.

5. The polymer of claim 1, wherein the diamine is selected from the group consisting of a 1,4-diaminobenzene, 1,3-diaminobenzene, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,3-diaminopyridine, 2,4-diaminopyrimidine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,3-diaminonaphthalene, 1,2-diaminonaphthalene, and a mixture of two or more of any of these.

6. The polymer of claim 1, wherein the diamine is 1,4-diaminobenzene.

7. The polymer of claim 1, wherein the mono-aldehyde is selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutanal, and a mixture of these.

8. The polymer of claim 1, wherein the mono-aldehyde is formaldehyde.

9. The polymer of claim 1, wherein the diamine, the mono-aldehyde, and the heteroaromatic ring monomer units make up 100 mol. % of the polymer.

10. The polymer of claim 1, wherein the diamine is 1,4-diaminobenzene, the mono-aldehyde is formaldehyde, and the heteroaromatic ring is pyrrole.

11. The polymer of claim 1, meets at least one of the following: a porosity in a range of from 250 to 350 m.sup.2/g; a CO.sub.2 uptake capacity in a range of from 25 to 45 cm.sup.3/g at 0 C. and 1 bar; a CO.sub.2 uptake capacity in a range of from 17.5 to 30 cm.sup.3/g at 25 C. and 1 bar; a coverage-dependent enthalpy of adsorption (Q.sub.st) in a range of from 25 to 45 kJ/mol; a CO.sub.2 uptake versus N.sub.2, with a selectivity in a range of from 200 to 300 at 273 K; a CO.sub.2 uptake versus N.sub.2, with a selectivity in a range of from 125 to 165 at 298 K; a dynamic CO.sub.2 uptake capacity in a range of from 5 to 12 cm.sup.3/g under dry conditions; a dynamic CO.sub.2 uptake capacity in a range of from 10 to 20 cm.sup.3/g in at least 90% relative humidity; and an absorption diminution of no more than 15% after 45 cycles or more.

12. The polymer of claim 1, which is an amine-functionalized cross linked porous polymer formed by acid catalyzed-condensation of 1,4-benzenediamine, paraformaldehyde, and pyrrole in a molar ratio of 1:2 to 8:1 to 4.

13. The polymer of claim 1, wherein the diamine is present in an amount of from 12.5 to 17.5 mol. %, the mono-aldehyde is present in an amount of from 55 to 60 mol. %, and the heteroaromatic ring is present in an amount of from 25 to 32.5 mol. %.

14. The polymer of claim 13, wherein the diamine is 1,4-diaminobenzene, the mono-aldehyde is formaldehyde, and the heteroaromatic ring is pyrrole.

15. An exhaust treatment or gas storage apparatus, comprising the polymer of claim 1.

16. A method, comprising: contacting a gas mixture, comprising a first gas and a second gas, with the polymer of claim 1, and thereby separating the first gas from the gas mixture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

(2) FIG. 1 illustrates structural features found on the backbone of a crosslinked, porous polymer according to the invention in a ball-and-stick model;

(3) FIG. 2A shows a CP-MAS .sup.13C NMR spectrum of an inventive polymer, with the corresponding core structure of the polymer provided in the inset for peak assignment, wherein TG means terminating group;

(4) FIG. 2B shows a Fourier transform-infrared (FT-IR) spectrum of an inventive polymer juxtaposed with pure 1,4-benzenediamine and pure pyrrole;

(5) FIG. 3A shows a N.sub.2 adsorption isotherm at 77 K for an inventive polymer;

(6) FIG. 3B shows CO.sub.2 (in triangles) and N.sub.2 (in circles) adsorption isotherms for an inventive polymer at 298 K;

(7) FIG. 4 shows an absorption isotherm for a 20:80 gas mixture containing CO.sub.2 and N.sub.2, under dry and wet (91% relative humidity) conditions was flowed through a fixed bed of a polymer within the scope of the invention at 298 K and 1 bar; and

(8) FIG. 5 shows CO.sub.2 breakthrough curves for an inventive polymer under wet to conditions indicating no loss in dynamic adsorption capacity over 45 consecutive breakthrough measurements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Aspects of the invention provide a polymer, comprising, in polymerized form: a C5 to C10 aryl diamine, a mono-aldehyde, and a 5-membered heteroaromatic ring, preferably 10 to 20 mol. %, 12.5 to 17.5 mol. %, 13.5 to 15.5 mol. %, or 14 to 15 mol. %, relative to total monomers, of the C5 to C10 aryl diamine, optionally a C5 to C6 aryl diamine; 50 to 65 mol. %, 52.5 to 62.5 mol. %, 55 to 60 mol. %, 56 to 59 mol. %, or 57 to 58 mol. %, relative to total monomers, of the mono-aldehyde, optionally a C1 to C3 mono-aldehyde; and 20 to 35 mol. %, relative to total monomers, of the 5-membered heteroaromatic ring, optionally N-heteroaromatic, wherein the polymer is cross-linked and porous. The porosity of the polymer (bulk) as used herein refers to the property of gas/fluid permeability of a three-dimensional mass of cross-linked polymer(s), i.e., a solid volume of polymer.

