ADSORPTION OF CARBON DIOXIDE BY SWING ADSORPTION METHODS

Abstract

A method is provided for capturing CO.sub.2 from a gas mixture comprising CO.sub.2. The method includes contacting the gas mixture with a sorbent comprising a porous polymer. The porous polymer selectively binds CO.sub.2 in the gas mixture to yield bound CO.sub.2, thereby removing CO.sub.2 from the gas. Upon exposure to moisture, the porous polymer releases the bound CO.sub.2 to yield a recycled porous polymer.

Claims

1. A method for capturing CO.sub.2 from a gas mixture comprising CO.sub.2, the method comprising: contacting the gas mixture with a sorbent comprising a porous polymer, the porous polymer comprising a repeat unit represented by the formula: ##STR00018## wherein each of R.sup.1, R.sup.4, and R.sup.5 is independently H, NH.sub.2, or a quaternary ammonium ion represented by ##STR00019## wherein each of R.sup.5 and R.sup.6 is independently a C.sub.1-C.sub.3 alkyl group, R.sup.7 is H or a C.sub.1-C.sub.2 alkyl group, and n is an integer from 1 to 8, wherein each of R.sup.2 and R.sup.3 is independently selected from H, ##STR00020## or a quaternary ammonium ion represented by ##STR00021## wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is a quaternary ammonium ion, wherein at least one of R.sup.2 and R.sup.3 is ##STR00022## wherein the porous polymer selectively binds CO.sub.2 in the gas mixture to yield bound CO.sub.2, thereby removing CO.sub.2 from the gas, and upon exposure to moisture, the porous polymer releases the bound CO.sub.2 to yield a recycled porous polymer.

2. The method of claim 1, wherein each repeat unit is electrically neutral.

3. The method of claim 1, wherein each repeat unit comprises one or more counterions X.sup., and each X.sup. is independently OH.sup. or HCO.sub.3.sup..

4. The method of claim 1, wherein one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is a quaternary ammonium ion.

5. The method of claim 1, wherein two of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions.

6. The method of claim 1, wherein three of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions.

7. The method of claim 1, wherein four of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions.

8. The method of claim 1, wherein one or more of R.sup.6 and R.sup.7 is a methyl group.

9. The method of claim 1, wherein each of R.sup.6 and R.sup.7 is a methyl group, and R.sup.8 is H.

10. The method of claim 1, wherein n is an integer from 1 to 3.

11. The method of claim 1, wherein the porous polymer is disposed on a substrate.

12. The method of claim 11, wherein the substrate comprises a contactor, a porous fiber, a non-woven fibrous mat, or a combination thereof.

13. The method of claim 1, wherein a carbon to nitrogen ratio of the repeat unit is in a range of 3:1 to 14:1.

14. The method of claim 1, wherein a surface area of the porous polymer is in a range of about 250 m.sup.2/g to about 950 m.sup.2/g.

15. The method of claim 1, wherein a CO.sub.2 capacity of the porous polymer is in a range of about 0.1 mmol/g to about 3 mmol/g at about 350 ppm to about 450 ppm CO.sub.2.

16. The method of claim 1, wherein, within 10 minutes of exposure to the gas mixture, the porous polymer adsorbs at least 90% of a total CO.sub.2 capacity of the porous polymer.

17. The method of claim 16, wherein, within 2 minutes of exposure to the gas mixture, the porous polymer adsorbs at least 90% of a total CO.sub.2 capacity of the porous polymer.

18. The method of claim 17, wherein, within 1 minute of exposure to the gas mixture, the porous polymer adsorbs at least 90% of a total CO.sub.2 capacity of the porous polymer.

19. The method of claim 1, wherein a heat of adsorption of the porous polymer for CO.sub.2 is less than 50 kJ/mol.

20. The method of claim 1, wherein the moisture comprises liquid water, water vapor, or a gas comprising water vapor.

21. The method of claim 1, further comprising contacting the recycled porous polymer with a dry gas, thereby removing excess water from the recycled porous polymer.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 shows a scheme for the synthesis of one-armed QA based ionic porous organic polymers (iPOPs) without NH.sub.2.

[0020] FIG. 2 shows an FT-IR spectrum of QA-POP-NH.sub.2-p-OH dosed with CO.sub.2.

[0021] FIG. 3 shows N.sub.2 physisorption data for QA-POP-OH.

[0022] FIG. 4 shows CO.sub.2 uptake of QA-POP-OH as a function of CO.sub.2 partial pressure at 25 C.

[0023] FIG. 5 shows the isosteric heat generated by adsorbing CO.sub.2 as a function of loading

[0024] FIG. 6 shows the uptake of CO.sub.2 vs. time for QA-POP-OH at 25 C. and 1361 ppm CO.sub.2.

[0025] FIG. 7 shows a scheme for the synthesis of one-armed QA based iPOPs with NH.sub.2.

[0026] FIG. 8A shows FT-IR spectra of QA-POP-NH.sub.2-p-OH dosed with CO.sub.2 (upper trace) and N.sub.2 (lower trace). FIG. 8B shows an enlarged portion of the spectra in FIG. 8A.

[0027] FIG. 9 shows N.sub.2 physisorption data for QA-POP-NH.sub.2-p-OH.

