Synthesis of bulk sorbents via co 2-assisted polymerization

Abstract

Methods are provided for forming cross-linked polymeric compounds based on polymerization of vinyl-aromatics, such as vinylbenzylamine and / or vinylbenzylamine derivatives. Compositions resulting from such polymerization are also provided. The polymerization is enabled in part by treating a monomer precursor for forming the polymer with CO2. This converts one or more amino-containing substituents on the monomer precursor(s) into protected amino-containing substituents. The CO2 serves as a protecting group during the polymer synthesis step. This allows for formation of cross-linked vinyl-aromatic polymers with improved CO2 sorption properties.

Description

SYNTHESIS OF BULK SORBENTS VIA CO2-ASSISTED POLYMERIZATION FIELD OF THE INVENTION

[0001] Methods are provided for improved synthesis of cross-linked polyvinyl- aromatic compositions with amino-containing substituents. Methods of use of such materials as adsorbents, such as adsorbents for CO2, are also provided. BACKGROUND OF THE INVENTION

[0002] Amines incorporated into solid supports are currently used in a variety of applications for sorption of CO2from various types of streams. Some of the more promising types of materials are cross-linked solid polyamine sorbents based on poly(vinylbenzylamine-divinylbenzene) resins. These materials can be referred to as PVBA-DVBs.

[0003] PVBA-DVBs are amenable for use in post-combustion CO2capture, direct air capture, and related industrial applications in pressure and temperature swing processes. PVBA-DVB resins exist commercially and exhibit high CO2capacities, fast kinetics, and favorable energetics compared to aqueous amine scrubbing in continuous process studies. The benzylamine moiety is advantageous for CO2 capture due to its differentiated structure compared to typical aliphatic amines. Liquid sorbents containing benzylamine and its blends with other amines exhibit a number of advantages over aqueous MEA, including biodegradability, lowered corrosion and oxidative degradation, and advantages in viscosity, mass transfer, and process energy usage.

[0004] One of the difficulties with PVBA-DVBs is that synthesis of the material is complex. Currently, a multi-step post-polymerization functionalization of base polystyrene-DVB or poly(chloromethylstyrene)-DVB resins is needed in order to add the amine functionality to the cross-linked polymer. While such synthesis methods are effective, these methods do not guarantee full conversion of the precursor polymer repeat units to amino-bearing units, and do not necessarily offer fine control of functional group positioning on the repeat units. It would be desirable to have improved synthesis methods that reduce the cost and / or complexity for forming PVBA-DVBs. Additionally, it would further be desirable to have improved synthesis methods that can allow for formation of cross-linked polymers where the vinylbenzene monomers are substituted with amine- or nitrogen-containing functional groups other than methanamine.

[0005] LANXESS Lewatit® VP OC 1065 resin is an example of a commercially available crosslinked PVBA resin. This can capture CO2 in both physisorbed and chemisorbed forms, and has a lower affinity for water than polyethylene imine (PEI), the polymer typically utilized in direct air capture applications. Examples of references that describe use of this resin for carbon capture applications are US Patent 8,414,689 and US Patent 9,028,590. Additional examples regarding carbon capture with this type of resin are provided in a journal article by Veneman et al. titled “Adsorption of H2O and CO2 on supported amine sorbents” (International Journal of Greenhouse Gas Control Vol.41 (2015) pages 268 – 275); a journal article by Alesi Jr. et al. titled “Evaluation of a Primary Amine-Functionalized Ion-Exchange Resin for CO2 Capture” (Ind. Eng. Chem. Res. (2012) vol.51 pages 6907 – 6915); and a journal article by Hallenbeck et al. titled “Effects of O2and SO2on the Capture Capacity of a Primary-Amine Based Polymeric CO2 Sorbent (Ind. Eng. Chem. Res. (2013) vol. 52 pages 10788 – 10794). Additional details regarding the synthesis route for this type of resin can be found in U.S. Patent Application Publication 2006 / 0173083; a journal article by Gravano et al. titled “Poly(4-(aminomethyl)styrene)-b-polystyrene: Synthesis and Unilamellar Vesicle Formation” (Langmuir (2002) Vol. 18 pages 1938 – 1941); a journal article by Nasirtabrizi et al. titled “Synthesis, Characterization and Thermal Behaviour of Amino Functional Polymers from 4-Chloromethyl Styrene Polymers” (Asian J. Chem. (2013) vol. 25 pg 2651 - 2656); and a journal article by Weinshenker et al. titled “Polymeric Reagents I. Synthesis of an Insoluble Polymeric Carbodiimide” (Tetrahedron Letters (1972) No.32 pages 3281-3284).

[0006] It is noted that U.S. Patent Application Publication 2006 / 0173083 also describes a synthesis pathway where functional groups are added to benzene rings in a polymer by using a reagent such as phthalimide / formalin / sodium hydroxide, followed by sulfuric acid, and finally aqueous sodium hydroxide. U.S. Patent 7,442,745 also describes such a synthesis pathway using N-hydroxymethylacetamide / trifluoroacetic acid, followed by hydrochloric acid, and then sodium hydroxide solution.

[0007] A journal article by Kobyashi et al. titled “A Carbohydrate-Containing Synthetic Polymer Obtained from N-p-Vinylbenzyl-D-gluconamide” describes polymerization of a carbohydrate-protected monomer. (Polymer Journal, Vol.15, No.9, pp 667-671 (1983).)

[0008] Functional group variants to a PVBA structure are known and have been prepared, most commonly through polymerization functionalization. PVBA- analogous secondary, tertiary, ammonium, and multiamine / ammonium resins are accessible through the direct reaction of poly(chloromethylstyrene) with alkylamines. For example, a journal article by Huang et al. describes synthesis, characterization, and adsorption behavior of aniline-modified polystyrene resins. (Journal of Colloid and Interface Science vol. 317 (2008) pages 434-441.) By post-synthesis substitution of a chloromethylated polystyrene polymer, aniline and nitro-aniline were added to the polymer. Based on residual chlorine content, it appears that up to 90% of the chlorine could be replaced. In another example, a journal article by Kolarz et al. describes performing a series of post-synthesis steps on a PVBA polymer in an effort to form guanidinyl groups, but the amount of formation of the guanidinyl groups was limited. (Polymer vol. 43 (2002) pages 1061 – 1068.) It is noted that the cross-linked polymers used in this article were formed with only 2% divinylbenzene as cross-linker. In still another example, another journal article by Kolarz describes formation of polymers with a variety of substituted guanidinyl substituents. (Reactive & Functional Polymers, vol. 48 (2001) 169 –179.) The article describes a maximum incorporation for guanidinyl of roughly 90%, with lower amounts of free amines for all other types of substituted guanidinyls. Still other articles by Kolarz et al. describe addition of guanidinyl groups to various types of co-polymers. (Reactive & Functional Polymers vol. 36 (1998) pages 185-195; Reactive & Functional Polymers vol.42 (1999) pages 213–222.)

[0009] A journal article by Kornreich et al. titled “Peptide N-alkylamides by Solid Phase Synthesis” is another example of substituting amino-containing groups in a chloromethylated polystyrene. (Int. J. Peptide Protein Res. vol. 25 (1985) pages 414- 420.) In this instance, resins bearing secondary amine groups are described. It is noted that the underlying polymer used was formed using only 1% divinylbenzene for cross- linking.

[0010] A journal article by Charreyre et al. describes kinetic studies of solution polymerization for non-crosslinked, soluble polymers of 4-vinylbenzylamine, its trifluoroacetamide derivative, styrene, and corresponding co-polymers. (Macromol. Chem. Phys. Vol.195, pages 2141 - 2152 (1994).)

[0011] A journal article by Thielbeer et al. (Bioconjugate Chem. (2011) Vol.22, pg. 144) describes preparation of the form of PVBA resin through an emulsion free radical polymerization process similar to that used to prepare commercial PVBAs. However, the resulting sorbents do not react with CO2 through the traditional nucleophilic-addition, carbamate-forming chemisorption pathway seen with free primary and secondary amines. Thus, the resulting solid resins would need a post-synthesis free basing step with a solution of a stronger base to be rendered active for chemisorptive carbon capture by amine-CO2 chemical reaction. SUMMARY OF THE INVENTION

[0012] In an aspect, a method for synthesizing a cross-linked polymer from vinyl- aromatic monomers that have an amino-containing substituent is provided. The method includes exposing a plurality of vinyl-aromatic monomers having at least one amino- containing substituent to CO2, to convert at least a portion of the at least one amino- containing substituent to a protected form. The at least one amino-containing substituent can have 1 to 14 carbon atoms. The at least one amino-containing substituent can be bonded to an aromatic ring of the vinyl-aromatic monomers via one or more carbon atoms in the amino-containing substituent. The method further includes reacting at least a portion of the vinyl-aromatic monomers having the protected amino-containing substituents under polymerization conditions with a plurality of copolymerizing cross- linkers and an initiator in a solvent to form a cross-linked polyvinyl-aromatic that contains at least a portion of the protected amino-containing substituents. Additionally, the method includes desorbing CO2 from the cross-linked polyvinyl-aromatic to convert at least a portion of the protected amino-containing substituents into amino-containing substituents.

[0013] In another aspect, a composition is provided, such as a composition formed by the method above. In some aspects, the composition includes 65 mol% or more of primary repeat units based on vinyl-aromatic monomers having at least one amino- containing substituent. The at least one amino-containing substituent can have 1 to 14 carbon atoms. The at least one amino-containing substituent can be bonded to an aromatic ring of the vinyl-aromatic monomer via one or more carbon atoms in the at least one amino-containing substituent. Additionally, the composition includes 3.0 mol% or more of cross-linker repeat units based on copolymerizing cross-linkers, counting theentire mass of a cross-linker repeat unit as one unit. In some aspects, at least 30% of the primary repeat units, relative to the of primary repeat units, can have an amino- containing substituent that is different from methanamine. BRIEF DESCRIPTION OF THE DRAWING

[0014] FIG. 1 shows examples of process flows for synthesizing a cross-linked polymer based on substituted vinylbenzene monomers, followed by addition of a methanamine group to the monomers after forming the cross-linked polymer.

[0015] FIG. 2 shows an example of a process flow for forming a cross-linked polymer based on vinylbenzene monomers having an amine group, where the amine group is present in a protected form during synthesis of the cross-linked polymer.

[0016] FIG. 3 shows chemical structures for various styrene monomers bearing amino-containing substituents that are referred to herein, and their abbreviations.

[0017] FIG. 4 shows additional styrene monomers bearing amino-containing substituents.

[0018] FIG. 5 shows styrene-, divinylbenzene, and divinyl-biphenyl-based cross- linkers bearing amino-containing substituents.

[0019] FIG.6 shows Attenuated Total Reflectance Infrared (ATR-IR) and solid state13C NMR (SS-NMR) spectra for an inventive cross-linked polymer sample.

[0020] FIG.7 shows scanning electron microscopy (SEM) images for one inventive and two comparative sorbents.

[0021] FIGS.8A, 8B, and 8C show solution13C NMR spectra for vinylbenzylamine in a dimethylsulfoxide solution (DMSO-d6) before treatment with CO2 (FIG. 8A); after treatment by bubbling CO2through the solution at 80°C (FIG. 8B); and after treatment of the CO2 sorption product by bubbling N2 through the solution at 80°C (FIG.8C).

[0022] FIG. 9 shows 30 °C Autosorb data for CO2 uptake with material 1D over a range of CO2 partial pressures of 0 to 1 atm.

[0023] FIG. 10 shows thermogravimetric CO2 multicycle uptake curves (35 °C sorption, 120 °C desorption, 1 atm dry CO2) for materials 1C and C1B.

[0024] FIG. 11 shows a 100% (1 atm) dry CO2 isobaric TGA sorption curve for material 6B (21°C sorption, 90°C desorption).

[0025] FIG.12 shows the humid direct air capture (400 ppm CO2in N2, 60% relative humidity, room temperature) TGA desorption curve for material 6E taken using a 50 °C / 3 hour pre-treat protocol.

[0026] FIG.13 shows a TGA water isotherm taken for material 6E at 25 °C using a stepped feed gas of N2containing increasing relative humidity at increments of 5 or 10% RH (steps at 0, 5, 10, 20, 30, 40, 50, 60, 70, and 80% RH).

[0027] FIG.14 shows additional styrene-containing monomers and cross-linkers.

[0028] FIG.15 shows a breakthrough curve for CO2 sorption. DETAILED DESCRIPTION OF THE INVENTION

[0029] In various aspects, improved methods are provided for forming cross-linked polymeric compounds based on polymerization of vinyl-aromatics, such as vinylbenzylamine and / or vinylbenzylamine derivatives. Compositions resulting from such polymerization are also provided. The polymerization is enabled in part by treating a monomer precursor for forming the polymer with CO2. This converts one or more amino-containing substituents on the monomer precursor(s) into protected amino- containing substituents. For example, when the monomer precursor is vinylbenzylamine, amino groups on the vinylbenzylamine monomer precursors are converted into ammonium carbamate / carbamic acid precursors. Analogous types of protected substituents can be formed to protect other types of amino-containing substituents. For example, a guanidinyl group is an example of an amino-containing group. Even though a guanidinyl is typically thought of as functional group itself, the two amino groups and imine in a guanidinyl group can be readily identified. Depending on the nature of the amino-containing group, the resulting analogous protected substituents may or may not correspond to carbamates / carbamic acids, depending on the exact nature of the amine- containing group that is being protected. Thus, the CO2 serves as a protecting group during the polymer synthesis step.

[0030] By performing this initial precursor conversion, a cross-linked polymer can be formed using a process where the desired amino-containing functional group is present (in a protected form) during formation of the cross-linked polymer. This is in contrast to conventional methods, where a cross-linked polymer is formed, and then the amino-containing group is added using post-synthesis processing. The ability to have theamino-containing group present in a protected form during polymerization can allow for incorporation of a greater variety of containing functional groups into a cross- linked polymer, as the ability to add the amine group is not dependent on the ability to insert the amino-containing group after the fact into the already formed polymer. Additionally, it has been discovered that the CO2added as a protecting group during synthesis also serves as a textural modifier, so that the resulting cross-linked polymer has different physical properties than a similar polymer formed without the presence of the CO2 protective group. Still another advantage is that no additional reagents are required to remove the CO2 protecting group after synthesis of the desired polymer. Instead, the CO2 can be desorbed in a manner that is similar to a desorption step for an industrial adsorption / desorption process cycle. Desorbing CO2 from a protected amino-containing substituent returns the amino-containing substituent to its original form.

[0031] Conventionally, formation of cross-linked poly(vinylbenzylamine- divinylbenzene) compositions has involved a multi-step process that includes substantial additional processing after formation of the initial cross-linked polymer material. A representation of a conventional synthesis route is shown in FIG. 1 (top). As shown in FIG. 1 (top), conventional synthesis of cross-linked poly(vinylbenzylamine- divinylbenzene) compositions may start with a poly(chloromethylstyrene-co- divinylbenzene) resin (120), either made by chloromethylating a styrene-co- divinylbenzene resin (150), or copolymerizing chloromethylstyrene with a divinylbenzene cross-linker. The styrene-co-divinylbenzene resin precursor is made by copolymerization of styrene with divinylbenzene. The cross-linked chloromethylated polymer 120 is then reacted 125 with a phthalimide reagent, such as potassium phthalimide, to replace the chlorine substituents in the polymer. The resulting phthalimide-substituted polymer 130 is then reacted 135 in the presence of a suitable reagent, such as hydrazine monohydrate, to convert the phthalimide substituents into methanamine groups, thus producing the cross-linked poly(vinylbenzylamine- divinylbenzene) (140).

[0032] An alternative route (FIG. 1, bottom) is amidomethylation (155) of polystyrene-co-divinylbenzene to give a protected poly(vinylbenzylamide-co- divinylbenzene) (160) followed by de-protection with acid and free basing (165). Again,all of these routes involve formation of the polymer, followed by efforts to use post- synthesis processing to add the desired functionality to the polymer.

[0033] The process flows shown in FIG.1 are effective specifically for making poly (vinylbenzylamine-divinylbenzene). However, there are a variety of difficulties with such process flows. First, the process flows shown in FIG. 1 require three steps. Each step in a synthesis process flow, in addition to increasing experimental complexity and cost, typically involves some losses due to incomplete conversion, formation of secondary products, impurity residues that may block pores, and / or other factors. Second, the process flows in FIG. 1 show formation of a cross-linked poly(vinylbenzylamine- divinylbenzene) product. But this is only one type of functional group that might be desirable. Different and / or additional synthetic steps would be needed to form a polymer with another type of amino-containing group in place of the amine. This can prove particularly challenging. The methanamine group that is added in FIG. 1 is the simplest form of amino-containing group that can be added having sufficient basicity and nucleophilicity for chemical reaction with CO2. Controlled addition of any other type of amino-containing group can pose a variety of additional challenges. A partial list of these challenges includes: the difficulty of introducing amino-containing groups at specific sites (ortho, meta, para) on the polystyrene ring; introduction of multiple groups onto one polystyrene ring for high functional group density; introduction of two or more different amino-containing groups on one resin (as in a random or block copolymer structure); spurious extra crosslinking reactions between chains upon functionalization, leading to a loss of porosity; inability to achieve an even distribution of desired functional groups in all regions of the resin (such as on the surface vs. inside pores); and difficulty characterizing conversion and other chemical and structural features of the solid resin.