(10) The heteroaromatic ring may comprise a pyrrole group, imidazole group, pyrazole group, thiazole group, oxazole group, furan group, thiophene group, or mixture of two or more of any of these groups, preferably a pyrrole group, whereby the reactive atom, which should generally be free of substituents for most applications, may be substituted on one or both alpha-positions to the electron directing heteroatom, esp. nitrogen.

(11) Any of the heteroaromatic rings may be substituted with, e.g., one or two methyl, ethyl, C3 alkyl, C4 alkyl, fluoro, chloro, bromo, iodo, methylene carboxylic acid, ethylene carboxylic acid, propylene carboxylic acid, (protected) methylene amine, (protected) ethylene amine, (protected) propylene amine, nitrile, isocyanate, MOM, EOM, POM, C1 alcohol, C2 alcohol, C3 alcohol, nitrate, C1 nitrate, C2 nitrate, C3 nitrate, C1 amide, C2 amide, and/or C3 amide groups. Optionally amine or alcohol substituents may be protected as known in the art, esp. as taught in Green's Protective Groups in Organic Synthesis, 5.sup.th ed., Ed. Wuts, Peter G. M., Wiley, Hoboken: 2014, which is incorporated by reference in its entirety herein, while acetyl protection may be most useful in low cost applications contemplated. The heteroaromatic ring is usually preferred in unsubstituted form, at least for reducing costs.

(12) The diamine may be substituted as discussed above and may comprise a 1,4-diaminobenzene, 1,3-diaminobenzene, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,3-diaminopyridine, 2,4-diaminopyrimidine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,3-diaminonaphthalene, 1,2-diaminonaphthalene, or a mixture of two or more of any of these, preferably a 1,3-diaminobenzene, 2,5-diaminopyridine, and/or 1,4-diaminobenzene, preferably 1,4-diaminobenzene having no further substitution. The para-substitution of the amines is generally preferred.

(13) The mono-aldehyde may comprise formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutanal, or a mixture of these, preferably formaldehyde. The formaldehyde may be in any form, e.g., formalin, 1,3,5-trioxane, or paraformaldehyde, preferably paraformaldehyde.

(14) The diamine may be present in an amount of from 10 to 20 mol. %, preferably 12.5 to 17.5 mol. % or 14 to 16 mol. %, the mono-aldehyde may be present in an amount of from 50 to 65 mol. %, preferably 55 to 60 mol. % or 57.5 to 59 mol. %, and the heteroaromatic ring may be present in an amount of from 20 to 35 mol. %, preferably 25 to 32.5 mol. % or 28 to 30 mol. %, wherein the diamine may be 1,4-diaminobenzene, the mono-aldehyde may be formaldehyde, and the heteroaromatic ring may be pyrrole.

(15) The diamine, the mono-aldehyde, and the heteroaromatic ring may make up 100 mol. % of the polymer, or these monomers may be at least 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % of a total weight of the polymers, i.e., of all monomers. The particular monomers 1,4-benzenediamine, paraformaldehyde, and pyrrole may make out at least 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, 99.9, 99.99, or 99.999 wt. % of a total weight of monomers used in the polymers. For example, the polymer may be an amine-functionalized cross linked porous polymer formed by acid catalyzed-condensation of 1,4-benzenediamine, paraformaldehyde, and pyrrole in a molar ratio in a range of 1:2 to 8:1 to 4, or 1:3 to 7:2 to 3, and generally centered around 1:4:2 (diamine:aldehyde:heteroaryl).

(16) Porosity as used herein generally means that the bulk polymer is permeable to the gases it is used to separate, though porosity herein may mean having (a) pores smaller than 2 nm in diameter, and/or (b) pores between 2 and 50 nm in diameter, and/or (c) pores greater than 50 nm in diameter, preferably (a), (b), or (a) and (b). Since N.sub.2 has a diameter of approximately 370 pm, O.sub.2 has a diameter of 304 pm (Van der Waals radius of 152 pm), and CO.sub.2 has a diameter of 324 pm, the average pore diameter should generally be above 300 pm, e.g., at least 325, 350, 400, 450, 500, 600, 750, 1000, 1500, 2000, or 2500 pm. These may be lower or upper endpoints of the average pore diameter of useful polymer bulks, as may upper limits of no more than 75, 50, 40, 33, 25, 20, 17.5, 15, 12.5, 11, 9, 8, 7.5, 7, 6, 5, 4, 3, 2.5, or 2 nm. Useful average pore sizes may have any of these endpoints, and/or may be in a range of from 0.4 to 45, 0.65 to 35, 0.7 to 27.5, 0.8 to 22.5, 0.85 to 18, 0.9 to 14, 0.95 to 12, or 1 to 10 nm. The pore volume may be at least 0.1 vol. % of the total bulk polymer volume, or at least 0.25, 0.5, 0.75, 1, 1.5, 2.5, 5, 6, 7, 8, 9, 10, 12.5, 15, 17.5, or 20 vol. %, and/or no more than 50, 40, 33, 30, 27.5, 25, 22.5, 20, 18, 16, 14, 12, 11, 7.5, or 5 vol. %, any of these endpoints being combinable according to the application.