[0028] FIG. 10 shows CO.sub.2 uptake of QA-POP-NH.sub.2-p-OH as a function of CO.sub.2 partial pressure at 25 C.

[0029] FIG. 11 shows the isosteric heat generated by adsorbing CO.sub.2 as a function of loading.

[0030] FIG. 12 shows the uptake of CO.sub.2 vs. time for QA-POP-NH.sub.2-p-OH at 25 C. and 300 ppm CO.sub.2.

[0031] FIG. 13 shows a procedure for the synthesis of one-armed QA based iPOPs.

[0032] FIG. 14 shows an FT-IR spectrum of QA-POP-o-OH dosed with CO.sub.2.

[0033] FIG. 15 shows N.sub.2 physisorption data for QA-POP-o-OH.

[0034] FIG. 16 shows CO.sub.2 uptake as a function of CO.sub.2 partial pressure at 25 C.

[0035] FIG. 17 shows a procedure for the synthesis of two-armed QA based iPOPs.

[0036] FIG. 18 shows an FT-IR spectrum of QA2-POP-OH dosed with CO.sub.2.

[0037] FIG. 19 shows N.sub.2 physisorption data for QA2-POP-OH.

[0038] FIG. 20 shows CO.sub.2 uptake as a function of CO.sub.2 partial pressure at 25 C.

[0039] FIG. 21 shows the isosteric heat generated by adsorbing CO.sub.2 as a function of loading.

[0040] FIG. 22 shows the uptake of CO.sub.2 vs. time for QA2-POP-OH at 25 C. and 208 ppm CO.sub.2.

[0041] FIG. 23 shows the conversion of one POP-2CH.sub.2NH.sub.2 sample.

[0042] FIG. 24 shows the CO.sub.2 adsorption performance of a QA2-POP-OH sample derived from POP-2CH.sub.2NH.sub.2.

[0043] FIG. 25 shows the relationship between the CO.sub.2 adsorption capacity at 400 ppm and the conversion ratio of QA2-POP-OH.

[0044] FIG. 26 shows a procedure for the synthesis of four-armed QA based iPOPs.

DETAILED DESCRIPTION

[0045] The present disclosure provides a method for capturing CO.sub.2 from a gas mixture by moisture swing adsorption. Moisture swing adsorption provides an alternative to temperature swing adsorption (TSA) for direct air capture (DCA). In moisture swing adsorption (MSA), exposure to high relative humidity results in water displacing CO.sub.2 that had been adsorbed under dry conditions. This process can remove or reduce heat transfer requirements that limit the thermodynamic efficiency in TSA designs.

[0046] The method includes contacting the gas mixture including CO.sub.2 with a sorbent including a porous polymer. The porous polymer selectively binds CO.sub.2 in the gas mixture to yield bound CO.sub.2, thereby removing CO.sub.2 from the gas. Upon exposure to moisture, the porous polymer releases the bound CO.sub.2 to yield a recycled porous polymer.

[0047] The porous polymer includes a repeat unit represented by the formula:

##STR00006##

wherein: [0048] each of R.sup.1, R.sup.4, and R.sup.5 is independently H, NH.sub.2, or a quaternary ammonium ion represented by

##STR00007##

wherein each of R.sup.6 and R.sup.7 is independently a C.sub.1-C.sub.3 alkyl group, R.sup.8 is H or a C.sub.1-C.sub.2 alkyl group, and n is an integer from 1 to 8; [0049] each of R.sup.2 and R.sup.3 is independently selected from H,

##STR00008##

or a quaternary ammonium ion represented by

##STR00009## [0050] at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is a quaternary ammonium ion; and [0051] at least one of R.sup.2 and R.sup.3 is

##STR00010##

As used herein in the definitions of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5,

##STR00011##

represents the point of attachment to the phenyl ring of the repeat unit.

[0052] The porous polymer includes at least one repeat unit. As used herein, parentheses ( ) refer to the point at which a repeat unit attaches to another repeat unit or a terminal functional group of the porous polymer. Parentheses are used interchangeably with

##STR00012##

to show where one repeat unit attaches to another repeat unit or a terminal functional group of the porous polymer. In some embodiments, the porous polymer is an insoluble powder.

[0053] In some embodiments, n is an integer from 1 to 8, from 1 to 6, from 1 to 4, or from 1 to 3. In some embodiments, n is an integer from 1 to 3. In some embodiments, n is 1.

[0054] In some embodiments, one or more of R.sup.6 and R.sup.7 is a methyl group. In some embodiments, R.sup.8 is H. In some embodiments, each of R.sup.6 and R.sup.7 is a methyl group, and R.sup.8 is H.

[0055] In some embodiments, each repeat unit of the porous polymer is electrically neutral. In some embodiments, each repeat unit comprises one or more counterions X.sup.. In some embodiments, each X.sup. is independently OH.sup. or HCO.sub.3.sup..

[0056] Without wishing to be bound by theory, the quaternary ammonium ion can swing back and forth between hydroxide anion (OH.sup.) and bicarbonate anion (HCO.sub.3.sup.), which has a low heat of reaction, so there is no need to manage heat evolution on adsorption. Rather, the swing can be carried out by exposing the porous polymer to moisture, which can shift the anion back to a hydroxide anion and liberate the CO.sub.2.