[0034] In contrast to the process flows in FIG. 1, in various aspects, a single step synthesis process is provided for forming bulk cross-linked polymers based on vinyl- aromatic monomers (also referred to as vinyl-aromatics). It is noted that in this discussion, vinyl-aromatic is an adjective (such as when used in front on “monomers”), and vinyl-aromatics is a noun to refer to vinyl-aromatic monomers. The vinyl-aromatic monomers correspond to single- or multi-ring (fused or unfused) vinyl-aromatics with an amino-containing substituent or substituents on the aromatic ring. Additionally, the amino-containing substituent of the vinyl-aromatic monomers is separated from thearomatic ring or rings by at least one -CH2- spacer. The simplest example of having an amino group separated by a -CH2- a methanamine group, which is –CH2-NH2. This group is bonded to the aromatic ring through the -CH2- group, so that the -CH2- group serves as a spacer between the aromatic ring and the amino group, placing the -NH2portion in the substituent position known as the benzylic position. Examples of such poly-vinyl-aromatics with amino-containing substituents are poly(vinylbenzylamine) products and derivatives. Another example of such a derivative is a cross-linked product including a benzylic guanidine group, e.g. a guanidine group separated from the aromatic ring by a -CH2- spacer, instead of methanamine, as at least a portion of the amino-containing groups. In such aspects, the synthesis process is enabled by starting with a monomer that includes the desired amino-containing functional group or groups, such as amine, or guanidine, as opposed to starting with a chloride or unfunctionalized resin as shown in the process flows of FIG.1. In order to protect this functional group, the starting monomer is reacted with CO2in a preliminary step to form groups that are analogous to carbamate / carbamic acid group monomers or pairs of the monomers, i.e., amine-CO2chemisorption products.

[0035] It has been discovered that by forming carbamate / carbamic acid groups, or corresponding analogous amine-CO2reaction product groups, the underlying amino- containing functional group (or groups) is protected by reduction of its chemical reactivity (basicity and nucleophilicity) and modified in character during the polymerization process. Since CO2 product salts such as ammonium carbamates have ionic bonds, in polymerization solvents that do not provide environments separating ionic solutes, this promotes close association and aggregation of the basic nitrogenous functionalities while the crosslinking polymerization is creating the solid state structure and pore structure of the material. These spatial relationships, which provide unexpected advantages for CO2 adsorption in the resulting cross-linked polymer, are advantageously locked into the resultant structure of the solid sorbent material. The underlying amino- containing functional groups are also transformed into a group or groups temporarily occupying greater molecular volume for the course of the polymerization. The polymerization can then be performed to form the cross-linked polymer, followed by exposure of the cross-linked polymer to conditions that remove the CO2, thus restoring the original functional groups. Removal of CO2 from these sites in the product solidsorbent generates extra free volume and pore space that are advantageous during CO2sorption processes utilizing the

[0036] Based on the above, without being bound by any particular theory, in addition to allowing formation of a protecting group, it is believed that CO2 serves as a textural modifier during polymerization (as crosslinking is also taking place). This contributes to enhanced surface area, decreased particle size, and improved CO2 uptake and sorption / desorption kinetics for the cross-linked polymers made by the synthesis methods described herein. It is noted that in various aspects, the CO2 used to form protective group is easily removed from the sorbent by thermal and pressure swing (or vacuum swing) desorption to generate the free amine version of the amino group and a sorbent with properties comparable to, and in some cases superior to, various commercially available poly(vinylbenzylamine-divinylbenzene) resins.

[0037] It is further noted that the “steps” for protecting the initial vinylbenzylamine monomers (and / or other monomers) with CO2and subsequently removing the CO2from the cross-linked polymer are not counted as being part of the synthesis. Protection of the amino-containing monomer groups is carried out by the simple switching of the existing air or inert gas present in the headspace (and dissolved in solution) of the polymerization reaction with CO2, in the form of a gas flow and sparge. The CO2is present in excess and is not required to be added according to a particular stoichiometry. It does not require dissolution of solid reagents, mixing and phase compatibility of liquid reagents, or any other such feature common to regular chemical reactions. Removal of the CO2 is accomplished by simple switching of the reaction headspace / sparge gas to another gas having a low partial pressure of CO2(e.g., nitrogen, air), typically in conjunction with heat, and / or application of vacuum. These gases, it should be noted, are already present as feeds or product streams in carbon capture processes and other industrial chemical manufacturing units. It is also noted that sorption and desorption of CO2 is one of the applications of the composition. Thus, at least the desorption of CO2simply represents a process that will be repeated as the cross-linked polymer is used for sorption and desorption of CO2.In one embodiment, for example, the product polymer could be maintained under a CO2 atmosphere after synthesis and during purification and workup, with process solvents and residual polymerization reagents removed by supercritical CO2drying, stored and transported as the CO2 adduct for stability, and then not fullydeprotected until installed into an actual carbon capture process unit. Furthermore, neither complete protection or (desorption) of the monomer with CO2 is necessary for the polymerization to succeed, or for the product sorbent to be useful in a carbon capture process cycle.

[0038] FIG. 2 shows an example of the process flow for the single-step synthesis process. In the example shown in FIG.2, vinylbenzylamine is used as the monomer, but other vinyl-aromatic monomers with amino-containing functional groups can also be used.

[0039] In FIG.2, the vinylbenzylamine monomer is pre-treated 210 with CO2 to form an ammonium carbamate complex between amine groups on two molecules. This pre- treatment step can be performed under conditions suitable for forming carbamates. For example, bubbling CO2through a liquid solution of the monomer for a convenient period of time, such as 10 minutes to 10 hours, is sufficient for converting the monomers to the carbamate. These carbamate complexes may be in equilibrium with a carbamic acid form of the monomer-CO2 product, depending on solvent polarity and other factors. If water is present, some of the carbamate complexes may be present as vinylbenzylammonium bicarbonates.

[0040] After converting the monomers to the carbamate / carbamic acid form, the resulting VBA-CO2 complex can be copolymerized 220 with divinylbenzene cross-linker (DVB) using simple free radical polymerization in an organic solvent to give a cross- linked, macromolecular polyamine-CO2 complex. The CO2 can then be removed 230 to provide the amine form of the cross-linked polymer. This can be accomplished by any convenient method. For example, simply exposing the cross-linked polymer to an N2atmosphere at room temperature (~ 20°C) for a period of time, such as 10 minutes to 10 hours, will allow the CO2to substantially desorb from the cross-linked polymer.

[0041] Still another advantage of using a synthesis method where CO2 protects an amino-containing substituent, as opposed to adding amino-containing substituent post- polymerization, is that the requirements for the synthesis environment are relaxed. In particular, olefin-amines are typically polymerized in ammonium salt form with a halide counterion, such as chloride, bromide, or iodide, giving polymeric ammonium species that are not useful for traditional CO2capture without further treatment to regenerate the free base form of the amines and remove the released salts from the bulk material.Further, the ammonium salt forms of olefin-amine monomers are rarely soluble in organic solvents. This limitation means many useful molecular design tools are not accessible (e.g. copolymerization with other, water-insoluble organic olefin monomers and cross-linkers). The use of CO2 to convert an amino-containing group into a protected group avoids use of the traditional ammonium salt forms of the monomer and alleviates the solvent limitations imposed on the polymerization.

[0042] Finally, it is noted that by forming a cross-linked polymer directly that includes the desired amino-containing substituent, the need to exchange out a chlorine or chloride substituent (present as a chloromethyl -CH2Cl substituent, or as the counterion of a traditional ammonium salt) and / or another type of substituent is avoided. As a result, the cross-linked polymers described herein can be substantially free of chlorine, such as having a chlorine content of 100 wppm or less (0.0001 g chlorine / g polymer), and potentially down to zero within detection limit. More generally, other types of substituents and / or byproduct ions and salts that might be present when using a conventional synthesis route are formates, sulfates, and alkali metal ions and salts. The presence of these other types of substituents, salts, and / or ions, which may be deleterious to material performance or stability, can also be avoided using the synthesis methods described herein. In some aspects, the cross-linked polymers described herein can be substantially free of formates, such as having a formate content of 1000 wppm or less (0.001 g formate / g polymer), and potentially down to zero within detection limit. Additionally or alternately, the cross-linked polymers described herein can be substantially free of sulfates, such as having a sulfate content of 1000 wppm or less, and potentially down to zero within detection limit. Further additionally or alternately, the cross-linked polymers can be substantially free of alkali metal ions, such as having an alkali metal content of 1000 wppm or less, or 100 wppm or less, and potentially down to zero within detection limit. DEFINITIONS

[0043] In this discussion, the numbering scheme for the Periodic Table Groups is according to the current version of the IUPAC Periodic Table of Elements.

[0044] The terms “substituent”, “radical”, “group”, and “moiety” may be used interchangeably.

[0045] In this discussion, a “vinyl” substituent on a benzene ring is defined in the traditional manner, where a carbon is to the benzene ring by a single carbon- carbon bond, and that carbon is bonded to only one other carbon by a double carbon- carbon bond. Vinylbenzylamine is an example of a compound that includes a vinyl substituent.

[0046] In this discussion, a “vinyl-aromatic” is a compound that includes one or more aromatic rings, with at least one vinyl substituent bonded to one of the one or more aromatic rings. Vinylbenzylamine is an example of a single-ring vinyl-aromatic.

[0047] In this discussion, unless otherwise specified, “vinylbenzylamine” is defined as the chemical structure labeled “VBA” in FIG.3. FIG. 3 also shows names used for other structures that may be referred to herein. In this discussion, unless otherwise specified, “methylvinylbenzylamine” is defined as the chemical structure labeled “Me- VBA” in FIG. 3; “meta, meta-di(aminomethyl)styrene” is defined as the chemical structure labeled “Di-mVBA” in FIG. 3; “para-(aminoethyl)styrene” is defined as the chemical structure labeled “ESA” in FIG. 3; “guanidinylated vinylbenzylamine” is defined as the chemical structure labeled “GVBA” in FIG. 3; “dimethyl guanidinylated vinylbenzylamine” is defined as the chemical structure labeled “Me2-GVBA” in FIG.3; and “trimethyl guanidinylated vinylbenzylamine” is defined as the chemical structure labeled “Me3-GVBA” in FIG.3. It is noted that the “guanidinylated vinylbenzylamine” that is labeled as “GVBA” in FIG. 3 can also be referred to as 1-(4- vinylbenzyl)guanidine.

[0048] In this discussion, vinylbenzylamine is an example of a vinyl-aromatic that is a single-ring aromatic with an amine-containing substituent in a para position relative to the vinyl substituent.

[0049] Vinylbenzylamine also provides an example of a methanamine functional group substituent. A methanamine group can also be referred to as an aminomethyl group. Methanamine corresponds to a functional group where the bond to the benzene ring is a carbon-carbon single bond, and then a nitrogen is bonded to the carbon that is bonded to the ring. This is in contrast to a functional group where a nitrogen is bonded directly to the benzene ring by a carbon-nitrogen single bond.

[0050] In this discussion, an “amino-containing substituent” or “amino-containing functional group” is defined as any substituent / functional group appended to a benzeneor other aromatic ring that a) is appended to the ring via a carbon-carbon bond, b) includes an amino group that is not to the ring, and c) contains from 1 to 14 carbon atoms in the functional group. A guanidinyl group (i.e., guanidine as a substituent on a benzene or other aromatic ring, where one of the guanidine nitrogen atoms is bonded to a carbon that is bonded to the ring through a carbon-carbon single bond) is an example of an amino-containing substituent that includes two carbon atoms. This is illustrated by the “GVBA” compound shown in FIG.3. It is noted that with additional substitution of the guanidinyl group, such as in the “Me2-GVBA” or “Me3- GVBA” compounds in FIG. 3, the number of carbons increases, with “Me2-GVBA” having four carbons and “Me3-GVBA” having five carbons. Guanidinyl groups that are substituted with additional alkyl groups are other examples, as are aminoguanidinyl groups, amidines, and biguanides. Methanamine and derivatives of methanamine that have other alkyl (or substituted alkyl) groups bonded to the nitrogen of the methanamine, or bonded to the carbon atom of the methanamine, are still other examples of amino- containing substituents. Further examples include amino-containing substituents that contain more than one amine group per attachment point to the benzene or other aromatic ring, such as a di-, tri-, or oligoamine. Cyclic amino-containing structures that are attached to the ring of the monomer through one, or through more than one, position of the ring are yet further examples. More than one type of amino-containing group may be present on the monomer, and more than one type of amino-containing monomer may be present on the monomer, and / or in the polymerization mixture and final product. More than one separate group may be attached to a single monomer, as in the monomer “Di- mVBA” shown in FIG.3.

[0051] Another example of an amino-containing group is an amidinyl group. An amidinyl group is the nitrogen analog of a carboxylic acid, including an imine and an amine bonded to the same carbon atom. It is understood that the imine and amine can correspond to a resonance structure, but in this discussion, an amidinyl group is defined as an amino-containing group based on the presence of the amine.

[0052] For an amino-containing group or substituent as described herein, in some aspects the amino-containing group can be a group where the amine is not in the benzylic position. By definition, an amino-containing group as described herein does not include an amine directly bonded to an aromatic ring. Therefore, a non-benzylic amino-containing group or substituent corresponds to an amino-containing group with at least two carbon atoms between an amine an aromatic ring.

[0053] The monomers shown in FIG.4 are further examples of monomers that bear amino-containing substituents. Compound “A” in FIG. 4 is defined herein as meta- vinylbenzylamine. Compound “B” in FIG. 4 is defined herein as meta,meta,para-tri- (aminomethyl)styrene. Compound “C” in FIG. 4 is defined herein as para- (aminopropyl)styrene. Compound “D” in FIG.4 is defined herein as para-(3-amino-2,2- dimethyl-propyl)styrene. Compound “E” in FIG.4 is defined herein as (N-aminopropyl)- vinylbenzylamine. Compound “F” in FIG. 4 is defined herein as N-(3-amino-2,2- dimethyl-propyl)-vinylbenzylamine. Compound “G” in FIG.4 is defined herein as N,N- di-(aminopropyl)-vinylbenzylamine. Compound “H” in FIG.4 is defined herein as N,N- di-(3-amino-2,2-dimethyl-propyl)-vinylbenzylamine. Compound “I” in FIG.4 is defined herein as para-(piperazinyl-methyl)styrene. Compound “J” in FIG. 4 is an example of a methyl guanidinylated vinylbenzylamine, specifically, 1-methyl-1-(4- vinylbenzyl)guanidine. As shown in FIG.3 and FIG.4, a methyl can be attached to either of the amino nitrogens in a guanidinyl group.

[0054] More generally, examples of amino-containing substituents include, but are not limited to, methanamine, ethanamine, N-methyl methanamine, amidinyl, guanidinyl, alkyl-substituted guanidinyl, aminoguanidinyl, biguanide, linear alkylamine, branched alkylamine, cyclic alkylamine, and combinations thereof. It is noted that the alkylamines can be multi-amines (multi-aminoalkyl substituents) with two or more amine functional groups in a single alkylamine substituent. When the alkylamine is a multi-amine, at least one of the amines is a primary or secondary amine.

[0055] Examples of monomers for forming a cross-linked vinyl-aromatic polymer include, but are not limited to vinylbenzylamine, methylvinylbenzylamine, meta,meta- di(aminomethyl)styrene, para-(aminoethyl)styrene, guanidinylated vinylbenzylamine, a methyl guanidinylated vinylbenzylamine, a dimethyl guanindinylated vinylbenzylamine, trimethyl guanidinylated vinylbenzylamine, or a combination thereof. Other examples of monomers include meta-vinylbenzylamine, meta,meta,para-tri-(aminomethyl)styrene, para-(aminopropyl)styrene, para-(3-amino-2,2-dimethyl-propyl)styrene, (N- aminopropyl)-vinylbenzylamine, N,N-di-(aminopropyl)-vinylbenzylamine, N-(3-amino-2,2-dimethyl-propyl)-vinylbenzylamine, N,N-di-(3-amino-2,2-dimethyl-propyl)- vinylbenzylamine, para-(piperazinyl- styrene, or a combination thereof.

[0056] The amino-containing monomers may be copolymerized with amino- containing cross-linkers. The cross-linkers shown in FIG. 5 are examples of amino- containing cross-linkers. The amino-containing monomers may further be copolymerized with co-monomers and cross-linkers bearing other groups that provide separate functionality useful for sorbents in carbon capture processes, for example, monomers bearing groups that provide electrical conductivity or good adhesion to substrates.