(17) The cross-linking degrees useful within the scope of the invention will vary depending upon the desired application, but may vary in a range of from 1 to 75% cross-links of polymerized monomer based on the total count of polymerized monomers, or 5 to 60, 10 to 50, 15 to 45, 20 to 40%, and/or at least 2.5, 5, 7.5, 12.5, 17.5%, and/or no more than 80, 65, 55, 45, 35, 33, 30, 27.5, or 25%, while any of these endpoints may be combined depending upon the desired application. Generally, the aldehyde is considered to be a condensation cross-linking agent in reactions of the sort described herein, whereby the aldehyde is normally condensed to a methylene bond between, e.g., the amine of the diamine and/or the alpha-position on the pyrrole and/or other heteroaromatic ring.

(18) The inventive polymers may have a porosity in a range of from 250 to 350, 267 to 333, 275 to 325, 290 to 315, or 300 to 310 m.sup.2/g. In addition or independently, inventive polymers, at 1 bar, may have a CO.sub.2 uptake capacity in a range of from 25 to 45, 27.5 to 42.5, 30 to 40, 32.5 to 37.5, or 33 to 36 cm.sup.3/g at 0 C., and/or in a range of from 17.5 to 30, 20 to 27.5, 21 to 26, 22 to 25, or 23 to 24 cm.sup.3/g at 25 C. In addition or independently, inventive polymers may have a coverage-dependent enthalpy of adsorption (Q.sub.st) in a range of from 25 to 45, 27.5 to 42.5, 30 to 40, 32 to 38, or 33 to 35 kJ/mol. In addition or independently, inventive polymers may have a CO.sub.2 uptake versus N.sub.2, with a selectivity in a range of from 200 to 300, 210 to 290, 220 to 280, 225 to 275, 233 to 267, 240 to 260, 245 to 255 at 273 K, and/or in a range of from 125 to 165, 130 to 160, 133 to 150, 135 to 145, or 137.5 to 142.5 at 298 K. In addition or independently, inventive polymers may have a dynamic CO.sub.2 uptake capacity in a range of from 5 to 12, 6 to 11, 7 to 10, 7.5 to 9.5, 8 to 9, or 8.25 to 8.75 cm.sup.3/g under dry conditions, and/or in a range of from 10 to 20, 11 to 19, 12 to 18, 12.5 to 17.5, 13.3 to 16.7, 14 to 16, or 14.5 to 15.5 cm.sup.3/g under at least 50, 67, 75, 85, 90, or 95% relative humidity. In addition or independently, inventive polymers may have an absorption diminution of no more than 15, 12.5, 10, 9, 8, 7.5, 7, 6, 5, 4, 3.33, 3, or 2.5% after at least 45, 50, 60, 75, 80, 90, 100, or even 150 cycles as long as the structure remains intact, though generally up to 1000, 750, 625, 500, 400, 350, 300, 250, 200, 150, 125, or 100 cycles.

(19) Aspects of the invention provide exhaust treatment and/or gas storage apparatuses, to comprising an inventive polymer in any permutation as described herein. Useful applications include disposition in a filter container, in a (pressure) storage container, in a pressure swing adsorber, or the like. The container could be a temporary pass-through container, before passing the separated gas off to further processing, compression, and/or final storage. Containers comprising the inventive polymers may be of a variety of sizes based on intended use, e.g., vehicles, households, plants, etc., 10 to 100 L, 1 to 10 m.sup.3, 10 to 100 m.sup.3, or 100 to 2000 m.sup.3.

(20) Aspects of the invention provide methods, comprising: contacting a gas mixture comprising a first gas and a second gas, with an inventive polymer in any permutation as described herein, and thereby separating the first gas from the gas mixture. Gases in the mixture may be CO.sub.2, N.sub.2, O.sub.2, H.sub.2O, CO, and/or Ar, particularly CO.sub.2 and N.sub.2, or CO.sub.2, N.sub.2, and H.sub.2O. The gas preferentially separated may be any of these, depending upon the tailoring of the polymer, but generally will be CO.sub.2.

(21) Aspects of the invention provide methods of obtaining an amine-functionalized cross linked porous polymer in any permutation as described herein, wherein the method may comprise: (a) adding hydrochloric acid to a C5 to C10 aryl diamine as described above, and a mono-aldehyde as described above, in a solvent to form a first reaction mixture; (b) combining a 5-membered heteroaromatic ring as described above with the first reaction mixture to form a second reaction mixture; and (c) heating the second reaction mixture at a temperature in a range of 70 to 120, 80 to 110, 85 to 100, or 87.5 to 95 C. The polymer generally should not be heated above 600, 500, 400, 300, or 250 C., if intended for use in gas separation. The solvent will generally be a polar, preferably aprotic, solvent, or may include N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), 1,4-dioxane, dichloromethane, chloroform, carbon tetrachloride, methanol, ethanol, isopropanol, and/or water, though DMF is particularly preferred (which may be dry, but is not required to be dry).

(22) Inventive methods may be ones in which the diamine comprises or is 1,4-benzenediamine and is present in at least 10 mol. %, and/or wherein the mono-aldehyde comprises or is formaldehyde and is present in at least 50 mol. %, and/or wherein the heteroaromatic ring comprises or is pyrrole and is present in at least 25 mol. %. The solvent may comprise N,N-dimethylformamide. The ratios of the monomers may be as described for the starting materials of any of the polymers above.