[0057] In some embodiments, the repeat unit is represented by formula:

##STR00013##

wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are as defined herein.

[0058] In some embodiments, one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is a quaternary ammonium ion. These porous polymers may be referred to as one-armed QA based iPOPs herein. In some embodiments, one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is a quaternary ammonium ion, and n is an integer from 1 to 8. In some embodiments, one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is a quaternary ammonium ion, and n is 1. In some embodiments, the repeat unit has a structure selected from:

##STR00014##

[0059] In some embodiments, two of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions. These porous polymers may be referred to as two-armed QA based iPOPs herein. In some embodiments, two of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions, and n is an integer from 1 to 6. In some embodiments, two of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions, and n is an integer from 1 to 3. In some embodiments, the repeat unit has a structure selected from:

##STR00015##

[0060] In some embodiments, three of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions. These porous polymers may be referred to as three-armed QA based iPOPs herein. In some embodiments, three of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions, and n is an integer from 1 to 4. In some embodiments, three of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions, and n is an integer from 1 to 3. In some embodiments, the repeat unit has a structure selected from:

##STR00016##

[0061] In some embodiments, four of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions. These porous polymers may be referred to as four-armed QA based iPOPs herein. In some embodiments, four of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions, and n is an integer from 1 to 4. In some embodiments, four of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are quaternary ammonium ions, and n is an integer from 1 to 3. In some embodiments, the repeat unit has a structure selected from:

##STR00017##

[0062] In some embodiments, a carbon to nitrogen ratio of the repeat unit is in a range from 3:1 to 18:1. In some embodiments, a carbon to nitrogen ratio of the repeat unit is in a range from 3:1 to 14:1. In some embodiments, a carbon to nitrogen ratio of the repeat unit is in a range from 4:1 to 12:1.

[0063] In some embodiments, the porous polymer is deposited on a substrate. In some examples, the substrate includes a contactor, a porous fiber, a non-woven fibrous mat, or a combination thereof.

[0064] In some embodiments, the surface area of the porous polymer is dependent on the amount of functionalization of the porous polymer (e.g., the identity of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5). In some embodiments, the degree of functionalization of the repeat unit is selected so that the CO.sub.2 is able to contact and bind to the N.sup.+ functional groups. In some cases, having too much functionalization can limit mass transport.

[0065] In some embodiments, a surface area of the porous polymer is in a range of about 250 m.sup.2/g to about 950 m.sup.2/g, about 550 m.sup.2/g to about 950 m.sup.2/g, or about 850 m.sup.2/g to about 950 m.sup.2/g. In some embodiments, a surface area of the porous polymer is about 900 m.sup.2/g. In some embodiments, a surface area of the porous polymer decreases with an increase in functionalization (e.g., an increase in the number of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 that are quaternary ammonium groups and/or an increase in the integer n). A high surface area adsorbent can allow for fast diffusion of CO.sub.2 to the active sites on the porous polymer. In some embodiments, the surface area of the polymer is controlled by the degree of functionalization to achieve fast diffusion of CO.sub.2 to the active sites of the porous polymer.

[0066] In some embodiments, a CO.sub.2 capacity of the porous polymer is in a range of about 0.1 mmol/g to about 3 mmol/g at about 350 ppm to about 450 ppm CO.sub.2. In some embodiments, a CO.sub.2 capacity of the porous polymer is about 0.1 mmol/g to about 1.5 mmol/g at about 350 ppm to about 450 ppm CO.sub.2. In some embodiments, the about 350 ppm to about 450 ppm CO.sub.2 is in nitrogen. In some embodiments, the about 350 ppm to about 450 ppm CO.sub.2 is in air. In some embodiments, a CO.sub.2 capacity of the porous polymer is in a range of about 0.05 mmol/g to about 0.6 mmol/g at 400 ppm CO.sub.2. In some embodiments, the CO.sub.2 capacity of the porous polymer increases with the degree of functionalization of the repeat unit. In some embodiments, the CO.sub.2 capacity of the porous polymer increases with a decreasing carbon to nitrogen ratio of the porous polymer. In one example, increasing the number of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 that are quaternary ammonium ions from one to two to three to four can increase CO.sub.2 capacity of the porous polymer linearly if the degree of functionalization is constant across each quaternary ammonium ion group.

[0067] The speed at which CO.sub.2 is bound by the porous polymer is a function at least in part of the kinetics of the reaction, the hydrodynamics of the direct air capture (DAC) system, and the morphology of the porous polymer. The hydrodynamics of the system can include, for example, gas flow rate and contactor geometry. The morphology of the polymer is related to the porosity and surface area of the polymer. In some embodiments, within 10 minutes of exposure to the gas mixture, the porous polymer adsorbs at least 90% of a total CO.sub.2 capacity of the porous polymer. In some embodiments, within 2 minutes of exposure to the gas mixture, the porous polymer adsorbs at least 90% of a total CO.sub.2 capacity of the porous polymer. In some embodiments, within 1 minute of exposure to the gas mixture, the porous polymer adsorbs at least 90% of a total CO.sub.2 capacity of the porous polymer. In some embodiments, within 45 seconds of exposure to the gas mixture, the porous polymer absorbs at least 90% of a total CO.sub.2 capacity of the porous polymer. In some embodiments, within 90 seconds of exposure to the gas mixture, the porous polymer adsorbs at least 95% of a total CO.sub.2 capacity of the porous polymer.