[0057] Compound “K” in FIG. 5 is defined herein as 1-aminomethyl-3,5- divinylbenzene. Compound “L” in FIG. 5 is defined herein as bis(4-vinylbenzyl)amine. Compound “M” in FIG. 5 is defined herein as 3,3’-divinyl-2,2’-di(aminomethyl)-p- biphenyl. Compound “N” in FIG. 5 is defined herein as 4,4’-divinyl-2,2’- di(aminomethyl)-p-biphenyl. Compound “O” in FIG. 5 is defined herein as 1- (guanidinylated aminomethyl)-3,5-divinylbenzene. Compound “P” in FIG. 5 is defined herein as 1,3-di(4-vinylbenzyl)guanidine.

[0058] More generally, examples of cross-linkers include, but are not limited to divinylbenzene, as either single or mixed ortho / meta / para isomers, 4,4’-divinyl-p- biphenyl, bis (4-vinylbenzyl)amine, 1-aminomethyl-3,5-divinylbenzene, 1- (guanidinylated aminomethyl)-3,5-divinylbenzene, 1,3-di(4-vinylbenzyl)guanidine, 4,4’-divinyl-2,2’-di(aminomethyl)-p-biphenyl, and 3,3’-divinyl-2,2’-di(aminomethyl)- p-biphenyl.

[0059] In this discussion, reference is made to both monomers and repeat units. Monomers are used to form a polymer. After the polymer is formed, the monomers used to form the polymer result in corresponding repeat units in the polymer. For example, vinylbenzylamine monomers can be used to form a polymer that includes repeat units based on the vinylbenzylamine structure, with the modification that the vinyl group is converted into a portion of the polymer backbone.

[0060] In this discussion, a cross-linked poly-vinylaromatic material can be described with regard to the number of repeat units present in the polymer. For this characterization, the mol% of each type of repeat unit is specified. The mol% of a repeat unit is the frequency of occurrence for that type of repeat unit in the polymer. To illustratethis, consider a cross-linked poly-vinylaromatic that includes a total of 1000 repeat units. In this example, the cross-linked poly- includes 850 repeat units based on vinylbenzylamine monomers, 100 repeat units based on the co-polymerizing cross-linker divinylbenzene, and 50 repeat units based on ethylvinylbenzene. In this example, the cross-linked poly-vinylaromatic has 85 mol% of repeat units based on vinylbenzylamine, 10 mol% of repeat units based on divinylbenzene, and 5 mol% of repeat units based on ethylvinylbenzene.

[0061] In the above example, it is noted that the divinylbenzene is a cross-linker repeat unit. This means that the divinylbenzene is incorporated as a “repeat unit” into two separate polymer chains, thus performing crosslinking. In this discussion, when determining the mol% of cross-linker in a cross-linked poly-vinylaromatic, the cross- linker is counted only once. This could be achieved by counting each “repeat unit” instance of the cross-linker as only half of a unit, or by counting the cross-linker the first time it is identified in a chain, but not counting it in the second chain it is a part of, or by any other convenient method so that the same cross-linker is not counted twice when determining the mol% of cross-linker.

[0062] The product polymers will contain pendant aromatic units that have stereochemical relationships to their nearest neighbors characterized as either isotactic (same side) or syndiotactic (opposite side) dyads. Overall, the tacticity of the polymer chain will be characterized as atactic (having a mixture of both isotactic and syndiotactic dyad units), or isotactic, or syndiotactic. While most free radical copolymerizations of the type described herein produce atactic sequences, the amount of each dyad type present will be a function of the monomer’s steric bulk and other conditional factors such as solvent and polymerization temperature.

[0063] Finally, a further class of examples is all of the above monomeric types in which the benzene ring of attachment is part of a larger polymerizable vinyl-aromatic structure, such as monomers in which the vinyl-aromatic comprises vinylnaphthalene, vinylfluorene, vinyl-p-biphenyl, vinyl-tetrahydronaphthalene, or similar. Larger polymerizable vinyl-aromatic structures may also include additional frameworks that include non-CO2-reactive heteroatoms, for example, vinylcarbazoles, vinylimidazoles, and vinylpyridines. In these cases, the aromatic ring bearing the amino-containing substituent might not be a benzene ring but instead a heterocycle. Any vinyl-substitutedaromatic, multiaromatic, or heterocyclic monomer that has an amino-containing substituent which can be treated with can be copolymerized with divinylbenzene or similar crosslinker in a free-radical polymerization process may be used.

[0064] In some aspects, the location of substituents may be defined relative to each other. The terms “ortho”, “meta”, and “para” are used in the expected manner. For a benzene ring, substituents that are bonded to carbons on opposing sides of the benzene ring have a “para” relationship. For example, 1,4-dimethylbenzene is an example of a benzene ring having para substituents. 4-(vinylphenyl)methanamine, also referred to herein as vinylbenzylamine, is another example of a benzene ring having para substituents.

[0065] As used herein, and unless otherwise specified, the term “Cn” means hydrocarbon(s) having n carbon atom(s) per molecule, wherein n is a positive integer.

[0066] As used herein, and unless otherwise specified, the term “hydrocarbon” means a class of compounds containing hydrogen bound to carbon, and encompasses (i) saturated hydrocarbon compounds, (ii) unsaturated hydrocarbon compounds, and (iii) mixtures of hydrocarbon compounds (saturated and / or unsaturated), including mixtures of hydrocarbon compounds having different values of n.

[0067] As used herein, and unless otherwise specified, the term “alkyl” refers to a saturated hydrocarbon radical having from 1 to 14 carbon atoms (i.e. C1–C14 alkyl), or from 1 to 12 carbon atoms (i.e. C1–C12alkyl), or from 1 to 8 carbon atoms (i.e. C1–C8alkyl). Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, and so forth. The alkyl group may be linear, branched or cyclic. “Alkyl” is intended to embrace all structural isomeric forms of an alkyl group. For example, as used herein, propyl encompasses both n-propyl and isopropyl; butyl encompasses n-butyl, sec-butyl, isobutyl and tert-butyl and so forth. As used herein, “C1 alkyl” refers to methyl (–CH3), “C2 alkyl” refers to ethyl (–CH2CH3), “C3alkyl” refers to propyl (–CH2CH2CH3) and “C4alkyl” refers to butyl (e.g. – CH2CH2CH2CH3, –(CH3)CHCH2CH3, –CH2CH(CH3)2, etc.). As used herein, and unless otherwise specified, the term “alkylene” refers to a divalent alkyl moiety containing 1 to 12 carbon atoms (i.e. C1–C12 alkylene) in length and meaning the alkylene moiety is attached to the rest of the molecule at both ends of the alkyl unit. For example, alkylenesinclude, but are not limited to, –CH2–, –CH2CH2–, -CH(CH3)CH2–, –CH2CH2CH2–, etc. The alkylene group may be linear or

[0068] The cross-linkers described herein generally correspond to copolymerizing cross-linkers. In this discussion, some types of cross-linkers may include more than one component. For example, divinylbenzene is one potential cross-linker that can be used. Divinylbenzene often contains some amount of ethylvinylbenzene. Divinylbenzene may also exist as a mixture of different isomers, for example, as a mixture of meta- and para- divinylbenzene. Any vinyl-aromatic structure, of the types described above, that bears two or more independently polymerizable vinyl groups, and that can be copolymerized with a main amine-group-containing vinyl-aromatic monomer, may be used as a cross- linker. The cross-linkers themselves may also bear amino-containing substituents of the various types described above, and or additional groups designed to provide separate functionality useful for sorbents in carbon capture processes.

[0069] In some aspects, additional monomers that are not cross-linkers and that also do not have an amino-containing substituent may also be included, such as the ethylvinylbenzene that is often present in divinylbenzene. In such aspects, the resulting cross-linked polymer can contain 0.1 mol% to 30 mol% of repeat units based on monomers that are not cross-linkers and do not have an amino-containing substituent, or 0.1 mol% to 20 mol%, or 0.1 mol% to 10 mol%, or 2.0 mol% to 30 mol%, or 2.0 mol% to 20 mol%, or 2.0 mol% to 10 mol%.

[0070] In this discussion, Brunauer-Emmett-Teller (BET) surface area and pore volume are determined by nitrogen isotherm using an Anton Paar iQ2 Autosorb at 77 K. Samples were pre-treated under vacuum as described in individual Examples followed by N2 backfill. Tolerance was set to 3 and equilibrium time was set to 3 min (tolerances (P / Po) for these experiments are set between 0 and 9, with level 0 representing + / - 0.001 atm and level 9 representing + / - 0.01 atm). Calculations were made using points collected in the range of 0.05 – 0.3 P / Po. Pore volume calculations were made using points collected at 0.95 P / Po. For the purpose of reporting micropore surface areas calculated by BET, micropores are considered to be pores having diameters of less than 2 nm.

[0071] CO2equilibrium (isotherm) sorption data was taken on an AS-1 Autosorb. Sample temperature was regulated using an external circulator bath. Samples were pre-treated under vacuum as described in individual Examples followed by N2backfill. Tolerance was set to 0 and equilibrium was set to 10 min. In most cases, material used for BET analysis was reused for isotherm data.

[0072] Scanning electron microscopy (SEM) images were taken with a Hitachi S4800 Cold Field Emissions High Resolution SEM. All samples were added to ~2 mL ethanol, then transferred to an aluminum stub and allowed to dry at 50 °C prior to analysis.

[0073] Dry 1 atmosphere, pressure / temperature swing CO2 multi-cycle thermogravimetric sorption experiments were conducted using a Toledo model TGA / DSC1. Adsorption was calculated from dry sample weight after pretreatment, using first cycle data. After initial pre-treatment at the conditions described in individual Examples under a 100 cc / min N2flow, the sample was cooled to 30 or 35 °C as noted in individual Examples at a rate of 20 °C / min under the same N2 flow, then held isothermal for 30 min. Then dry CO2(100%) was passed over the sample at the same flow rate for 30 min. The sample was subsequently heated to 120 °C at a rate of 20 °C / min under N2 and held for 20 min for desorption. This cycle was repeated three or six times.

[0074] Dry 4% CO2, isobaric temperature swing CO2 multi-cycle thermogravimetric sorption experiments were conducted in a similar manner. For 45 °C sorption, the sample was first held at 25 °C for 15 min. under a N2 flow of 100 cc / min and then heated to 90 °C under identical flow at a rate of 4 °C / min. It was then held at 90 °C for 3 hours (same flow) and cooled to 45 °C at a rate of 1 °C / min. and held for 30 min. The sample was subsequently treated with 100 cc / min dry 4% CO2 in N2 at 45 °C for 4 h for sorption, followed by heating back to 90 °C at a rate of 1 °C / min (under the same flow of dry 4% CO2). It was then held at 90 °C for 2 h (under the same flow of dry 4% CO2).

[0075] For 1 atm dry CO2isobaric thermal swing room temperature (21 - 25 °C) sorption, the sample was first held at 21, or 25 °C (“room temperature”; which varies and is determined by the ambient conditions and thermostatting of the instrument) for 15 min under N2 then heated to 90 °C at a rate of 4 °C / min. It was then held at 90 °C for 2 hours and cooled back to 21, or 25 °C at a rate of 1 °C / min. and held for 30 min. The sample was subsequently treated with dry 100% CO2 at 21 or 25 °C for 4 h for sorption, followed by heating back to 90 °C at a rate of 1 °C / min, then held at 90 °C for 1 h. Similar experiments were conducted replacing 90 °C steps with identical steps at 110 or 120 °C.

[0076] Humid 4% and 400 wppm CO2sorption experiments were conducted using a Mettler Toledo TGADSC3 analyzer with a MHG ProHumid 100 humidifier. Approximately 7-30 mg of sample was loaded into a 150 uL alumina sample holder. The sample was heated to the pre-treat temperature specified in individual Examples at a rate of 5 or 10 °C / minute under a flow of 100 cc / min N2and then held under the same gas flow for the specified pre-treat period. It was then cooled under the same gas flow to the analysis temperature (45 °C) and held for 30 minutes to stabilize weight prior to adsorption. Subsequently, a flow gas of N2 containing 30% relative humidity was introduced for a 240 min. period at 100 cc / min. The flow gas was then switched to 4% CO2 in N2 with 30% relative humidity at 100 cc / min for 480 min. The humidifier was subsequently set to 0% relative humidity and gas flow (4% CO2 in N2) was continued for 120 min. H2O uptake was calculated by weight change between the start and end of introduction of water as 30% relative humidity in N2. CO2 uptake was calculated as the weight change between the introduction of the water and the end of the dry CO2 desorption step. Humid 400 ppm CO2 sorption experiments were conducted similarly, except that 60% relative humidity was used, sorption was performed at 25 °C, and the CO2-containing gas had a CO2 concentration of 400 ppm.

[0077] Dry 400 ppm CO2uptake (Dry) Direct Air Capture evaluations were performed similarly by TGA at 18°C at roughly 400 wppm CO2. Samples were pre- treated by heating to 120°C at 15°C / min under a 50 cc / min N2flow followed by an isothermal hold at 120°C for 5 hours. Subsequently, samples were cooled at 1°C / min to 21°C and held under CO2 for an 8 hour sorption period. Temperature was then ramped to 120°C at 1°C / min under 50 cc / min N2containing roughly 400 vppm CO2and held for 2 hours at this temperature for isobaric desorption. Weights were adjusted to post- pretreatment sample weights.

[0078] Water isotherm measurements were taken using a Mettler Toledo TGADSC3 instrument. Samples were pre-treated prior to isotherm measurements at 90 °C for 6 hours under a flow of 100cc / min dry N2. It was then cooled to 25 °C under the same flow rate at a rate of 5 °C / min. Subsequently, a flow of N2containing 5% relative humidity was introduced at a rate of 100 cc / min. This flow was held for 240 minutes and water uptake was recorded. Subsequently the relative humidity in the flowing N2was increased to 10% and this flow was held for another 240 min. These steps were repeated(at 25 °C) for 20%, 30%, 40%, 50%, 60%, 70%, and 80% relative humidity. Finally, dry N2 (0% RH) was introduced at the and same flow rate for a period of 180 minutes to affect desorption. Capacities at each relative humidity were calculated as cumulative water uptakes, using sample weight after pre-treat as a baseline. Synthesis Conditions

[0079] In various aspects, a variety of conditions can be suitable for synthesizing cross-linked polymers from vinylbenzene monomers that include an amino-containing substituent on the benzene ring. The synthesis conditions can include conditions for protecting at least a portion of the amino-containing substituent with CO2, conditions for performing the polymerization, and conditions for removing at least a portion of the CO2 from the resulting cross-linked polymer.

[0080] For the initial step of protecting the amino-containing substituent with CO2, any convenient conditions for reacting CO2 with the amino-containing substituent without otherwise modifying the amino-containing substituent can be used. One option is to bubble CO2 through a solution containing the amino-containing substituent, such as a solution of the amino-containing substituent in an organic solvent. Non-limiting examples of suitable organic solvents include dimethylsulfoxide, toluene, 1,2- dichloroethane, and mixtures thereof. Other organic solvents, particularly those of a highly polar nature that provide good stabilization and solubilization of the amine-CO2 products, are suitable, as are mixtures of two or more solvents.

[0081] In some aspects, the amount of amino-containing substituents that are protected by the CO2 can correspond to the substantial majority of the amino-containing substituents, such as up to substantially all of the amino-containing substituents. In such aspects, 60 mol% or more of the amino-containing substituents can react with CO2 to form a reaction product, or 70 mol% or more, or 80 mol% or more, such as up to quantitative reaction (i.e., up to 100 mol%). In the case of formation of a 60 mol% product, a product present in this form as pure ammonium carbamate (or the corresponding analogue) would contain 30% of the amines as the ammonium cation portion of the carbamate ion pair, and 30% as the carbamate anion portion of the pair. A 60 mol% product could alternatively contain a mixture of carbamic acid and carbamate groups, for example, 20 mol% of the amines present as carbamic acid type products, 20 mol% present as the ammonium cation portion of the carbamate ion pair, and 20% as thecarbamate anion portion of the pair. The amino-containing substituent is protected by being converted from an amino- substituent to an ammonium carbamate, a carbamic acid, or possibly a mixture of carbamate ion pairs and carbamic acids in a given sample of monomers containing an amino-containing substituent.