(23) Working ExampleMaterials: Pyrrole (98% purity), 1,4-benzenediamine (98% purity), methanol (99.9% purity), N,N-dimethylformamide (DMF, 99% purity), and hydrochloric acid (37 wt. %) were purchased from Sigma Aldrich Co. Anhydrous iron(III) chloride (99.99% purity) was acquired from Alpha Chemika. Paraformaldehyde (99% purity) was obtained from Fluka. Ammonium hydroxide (28-30 w/w %) was purchased from Fisher Scientific. Pyrrole was distilled under N.sub.2 flow at 145 C. and stored under a N.sub.2 environment at 4 C. prior to use. All other chemicals were used without further purification. For gas sorption measurements, ultrahigh purity grade nitrogen (99.999%), helium (99.999%), and high purity CO.sub.2 (99.9%) were obtained from Abdullah Hashem Industrial Co., Dammam, Saudi Arabia.

(24) Working ExampleAnalytical Methods: .sup.13C solid state nuclear magnetic resonance (NMR) spectroscopy measurements were performed on a Bruker 400 MHz spectrometer operating at 125.65 MHz (11.74 T) and at ambient temperature (298 K). Samples were packed into 4 mm ZrO.sub.2 rotors and cross-polarization magic angle spinning (CP-MAS) was employed with a pulse delay of 5.0 s and a magic angle spinning rate of 10 kHz for the 1,4-benzenediamine monomer or 14 kHz for the polymer. Fourier transform infrared (FT-IR) spectroscopy measurements were performed from KBr pellets using a PerkinElmer 16 PC spectrometer. The spectra were recorded over 4000 to 400 cm.sub.1 in transmission mode and the output signals were described as follows: s, strong; m, medium; w, weak; and br, broad. Thermal gravimetric analysis (TGA) was run on a TA Q-500 instrument with the sample held in a platinum pan under air flow with a 10 C. per min heating rate. To identify the type of gases trapped within the pores, thermogravimetric analysis-mass spectrometry (TGA-MS) was performed using a QMS 403 C A{tilde over (e)}olos with an STA 449 F1 Jupiter instrument. Powder X-ray diffraction (PXRD) measurements were carried out using a Rigaku MiniFlex II X-ray diffractometer with Cu K.sub. radiation (=1.54178 ). Low pressure nitrogen sorption isotherms were collected on a Micromeritics ASAP 2020. A liquid nitrogen bath was used for the measurements at 77 K. Isotherms of CO.sub.2 sorption were carried out on an Autosorb iQ2 volumetric gas adsorption analyzer. The measurement temperatures at 273 K (0 C.) and 298 K (25 C.) were controlled with a water circulator. Water adsorption measurements were performed on a DVS Vacuum, Surface Measurement Systems Ltd, London, UK. Prior to these measurements, the porous polymer material synthesized according to the Example was pre-treated by heating (383 K, i.e., 110 C.) under vacuum for 10 hours using the Dynamic Vapor Sorption Analyzer.

(25) Working ExampleSynthesis: 1,4-Benzenediamine (1.08 g, 10.0 mmol) and paraformaldehyde (1.20 g, 40.0 mmol) were added with 70 mL DMF to a 100 mL round bottom flask and stirred at room temperature for 5 min. After this, 1.6 mL conc. HCl (12 M) was added dropwise into the reaction mixture and the flask was sealed with a rubber septum and purged with N.sub.2 for 2-3 min. Pyrrole (1.34 g, 20.0 mmol) was then added into the reaction mixture and stirred for an additional 5 min. The mixture was subsequently heated at 363 K (90 C.) in an oil bath for 24 h with continuous stirring at a rate of 200 rpm. After this time elapsed, a black solid was isolated by centrifugation and filtration. The solid was washed with 40 mL of methanol followed by sonication for 30 min. The solid was filtered and immersed in an ammonium hydroxide solution (25% w/w) for 24 h, 40 mL distilled water for 24 h, and 60 mL of methanol per day for 3 days with stirring, at which time a clear filtrate solution was obtained. Finally, the product was dried at 348 K (75 C.) under vacuum (<0.1 bar) for 20 h. The final yield (2.56 g) was 88% based on the monomers weights. FT-IR (KBr, 4000 to 400 cm.sub.1): 3413 (br), 3240 (br), 2918 (w), 2852 (w), 1618 (m), 1510 (w), 1423 (w), 1024 (w), 671 (m).

(26) Working ExampleMeasurements: A bed was packed with a powder (1.12 g) of the polymer and the sample was activated at 373 K (100 C.) under vacuum for 24 hours prior to carrying out the breakthrough measurements. The breakthrough experiments were conducted under ambient conditions (298 K25 C.and 1 bar) with a 10 sccm flowrate of CO.sub.2:N.sub.2 (20:80 v/v) feed mixture. For the measurements under humid conditions, the sample bed was subjected to a stream of wet N.sub.2 gas (91% relative humidity, RH), in which the water level in the gas stream was monitored until saturation was obtained as detected by mass spectrometry. At this point, dry CO.sub.2 was introduced into the wet N.sub.2 stream with the same flowrate as the dry conditions noted above. The full breakthrough capacity of CO.sub.2 and N.sub.2 was measured by evaluating the ratio of compositions of the downstream gas and the feed gas.