[0068] The porous polymer disclosed herein can be advantageous because it has a low heat of adsorption as compared to conventional amine-based adsorbents. In some embodiments, a heat of adsorption of the porous polymer for CO.sub.2 is less than 50 kJ/mol.

[0069] The method includes exposing the porous polymer to moisture. In some embodiments, the moisture comprises liquid water, water vapor, or a gas comprising water vapor. Exposing the porous polymer to moisture desorbs the CO.sub.2 bound to the porous polymer.

[0070] In some embodiments, the method further includes contacting the recycled porous polymer with a dry gas, thereby removing excess water from the recycled porous polymer. In one example, the dry gas is dry air with a relative humidity below about 30%. The porous polymer can retain CO.sub.2 capacity upon being recycled. In some embodiments, contacting the gas mixture with a sorbent comprising a porous polymer, exposing the porous polymer to moisture, and contacting the recycled porous polymer with a dry gas is repeated one or more times.

EXAMPLES

[0071] Commercially available reagents were purchased in high purity and used without further purification.

[0072] All .sup.1H nuclear magnetic resonance (NMR) spectra were recorded on 400 MHz Varian NMR spectrometer in CDCl.sub.3.

[0073] The polymerization and chemical structure of different POP-MeNH.sub.2 samples were investigated by Fourier transform infrared spectroscopy (FT-IR; Nicolet Nexus 670, USA).

[0074] N.sub.2 sorption isotherm measurements were conducted with the Micromeritics ASAP 2020 at 77K. The samples were outgassed for 24 h at 55 C. before the measurements.

[0075] CO.sub.2 sorption isotherms were collected on an automatic volumetric adsorption apparatus (Micromeritics ASAP 2020 plus surface area analyzer) at 298K. The as-synthesized sample was activated at 55 C. for 24 h under ultrahigh vacuum before single-component gas adsorption to remove the guest molecules.

[0076] The binding energy of CO.sub.2 is reflected in the isosteric heat of adsorption, Q.sub.st. The Clausius-Clapeyron equation was employed to calculate the enthalpies of CO.sub.2 adsorption:

[00001]$\frac{\left(\mathrm{Ln}P\right)}{\left(1/T\right)}=-\frac{Q_{\mathrm{st}}}{R}$

where P is pressure, T is temperature, and Ris the universal gas constant. The adsorption heats (Q.sub.st) of the quaternary ammonium porous polymers disclosed herein (QA-POPs) for carbon dioxide were estimated using pure-component isotherms collected at 273K and 298K.

[0077] The porous polymer may be referred to as POP (porous organic polymer) or iPOP (ionic porous organic polymer).

Synthesis of One-Armed QA Based iPOPs Without NH.SUB.2 .(QA-POP-OH)

[0078] FIG. 1 shows a scheme for the synthesis of one-armed QA based iPOPs without NH.sub.2.

[0079] 3,5-Diethenylbenzonitrile (1) 3,5-Dibromobenzonitrile (5.22 g, 20.0 mmol), potassium vinyltrifluoroborate (6.70 g, 50 mmol), and tetrakis(triphenylphosphine) palladium(0) (0.577 g, 0.50 mmol) were dissolved in a mixture of tetrahydrofuran (THF) (50 mL), toluene (50mL), and deionized water (10 mL) under N2 atmosphere. The resulting mixture was refluxed at 90 C. under N.sub.2 atmosphere for 48 hr. The product was extracted with ethyl acetate, washed with brine, dried over magnesium sulfate, and evaporated under reduced pressure. The crude product was purified by flash chromatography with ethyl acetate:hexane (1:5) as the eluent to yield 3,5-diethenylbenzonitrile. .sup.1H NMR (400 MHz, CDCl.sub.3) 7.56 (s, 1H), 7.52 (d, 2H), 6.6-6.7 (m, 2H), 5.75-5.84 (d, 2H), 5.35-5.42 (d, 2H) ppm.

[0080] POP-CN (2) To a solvothermal autoclave, 3,5-diethenylbenzonitrile (1 g) was combined with azobisisobutyronitrile (25 mg) and dimethylformamide (10 mL). The autoclave was placed in an oven and heated to 100 C. for 24 hr. The resulting product was collected by filtration, washed with acetone, and dried under vacuum to yield POP-CN as a brown powder.

[0081] POP-CH.sub.2NH.sub.2 (3) POP-CN (200 mg) was dispersed in THF (10 mL) under N.sub.2 atmosphere. Borane-tetrahydrofuran complex (40 mL, 1 M in THF) was added in batches by a glass syringe at 0 C. Then the resulting mixture was reflux at 70 C. for 24 hr. After cooling to room temperature, pure ethanol was added dropwise to decant the excess borane. The raw POP-CH.sub.2NH.sub.2 powder was soaked in ethanol (100 mL) overnight. Subsequently, the powder was washed with HCl and neutralized by sodium hydroxide solution. Then the powder was washed with water. The obtained POP-CH.sub.2NH.sub.2 was finally dried overnight at 80 C. under vacuum.