[0082] In other aspects, the amount of amino-containing substituents that are protected by CO2 may be lower. Depending on the aspect, the amount of amino- containing substituents protected by CO2can be 6.0 mol% to 100 mol%, or 6.0 mol% to 80 mol%, or 6.0 mol% to 60 mol%, or 6.0 mol% to 40 mol%, or 6.0 mol% to 30 mol%, or 6.0 mol% to 15%, or 10 mol% to 100 mol%, or 10 mol% to 80 mol%, or 10 mol% to 60 mol%, or 10 mol% to 40 mol%, or 15 mol% to 100 mol%, or 15 mol% to 80 mol%, or 15 mol% to 60 mol%, or 15 mol% to 40 mol%, or 30 mol% to 100 mol%, or 30 mol% to 80 mol%, or 30 mol% to 60 mol%. Any amount of reaction with CO2that effects a change in texture and sorption performance of the resultant product polymer, as compared to those observed for a material prepared in the absence of CO2protection, is considered sufficient to constitute protection. Furthermore, if water is present, some portion of the CO2-reacted amino-containing substituents may be present as ammonium (or guanidinium, or other analogous) groups in ammonium bicarbonate ion pairs. In some aspects, after exposing the amine-containing substituents to CO2to form protected amino-containing substituents, less than 10 mol% of the protected amino-containing substituents correspond to ammonium bicarbonate ion pairs, such as down to having no bicarbonate ion pairs within detection limit. It is noted that the quantity of bicarbonate ion pairs present may be determined by known techniques in the art, such as performing13C NMR (nuclear magnetic resonance) spectroscopy under conditions that mimic those of polymerization (for example, at a temperature similar to the temperature of polymerization, under an atmosphere of CO2).

[0083] After protecting the amino-containing substituents, the protected monomers can be exposed to polymer synthesis conditions to form a cross-linked polymer. This can include mixing the monomers with a cross-linking agent and an initiator in a suitable solvent. CO2is also introduced into the polymerization solution during the reaction, to assist with maintaining the protected state of the amino-containing substituents. The CO2 can be introduced at atmospheric pressure (1 atm absolute pressure), or, using anappropriate pressure vessel configuration, at pressures exceeding atmospheric pressure (> 1 atm absolute pressure).

[0084] The polymerization solution can be characterized based on the molar amounts of amino-functionalized monomer (vinyl aromatic with amino-containing substituent), cross-linker, and any other polymerizing components (such as non-amino-functionalized termonomers) present in the polymerization solution. Without being bound by any particular theory, this is believed to result in a cross-linked polymer having roughly comparable molar amounts of amino-functionalized monomer, cross-linker, and other polymerizing components to those present in the polymerization solution. In various aspects, the molar quantity of amino-functionalized monomer in the polymerization solution, relative to the total moles of monomer, cross-linker and other polymerizing components, can be 65 mol% or more, or 70 mol% or more, or 80 mol% or more, or 90 mol% or more, such as up to 97 mol%. For example, the molar quantity of amino- functionalized monomer, relative to the total moles of monomer, cross-linker, and other polymerizing components, can be 65 mol% to 97 mol%, or 65 mol% to 90 mol%, or 80 mol% to 97 mol%. Additionally or alternately, the molar amount of cross-linker in the polymerization solution, relative to the combined total moles of amino-functionalized monomer, cross-linker, and other polymerizing components, can be 3.0 mol% to 35 mol%, or 3.0 mol% to 30 mol%, or 3.0 mol% to 20 mol%, or 3.0 mol% to 10 mol%, or 10 mol% to 35 mol%, or 10 mol% to 30 mol%, or 20 mol% to 35 mol%. Further additionally or alternately, the molar ratio of all polymerizing monomers and crosslinkers to initiator in the polymerization solution (presuming that the initiator molecule provides two initiating fragments but counting the entire initiator molecule as one molar unit) can be from 5.0 to 100 (i.e., between 5.0 : 1 and 100 : 1), or from 5.0 to 40, or from 5.0 to 15, or from 8.0 to 100, or from 8.0 to 40, or from 8.0 to 15, or from 10 to 100, or from 10 to 40, or from 10 to 15.

[0085] A cross-linked polymer made from such a polymerization solution can have comparable molar amounts of amino-functionalized monomer, cross-linker, and other polymerizing components to the amounts in the polymerization solution. Thus, the resulting cross-linked polymer can have a molar amount of amino-functionalized monomer of 65 mol% or more, or 70 mol% or more, or 80 mol% or more, or 90 mol% or more, such as up to 97 mol%. For example, the molar quantity of amino-functionalizedmonomer in the cross-linked polymer can be 65 mol% to 97 mol%, or 65 mol% to 90 mol%, or 80 mol% to 97 mol%. or alternately, the resulting cross-linked polymer can have a molar amount of cross-linker of 3.0 mol% to 35 mol%, or 3.0 mol% to 30 mol%, or 3.0 mol% to 20 mol%, or 3.0 mol% to 10 mol%, or 10 mol% to 35 mol%, or 10 mol% to 30 mol%, or 20 mol% to 35 mol%.

[0086] During polymer synthesis, the synthesis solution can be stirred. The temperature during polymerization can be between 50°C and 120°C, or between 50°C and 100°C, or between 70°C and 120°C, or between 70°C and 100°C. Preferably, the temperature during polymerization is lower than the boiling point of the solvent (or the combination of solvents) used as the reaction medium for performing the polymerization. The length of time for forming the cross-linked polymer can range from 10 hours to 100 hours, or possibly longer.

[0087] In some aspects, a plurality of types of vinyl-aromatic monomers having amino-containing substituents can be present in the synthesis mixture, in order to form a polymer with a plurality of types of repeat units having amino-containing substituents. In such aspects where at least two types of vinyl-aromatic monomers having amino- containing substituents are present, a molar ratio between a first vinyl aromatic monomer and a second vinyl aromatic monomer can range from 5 : 95 to 95 : 5, or from 10 : 90 to 90 : 10, or from 25 : 75 to 75 : 25.

[0088] Additionally or alternately, in some aspects a plurality of types of vinyl- aromatic monomers can be present in the synthesis mixture, with at least a first type including an amino-containing substituent, and at least a second type not including an amino-containing substituent. In such aspects, a molar ratio of the first monomer type to the second monomer type can range from 1 : 1 to 1000 : 1, or 1 : 1 to 100 : 1. Additionally or alternately, the amount of the second vinyl-aromatic monomer type (without the amino-containing substituent) can be characterized relative to the amount of co-polymerizing cross-linker in the synthesis mixture. In such aspects, a molar ratio of the co-polymerizing cross-linker to the second vinyl-aromatic monomer type can range from 1 : 20 to 50 : 1, or 1 : 10 to 50 : 1, or 1 : 20 to 20 : 1, or 1 : 10 to 20 : 1.

[0089] After forming the cross-linked polymer, at least a portion of the CO2can be removed, thus converting the protected amino-containing substituents back into theiroriginal reactive form prior to the addition of the CO2.This can be performed in any convenient manner. For forming the cross-linked polymer, the solution that the cross-linked polymer was formed in can be sparged with N2or another convenient gas to remove the CO2, or treated with vacuum with or without the addition of heat.

[0090] The resulting cross-linked polymer can have a variety of properties. The BET surface area of the polymer can be 5.0 m2 / g to 90 m2 / g, or 5.0 m2 / g to 70 m2 / g, or 10 m2 / g to 90 m2 / g, or 10 m2 / g to 70 m2 / g. The pore volume can range from 0.002 cm3 / g to 0.2 cm3 / g, or 0.01 cm3 / g to 0.2 cm3 / g. The average pore diameter can range from 2.0 to 10 nm. Use of Materials for CO2 Sorption

[0091] One application for the cross-linked polymers described herein is for sorption of components from a gas phase flow. As an example, the cross-linked polymer can be used for selective adsorption of CO2from a gas flow.

[0092] A variety of different types of CO2-containing gases can be used as an input flow for a CO2adsorption process. For direct air capture, where air is the input flow gas, a typical CO2 concentration in air is roughly 400 vppm. More generally, for direct air capture, the CO2content of the input flow can be from 300 vppm to 500 vppm. Another typical source of CO2-containing gas are flue gases from combustion reactions, such as power plants, boilers, furnaces, turbines, or any other type equipment that uses hydrocarbon combustion to generate heat. When the hydrocarbon for the combustion reaction is natural gas, the CO2 content of the resulting flue gas is typically in the range of 3.0 vol% to 6.0 vol%, or 3.5 vol% to 5.0 vol%. For combustion reactions involving other types of fuels, such as coal, still higher CO2 contents can be present in the flue gas.

[0093] A CO2-containing gas flow can be used as the input flow for an adsorption process, where the adsorbent is a cross-linked polymer as described herein. During adsorption, the CO2-containing gas can be exposed to the cross-linked polymer in an adsorption environment where the temperature is from 0°C to 100°C, or 0°C to 50°C, or 0°C to 30°C, or 15°C to 100°C, or 15°C to 50°C, or 15°C to 30°C. It is noted that during direct air capture, it is often a goal to perform CO2 adsorption while modifying the input gas flow as little as possible prior to adsorption, in order to minimize energy costs duringthe direct air capture process. Thus, in some aspects, the temperature during direct air capture is 0°C to 50°C, or 0°C to 30°C, to 50°C, or 15°C to 30°C.

[0094] After sorption of CO2, the adsorbed CO2can be at least partially desorbed to regenerate the adsorbent to allow for a cyclic process. One option for doing this is to increase the temperature in the sorbent environment. For example, in a direct air capture process, desorption can occur by sufficiently increasing the temperature while still exposing the sorbent to air, or alternatively, exposing the sorbent to another non-CO2- containing gas flow. Desorption can be performed at a temperature of 50°C to 180°C, or 50°C to 100°C, or 90°C to 150°C. EXAMPLES Properties of Material Made by Conventional Methods (Comparative)

[0095] Commercially available cross-linked poly(vinylbenzylamine- divinylbenzene) materials are known. For example, such cross-linked polymers are available commercially from LANXESS® Corporation in the Lewatit® product line. Table 1 shows examples of properties that have been reported for Lewatit® VP OC 1065 PVBA-DVB Resin. Table 1 – Properties of Commercially Available PVBA-DVB Resin Bead size 0.3-1.25 mm Water retention as 47-55% shipped N2on N2Average pore 25 nm Maximum theoretical ca.6.7 mmol / g diameter N for r link r nt nt)noted under conditions where the CO2 concentration was at least 4.0 vol% at a temperature of 30°C. Under ambient (non-process) conditions, a reported CO2 uptake value for commercially available poly(vinylbenzylamine-divinylbenzene) is roughly 1.0 mmol / g. Examples 1A – 1F and Comparative Examples C1A – C1D: Synthesis of PVBA-DVB Sorbents by Direct Copolymerization using CO2Textural Modification.

[0097] Vinylbenzylamine (VBA) as a monomer and divinylbenzene (DVB) as a cross-linking agent were used to form a series of poly(vinylbenzylamine-divinylbenzene) cross-linked polymer compositions as shown in Table 2. AIBN (2,2’-azobis(2- methylpropionitrile)) was also included in the synthesis mixture as an initiator. These compositions can be referred to as PVBA-DVB. It is noted that some ethylvinylbenzene (EVB) was also present in the synthesis mixture due to inclusion as part of the DVB reagent. Table 2 - PVBA-DVB Samples Sample Molar Ratio Elem. BET Surf. Area Avg. Pore Dia. VBA:DVB:EVB; Analysis (m2 / g) (nm) f.1D 73:22:5 10.6 6.2

[0098] In Table 2, the first column identifies the sample. The second column provides the molar ratio of VBA to DVB to EVB. The second column also provides the number-average molecular weight between crosslinks. The remaining columns in Table 2 are discussed below and in Example 2.

[0099] In Table 2, the number average molecular weight between crosslinks, or Mnb / w Crosslinks, is defined by formula I. It is noted that formula I does not account for initiator residues.

[0100] (I) Mn b / w Crosslinks = (molar VBA:DVB ratio)(MW of VBA) + (molar EVB:DVB ratio)(MW of EVB) + (0.5)(MW of DVB).

[0101] The general conditions for the polymer synthesis included a temperature of 90 °C, and a reaction time of 48 hours to 72 hours. VBA monomer pre-treated with CO2was polymerized using AIBN (azobisisobutyronitrile) initiator under an atmosphere of CO2with different amounts of divinylbenzene (DVB) cross-linker (examples 1A-D). Depending on the Example, the divinylbenzene cross-linker used corresponded to one of two samples, with both samples being similar in composition. Some examples used a DVB that contained 18.9% of ethylvinylbenzene (EVB). The DVB was present as a 2.1:1meta:para mixture and the EVB was present as a 1.3:1 meta:para mixture. Alternatively, the DVB used had 80.6% purity (57% 24% para isomer mixture), and contained 17.9% EVB and 0.05% diethylbenzene. The synthesis mixtures included a molar ratio of VBA monomer to molecular AIBN of roughly 10-14:1. Molar ratios of monomer to crosslinker given in the Examples and Tables are feed ratios, are rounded to units of 5, and represent the nominal DVB loading without consideration of ethylvinylbenzene (for example, a sample noted as “80:20 VBA:DVB” was prepared using 80 parts VBA and 20 parts DVB on a molar basis, with the 20 parts DVB providing ~16 parts DVB and ~4 parts ethylbenzene); if desired, pure DVB (lacking ethylvinylbenzene) could be substituted; and / or DVB that is a single isomer rather than an isomeric mixture. Each mole of AIBN generates two moles of free radical initiating groups. The initial total molar concentration of the monomers (VBA, DVB, and EVB) in the solution was between 0.3 – 0.6 M. The solvent was dimethyl sulfoxide (DMSO). Examples 1E and 1F were formed from synthesis mixtures that are similar to Example 1C, to demonstrate the scalability of the direct copolymerization process.

[0102] The synthesis of Samples 1A, 1B, 1C, 1D, 1E, 1F, C1A, and C1B was performed as follows:

[0103] Example 1A. 95:5 PVBA-DVB sorbent. In the glove box, a 100 mL three- necked bottomed flask was loaded with a mixture of 1.33 g VBA (9.99 mmol), 0.065 g 81% purity DVB (0.40 mmol DVB and 0.09 mmol EVB), 25 mL anhydrous, reagent grade dimethylsulfoxide (DMSO), and a stirbar. The DVB and VBA were passed through Scientific Polymer Products SDHR-4 inhibitor removal column resin in the drybox prior to use to remove inhibitors (1000 ppm t-butylcatechol and an unspecified amount of MEHQ (4-methoxyphenol), respectively). Separately, an 0.165 g portion of AIBN (2,2’- azobis(2-methylpropionitrile), 1.0 mmol) was weighed into a small vial with a stirbar and dissolved in 5 mL DMSO. The vial and flask were each sealed with septa and removed from the drybox. The monomer solution was degassed with inert gas sparging through the liquid (using a needle) while stirring for 1 hour, then heated to 80°C in an oil bath. CO2(AirGas 5.0 grade, approximate flow rate 110 bubbles / min through a 1 / 32” diameter orifice) was bubbled through the stirred solution for 30 min. The AIBN solution (degassed with inert gas sparging for 0.5 h) was added to the monomer solution by syringe. The polymerization solution was stirred at 90°C for 48 h continuing the CO2sparge under dynamic CO2flow. A white precipitate was formed. The reaction flask was subsequently cooled to room which the CO2 sparge was changed to a N2sparge. The solution was sparged for 30 minutes to desorb the CO2from the product polymer. A 75 mL portion of isopropanol was added to the polymerization flask. The slurry was stirred for 1 h and the white solid polymer was collected, washed with an additional 25 mL isopropanol, and dried at 60 °C for 60 h in a vacuum oven (~1.2 g, 86%). Only a very small amount of additional material was obtained by evaporation of the mother liquor indicating excellent conversion.

[0104] Example 1B. 90:10 PVBA-DVB sorbent. Similar to Example 1A, with the following reagent amounts: 1.33 g (9.99 mmol) VBA, 0.163 g DVB / EVB (1.01 mmol DVB / 0.23 mmol EVB) / 30 mL DMSO, 0.165 g (1.0 mmol) AIBN / 5 mL DMSO; pale yellow product (~1.2 g, 80%).

[0105] Example 1C.80:20 PVBA-DVB sorbent. Similar to Example 1A, with the following reagent amounts: 1.33 g (9.99 mmol) VBA, 0.325 g DVB / EVB (2.02 mmol DVB / 0.47 mmol EVB) / 30 mL DMSO, 0.165 g (1.0 mmol) AIBN / 5 mL DMSO; white product after 72 h (1.26 g, 76%) insoluble in toluene, DMSO, dimethylformamide, N- methyl-2-pyrrolidone, ethanol, and 1:1 ethanol:water.

[0106] Example 1D.70:30 PVBA-DVB sorbent. Similar to Example 1A, with the following reagent amounts: 1.33 g (9.99 mmol) VBA, 0.488 g DVB / EVB (3.03 mmol DVB / 0.70 mmol EVB) / 30 mL DMSO, 0.165 g (1.0 mmol) AIBN / 5 mL DMSO; white product (1.4 g, 77%).