(27) With an aim to synthesize a porous polymer based on inexpensive monomers containing accessible CO.sub.2-philic functional groups. Simple pyrrole and 1,4-benzenediamine were determined to be useful monomers since pyrrole and 1,4-benzenediamine have integrated polar aromatic amine moieties, which can induce strong interactions with CO.sub.2, within their molecular structures. The synthetic strategy used to crosslink these CO.sub.2-philic monomers was based on an acid catalyzed polycondensation reaction whereby p-formaldehyde, or other forms of formaldehyde or appropriate aldehydes, can serve as a linking agent.

(28) Experiments to optimize the reaction conditions, the solvent (dichloroethane, DMF, or to dimethylsulfoxide) and the catalyst (conc. HCl, FeCl.sub.3, or CuCl) were undertaken. While conventional Lewis acid catalyzed polycondensation reactions typically use FeCl.sub.3 as the catalyst, in equimolar amounts, in order to activate the linking agent, our findings indicate that a catalytic amount of conc. HCl (10 mol % of p-formaldehyde), generally with DMF as the solvent, can provide unexpectedly superior results. These conditions can produce crosslinked, porous polymer product in up to 88% yield, i.e., at least 50, 60, 70, 75, 80, 85, 90, or even 95%. However, inventive porous polymer materials can be synthesized using the other catalysts or solvents, though such products can suffer lower yield, surface area, or CO.sub.2 sorption uptake. After synthesis, the inventive porous polymer materials may be washed with water and methanol followed by a solution of ammonium hydroxide in order to remove any unreacted starting materials and to neutralize any residual acid. Prior to use in further characterization, the inventive porous polymer materials can be activated at 75 C. under dynamic vacuum for 20 hours, as done in the Example, or, e.g., at least 2, 3, 5, 8, 10, 12, 16, 18, or 24 hours.

(29) Inventive polymer materials and/or compositions may combine in any permutation any of the following features. Polymeric materials within the scope of the invention may exclude poly-aldehydes, i.e., molecules with more than one aldehyde per molecular weights of 500 g/mol or less, or may contain no more than 15, 10, 7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, relative to the total aldehyde weight, of poly-aldehydes. Polymeric materials within the scope of the invention may exclude polyimide(s), polyethersulfone(s) (PES), polystyrene(s) (PS), polylactic acid(s) (PLA), polyvinylidene fluoride(s) (PVdF), polymethyl methacrylate(s) (PMMA), epoxy resin(s), phenolic resin(s), urea-formaldehyde resin(s), divinylbenzene-maleic anhydride copolymer, and/or polyether (esp. pluronic P-123, i.e., poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide),), or may contain no more than 15, 10, 7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, relative to the total polymer weight, of polyimide(s), PES, PS, PLA, PVdF, PMMA, epoxy resin(s), phenolic resin(s), urea-formaldehyde resin(s), divinylbenzene-maleic anhydride copolymer(s), and/or polyether(s). Inventive compositions comprising the porous polymeric material may contain no more than 10, 5, 2.5, 1, 0.5, 0.1, 0.01, 0.001, 0.0001 wt. % carbon black and/or pyrolyzed carbon, or no more than the minimum detectable amount of carbon black and/or pyrolyzed carbon. Inventive compositions comprising the porous polymeric material may contain no more than 10, 5, 2.5, 1, 0.5, 0.1, 0.01, 0.001, 0.0001 wt. % foaming agent(s), relative to the total composition weight, or no more than the minimum detectable amount of foaming agent(s). Inventive polymeric materials may contain, in polymerized form, no more than 5, 2.5, 1, 0.5, 0.1, 0.01, 0.001, 0.0001 mol. % carbazole(s), triazole(s), organic anhydride(s), and/or methacrylate (esp. glycidyl methacrylate). Compositions including the polymeric materials within the scope of the invention may exclude metal-organic frameworks (MOFs), or comprise no more than 40, 33, 25, 20, 15, 10, 7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, relative to the total composition weight, of MOFs. Inventive polymeric materials generally have no surface modification, and/or may contain, in polymerized form, at least 75, 80, 85, 90, 92.5, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 mol. % monomers having Mn (or MW) of no more than 950, 750, 625, or 500 (g/mol).

(30) Inventive porous polymers described herein can be synthesized via acid catalyzed polycondensation of the inexpensive, CO.sub.2-philic monomers pyrrole and 1,4-benzenediamine with p-formaldehyhde as the linking agent, which can fulfill criterion (vii) discussed herein. Synthetic design strategies can be established to increase the density of polar aromatic amines within the backbone of the resulting polymer, and thus increase the material's affinity to CO.sub.2. Inventive porous polymer materials can be produced, particularly as described herein, that are permanently (micro)porous with relatively high CO.sub.2 uptake capacity at relevant partial pressures, fulfilling criterion (i), and good CO.sub.2-vs.-N.sub.2 selectivity, fulfilling criterion (ii). Dynamic breakthrough measurements were then performed, in which inventive polymeric material was demonstrated capable of separating CO.sub.2 from both dry and wet (91% relative humidity) gas mixturesmixtures whose composition mimicked those found in a flue gas stream, fulfilling criteria (iii) and (vi). Continuous multicycle breakthrough experiments (>45 cycles) were carried out under wet conditions, which proved that the dynamic CO.sub.2 uptake capacity in the presence of water remained relatively unchanged over 45 cycles fulfilling criterion (v). The ease of regeneration between each cycle was also accomplished under mild conditions, fulfilling criterion (iv).