[0082] QA-POP-I (4) The POP-CH.sub.2NH.sub.2 powder (200 mg) was dispersed in acetonitrile (20 mL) under N.sub.2 atmosphere. Iodomethane (1 mL) was added at room temperature. Then the resulting mixture was refluxed at 80 C. for 24 hr. After cooling to room temperature, the raw QA-POP-I powder was washed with acetonitrile. The obtained QA-POP-I was finally dried overnight at 55 C. under vacuum.

[0083] QA-POP-OH (5) The QA-POP-I powder (200 mg) was dispersed in sodium hydroxide solution (0.5 M, 10 mL) several times for ion exchange. Then the powder was washed with water and finally dried overnight at 55 C. under vacuum for CO.sub.2 capture testing. FIG. 2 shows an FT-IR spectrum of QA-POP-OH dosed with CO.sub.2. The indicated peak was assigned to the carbonyl stretch of a HCO.sub.3 species generated from reaction of OH-in the QA-POP-OH with CO.sub.2.

[0084] FIG. 3 shows N.sub.2 physisorption data for QA-POP-OH. The solid circles are adsorption and open circles are desorption. The hysteresis is an indicator of mesoporosity (pore diameters between 2 nm and 20 nm).

[0085] FIG. 4 shows CO.sub.2 uptake of QA-POP-OH as a function of CO.sub.2 partial pressure at 25 C. This material had a CO.sub.2 capacity of 0.28 mmol/g at 400 ppm.

[0086] FIG. 5 shows the isosteric heat generated by adsorbing CO.sub.2 as a function of loading.

[0087] FIG. 6 shows the uptake of CO.sub.2 vs. time for QA-POP-OH at 25 C. and 1361 ppm CO.sub.2. The y axis is plotted as instantaneous mass vs. fully saturated (1=saturation), wherein M.sub.t refers to mass uptake at time t and M.sub.e refers to mass uptake at equilibrium. The material reaches 95% of saturation in about 20 minutes.

Synthesis of One-Armed QA Based iPOPs With NH.SUB.2 .(QA-POP-NH.SUB.2.-p-OH)

[0088] FIG. 7 shows a scheme for the synthesis of one-armed QA based iPOPs with NH.sub.2.

[0089] 4-Amino-3,5-diethenylbenzonitrile (1) 4-Amino-3,5-dibromobenzonitrile (5.52 g, 20.0 mmol), potassium vinyltrifluoroborate (6.70 g, 50 mmol), and tetrakis(triphenylphosphine) palladium(0) (0.577 g, 0.50 mmol) were dissolved in a mixture of THF (50 mL), toluene (50 mL), and deionized water (10 mL) under N.sub.2 atmosphere. The resulting mixture was refluxed at 90 C. under N.sub.2 atmosphere for 48 hr. The product was extracted with ethyl acetate, washed with brine, dried over magnesium sulfate, and evaporated under reduced pressure. The crude product was purified by flash chromatography with ethyl acetate:hexane (1:5) as the eluent to yield 4-amino-3,5-diethenylbenzonitrile. .sup.1H NMR (400 MHz, CDCl.sub.3) 7.44 (s, 2H), 6.60-6.72 (d, 2H), 5.62-5.72 (d, 2H), 5.43-5.52 (d, 2H), 4.35 (br, 2H) ppm.

[0090] POP-NH.sub.2-p-CN (2) To a solvothermal autoclave, 4-amino-3,5-diethenylbenzonitrile (1 g) was added with azobisisobutyronitrile (25 mg) and dimethylformamide (10 mL). The autoclave was placed in an oven and heated to 100 C. for 24 hr. The resulting product was collected by filtration, washed with acetone, and dried under vacuum to produce POP-NH.sub.2-p-CN as a brown powder.

[0091] POP-NH.sub.2-p-CH.sub.2NH.sub.2 (3) POP-NH.sub.2-p-CN (200 mg) was dispersed in the solvent of THF (10 mL) under N.sub.2 atmosphere. Borane-tetrahydrofuran complex (40 mL, 1 M in THF) was added in batches by a glass syringe at 0 C. Then the resulting mixture was reflux at 70 C. for 24 hr. After cooling to room temperature, pure ethanol was added dropwise to decant the excess borane. The raw POP-NH.sub.2-p-CH.sub.2NH.sub.2 powder was soaked in ethanol (100 mL) overnight. Subsequently, the powder was washed by HCl and neutralized by sodium hydroxide solution. Then the powder was washed by the water. The obtained POP-NH.sub.2-p-CH.sub.2NH.sub.2 was finally dried overnight at 80 C. under vacuum.

[0092] QA-POP-NH.sub.2-p-I (4) The POP-NH.sub.2-p-CH.sub.2NH.sub.2 powder (200 mg) was dispersed in acetonitrile (20 mL) under N.sub.2 atmosphere. Iodomethane (1 mL) was added at room temperature. Then the resulting mixture was refluxed at 80 C. for 24 hr. After cooling to room temperature, the raw QA-POP-NH.sub.2-p-I powder was washed with acetonitrile. The obtained QA-POP-NH.sub.2-p-I was finally dried overnight at 55 C. under vacuum.