[0107] Example 1E. 80:20 PVBA-DVB sorbent, 2X scaleup: Similar to Example 1A, with the following reagent amounts: 2.66 g (19.97 mmol) VBA and 0.650 g DVB (4.044 mmol DVB, 0.929 mmol EVB) in 60 mL DMSO, and 0.165 g (1.00 mmol) AIBN / 10 mL DMSO; 90 °C, 24 h. An off white precipitate was formed. Isopropanol (150 mL) was added and the resultant slurry stirred for 2 hours prior to re-filtration. The collected pale-yellow solids were dried at 60 °C in a vacuum oven for 18 h (2 g, 60%, theo. yield 3.31 g). It is noted that in Table 2, the resulting BET surface area of this sample was slightly lower than the surface area of Example 1A, but the pore volume was similar to Example 1A.

[0108] Example 1F. 80:20 PVBA-DVB sorbent, 5x scaleup: Similar to Example 1A, with the following reagent amounts: 5.32 g (39.94 mmol) VBA and 1.34 g DVB(8.34 mmol DVB, 1.92 mmol EVB) in 75 mL DMSO), and 0.656 g (4.00 mmol) AIBN / 20 mL DMSO; 90 °C, 72 h. white precipitate was formed. Isopropanol (150 mL) was added and the resultant slurry stirred for 2 hours prior to re-filtration. The collected solids were then stirred in refluxing ethanol for 4 h, recollected, and dried under vacuum at 60 °C in a vacuum oven for 60 h (4.8 g, 72%, theo. yield 6.66 g).

[0109] Comparative Example C1A. 99:1 PVBA-DVB sorbent. Similar to Example 1A, with the following reagent amounts: 1.33 g (9.99 mmol) VBA, 0.016 g DVB / EVB (0.10 mmol DVB / 0.023 mmol EVB) / 10 mL DMSO, 0.164 g (1.0 mmol) AIBN / 5 mL DMSO; pale yellow polymer after 72 h (0.64 g, 48%). Comparative Example C1A exemplifies a material containing insufficient cross-linker to provide a robust bulk structure. Generally, the C1A material was qualitatively different from the other materials. For example, as described below, the C1A material had a glass transition in its second DSC heat, while the other materials synthesized with greater amounts of cross-linker did not. It is further noted that sample C1A (1% cross-linker) showed partial solubility in N-methyl-2-pyrrolidone containing 0.1 M LiCl at 80 °C and was obtained in much lower yield than samples 1A-D.

[0110] Comparative Example C1B. 80:20 non-CO2-prepared PVBA-DVB sorbent. Similar to Example 1A, but the initial bubbling of CO2into the stirred solution was not performed, and no sparging with CO2 was performed during synthesis. The polymerization was conducted under nitrogen. The following reagent amounts were used: 1.33 g (9.99 mmol) VBA, 0.325 g DVB / EVB (2.02 mmol DVB / 0.47 mmol EVB) / 30 mL DMSO, 0.164 g (1.0 mmol) AIBN / 5 mL DMSO; white product after 72 h (1.04 g, 63%). It is noted that performing this synthesis without having CO2protective groups resulted in both substantially lower BET surface area and substantially reduced pore volume.

[0111] As additional comparative examples, properties of two additional commercial vinylbenzylamine-divinylbenzene comparative copolymer resins, obtained from BOC Sciences (C1C) and BA Chem (C1D), are shown in Table 3. It is believed that these resins were synthesized using post-polymerization functionalization routes starting with a cross-linked styrene-divinylbenzene resin, similar to those shown in FIG.1.Table 3 - Chemical and Textural Properties of Additional Commercial PVBA- DVB Resins BET Surface Area Avg. Pore (m2 / g) Diameter (nm) P V l Mi f

[0112] For the samples shown in Table 3, before characterization, Sample C1C was dried overnight at 60-65°C in a vacuum oven. This caused the sample to lose 1.4 wt%. For Sample C1D, the sample was dried for 8 days at 60-65°C in a vacuum oven. This caused the sample to lose 4 wt%.

[0113] As shown in Table 3, comparing samples C1C and C1D to each other, the C1C sample had a larger particle size and a higher amine content. The C1D sample had a higher surface area and pore volume, along with larger average pore diameter. It is noted that the PVBA-DVB resin shown in Table 1 has higher BET surface area, higher pore volume, and larger pore diameter than the materials shown in Table 3. The available nitrogen content of the material in Table 1 as determined by titration is also substantially higher than the nitrogen content of the materials in Table 3. Example 2: Properties of Cross-Linked Polymer Compositions in Examples 1A – 1F

[0114] Tables 2 and 3 also show characterization details for the cross-linked polymer compositions corresponding to Examples 1A – 1F and Comparative Examples C1A – C1D.

[0115] In Table 2, the third column provides millimoles of nitrogen per gram of sorbent, as determined by analysis after drying for 2 h under vacuum at 150 °C followed by inert atmosphere handling. Thes values represent total nitrogen present, rather than nitrogen accessible to titrimetric reagents. The weight per cent of nitrogen (%N) is also provided. Both an “observed” value and a “theoretical” value (in parentheses) are provided for the weight per cent nitrogen. The “observed” value for the weight per cent nitrogen is based on elemental analysis for the materials. The “theoretical” value, shown in parentheses, is calculated based on the composition of the synthesis mixture used for forming the polymer, although nitrogen due to initiator residues is not considered in the theoretical calculation. The lowered %N observed by elemental analysis could suggest that these samples were not adequately dried before sampling and / or did not fully combust. It is noted that total CHN was 92-96% of the sample. Alternatively, the lowered %N may reflect differences in the true polymer molar composition as compared to the mixture of monomers and crosslinkers added, due to selective removal of one polymerizing component during inhibitor removal, or differences in relative reactivity.

[0116] In Table 2, the fourth column provides the BET surface area and the total pore volume, while the fifth column provides average pore diameter and micropore volume. These values were determined based on BET N2 isotherms as previously described. In Table 3, these values are shown in columns 3 and 4.

[0117] In addition to the characterization data given in Table 2, Attenuated Total Reflectance Infrared (ATR-IR) and solid state13C NMR (SS-NMR) spectra for sample 1C (80:20 VBA:DVB) are shown in FIG.6. SS-NMR was taken on a Bruker Avance NEO 600 MHz spectrometer using an hpdec pulse program (2000 scans, 30 sec recycle delay). ATR-IR was taken using a Bruker Alpha II spectrometer.

[0118] Qualitatively, Examples 1A – 1D in Table 2 are comparable in properties to the commercial material shown in Table 1, but there are some differences. The DVB content of Examples 1A – 1D in Table 2 ranges from roughly 4.0 mol% to roughly 22 mol%. The commercial material in Table 1 is reported to have a DVB content between 8 – 10%. This is similar to sample 1B. Additionally, the BET surface area, pore volume, and average pore size of the material in Table 1 is somewhat higher than the examples in Table 2. It is noted that Example 1C has a higher BET surface area than the materialin Table 1. However, the 2x scale up Example 1E has a BET surface area that is more similar to the BET surface areas seen 1A, 1B, and 1D. Generally, the data in Table 2 show that the materials of Examples 1A – 1D are comparable to the material in Table 1, and would be expected to have comparable performance to the material in Table 1, even though the Examples 1A – 1D were made by a simpler and more flexible synthesis method.

[0119] In addition to the above, SEM (scanning electron microscopy) images of the materials generated in Examples 1A – 1E and Comparative Examples C1B, C1C, and C1D were obtained. Generally, Examples 1A – 1E show finely dispersed SEM morphologies of discrete particles, while the Comparative Examples showed larger particle sizes and / or a less discrete, larger mass of particles. It is noted that for Comparative Examples C2A and C2B, the particle sizes were on the order of tens of microns. FIG. 7 shows SEM images for the inventive material 1C and comparative materials C1B and C1D. Relative to Comparative Example C1B (no CO2protective group), Examples 1A – 1E had larger pore diameters (4.8-7.8 vs. <4.3 nm) and greater pore volumes (0.012-0.128 vs. <0.089 cc / g). Examples 1A – 1E generally had much smaller pores than Lewatit®VP OC 1065 (25 nm average pore diameter). Both Example 1C and Comparative Example C1B correspond to using a synthesis mixture with an 80 : 20 ratio of vinylbenzylamine monomer to divinylbenzene cross-linker. Thus, the primary difference between Example 1C and Comparative Example C1B is the presence or absence of CO2 as a protective agent during polymer synthesis. As shown in FIG.7, the cross-linked polymer formed with a CO2 protective group qualitatively has a superior texture and surface area than the cross-linked polymer where CO2was not used to protect the amino-containing substituents during polymer synthesis.

[0120] Table 4 provides thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) profiles for the inventive and comparative resins. The thermogravimetric analysis was conducted using a Mettler Toledo Model ED-DSC1 TGA or a Mettler Toledo TGADSC1. All samples except for Examples C1C and C1D were heated in 50 cc / min N2from 30-800°C at 4°C / min and held at 800°C for 30 min. The materials of Examples C1C and C1D were heated from 30 to 600°C at 10 °C / min under 50 cc / min flow of N2, and then held at 600°C for 1 h. The initial drying loss (wt%) corresponds to the loss from room temperature to onset of minordecomposition. This loss is attributed to drying. For the % loss from onset of minor decomposition to onset of major the weight at onset of minor decomposition considered as 100% of the sample weight. DSC analysis was performed using a TA Instruments Discovery DSC with RCS 90 intercooler. The samples were run in Tzero aluminum pans. The samples were held at 40°C for 3 min; heated to 200°C at 10°C / min and held for 3 min; cooled to 0°C at 10°C / min; and re-heated to 200°C at 10°C / min. Glass transitions were calculated as midpoints of the re-heat (second heat) cycle. All samples showed a first heat exotherm (peak 85-110°C) attributed to water vaporization. Table 4. Chemical and Thermal Properties of PVBA-DVB Sorbents Sample TGA Decomposition Profile Under N2, TGA CO2 Sorption DSC RT-800 or 600 °C Pre-Treat, 140 °C s. s. s. s.not taken not taken not taken 104 C1A s.

[0121] TGA decomposition profiling from room temperature to 800 C (Table 4 col. 2-3) indicated that all materials characteristically showed an initial small mass loss (<8%) attributed to drying, followed by maintaining of stability to >230 °C. A minor decomposition onset was observed at 230-280°C, with major decomposition onsetting at > 390°C. Inventive sorbents 1A-D were slightly disadvantaged compared to the commercial sorbents regarding initial drying and minor decomposition onset (lower onset temperature and higher loss), but still showed sufficient stability for use in a thermal desorption process. Further stability information (col.4) was obtained by drying the materials in a TGA under N2at a constant 140°C as part of the 1 atm dry CO2sorption experiments; all samples had reached constant weight after a 5 hour period.

[0122] DSC analysis of materials 1A-D and C1A (Table 4, col.5) indicated absence of a second heat glass transition (Tg) for 1A-D. In contrast, C1A (prepared identically to 1A-D but with 1% rather than 5-30% cross-linker) showed a Tg at 104 °C. A linear sample of poly(vinylbenzylamine) homopolymer (not further described herein) showed a second heat Tg at 156 °C. The DSC results demonstrate the robust, glassy nature of the bulksorbents’ morphology for potential use at elevated temperature in a temperature swing process. Example 3. Confirmation of VBA-carbamate Formation Under Polymerization Conditions and Facile Desorption.

[0123] A 300 mg portion of de-inhibited VBA was dissolved in 3 mL DMSO-d6in a small round-bottomed flask. CO2 was bubbled through the stirred solution at 80°C for 20 min. No precipitate was observed. Subsequently, N2was bubbled through the solution for 20 min at 80°C. Solution13C NMR spectra were recorded after dissolution in the DMSO-d6 before protection with CO2 (FIG.8A); after protection with CO2 by bubbling CO2 through the solution at 80°C (FIG. 8B); and after the final N2 treatment at 80°C to remove CO2 (FIG.8C). Persistent formation of the VBA-CO2 complex is seen at δ = 159 ppm and VBA structural peaks split into two species (VBA-H+ / free VBA and VBA-CO2- carbamate / carbamic acid species). The VBA-CO2 complex is completely decomposed by the N2purge; the NMR spectrum of the solution after purge is identical to fresh VBA monomer. Example 4 – Dry CO2sorption properties of PVBA-DVB sorbents.

[0124] Table 5 summarizes dry CO2 sorption experiments conducted via Autosorb (100% and 4% CO2, 30 °C) and TGA (100% CO2, 35 °C, desorption at 120 °C under 100 cc / min N2). To generate the Autosorb data, samples were pre-treated at 140°C for 3-4 h. FIG.9 shows Autosorb data for CO2uptake with material 1D over a range of CO2partial pressures of 0 to 1 atm. To generate the TGA data, samples were pre-treated at 140°C for 3-5 h. Adsorption (uptake) in the third column was calculated from dry weight after pretreatment using first cycle. Table 5. Dry CO2 Sorption Properties of PVBA-DVB Sorbents Sample Autosorb 30°C CO2 TGA 35°C CO2 Normalized Autosorb 1 k k k l O290:10 PVBA-DVB 1.35 (0.96 @50 °C)

[0125] As shown in Table 5, in all cases, uptake for 1A – 1E was superior to that for comparatives C1B, C1C, and C1D. Sorbents 1B, 1D, and 1E showed 30 °C Autosorb uptakes at 1 atm CO2 of over 2 mmol CO2 / g, retaining high activity (~1.3-1.6 mmol CO2 / g) at 4% CO2. Values for the comparative materials C1B, C1C, and C1D at 1 atm and 4% CO2were, respectively, <0.65 and <0.2 mmol / g.

[0126] All samples exhibited good TGA desorption and multi-cycle capacity retention over multiple (3 or 6) thermal-pressure swing (PTSA) cycles. A direct comparison of uptake values for sorbents prepared with and without CO2 at a nominal20% cross-linker feed shows the inventive effects of the CO2textural modification strategy. CO2-Synthesis-assisted a ~3x capacity increase and superior kinetics at 1 atm CO2, and a > 10x capacity increase at 4% CO2, as compared to sample C1B. Sample C1B, in fact, showed no improvements over the two commercial resins tested in house (C1C and C1D). FIG.10 shows TGA CO2sorption curves for materials 1C and C1B corresponding to the data in Table 5, col.2. Sample 1C’s TGA sorption curve exhibits a much sharper (squarer) leading edge in its sorption profile than sample C1B, indicating fast adsorption kinetics. The analogous TGA curve for sample 1D (not shown) also showed a relatively sharp leading edge, although not quite as good as sample 1C. This sample (nominal ~30% cross-linker in feed) appears to provide a favorable balance of capacity and kinetics. Example 5 - Synthesis of additional primary benzylamine sorbents via direct VBA polymerization with CO2 textural modification.

[0127] Additional inventive sorbents were prepared using procedures similar to those for 1A-D having the compositions shown below in Table 6. These illustrate materials made with further comonomers, functionalized or variant cross-linkers (including an amino-functionalized cross-linker, bis(4-vinylbenzyl)amine, structure “L” in FIG. 5), and modification of the polymerization solvent (use of a mixed solvent with lower polarity, which alters the CO2 protection product balance between carbamic acid and ammonium carbamate species).. The samples were pre-treated under vacuum for BET analysis at 140 °C for 3.2 – 4.2 h and for Autosorb CO2 uptake analysis at 140 °C for 3 – 4 h.

[0128] The three-cycle TGA data reported in Col. 4 for 5E utilized a 120 °C, N2desorption step in a similar fashion to the thermal-pressure swing (PTSA) cycles similar to that discussed for the data in Table 5. The sample was pre-treated at 140 °C for 3 h and exhibited good kinetics, as evidenced by a relatively squarish shape of its sorption- desorption step weight change profile.

[0129] Example 5A. 80:20 PVBA-Divinylferrocene sorbent: Similar to Example 1A, with the following reagent amounts: 1.33 g (9.99 mmol) VBA and 0.476 g 1,1- divinylferrocene (2.00 mmol, unstabilized, not passed through inhibitor removal column) in 30 mL DMSO, and 0.165 g (1.0 mmol) AIBN in 10 mL DMSO; 90 °C, 48 h. A brick- red product was formed (0.3 g, 17%).

[0130] Example 5B.80:20 PVBA-Divinylbiphenyl sorbent: Similar to Example 1, with the following reagent amounts: mmol) VBA and 0.412 g 4,4’-divinyl- p-biphenyl (2.00 mmol, unstabilized, not passed through inhibitor removal column) in 30 mL DMSO, and 0.165 g AIBN in 5 mL DMSO; 90 °C, 48 h. A white product was formed (1.3 g, 75%).

[0131] Example 5C. 75:20:5 PVBA-DVB-styrene sorbent: Similar to Example 1A, with the following reagents: 1.3 g (9.99 mmol) VBA, 0.327 g DVB (81%, balance EVB, 2.03 mmol DVB, 0.47 mmol EVB), and 0.104 g styrene (1.00 mmol, stabilized, passed through inhibitor removal column) in 30 mL DMSO, and 0.165 g AIBN in 5 mL DMSO; 90 °C, 32 h. A white product was formed (1.5 g, 85%).