(31) Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views.

(32) FIG. 1. illustrates important structural features found on the backbone of a crosslinked, porous polymer synthesized by the method disclosed herein. The structural features are a pyrrole monomer linked to 1,4-benzenediamine monomer by a methylene unit that is derived from p-formaldehyde.

(33) FIG. 2A shows a CP-MAS .sup.13C NMR spectrum of a porous polymer material made according to the Example, with a corresponding core structure of the inventive material provided in the inset for peak assignment. The term TG in FIG. 2A means terminating group.

(34) Due to the amorphous nature of inventive porous polymer materials, as evidenced by powder x-ray diffraction (PXRD), the connectivity of the constituents of the materials produced was assessed using a combination of cross polarization-magic angle spinning (CP-MAS), .sup.13C NMR, and FT-IR spectroscopies. The .sup.13C NMR spectra of inventive porous polymer materials revealed two resonances corresponding to CH.sub.2 species: (i) a broad peak centered at =24 ppm, which was assigned to a chemical shift for a CH.sub.2 that links aromatic C atoms from either monomer; and (ii) a lower intensity peak at =40 ppm, which was assigned to a CH.sub.2 linked to the N atom in 1,4-benzenediamine, as seen in FIG. 2A. An additional broad resonance, centered at =129 ppm, was assigned to the chemical shifts of aromatic C atoms. A shoulder peak at =140 ppm was also noted and attributed to the aromatic C atom to which the amine functionality is located. Further support for these assignments came from observing similar resonances in the .sup.13C NMR spectrum for a model polymer based on the polycondensation of 1,4-bezenediamine with p-formaldehyde.

(35) FIG. 2B shows a Fourier transform-infrared spectroscopy (FT-IR) analysis of the exemplary inventive material (below) in comparison to pure 1,4-benzenediamine (middle) and pure pyrrole (top). Absorption bands directly related to characteristic functionalities of the inventive material produced in the Example are highlighted in gray with an indicator near the (wavenumber) x-axis.

(36) To further support the .sup.13C NMR data from FIG. 2A, FT-IR spectra were collected in FIG. 2B for the pure pyrrole and 1,4-benzenediamine monomers as well as for the material produced according to the Example. The FT-IR spectra for the inventive material exhibited a broad absorption band centered at 3413 cm.sup.1, which is characteristic of the v.sub.N-H (pyrrole) stretching frequency. This 3413 cm.sup.1 absorption band is confirmed by the spectrum for the pure pyrrole. Evidence for free amine moieties in the material produced according to the Example was provided by the appearance of a shoulder absorption band at approx. 3240 cm.sup.1, which is also present in the spectrum for the pure 1,4-benzenediamine. The broadening of this band (approx. 3240 cm.sup.1) was attributed to trapped water molecules, i.e., V.sub.O-H stretching, as evidenced by TGA-MS spectrum. The TGA-MS spectrum demonstrates that only water molecules were released prior to structural decomposition occurring at 220 C. The FT-IR spectra of inventive materials prepared according to the Example indicate a new absorption band at 2918 cm.sup.1 for methylene V.sub.C-H stretching modes, as seen in FIG. 2B. This band was distinctly absent in the spectra for both pure monomers. The aromatic v.sub.C-C vibrational mode, situated at 1515 cm.sup.1, indicative of 1,4-benzenediamine was present in the spectrum of inventive materials, indicating the incorporation of 1,4-benzenediamine within the polymer produced according to the Example.

(37) FIG. 3A shows a N.sub.2 adsorption isotherm at 77 K for polymer material prepared according to the Example. The architectural stability and permanent porosity of the porous polymer made by the Example was investigated by N.sub.2 adsorption isotherm at 77 K (196 C., or liquid nitrogen temperature), as shown in FIG. 3A. At low relative pressures (P/P.sub.0<0.6), the inventive material exhibited a Type-I profile, which is characteristic of a microporous material. At P/P.sub.0>0.6, a sharp uptake was observed, indicating the occurrence of inter-particle condensation, i.e., the presence of meso-/macropores between particles. Upon desorption, a small hysteresis was noted, likely as a result of elastic deformation or swelling. Notwithstanding, the Brunauer-Emmett-Teller (BET) model was applied over the P/P.sub.0=0.01 to 0.3 range to yield a calculated surface area of 305 m.sup.2/g. In terms of practical applicability, the stability of material toward water was examined by carrying out water adsorption measurements. The water adsorption isotherm at 298 K (25 C.) for the porous polymer material produced according to the Example displayed a Type-II profile, which indicates that the material is capable of adsorbing 33.5 wt % water at P/P.sub.0>0.9 (90% RH). To assess the long-term stability of the inventive material toward water, a multicycle continuous water isotherm at 40 C. (>20 cycles) was carried out, which demonstrated that porous polymer material produced according to the Example was able to retain its water adsorption properties over long periods of time and use.