[0093] QA-POP-NH.sub.2-p-OH (5) The QA-POP-NH.sub.2-p-I powder (200 mg) was dispersed in sodium hydroxide solution (0.5 M, 10 mL) several times for ion exchange. Then the powder was washed with water and finally dried overnight at 55 C. under vacuum for CO.sub.2 capture testing. FIG. 8A shows FT-IR spectra of QA-POP-NH.sub.2-p-OH dosed with CO.sub.2 (upper trace) and N.sub.2 (lower trace). FIG. 8B shows an enlarged portion of the spectra in FIG. 8A. As shown in FIG. 8B, a new peak at 1670 cm.sup.1 was observed after dosing with CO.sub.2. The new peak was assigned to the carbonyl stretch of a HCO.sub.3.sup. species generated from reaction of OH.sup. in the QA-POP-NH.sub.2-p-OH with CO.sub.2.

[0094] FIG. 9 shows N.sub.2 physisorption data for QA-POP-NH.sub.2-p-OH. The solid circles are adsorption and open circles are desorption. The hysteresis is an indicator of mesoporosity (pore diameters between 2 nm and 20 nm).

[0095] FIG. 10 shows CO.sub.2 uptake of QA-POP-NH.sub.2-p-OH as a function of CO.sub.2 partial pressure at 25 C. This material had a CO.sub.2 capacity of 0.29 mmol/g at 400 ppm.

[0096] FIG. 11 shows the isosteric heat generated by adsorbing CO.sub.2 as a function of loading.

[0097] FIG. 12 shows the uptake of CO.sub.2 vs. time for QA-POP-NH.sub.2-p-OH at 25 C. and 300 ppm CO.sub.2. The y axis is plotted as instantaneous mass vs. fully saturated (1=saturation). The material reaches 95% of saturation in about a minute. Compared with the QA-POP-OH, the QA-POP-NH.sub.2-p-OH (with the existence of the NH.sub.2 group) exhibited much greater adsorption kinetics, which may be attributed to the cooperative CO.sub.2 binding by the amine group and hydroxide ions.

Synthesis of One-Armed QA Based iPOPs (QA-POP-o-OH)

[0098] FIG. 13 shows a procedure for the synthesis of one-armed QA based iPOPs.

[0099] 2,5-Diethenylbenzonitrile (1) 2,5-Dibromobenzonitrile (5.22 g, 20.0 mmol),

[0100] potassium vinyltrifluoroborate (6.70 g, 50 mmol), and tetrakis(triphenylphosphine) palladium(0) (0.577 g, 0.50 mmol) were dissolved in a mixture of THF (50 mL), toluene (50 mL), and deionized water (10 mL) under N.sub.2 atmosphere. The resulting mixture was refluxed at 90 C. under N.sub.2 atmosphere for 48 hr. The product was extracted with ethyl acetate, washed with brine, dried over magnesium sulfate, and evaporated under reduced pressure. The crude product was purified by flash chromatography with ethyl acetate:hexane (1:5) as the eluent to yield 2,5-diethenylbenzonitrile. .sup.1H NMR (400 MHz, CDCl.sub.3) 7.50-7.65 (m, 3H), 6.95-7.06 (q, 1H), 6.58-6.67 (q, 1H), 5.32-5.96 (d, 4H) ppm.

[0101] POP-o-CN (2) To a solvothermal autoclave, 2,5-diethenylbenzonitrile (1 g) was added with azobisisobutyronitrile (25 mg) and dimethylformamide (10 mL). The autoclave was placed in an oven and heated to 100 C. for 24 hr. The resulting product was collected by filtration, washed with acetone, and dried under vacuum to produce POP-o-CN as a brown powder.

[0102] POP-o-CH.sub.2NH.sub.2 (3) POP-o-CN (200 mg) was dispersed in THF (10 mL) under N.sub.2 atmosphere. Borane-tetrahydrofuran complex (40 mL, 1 M in THF) was added in batches by a glass syringe at 0 C. Then the resulting mixture was refluxed at 70 C. for 24 hr. After cooling to room temperature, pure ethanol was added dropwise to decant the excess borane. The raw POP-o-CH.sub.2NH.sub.2 powder was soaked in ethanol (100 mL) overnight. Subsequently, the powder was washed with HCl and neutralized with sodium hydroxide solution. Then the powder was washed with water. The obtained POP-o-CH.sub.2NH.sub.2 was finally dried overnight at 80 C. under vacuum.

[0103] QA-POP-o-I (4) The POP-o-CH.sub.2NH.sub.2 powder (200 mg) was dispersed in acetonitrile (20 mL) under N.sub.2 atmosphere. Iodomethane (1 mL) was added at room temperature. Then the resulting mixture was refluxed at 80 C. for 24 hr. After cooling to room temperature, the raw QA-POP-o-I powder was washed with acetonitrile. The obtained QA-POP-o-I was finally dried overnight at 55 C. under vacuum.