[0132] Example 5D. 80:20 PVBA-bis(4-vinylbenzyl)amine sorbent: Similar to Example 1A, with the following reagents: 1.33 g VBA (9.99 mmol) and 0.499 g bis(4- vinylbenzyl)amine (2.00 mmol, stabilized, passed through inhibitor removal column and a Teflon filter to remove insolubles prior to use) in 20 mL DMSO, and 0.165 g (1.0 mmol) AIBN in 5 mL DMSO; 90 °C, 68 h. A white product was formed (1.0 g, 55%).

[0133] Example 5E. 80:20 PVBA-DVB sorbent prepared in a reduced polarity solvent mixture: Similar to Example 1A, with the following reagents: 1.33 g (9.99 mmol) VBA and 0.325 g DVB (81%, balance EVB, 2.02 mmol DVB, 0.47 mmol EVB) in 30 mL of 4:1 toluene:DMSO, and 0.165 g (1.0 mmol) AIBN in 5 mL of 4:1 toluene:DMSO; 90 °C, 48 h. A white product was formed (1.1 g, 66%). Table 6. Additional Sorbent Compositions and Properties. Ex. Monomer Feed Composition BET Surf. Area (m2 / g), CO2 Uptake (mmol / g), (M l ) P r V l ( / )100% and 4% COat5B 83:17 PVBA-4,4’-divinyl- 17.9, 0.01, 2.7, 0 2.17, 0.53 biphenyl

[0003] CO2 pressures grea er an amb en can be emp oyed durng po ymer za on by carrying out polymerization in a pressure vessel. This will result in a higher loading of CO2 onto the monomer, and into the resultant polymer, during backbone formation and crosslinking, which may serve to further enhance sorbent texture and morphology.

[0135] Furthermore, the identity of the polymerization solvent may prove important for modulating textural properties. Polymerizations conducted with water present will have at least some of the VBA-CO2monomer complex present in an ammonium bicarbonate form (rather than as ammonium carbamate / carbamic acid). Substituting some or all of the DMSO solvent with a less polar polymerization solvent, or alternatively a protic solvent, will also change the nature of the VBA-CO2 monomer complex. For example, a less polar solvent will cause the monomer complex equilibrium to tend toward ammonium carbamate. This will likely affect the textural properties of the cross-linked materials obtained. Traditional porogens may also be added during polymerization to assist with textural modification. These include inert, soluble linear polymers such as poly(4-vinylpyrrolidone), available in a range of molecular weights, or polyethers and other commonly known porogens, which dissolve in the polymerization medium andmay be removed by extraction with alcohols or other solvents during workup of the insoluble, bulk cross-linked PVBA- Example 6 – Synthesis of Additional Compositions of PVBA-DVB Sorbents with Functional Group Variation by Direct Copolymerization using CO2 Textural Modification

[0136] An additional advantage of using CO2 as a protective group during synthesis of cross-linked polymers from styrene-based free amine monomers (such as according to the synthesis scheme shown in FIG.2) is that other amino-containing monomers can be incorporated into the polymer. This is in contrast to the synthesis schemes shown in FIG. 1, where the installment of other groups is limited by the chemical structure of the precursor polymers. Furthermore, other amino-containing groups can be incorporated into the polymer using one general reaction process scheme (CO2protection and polymerization), instead of having to vary reagents and conditions in order to introduce different groups. One simple, general route is therefore provided into a variety of bulk sorbent materials having tailorable CO2 sorption energetics dependent upon the nature of the amino-containing groups.

[0137] A series of additional cross-linked polymers were formed using monomers other than VBA and / or with both VBA and a co-monomer. The additional cross-linked polymers correspond to Examples 6A – 6H. The synthesis method for forming the cross- linked polymers in Examples 6A – 6H was similar to the synthesis method for Examples 1A – 1D.

[0138] Example 6A: 80:20 Poly-Me-VBA-DVB Sorbent: Similar to Example 1A, with the following reagent amounts: 0.625 g (4.25 mmol) N-methyl-1-(4-vinylbenzyl)- methanamine (Me-VBA, unstabilized, not passed through inhibitor removal column) and 0.137 g DVB (81% with balance EVB, 0.852 mmol DVB, 0.196 mmol EVB) in 10 mL DMSO, and 0.07 g (0.43 mmol) AIBN in 2 mL DMSO; 90 °C, 24 h. The structure of Me-VBA is shown in FIG.3. The resultant pale yellow precipitate was slurried with 25 mL isopropanol for 2 h after collection by filtration (0.402 g, 53%).

[0139] Example 6B:80:20 Poly-Me-VBA-DVB Sorbent by polymerization in toluene: Similar to Example 1A, with the following reagent amounts: 1 g Me-VBA (6.79 mmol, unstabilized, not passed through inhibitor removal column) and 0.219 g DVB (81% with balance EVB, 1.363 mmol DVB, 0.313 mmol EVB) in 20 mL toluene,and 0.112 g (0.68 mmol) AIBN in 2 mL toluene; 90°C, 24 h. The resultant pale yellow precipitate was slurried with 25 mL for 2 h after collection by filtration (0.42 g, 34%).

[0140] Example 6C: 80:20 Poly-Di-mVBA-DVB Sorbent: Similar to Example 1A, with the following reagent amounts: 0.750 g meta, meta-di(aminomethyl)styrene (Di- mVBA); (4.62 mmol, inhibited, passed through inhibitor removal column before use) and 0.148 g DVB (81%, balance EVB, 0.921 mmol DVB, 0.212 mmol EVB) in 20 mL DMSO, and 0.121 g (0.74 mmol) AIBN in 2 mL DMSO; 90°C, 48 h. The structure of Di-mVBA is shown in FIG.3. The resultant pale yellow precipitate was slurried with 50 mL isopropanol for 2 h after collection by filtration (0.3 g, 33%).

[0141] Example 6D: 40:40:20 Poly-VBA-GVBA-DVB Sorbent: Similar to Example 1A, with the following reagent amounts: 0.665 g (4.99 mmol) VBA, 0.876 g 1- (4-vinylbenzyl)guanidine (GVBA, 4.99 mmol, unstabilized, not passed through inhibitor removal column), and 0.163 g DVB (81%, balance EVB, 1.014 mmol DVB, 0.233 mmol EVB) in 25 mL DMSO, and 0.162 g (0.99 mmol) AIBN in 2 mL DMSO; 90°C, 48 h. The structure of GVBA is shown in FIG.3. The resultant pale yellow precipitate was slurried with 30 mL isopropanol for 1 h after collection by filtration (0.82 g, 42%).

[0142] Example 6E: 80:20 Poly-GVBA-DVB Sorbent: Similar to Example 1A, with the following reagent amounts: 0.875 g (4.99 mmol) GVBA (unstabilized, not passed through inhibitor removal column) and 0.163 g DVB (81%, balance EVB, 1.014 mmol DVB, 0.233 mmol EVB) in 20 mL DMSO, and 0.082 g (0.50 mmol) AIBN in 5 mL DMSO; 90°C, 48 h. The resultant pale yellow precipitate was slurried with 20 mL isopropanol for 1 h after collection by filtration (0.3 g, 29%).

[0143] Example 6F: 80:20 Poly-Me2-GVBA-DVB Sorbent: Similar to Example 1A, with the following reagent amounts: 1.0 g 1-(4-vinylbenzyl)-3,3-dimethylguanidine (Me2-GVBA, 4.92 mmol, unstabilized, not passed through inhibitor removal column) and 0.158 g DVB (81%, balance EVB, 0.83 mmol DVB, 0.226 mmol EVB) in 20 mL of 3:1 toluene:DMSO, and 0.140 g (0.85 mmol) AIBN in 5 mL of 3:1 toluene:DMSO. The structure of Me2GVBA is shown in FIG. 3.90°C, 24 h. A pale yellow precipitate was formed. Heptane (15 mL) was added and the resultant slurry stirred for 2 hours. Solids were collected by filtration and rinsed with 10 mL clean heptane, then dried under vacuum at 60 °C for 24 h (0.34 g, 29%).

[0144] Example 6G: 80:20 Poly-Me3-GVBA-DVB Sorbent: Similar to Example 1A, with the following reagent 0.75 g (1-(4-vinylbenzyl)-1,3,3- trimethylguanidine (Me3-GVBA, 3.45 mmol, unstabilized, not passed through inhibitor removal column) and 0.1138 g DVB (81%, balance EVB, 0.708 mmol DVB, 0.163 mmol EVB) in 20 mL of 1,2-dichloroethane (1,2-DCE), and 0.140 g (0.85 mmol) AIBN in 2 mL 1,2-dichloroethane; 70 °C, 24 h. The structure of Me3GVBA is shown in FIG. 3. A pale yellow precipitate was formed. Heptane (20 mL) was added and the resultant slurry stirred for 2 hours. Solids were collected by filtration and rinsed with 10 mL clean heptane, then dried under vacuum at 60 °C for 24 h (0.32 g, 37%).

[0145] Example 6H: 80:20 poly(ethylstyreneamine)-DVB Sorbent: Similar to Example 1A, with the following reagent amounts: 1.0 g (6.79 mmol) para- (aminoethyl)styrene (ethylstyreneamine, ESA), stabilized, passed through inhibitor removal column before use) and 0.219 g DVB (81%, balance EVB, 1.36 mmol DVB, 0.31 mmol EVB), in 20 mL DMSO, and 0.112 g (0.68 mmol) AIBN in 3 mL DMSO; 90 °C, 42 h. The structure of ESA is shown in FIG.3. The resultant pale yellow precipitate was collected by filtration after adding 30 mL isopropanol to the reaction flask and stirring for 2 h. It was then washed with 30 mL clean isopropanol and dried under vacuum for 18 h at 60 °C (0.38 g, 31%).

[0146] Examples 6A – 6H illustrate utilization of the general synthesis method shown in FIG.2 to generate other compositions of bulk polymeric sorbents with a variety of basic functional groups capable of reversible chemical reaction with CO2. In all cases polymerization was successful, including instances where alternative solvents were used. The alternative functional groups represent those having, compared to vinylbenzylamine, higher amine densities per gram (6C), lower Brønsted basicity and greater steric hindrance (6A, 6B), higher Brønsted basicity with varying degrees of steric hindrance, delocalization, and amino character (6E, 6F, 6G, 6H), and sorbents having a mixture of different functionalities (6D). These varying parameters may be used to tune and optimize the energetics of the CO2 sorption and desorption cycle, i.e. to create more strongly or weakly bound sorbents for use at varying temperatures or sorption or desorption and with varying feed stream concentrations of CO2. For example, a sorbent that binds CO2more strongly may have greater applicability for high temperature sorption or sorption from streams having very low concentrations of CO2. A sorbentthat binds CO2less strongly will assist in optimizing energy for other sorption processes by enabling lower desorption and will be useful for minimizing energy usage for sorption from streams containing large quantities of CO2. Table 7 presents dry CO2 sorption data for the additional compositions of Examples 6A – 6G under various conditions. The samples were pre-treated at conditions designed to provide adequate drying while minimizing thermal decomposition. All of the sorbents in Examples 6A – 6G showed activity for CO2capture under the tested conditions. It is noted that for Example 6A, it is believed that an error occurred during the attempt to obtain the BET surface area. A low surface area value was obtained, but is believed to not be correct, so a BET surface area is not available. The three-cycle TGA data reported in Col.6 utilized a 120°C, N2 desorption step in a similar fashion to the thermal-pressure swing (PTSA) cycles. Table 7 – Synthesis, Textural Properties, and Dry CO2 Sorption Performance of Materials with Functional Group Variations on PVBA-DVB Sorbents Sample Molar Ratio of BET Surf. Area Thermal CO2 Uptake TGA 30 °C (polymerization monomer:DVB: (m2 / g) stability under (mmol / g), CO2 Uptake at ) h)6C 80:16:4 15.3 18% steady loss 0.38 Not taken to 255 °C, sharp 80:20 P-Di- 910 0.02 0.08 ent

[0147] As shown in Table 7, the tested samples generally provided higher CO2uptake than Comparative Example C1B.The results in Table 7 demonstrate that a widevariety of cross-linked polymers with amino-containing functionalities can be synthesized using the general method herein. Example 7 - CO2dry sorption and desorption under isobaric conditions

[0148] Isobaric TGA sorption data for the sorbents, containing a variety of functional groups, in which CO2is sorbed and then released without need for a purge gas, is summarized in Table 8. This data demonstrates the utility of the sorbents for CO2 sorption process utilizing solely thermal swing for desorption (CO2desorption facilitated by heat alone). For the data shown in the second column of Table 8, samples were dried at the upper temperature listed (90°C, 110°C, or 120°C) for 2 hours, then exposed to 1 atm CO2 feed flow at 21 or 25 °C (room temperature, RT) followed by desorption at the earlier elevated temperature, as previously described in detail. For the data shown in the third column, samples were dried at 90°C for 3 h, then exposed to 4% CO2in N2feed flow at 45 °C followed by desorption at 90 °C as previously described in detail. For the final column, data taken at 400 ppm CO2concentration represents conditions applicable to dry Direct Air Capture (DAC) with a pre-dried air feed gas. Samples were dried at 120 °C for 5 h, then exposed to a 400 ppm CO2in N2feed flow at 18 °C (room temperature) as previously described in detail.

[0149] FIG. 11 shows a 100% (1 atm) dry CO2isobaric TGA sorption curve for material 6B. The initial portion of the curve shows the sample losing ambient sorption products and moisture, and reaching constant weight during drying at 90 °C. The sharp increase in weight in the center portion of the plot represents temperature being lowered to 25 °C and rapid uptake of CO2. Finally, the decrease in weight at the end of the plot represents temperature being raised again to 90 °C and loss of CO2from the sample in a temperature-only (isobaric) swing (desorption step). Table 8 - Thermal Swing (Isobaric) Sorption / Desorption for PVBA-DVB-based sorbents Sample 1 atm dry CO2uptake, 4% dry CO2400 wppm dry CO2GA °C1C 1.65 (25 to 110 0.29 0.16 80:20 PVBA-DVB

[0150] As shown in Table 8, all of the sorbents showed uptake of CO2 under the tested conditions. This demonstrates the ability to synthesize cross-linked polymers with CO2 sorption capacity using monomers other than VBA. It is noted that the relatively low value for CO2 uptake for Example 6A versus Example 6B is believed to be due toloss of sample integrity at 110°C (Example 6A), while the sample is stable at 90°C (Example 6B). Example 8. CO2wet sorption and desorption under conditions relevant to Direct Air Capture and post-combustion power plant flue gas capture.

[0151] Table 9 presents data for various sorbents under conditions where the CO2- containing feed stream also contains water. Conditions relevant to post-combustion streams (4% CO2in N2, 45 °C, 30% relative humidity) and Direct Air Capture (400 ppm CO2 in N2, 25°C, 60% relative humidity) are shown along with water isobars taken stepwise at 25°C under a constant flow of N2 containing various amounts of relative humidity (0, 5, 10, 20, 30, 40, 50, 60, 70, and 80%). For the data in Columns 2 and 4, samples were pre-treated at 90 °C for 3 h (1C, 1E, 6A, 6B) or 2 h (6C – 6G). For the data in Columns 3 and 5, samples were pre-treated at 90 °C for 2 h. For the data in Column 6, samples were pre-treated at 90 °C for 6 h. Table 9. Humidified CO2 Uptake for Additional Sorbents (RH = Relative Humidity Sample 4% humid 400 ppm H2O TGA H2O TGA H2O TGA CO2:H2O Uptake CO TGA h mid CO uptake, uptake, uptake, 25 Ratio at Point ns e ir2X Scaleup 6.26 (80%) 6A 065 013 068 184 082 30% 0961

[0152] As shown in Table 9, the different types of sorbents had varying degrees of CO2and H2O uptake under the various conditions, with most of the sorbents being effective for at least some CO2 uptake in the presence of water. The CO2 sorption- desorption cycle utilized in both the point source (4%) and Direct Air Capture (400 wppm) experiments exemplifies an isothermal, CO2-isobaric humidity swing process.FIG. 12 shows the humid DAC TGA CO2sorption- desorption curve for 6E (data in Table 9, column 3) taken using a 50 °C pre-treat protocol. The initial portion of the curve shows the sample losing ambient sorption products and moisture, and reaching constant weight during drying at 50 °C, followed by adjustment of temperature to 25 °C. The sharp increase in weight shortly after 200 min represents the sample being exposed to a nitrogen flow gas containing 60% relative humidity and sorbing water until its saturation point has been reached. The amount of sorbed water is quantified. The smaller increase in weight seen at ~ 500 min represents the sample being exposed to a nitrogen flow gas containing both 400 wppm CO2 and 60% relative humidity, and gaining further weight as a result of CO2 sorption. Finally, the decrease in weight at the end of the plot, ~950 min, represents switching of the flow gas to dry nitrogen containing only 400 vppm CO2.In this step, the flow gas contains 0% relative humidity, resulting in the isothermal (and CO2-isobaric) desorption of water. The remaining added weight of the sample represents sorbed CO2, which can be quantified on a net basis as described previously in detail.