(38) In view of its aromatic amine-rich structure, permanent porosity, and water stability, the inventive material's thermodynamic gas adsorption properties were assessed. Low-pressure, single-component gas adsorption isotherms for CO.sub.2 and N.sub.2 were measured at 273 K (0 C.) and 298 K (25 C.) up to 760 Torr, as shown in FIG. 3B. FIG. 3B shows a CO.sub.2 (triangles) and N.sub.2 (circles) adsorption isotherms for polymer material prepared according to the Example at 298 K (25 C.). Filled and open symbols represent adsorption and desorption branches, respectively. The connecting lines serve as a guide to the eye. As depicted in FIG. 3B, polymer material made according to the Example can exhibit steeper CO.sub.2 uptake in the low-pressure region at 298 K (25 C.) compared to the N.sub.2 uptake. This observation is indicative of stronger polymer-CO.sub.2 interactions, i.e., higher affinity, than for N.sub.2, which indicates that the inventive materials could serve as an adsorbent for selective CO.sub.2 capture, e.g., from flue gas or from other combustion exhaust systems, such as auto, watercraft, or even aircraft exhaust, energy production exhaust, household furnace and/or chimney exhaust, etc. Materials made according to the Example can exhibit CO.sub.2 uptake capacities of 34.0 cm.sup.3/g at 273 K (0 C.) and 760 Torr and 23.4 cm.sup.3/g at 298 K (25 C.) and 760 Torr. In contrast, the N.sub.2 uptake capacities under the same experimental conditions were found to be 1.2 cm.sup.3/g at 273 K and 1.0 cm.sup.3/g at 298 K, each at 760 Torr.

(39) The coverage-dependent enthalpy of adsorption (Q.sub.st) for CO.sub.2 was estimated by fitting the isotherms collected at 273 and 298 K with a virial-type expansion equation. The resulting initial Q.sub.st value was calculated to be 34 kJ/mol, which indicates the inventive material's strong binding affinity to CO.sub.2. The Q.sub.st remained relatively constant, reflecting the homogeneous binding strengths over multiple sites at low coverage. The Q.sub.st value is moderately high for physisorption-driven materials as compared to materials reported in the art: such as BILP-1 (26.5 kJ/mol) from Chem. Mater. 2012, 24, 1511-1517, Azo-COP-1 (29.3 kJ/mol) from Nat. Commun. 2013, 4, 1357, and PAF-1 (15.6 kJ/mol) from Angew. Chem. Int. Ed. 2012, 51, 7480-7484.

(40) With these results, the CO.sub.2/N.sub.2 selectivity was then estimated based on Henry's law. The inventive material demonstrated a unexpectedly high CO.sub.2/N.sub.2 selectivities of 249 at 273 K (0 C.) and 141 at 298 K (25 C.). These selectivities are among the highest values reported for crosslinked, porous polymers to date, as seen below in Table 1.

(41) TABLE-US-00001 TABLE 1 Surface area, CO.sub.2 capture properties, and CO.sub.2/N.sub.2 selectivity for the inventive materials compared to selected polymeric materials in related application. CO.sub.2 CO.sub.2 CO.sub.2 Uptake Uptake Regeneration A.sub.BET Uptake CO.sub.2/N.sub.2 Capacity - Dry Capacity - Wet Temperature Material (m.sup.2g.sup.1) (cm.sup.3 g.sup.1).sup.c Selectivity.sup.b (cm.sup.3 g.sup.1).sup.c (cm.sup.3 g.sup.1).sup.c (K) Ref. KFUPM-1 305 23.4 141 8.5 15.1 298 This work CTF-FUM-350 230 57.2 102 11.4 32 CTF-DCN-500 735 38.4 37 8.3 32 LZU-301 654 35.6 4.9 8.2 33 [HO.sub.2C].sub.100%H.sub.2PCOF 364 76 .sup.77.sup.d 16.4 353 34 FCTF-1 662 72 .sup.31.sup.d 16.1 14.2 .sup.298.sup.e 22 TB-COP-1 1340 70.7 .sup.68.sup.d 39 PPN-6-SO.sub.3NH.sub.4 593 81 196 25.8.sup.f 363 8 BPL Carbon 1210 47 6.0 4.2 36 Carbon Monolith 670 58.2 28 20.9 20.3 298 24 (HCM-DAH-1)

(42) In Table 1: .sup.aat 298 K and 760 Torr; .sup.bcalculated from single component isotherms by Henry's law; .sup.ccalculated from dynamic breakthrough experiments with composition 20:80 CO.sub.2:N.sub.2 v/v; .sup.dcalculated by Ideal Adsorbed Solution Theory at 298 K and 1 bar; .sup.eregenerated under vacuum; .sup.fat 313 K; properties not reported are identified with ; A is Environ. Sci. Technol. 2016, 50, 4869-4876; B is J. Am. Chem. Soc. 2017, 139, 4995-4998; C is Angew. Chem. Int. Ed. 2015, 54, 2986-2990; D is Energy Environ. Sci. 2013, 6, 3684-3692; E is J. Mater. Chem. A 2014, 2, 12507-12512; F is Energy Environ. Sci. 2013, 6, 3559-3564; G is Inorg. Chem. 2016, 55, 6201-6207; and H is J. Am. Chem. Soc. 2011, 133, 11378-11388.