[0104] QA-POP-o-OH (5) The QA-POP-o-I powder (200 mg) was dispersed in sodium hydroxide solution (0.5 M, 10 mL) several times for ion exchange. Then the powder was washed with water and finally dried overnight at 55 C. under vacuum for CO.sub.2 capture testing. FIG. 14 shows an FT-IR spectrum of QA-POP-o-OH dosed with CO.sub.2. The indicated peak was assigned to the carbonyl stretch of a HCO.sub.3 species generated from reaction of OH.sup. in the QA-POP-OH with CO.sub.2.

[0105] FIG. 15 shows N.sub.2 physisorption data for QA-POP-o-OH. The solid circles are adsorption and the open circles are desorption. The hysteresis is an indicator of mesoporosity (pore diameters between 2 and 20 nm).

[0106] FIG. 16 shows CO.sub.2 uptake as a function of CO.sub.2 partial pressure at 25 C. QA-POP-o-OH had a CO.sub.2 capacity of 0.10 mmol/g at 400 ppm.

Synthesis of Two-Armed QA Based iPOPs (QA2-POP-OH)

[0107] FIG. 17 shows a scheme for the synthesis of two-armed QA based iPOPs.

[0108] 2,5-Diethenyl-1,4-benzenedicarbonitrile (1) 2,5-Dibromoterephthalonitrile (5.72 g, 20.0 mmol), potassium vinyltrifluoroborate (6.70 g, 50 mmol), and tetrakis(triphenylphosphine) palladium(0) (0.577 g, 0.50 mmol) were dissolved in a mixture of THF (50 mL), toluene (50 mL), and deionized water (10 mL) under N.sub.2 atmosphere. The resulting mixture was refluxed at 90 C. under N.sub.2 atmosphere for 48 hr. The product was extracted with ethyl acetate, washed with brine, dried over magnesium sulfate, and evaporated under reduced pressure. The crude product was purified by flash chromatography with ethyl acetate:hexane (1:5) as the eluent to yield 2,5-diethenyl-1,4-benzenedicarbonitrile. .sup.1H NMR (400 MHz, CDCl.sub.3) 7.92 (s, 2H), 6.97-7.06 (q, 2H), 5.96-6.05 (d, 1H), 5.65-5.70 (d, 1H) ppm.

[0109] POP-2CN (2) To a solvothermal autoclave, 2,5-diethenyl-1,4-benzenedicarbonitrile (1 g) was added with azobisisobutyronitrile (25 mg) and dimethylformamide (10 mL). The autoclave was placed in an oven and heated to 100 C. for 24 hr. The resulting product was collected by filtration, washed with acetone, and dried under vacuum to produce POP-2CN as a brown powder.

[0110] POP-2CH.sub.2NH.sub.2 (3) POP-2CN (200 mg) was dispersed in the solvent of THF (10 mL) under N.sub.2 atmosphere. Borane-tetrahydrofuran complex (40 mL, 1 M in THF) was added in batches by a glass syringe at 0 C. Then the resulting mixture was refluxed at 70 C. for 24 hr. After cooling to room temperature, pure ethanol was added dropwise to decant the excess borane. The raw POP-2CH.sub.2NH.sub.2 powder was soaked in ethanol overnight. Subsequently, the powder was washed with HCl and neutralized with sodium hydroxide solution. Then the powder was washed with water. The obtained POP-2CH.sub.2NH.sub.2 was finally dried overnight at 80 C. under vacuum.

[0111] QA2-POP-I (4) The POP-2CH.sub.2NH.sub.2 powder (200 mg) was dispersed in acetonitrile (20 mL) under N.sub.2 atmosphere. Iodomethane (1 mL) was added at room temperature. Then the resulting mixture was refluxed at 80 C. for 24 hr. After cooling to room temperature, the raw QA2-POP-I powder was washed with acetonitrile. The obtained QA2-POP-I was finally dried overnight at 55 C. under vacuum.

[0112] QA2-POP-OH (5) The QA2-POP-I powder (200 mg) was dispersed in the solvent of sodium hydroxide solution (0.5 M, 10 mL) several times for ion exchange. Then the powder was washed with water and finally dried overnight at 55 C. under vacuum for CO.sub.2 capture testing. FIG. 18 shows an FT-IR spectrum of QA2-POP-OH dosed with CO.sub.2. The indicated peak was assigned to the carbonyl stretch of a HCO.sub.3.sup. species generated from reaction of OH.sup. in the QA2-POP-OH with CO.sub.2.

[0113] FIG. 19 shows N.sub.2 physisorption data for QA2-POP-OH. The solid circles are adsorption and the open circles are desorption. The hysteresis is an indicator of mesoporosity (pore diameters between 2 nm and 20 nm).

[0114] FIG. 20 shows CO.sub.2 uptake as a function of CO.sub.2 partial pressure at 25 C. QA2-POP-OH had a CO.sub.2 capacity of 0.57 mmol/g at 400 ppm.

[0115] FIG. 21 shows the isosteric heat generated by adsorbing CO.sub.2 as a function of loading.

[0116] FIG. 22 shows the uptake of CO.sub.2 vs. time for QA2-POP-OH at 25 C. and 208 ppm CO.sub.2. The y axis is plotted as instantaneous mass vs. fully saturated (1=saturation). The material reaches 95% of saturation in about 75 seconds.