[0153] FIG. 13 shows a water isotherm collected by TGA for 6E (data in Table 9, column 6). In this plot, after an initial drying period, the sample is exposed at 25 °C to a nitrogen flow containing increasing amounts of relative humidity (stepped at intervals of 5 or 10% RH). These steps are seen as the small rises in sample weight. Finally, the decrease in weight at the end of the plot, represents switching of the flow gas to dry nitrogen (0% RH) to desorb water from the sample. This TGA experiment provides information on water sorption at various partial pressures and is analogous to the CO2 autosorb curves, shown and discussed earlier, that provide information on a material’s CO2 sorption profile at various partial pressures.

[0154] Further, is possible to obtain relative profiles of each material’s affinities for CO2 and water sorption. Using the water and CO2 sorption amounts calculated from the sorption experiments (Table 9, columns 2-5) it is possible to measure the relative affinities (molar uptakes) of CO2 and water for samples (Table 9, column 7). Notably, changing the structure of the amine-containing functional group changes the relative affinity of the material for sorption of CO2 and water, and allows for the tailoring of the amine-containing sorbent’s structure to a variety of humid feed streams of industrial interest having varying water contents.

[0155] Examples 9A-9I. Synthesis of Further Compositions of PVBA-DVB Sorbents with Functional Group Variation by Copolymerization using CO2 Textural Modification

[0156] A further series of cross-linked polymers, described below in Examples 9A- I, were formed using additional monomers other than VBA or the monomers named in Examples 6A-6H. These illustrate successful synthesis of an even broader range of sorbents, including those with flexible, multi-amine substituents and amines appended to branched, rather than linear, alkyl tethers. FIG. 14 shows additional monomers and crosslinkers.

[0157] Example 9A: 80:20 Poly-(meta-vinylbenzylamine)-DVB sorbent (meta- vinylbenzylamine (m-VBA) is shown FIG. 14): Similar to Example 1A, with the following reagent amounts: 1.33 g m-VBA (10 mmol) and 0.325 g DVB (2.02 mmol DVB and 0.47 mmol EVB) in 30 mL DMSO (both passed through inhibitor removal resin), and 0.164 g (1 mmol) AIBN / 5 mL DMSO; 90 °C, 48 h. Polymer precipitation was observed. Isopropanol (50 mL) was added. The slurry was stirred for 2 h and the pale- yellow solid polymer was collected and washed with an additional 50 mL isopropanol. The final solid was dried at 60 °C for 66 h in a vacuum oven (~0.115 g, 7%). (Total volume 36.71 mL, [Mon]o0.34 M, 80:16:4 m-VBA:DVB:EVB, M:I 6.2:1, Mn (calc lin.)830 g / mol, Mn between crosslinks 750 g / mol).

[0158] Example 9B-1: 80:20 Poly-(para-(aminopropylstyrene))-DVB sorbent (para-(aminopropylstyrene) is Compound C in FIG. 4 and is abbreviated as PSA): Similar to Example 1A, with the following reagent amounts: 1.0 g PSA (6.2 mmol) and 0.200 g DVB (1.24 mmol DVB and 0.29 mmol EVB), in 20 mL DMSO (both passed through inhibitor removal resin), and 0.112 g (1.30 mmol) AIBN / 2 mL DMSO; 90 °C, 26 h. No change was observed and an additional portion of AIBN (0.101 g, cumulative 1.30 mmol, in ~2 mL DMSO) was added and the polymerization mixture was stirred for an additional ~66 h. Isopropanol (30 mL) was added, and the resultant slurry was stirred for 1 h. The pale-yellow solid polymer was collected and washed with an additional 75 mL isopropanol. The final solid was dried at 60 °C for 18 h in a vacuum oven (~0.34 g, 28%). (Total volume 25.26 mL, [Mon]o 0.31 M, 80:16:4 PSA:DVB:EVB, M:I 3.0:1, Mn(calc lin.)460 g / mol, Mnbetween crosslinks 900 g / mol).Example 9B-2: 80:20 Poly-(para-(aminopropylstyrene))-DVB sorbent, repeat synthesis: Similar to Example 1A, with reagent amounts: 1.0 g PSA (6.2 mmol) and 0.200 g DVB (1.24 mmol DVB and 0.29 mmol EVB), in 20 mL anhydrous DMSO (the PSA was passed through both inhibitor removal and also through Amberlite IRA-402(OH) ion exchange resin (1 g, pre-washed with DMSO; packed in a separate column in a similar manner to that previously described for inhibitor removal beads) and the DVB was passed through inhibitor removal resin), and 0.153 g (0.93 mmol) AIBN / 3 mL DMSO; 90 °C, 72 h. Isopropanol (30 mL) was added to the light- yellow solution, and the resultant slurry was stirred for 1 h. The pale-yellow solid was collected and washed with an additional 75 mL isopropanol. The collected solid was dried at 60 °C for 18 h in a vacuum oven (~0.450 g, 38%). (Total volume 24.26 mL, [Mon]o0.32 M, 80:16:4 PSA:DVB:EVB, M:I 4.1:1, Mn (calc lin.)640 g / mol, Mnbetween crosslinks 900 g / mol).

[0159] Example 9C: 70:30 80:20 Poly-(para-(aminopropylstyrene))-DVB sorbent: Similar to Example 1A, with the following reagent amounts: 0.5 g PSA (3.1 mmol) and 0.150 g DVB (0.93 mmol DVB and 0.21 mmol EVB) in 20 mL DMSO (both passed through inhibitor removal resin), and 0.057 g (0.35 mmol) AIBN / 3 mL DMSO; 90 °C, 72 h; the polymerization solution had low viscosity. Isopropanol (30 mL) was added and the resultant slurry was stirred for 1 h. The pale-yellow solid polymer was collected and washed with an additional 75 mL isopropanol. The final solid was dried at 60 °C for 18 h in a vacuum oven (~0.450 g, 69%). (Total volume 23.69 mL, [Mon]o 0.18 M, 73:22:5 PSA:DVB:EVB, M:I 6.1:1, Mn (calc lin.) 940 g / mol, Mn between crosslinks 630 g / mol).

[0160] Example 9D: 80:20 Poly-(para-(3-amino-2,2-dimethyl-propyl)styrene)- DVB sorbent (para-(3-amino-2,2-dimethyl-propyl)styrene is Compound D in FIG.4 and is abbreviated as neo-PSA): Similar to Example 1A, with the following reagent amounts: 1.0 g neo-PSA (5.28 mmol) and 0.170 g DVB (1.06 mmol DVB and 0.24 mmol EVB) in 20 mL DMSO (both passed through a column layered with both Amberlite IRA- 402(OH) ion exchange resin and inhibitor removal resin), and 0.087 (0.53 mmol) AIBN / 3 mL DMSO; 90 °C, 72 h. Isopropanol (30 mL) was added, and the resultant slurry was stirred for 2 h. The pale-yellow solid polymer was collected, washed with an additional 75 mL isopropanol by stirring for 2 h. The final solid was dried at 60 °C for18 h in a vacuum oven (~0.053 g, 5%). (Total volume 24.25 mL, [Mon]o0.27 M, 80:16:4 neo-PSA:DVB:EVB, M:I 6.2:1, Mn 1100 g / mol, Mn between crosslinks 1040 g / mol).

[0161] Example 9E: 80:20 Poly-((N-aminopropyl)-vinylbenzylamine)-DVB sorbent ((N-aminopropyl)-vinylbenzylamine is Compound E in FIG. 4 and is abbreviated PDA-VBA): Similar to Example 1A, with the following reagent amounts: 1.00 g PDA-VBA (5.26 mmol) and 0.170 g DVB (1.06 mmol DVB and 0.24 mmol EVB) in 16 mL DMSO (11 mL for initial dissolution of PDA-VBA and 5 mL for DVB; both passed through inhibitor removal resin), and 0.086 g (0.52 mmol) AIBN / 3 mL DMSO; 90 °C, 72 h. Isopropanol (30 mL) was added and the resultant slurry was stirred for 2 h. The white solid polymer was collected and dried at 60 °C for 18 h in a vacuum oven (0.798 g, 68%). (Total volume 20.20 mL, [Mon]o0.32 M, 80:16:4 PDA- VBA:DVB:EVB, M:I 6.3:1, Mn (calc lin.) 1120 g / mol, Mn between crosslinks 1040 g / mol).

[0162] Example 9F: 80:20(3-amino-2,2-dimethyl-propyl)- vinylbenzylamine)-DVB sorbent (N-(3-amino-2,2-dimethyl-propyl)-vinylbenzylamine is Compound F in FIG. 4 and is abbreviated neo-PDA-VBA): Similar to Example 1A, with the following reagent amounts: 1.0 g neo-PDA-VBA (4.58 mmol) and 0.119 g DVB (0.74 mmol DVB and 0.17 mmol EVB) in 20 mL DMSO (both passed through inhibitor removal resin), and 0.075 g (0.46 mmol) AIBN / 3 mL DMSO; 90 °C, 72 h. Isopropanol (25 mL) was added, and the resultant slurry was stirred for 2 h. The pale-yellow solid polymer was collected, washed with an additional 20 mL isopropanol. The final solid was dried at 60 °C for 18 h in a vacuum oven (~0.05g, 4%). (Total volume 24.15 mL, [Mon]o0.23 M, 83:14:3 neo-PDA-VBA:DVB:EVB, M:I 6.0:1, Mn (calc lin.)1220 g / mol, Mn between crosslinks 1450 g / mol).

[0163] Example 9G: 80:20 Poly-(N,N-di-(aminopropyl)-vinylbenzylamine)- DVB sorbent (N,N-di-(aminopropyl)-vinylbenzylamine is Compound G in FIG. 4 and is abbreviated Di-PDA-VBA): Similar to Example 1A, with the following reagent amounts: 2.47 g Di-PDA-VBA (10 mmol) and 0.325 g DVB (2.02 mmol DVB and 0.465 mmol EVB) in 25 mL DMSO (Di-PDA-VBA was passed through inhibitor removal resin and Amberlite IRA-402(OH) ion exchange resin and DVB was passed through inhibitor removal resin), and 0.164 g (1.0 mmol) AIBN / 5 mL DMSO; 90 °C, 20 h. A white solid formed during polymerization at elevated temperature. Following cooling to roomtemperature, isopropanol (75 mL) was added, and the resultant slurry was stirred for 1 h. The white solid polymer was collected with an additional 20 mL isopropanol. The final solid was dried at RT for 20 h under vacuum (2.56 g, 92%). (Total volume 32.81 mL, [Mon]0 = 0.38 M, M:I 6.2:1, 80:16:4 Di-PDA-VBA:DVB:EVB, Mn (calc lin.) 1400 g / mol, Mnbetween crosslinks 1320 g / mol).

[0164] Example 9H-1: 80:20 Poly-(1-methyl-1-(4-vinylbenzyl)guanidine)-DVBsorbent (1- 1-(4-vinylbenzyl)guanidine is Compound J in FIG. 4 and is abbreviated Me-GVBA): Similar to Example 1A, with the following reagent amounts: 1.0 g Me-GVBA (5.28 mmol) and 0.170 g DVB (10.6 mmol DVB and 0.24 mmol EVB) in 20 mL DMSO (the Me-GVBA was passed through both inhibitor removal and ion exchange resin and the DVB was passed through inhibitor removal resin) and 0.086 g (0.53 mmol) AIBN / 3 mL DMSO; 90 °C, 48 h. After addition of 30 mL isopropanol, the resultant slurry was stirred for 2 h and pale-yellow solids were collected, restirred with 75 mL isopropanol, and dried at 60 °C for 18 h in a vacuum oven (0.830 g, 71%). (Total volume 24.12 mL, [Mon]o 0.28 M, 80:16:4 Me-VBA:DVB:EVB, M:I 6.3:1, Mn (calc lin.) 1120 g / mol, Mnbetween crosslinks 1040 g / mol).

[0165] Example 9H-2: 80:20 Poly-(1-methyl-1-(4-vinylbenzyl)guanidine)-DVB sorbent, repeat synthesis: Similar to Example 1A, with the following reagent amounts: 1.33 g Me-GVBA (6.87 mmol) and 0.221 g DVB (1.375 mmol DVB and 0.316 mmol EVB) in 20 mL DMSO (Me-GVBA was passed through inhibitor removal resin and Amberlite IRA-402(OH) ion exchange resin; DVB was passed through inhibitor removal resin, and 0.113 g (0.687 mmol) AIBN / 3 mL DMSO; 90 °C, 56 h. Isopropanol (60 mL) was added to the light yellow solution, and the resultant slurry was stirred for 1 h. The pale-yellow solid polymer was collected and washed with an additional 20 mL isopropanol. The final solid was dried at 60 °C for 18 h in a vacuum oven (~0.76 g, 49%). (Total volume 24.48 mL, 80:16:4 Me-GVBA:DVB:EVB, [Mon]0 = 0.36 M, M:I = 6.3:1, Mn (calc lin.)1130, Mnbetween crosslinks 1060 g / mol).

[0166] Example 9I: 80:20 Poly-(1,3-dimethyl-1-(4-vinylbenzyl)guanidine)-DVB sorbent (1,3-dimethyl-1-(4-vinylbenzyl)guanidine is shown in in FIG. 14 and abbreviated as 1,3-Me2-GVBA): Similar to Example 1A, with the following reagent amounts: 0.5 g (2.46 mmol) 1,3-Me2-GVBA and 0.079 g DVB (0.299 mmol DVB and 0.113 mmol EVB) in 20 mL DMSO (DVB only was passed through inhibitor removalresin as the 1,3-Me2-GVBA did not contain inhibitor), and 0.040 g (0.24 mmol) AIBN / 5 mL DMSO; 90 °C, 26 h. The solution was cloudy. Isopropanol (150 mL) was added after cooling to room temperature and N2sparge and the resultant slurry stirred for 18 h. The granular white solid product was collected and washed with an additional 25 mL isopropanol. The final solid was dried at room temperature for 18 h under vacuum (~0.025 g, 4%). (Total volume 25.55 mL, 80:16:41,3-Me2-GVBA:DVB:EVB, [Mon]0 = 0.12 M, M:I = 6.3:1, Mn (calc lin.)1190, Mnbetween crosslinks 1110 g / mol).

[0167] Examples 10A-10F. Synthesis of Further Compositions of PVBA Sorbents Having Amino- or Guanidino-Functionalized Crosslinkers by Direct Copolymerization using CO2 Textural Modification

[0168] A series of cross-linked polymers in which the DVB crosslinker was replaced with a crosslinker bearing a CO2-active sorbing group were prepared. This substitution increases the overall theoretical CO2 sorption capacity of the bulk sorbent on a per-gram basis. These sorbents are described below in Examples 10A-F.

[0169] In addition to sorbents bearing the same type of CO2-active sorbing functionalities on the main chain monomer (for example, VBA monomer combined with a crosslinker also having a benzylic primary amine), it is possible to prepare sorbents having a mixture of CO2-active groups (for example, VBA monomer combined with a crosslinker having a guanidine substituent). In this latter class of materials, the different preferences of the two incorporated groups offer the possibility of CO2sorption with sorbents having chemical components tailored for different roles in the CO2 sorption mechanism. For example, a sorbent containing both a primary amine (VBA) (on the main chain) and a guanidine (on the crosslinker) may form products in which the very highly basic guanidine functions primarily as a Brønsted base (proton acceptor), forming guanidinium carbamate products (in which the carbamate portion is composed of VBA- CO2- adducts and the counterion is a protonated guanidine functionality), as well as more traditional ammonium carbamate products (incorporating VBA-CO2- carbamate adducts and protonated VBA vinylbenzylammonium counterions).

[0170] Example 10A: 80:20 PVBA-bis(4-vinylbenzylamine) sorbent (bis(4- vinylbenzylamine) is Compound L in FIG. 5 and is abbreviated Di-VBA): Similar to Example 1A, with the following reagent amounts: 1.33 g VBA (9.99 mmol) and 0.499 g Di-VBA (2.00 mmol) in 20 mL DMSO (15 mL for initial dissolution of VBA and 5mL for Di-VBA; both passed through inhibitor removal resin; Di-VBA had limited solubility and was also passed through a membrane filter), and 0.165 g (1.0 mmol) AIBN / 5 mL DMSO; 90 °C, 68 h. A white precipitate was formed. A 75 mL portion of isopropanol was added to the polymerization flask. The slurry was stirred for 1 h and the white solid polymer was collected, washed with an additional 25 mL isopropanol, then dried at 60 °C for 60 h in a vacuum oven (1.0 g, 55%). (Total volume 26.84 mL, [Mon]o 0.45 M, 83:17 VBA:Di-VBA, M:I 6.0:1, Mn (calc lin.)910 g / mol, Mnbetween crosslinks 790 g / mol).