(43) FIG. 4 shows dynamic CO.sub.2 capture by breakthrough experiments with a 20:80 gas mixture containing (CO.sub.2:N.sub.2), under dry conditions (closed symbols) and wet conditions (91% RH, open symbols), passed at 298 K and 1 bar through a fixed bed of the porous, polymeric material prepared according to the Example. To evaluate the performance of the inventive materials in effectively and selectively capturing CO.sub.2 under practical flue gas conditions, dynamic breakthrough experiments were conducted. In a typical experiment, an activated sample of the inventive material was loaded onto a bed and exposed to a gaseous mixture of 20% (v/v) CO.sub.2 and 80% (v/v) N.sub.2, i.e., volumetric percentages closely resembling flue gas composition. The effluent from the bed was monitored for the breakthrough time, i.e., the time in which adsorbed CO.sub.2 breaks through the bed, by an online mass spectrometer.

(44) As seen in FIG. 4, N.sub.2 (filled triangles) is solely present in the effluent for 4.79 min, at which point the CO.sub.2 (filled diamonds) breakthrough point is observed. Inventive materials can selectively retain CO.sub.2 for a significant period of time while N.sub.2 passes freely through the material. The corresponding dynamic CO.sub.2 uptake capacity of inventive materials, calculated from the breakthrough time, was 8.6 cm.sup.3/g. As seen above in Table 1, the capacity of inventive materials is comparable to other porous polymers, such as CTF-FUM-350 (11.4 cm.sup.3/g) and CTF-DCN-500 (8.3 cm.sup.3/g) described in Environ. Sci. Technol. 2016, 50, 4869-4876, as well as COFs, such as LZU-301 (4.9 cm.sup.3/g), disclosed in J. Am. Chem. Soc. 2017, 139, 4995-4998, and [HO.sub.2C].sub.100%-H.sub.2P-COF (16.4 cm.sup.3/g), disclosed in Angew. Chem. Int. Ed. 2015, 54, 2986-2990.

(45) Water is the third major component in flue gas by volumetric concentration (5-7%). Porous materials typically experience difficulty in selectively capturing CO.sub.2 in the presence of water due to competitive adsorption, decreasing CO.sub.2 uptake capacity and/or long-term stability and/or recyclability of the material. Porous materials such as metal-organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs), and copper silicates have shown an ability to capture CO.sub.2 in the presence of water, but few porous polymers have been investigated for this property.

(46) Porous polymeric material made according to the Example was exposed to a ternary gas mixture containing CO.sub.2 (20% v/v), N.sub.2 (80% v/v), and H.sub.2O (91% RH). As shown in FIG. 4, the inventive material was again able to selectively retain CO.sub.2 (open diamonds) while N.sub.2 (open triangles) passed through unencumbered. The longer CO.sub.2 retention time, i.e., 5.29 min, under wet conditions may be attributed to the inventive material's adsorption of 33.5 wt % water at 91% RH, which can lead to stronger interactions with CO.sub.2. Longer retention times under wet conditions have been observed in other systems. The (wet) dynamic CO.sub.2 uptake capacity from the ternary gas mixture (CO.sub.2/N.sub.2/H.sub.2O) was calculated to be 9.5 cm.sup.3/g for the inventive material.

(47) For implementation in an industrial setting, an adsorbent material's long-term use and recyclability, without loss in performance, is a critical factor to be considered. FIG. 5. shows CO.sub.2 breakthrough curves for the inventive material under wet conditions after cycling. The curves in FIG. 5 indicate that there can be little to no loss in dynamic adsorption capacity over 45 consecutive breakthrough measurements. Multicycle continuous breakthrough measurement (>45 cycles) at 298 K are shown in FIG. 5. For each cycle of the experiment, the results of which are presented in FIG. 5, the inventive material was first exposed to a wet N.sub.2 stream (91% RH) until water saturation was detected. At the point of saturation, a dry stream of CO.sub.2 (20% v/v) was then added to the wet N.sub.2 stream and the effluent was monitored for the breakthrough time. Between each cycle, the inventive material was regenerated by flowing a wet N.sub.2 stream through the material at 298 K (25 C.), which regeneration, from an energy cost standpoint, represents a remarkably attractive feature for using the inventive materials as adsorbents for the selective capture of CO.sub.2 from real flue gas mixtures.

(48) The inventive material exhibited a surprisingly exceptional stability and recyclability over the course of the multicycle measurements, as seen in FIG. 5. Although the breakthrough time exhibited non-negligible fluctuation over the course of these cycles, the performance, i.e., dynamic CO.sub.2 uptake capacity as measured by breakthrough time, remained relatively unchanged at 15 cm.sup.3/g comparing the 2.sup.nd and the 45.sup.th cycles, which is seen in Table 1, above, and in FIG. 5.

(49) Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.