[0117] For the QA2-POP-OH, the POP-2CH.sub.2NH.sub.2 samples were obtained from POP-2CN by reducing the nitrile group. Then, the POP-2CH.sub.2NH.sub.2 samples were fully reacted with excess iodomethane and ions exchange by sodium hydroxide solution. The conversion ratio here is defined as how many nitrile groups have been reduced to the primary amine group. The reduction of nitrile groups in the POP-2CN was evaluated by the absorbance variety with IR spectra. The conversion ratio can be calculated by the equation as follows:

[00002]$\mathrm{Conversion}\left(\%\right)=\frac{I_{\mathrm{CN}}\left(\mathrm{POP}-2{\mathrm{CH}}_2{\mathrm{NH}}_2\right)}{I_{\mathrm{CN}}\left(\mathrm{POP}-2\mathrm{CN}\right)}100\%$

where I.sub.CN(POP-2CH.sub.2NH.sub.2) is the strength of nitrile peak in the POP-2CH.sub.2NH.sub.2 samples and I.sub.CN(POP-2CN) is the strength of nitrile peak in the POP-2CN sample.

[0118] The conversion of the POP-2CN sample is zero, and the conversion of one POP-2CH.sub.2NH.sub.2 sample was calculated as shown in FIG. 23. From the IR spectra, the conversion ratio of nitrile for POP-2CH.sub.2NH.sub.2-8 # was calculated as 77.1%. The CO.sub.2 adsorption performance of QA2-POP-OH-8 # derived from POP-2CH.sub.2NH.sub.2-8 #was also measured by ASAP 2020 PLUS. The results are show in FIG. 24.

[0119] By adjusting the reduction time, the QA2-POP-OH samples with different conversion ratios were obtained. The relationship between the CO.sub.2 adsorption capacity at 400 ppm and the conversion ratio of QA2-POP-OH is shown in FIG. 25.

Synthesis of Four-Armed QA Based iPOPs (QA4-POP-OH)

[0120] FIG. 26 shows a procedure for the synthesis of four-armed QA based iPOPs.

[0121] 3,6-Diethenyl-1,2,4,5-benzenetetracarbonitrile (1) 3,6-Dibromo-1,2,4,5-benzenetetracarbonitrile (3.36 g, 10.0 mmol), potassium vinyltrifluoroborate (6.70 g, 50 mmol), and tetrakis(triphenylphosphine) palladium(0) (0.577 g, 0.50 mmol) were dissolved in a mixture of THF (50 mL), toluene (50 mL), and deionized water (10 mL) under N.sub.2 atmosphere. The resulting mixture was refluxed at 90 C. under N.sub.2 atmosphere for 48 hr. The product was extracted with ethyl acetate, washed with brine, dried over magnesium sulfate, and evaporated under reduced pressure. The crude product was purified by flash chromatography with ethyl acetate:hexane (1:5) as the eluent to yield 3,6-diethenyl-1,2,4,5-benzenetetracarbonitrile.

[0122] POP-4CN (2) To a solvothermal autoclave, 3,6-diethenyl-1,2,4,5-benzenetetracarbonitrile (1 g) was added with azobisisobutyronitrile (25 mg) and dimethylformamide (10 mL). The autoclave was placed in an oven and heated to 100 C. for 24 hr. The resulting product was collected by filtration, washed with acetone, and dried under vacuum to yield POP-4CN as a brown powder.

[0123] POP-4CH.sub.2NH.sub.2 (3) POP-4CN (200 mg) was dispersed in the solvent of THF (10 mL) under N.sub.2 atmosphere. Borane-tetrahydrofuran complex (40 mL, 1 M in THF) was added in batches by a glass syringe at 0 C. Then the resulting mixture was refluxed at 70 C. for 24 hr. After cooling to room temperature, pure ethanol was added dropwise to decant the excess borane. The raw POP-4CH.sub.2NH.sub.2 powder was soaked in ethanol overnight. Subsequently, the powder was washed with HCl and neutralized with sodium hydroxide solution. Then the powder was washed with water. The obtained POP-4CH.sub.2NH.sub.2 was finally dried overnight at 80 C. under vacuum.

[0124] QA4-POP-I (4) The POP-4CH.sub.2NH.sub.2 powder (200 mg) was dispersed in acetonitrile (20 mL) under N.sub.2 atmosphere. Iodomethane (2 mL) was added at room temperature. Then the resulting mixture was refluxed at 80 C. for 24 hr. After cooling to room temperature, the raw QA4-POP-I powder was washed with acetonitrile. The obtained QA4-POP-I was finally dried overnight at 55 C. under vacuum.

[0125] QA4-POP-OH (5) The QA4-POP-I powder (200 mg) was dispersed in sodium hydroxide solution (0.5 M, 10 mL) several times for ion exchange. Then the powder was washed by water and finally dried overnight at 55 C. under vacuum for CO.sub.2 capture testing.

[0126] The polymerization and chemical structure of different POP-MeNH.sub.2 samples were investigated by Fourier transform infrared spectroscopy (FT-IR; Nicolet Nexus 670, USA).

[0127] Although this disclosure contains many specific embodiment details, these should not be construed as limitations on the scope of the subject matter or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments can also be implemented, in combination, in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments, separately, or in any suitable sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0128] Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results.

[0129] Accordingly, the previously described example embodiments do not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.