[0171] Example 10B: 80:20 PVBA-(1,4-bis(4-vinylbenzyl)piperazine) sorbent (1,4-bis(4-vinylbenzyl)piperazine is shown in FIG. 14 and is abbreviated Di-PZ-VBA): Similar to Example 1A, with the following reagent amounts: 1.33 g VBA (9.99 mmol) and 0.637 g Di-PZ-VBA (2.0 mmol) in 27 mL DMSO) (10 mL for initial dissolution of VBA, 17 mL for Di-PZ-VBA; both solutions were sonicated to assist with dissolution and passed through inhibitor removal resin), and 0.164 g (1.0 mmol) AIBN / 5 mL DMSO; 90 °C, 72 h. A 50 mL portion of isopropanol was added to the polymerization and the resultant slurry was stirred for 2 h; the white solid polymer was collected by filtration and washed with another 20 mL isopropanol. The solid was re-stirred in 60 mL isopropanol for 2 h, re-collected by filtration, the dried under house vacuum overnight followed by drying at 60°C for 18 h in a vacuum oven (1.25 g, 64%). (Total volume 33.95 mL, [Mon]o0.35 M, 83:17 VBA:Di-PZ-VBA, M:I 6.0:1, Mn (calc lin.)980 g / mol, Mnbetween crosslinks 820 g / mol).

[0172] Example 10C: 80:20 PVBA-(4,4’-divinyl-2,2’-di(aminomethyl)-p- biphenyl) sorbent (4,4’-divinyl-2,2’-di(aminomethyl)-p-biphenyl) is Compound N in FIG. 5 and is abbreviated m-DV-o-BPBA): Similar to Example 1A, with the following reagent amounts: 0.754 g VBA (5.67 mmol) and 0.300 g m-DV-o-BPBA (1.13 mmol) in 25 mL DMSO (Di-PDA-VBA was passed through inhibitor removal resin and Amberlite IRA-402(OH) ion exchange resin and DVB was passed through inhibitor removal resin), and 0.093 g (0.567 mmol) AIBN / 5 mL DMSO; 90 °C, 64 h. A pale- yellow solid was formed at elevated temperature during polymerization. Following cooling, isopropanol (100 mL) was added, and the resultant slurry was stirred for 1 h. The white solid polymer was collected and washed with an additional 50 mL isopropanol. The final solid was dried at RT for 4 h under vacuum (0.706 g, 67%). (Total volume31.08 mL, [Mon]o0.22 M, 83:17 VBA:m-DV-o-BPBA, M:I 6.0:1, Mn (calc lin.)930 g / mol, Mn between crosslinks 800 g / mol).

[0173] Example 10D: 80:20 Poly-GVBA-(1-guanidinylated aminomethyl)-3,5- divinylbenzene sorbent ((1-guanidinylated aminomethyl)-3,5-divinylbenzene is Compound O in FIG.5 and is abbreviated m-DV-GVBA): Similar to Example 1A, with the following reagent amounts: 1.00 g GVBA (5.7 mmol) and 0.230 g (1.14 mmol) m- DV-GVBA in 26 mL DMSO (21 mL for initial dissolution of GVBA and 5 mL for m- DV-GVBA; both solutions were sonicated to improve solubility, then passed through both Amberlite IRA-402(OH) ion exchange resin and inhibitor removal resin), and 0.094 g (0.57 mmol) AIBN / 5 mL DMSO; 90 °C, 48 h. A yellow precipitate was formed. An 80 mL portion of isopropanol was added to the polymerization flask and the slurry was stirred overnight. It filtered and solids were washed with 30 mL isoptopanol, then dried at 60°C for 24 h in a vacuum oven (0.416 g, 34%). (Total volume 32.15 mL, [Mon]o 0.21 M, 83:17 GVBA:m-GVBA, M:I 6.0:1, Mn (calc lin.)1070 g / mol, Mnbetween crosslinks 980

[0174] Example 10E: 80:20 Poly-GVBA-1,3-di(4-vinylbenzyl)guanidine sorbent (1,3-di(4-vinylbenzyl)guanidine is Compound P in FIG.5 and is abbreviated Di-GVBA) Similar to Example 1A, with the following reagent amounts: 1.0 g GVBA (5.71 mmol) and 0.332 g Di-GVBA (1.14 mmol) in 40 mL DMSO (both passed through both Amberlite IRA-402(OH) ion exchange resin and inhibitor removal resin), and 0.094 g (0.571 mmol) AIBN / 5 mL DMSO; 90 °C, 66 h. Isopropanol (50 mL) was added to the light-yellow polymer solution, and the resultant slurry was stirred for 1 h. The pale- yellow solid polymer was collected and washed with an additional 20 mL isopropanol. The final solid was dried at 60 °C for 18h in a vacuum oven (~1.05 g, 79%). (Total volume 46.24 mL, [Mon]o0.15 M, 83:17 GVBA:Di-GVBA, M:I 6.0:1, Mn (calc lin.)1160 g / mol, Mn between crosslinks 1020 g / mol).

[0175] Example 10F: 80:20 PVBA:Di-GVBA sorbent: Similar to Example 1A, with the following reagent amounts: 1.33 g VBA (10 mmol) and 0.583 g Di-GVBA (2.0 mmol) in 30 mL DMSO (VBA was passed in solution through inhibitor removal resin and Di-GVBA was passed in solution through both Amberlite IRA-402(OH) ion exchange resin and inhibitor removal resin), and 0.164 g (1.0 mmol) AIBN / 5 mL DMSO; 90 °C, 48 h. Isopropanol (50 mL) was added to the light-yellow polymer solution and theresultant slurry was stirred for 1 h. The white solid polymer was collected and washed with an additional 25 mL isopropanol. final solid was dried at 60 °C for 18h in a vacuum oven (1.53 g, 80%). (Total volume 36.90 mL, [Mon]o0.33 M, 83:17 VBA:Di- GVBA, M:I 6.0:1, Mn (calc lin.) 960 g / mol, Mn between crosslinks 810 g / mol).

[0176] Examples 11A-H. Synthesis of Further Compositions of PVBA-DVB Type Sorbents by Direct Copolymerization using CO2 Textural Modification

[0177] Examples 11A-H present additional PVBA-DVB type materials prepared for CO2 sorption evaluation. These materials illustrate additional variations in composition or synthesis / purification procedure, or repeat preparations designed to generate material for testing as subsequently described. All monomers and crosslinkers and their abbreviations have been previously described.

[0178] Example 11A: 80:20 PVBA:DVB sorbent, greater initial monomer concentration: Similar to Example 1A, with the following reagent amounts: 2.66 g VBA (20 mmol) and 0.650 g DVB (4.04 mmol DVB and 0.93 mmol EVB) in 25 mL DMSO (both were passed through inhibitor removal resin), and 0.328 g (2.0 mmol) AIBN / 5 mL DMSO; 90 °C, 72 h. A 50 mL portion of isopropanol was added to the polymerization flask. The slurry was stirred for 1 h and the white solid polymer was collected and washed with an additional 20 mL isopropanol. The collected white solid polymer was dried under vacuum at room temperature for 2 h (2.90 g, 88%). (Total volume 33.43 mL, [Mon]o0.75 M, 80:16:4 VBA:DVB:EVB, M:I 6.2:1, Mn (calc lin.)830 g / mol, Mn between crosslinks 750 g / mol).

[0179] Example 11B: 75:25 PVBA:DVB sorbent: Similar to Example 1A, with the following reagent amounts: 1.33 g (9.99 mmol) VBA, 0.407 g DVB (2.53 mmol DVB and 0.59 mmol EVB) (both were passed through inhibitor removal resin) in 30 mL DMSO, and 0.165 g (1.0 mmol) AIBN / 5 mL DMSO; white product after 72 h (1.5 g, 0.86%). (Total volume 36.73 mL; [Mon]o 0.36 M, VBA:DVB:EVB 76:19:4, M:I 6.5:1, Mn (calc lin.)870 g / mol, Mnbetween crosslinks 620 g / mol). Example 11C-1, C-2, C-3: 80:20 PVBA:DVB sorbent with workup variations: Similar to Example 1A, with the following reagent amounts: 2.66 g VBA (20 mmol) and 0.650 g DVB (4.04 mmol DVB and 0.93 mmol EVB) in 50 mL DMSO (both were passed through inhibitor removal resin), and 0.328 g (2.0 mmol) AIBN / 10 mL DMSO; 90 °C, 72 h. After cooldown the DMSO was carefully pipetted away from the productpolymer, which was then slurried in 75 mL fresh DMSO and stirred for 2 h under N2and again isolated by pipetting away supernatant. This slurry / pipetting process was repeated twice for a total of three cycles of fresh 75 mL DMSO + pipetting of supernatant. The solids were never allowed to become completely dry. [The combined mother liquor / supernatants were set aside; solids that were later observed to precipitate upon standing were collected and dried under house vacuum a room temperature (~1.0 g, Material 11C-3, 30%).] The original, main portion of product solids was divided into two roughly equivalent portions. One portion was frozen at -80 °C and freeze-dried overnight in a LabConco tray freeze dryer to apparent dryness (1.2 g, Material 11C-1, 36%). The second portion was extracted three times with 75 mL isopropanol and isolated by pipetting away supernatant, as described above, never allowing the solids to become completely dry. The final solids were collected by filtration using a weak vacuum and dried under house vacuum at room temperature (0.75 g, Material 11C-2, 23%). (Overall yield 89%, total volume 63.43 mL, [Mon]o0.39 M, 80:16:4 VBA:DVB:EVB, M:I 6.2:1, Mn (calc lin.) 830 g / mol, Mn between crosslinks 750 g / mol.)

[0180] Example 11D-1: 80:20 Poly-GVBA-DVB sorbent, repeat 1: Similar to Example 1A, with the following reagent amounts: 0.875 g GVBA (4.99 mmol, passed through inhibitor removal column) and 0.163 g DVB (1.014 mmol DVB and 0.233 mmol EVB, also passed through inhibitor removal column) in 20 mL DMSO, and 0.082 g (0.50 mmol) AIBN / 5 mL DMSO; 90 °C, 66 h. A pale-yellow precipitate was formed. Isopropanol (20 mL) was added, and the resultant slurry stirred for 2 h prior to re- filtration. The collected pale-yellow solid was washed with 30 mL isopropanol and split. One portion was dried at 60 °C for 24 h in a vacuum oven (0.532 g, 51%) and a second portion was dried at room temperature under vacuum (unweighed). (Total volume 26.0 mL, [Mon]o 0.24 M, 80:16:4 VBA:DVB:EVB, M:I 6.2:1, Mn (calc lin.) 1040 g / mol, Mn between crosslinks 960 g / mol.)

[0181] Example 11D-2: 80:20 Poly-GVBA-DVB sorbent, repeat 2: Similar to Example 1A, with the following reagent amounts: 0.875 g GVBA (4.99 mmol) and 0.163 g DVB (1.014 mmol DVB and 0.233 nmol EVB) in 20 mL DMSO (both passed through a column layered with both Amberlite IRA-402(OH) ion exchange resin and inhibitor removal resin), and 0.082 g (0.50 mmol) AIBN / 5 mL DMSO; 90 °C deg, 48 h. A light-yellow precipitate was formed. Isopropanol (20 mL) was added, and the resultant slurry stirred for 1 h prior to re-filtration. The pale-yellow solid washed with 10 mL isopropanol and dried at 60 °C for 18 h in a vacuum oven (0.735 g, 71%). (Total volume 26 mL, [Mon]o 0.24 M, 80:16:4 GVBA:DVB:EVB, M:I 6.2:1, Mn (calc lin.) 1040 g / mol, Mn between crosslinks 960 g / mol.)

[0182] Example 11E-1: 80:20 Poly-di-m-VBA-DVB sorbent, repeat: Similar to Example 1A, with the following reagent amounts: 0.743 g di-m-VBA (4.58 mmol) and 0.124 g DVB (0.77 mmol DVB and 0.18 mmol EVB) were dissolved in 25 mL DMSO (15 mL for initial dissolution of low solubility di-m-VBA, with filtration through a Teflon filter, and 10 mL for DVB; only DVB was passed through inhibitor removal resin), along with 0.074 g of a commercial poly(4-vinylpyrrolidone) having nominal molecular weight of 10,000 g / mol (“PVP-10K”, 10 wt% based on monomer); and 0.121 g (0.743 mmol) AIBN / 5 mL DMSO; 90 °C, 29 h. A 70 mL portion of isopropanol was added to the polymerization flask. The slurry was stirred for 1 h and the white solid polymer was collected, washed with an additional 25 mL isopropanol, and dried at 60 °C for 60 h in a vacuum oven (0.31 g, 36%). The PVP-10K (added to effect potential pore- forming(porogenation) during crosslinking polymerization) was presumed to be removed by isopropanol extraction (Total volume 30.95 mL, [Mon]o0.18 M, 83:14:3 di- m-VBA:DVB:EVB, M:I 3.8:1, Mn (calc lin.) 590 g / mol, Mn between crosslinks 1060 g / mol).

[0183] Example 11E-2: 80:20 Poly-di-m-VBA-DVB sorbent, repeat: Similar to Example 1A, with the following reagent amounts: 0.743 g di-m-VBA (4.58 mmol) and 0.125 g DVB (0.778 mmol DVB and 0.179 mmol EVB) in 25 mL DMSO, with 0.074 g (10 wt%) PVP-10K (15 mL for initial dissolution of low-solubility di-m-VBA, followed by filtration through a Teflon filter, and 10 mL for DVB; only DVB was passed through inhibitor removal resin), and 0.121 g (0.74 mmol) AIBN / 5 mL DMSO; 90 °C, 48h. A 50 mL portion of isopropanol was added to the polymerization flask and the slurry was stirred over the weekend. The white solid polymer was collected, washed with an additional 25 mL isopropanol, and restirred overnight as a slurry in 50 mL of isopropanol. The solid was collected and dried at 60 °C for 60 h in a vacuum oven (0.50 g, 58%). (Total volume 30.95 mL, [Mon]o 0.18 M, 83:14:3 di-m-VBA:DVB:EVB, M:I 3.8:1, Mn(calc lin.)590 g / mol, Mnbetween crosslinks 1050 g / mol).

[0184] Example 11F: 80:20 Poly-Me-VBA-DVB sorbent, repeat: Similar to Example 1A, with the following 1.0 g Me-VBA (6.8 mmol) and 0.219 g DVB (1.36 mmol DVB and 0.31 mmol EVB) in 20 mL DMSO (DVB only was passed through inhibitor removal resin as the Me-VBA had no stabilizer added) with 0.110 g PVP-10K (10 wt%), and 0.112 g (0.68 mmol) AIBN / 2 mL DMSO; 90 °C, 28 h. Precipitation was observed. Isopropanol (50 mL) was added to the polymerization flask. The slurry was stirred for 2 h and the white solid polymer was collected and re-slurried for 4 h with another 50 mL isopropanol. The collected solid polymer was once again washed with an additional 20 mL isopropanol to remove the PVP-10K from final polymer solid. The final solid was dried at 60 °C for 18h in a vacuum oven (~0.42 g, 34%). (Total volume 23.39 mL, [Mon]o 0.36 M, 80:16:4 Me-VBA:DVB:EVB, M:I 6.2:1, Mn (calc lin.)890 g / mol, Mnbetween crosslinks 830 g / mol).

[0185] Example 11G: 80:20 Poly-Me2-GVBA-DVB sorbent, repeat: Similar to Example 1A, with the following reagent amounts: 1.0 g (4.92 mmol) Me2-GVBA and 0.158 g DVB (0.983 mmol DVB and 0.226 mmol EVB) in 20 mL of a 1:3 DMSO:toluene mixed solvent (only DVB was passed through inhibitor removal resin as the Me2-GVBA monomer had no added initiator), with 0.079 g PVP-10K (8 wt%), and 0.140 g (0.85 mmol) AIBN / 5 mL 1:3 DMSO:toluene; 90 °C, 24 h. Formation of solids was observed. A 30 mL portion of heptane was added to the polymerization flask. The resultant slurry was stirred for 2 h and the pale-yellow solid polymer was collected and washed with an additional 20 mL heptane. Solids were collected by filtration and washed with an additional 10 mL isopropanol to remove the PVP-10K. The final solid was dried at 60 °C for 18h in a vacuum oven (~0.34 g, 29%). (Total volume 26.17 mL, [Mon]o0.23 M, 80:16:4 Me2-GVBA:DVB:EVB, M:I 3.6:1, Mn (calc lin.) 680 g / mol, Mn between crosslinks 1110 g / mol).

[0186] Example 11H: 80:20 PVBA-DVB sorbent, repeat: Similar to Example 1A, with the following reagent amounts: 1.33 g VBA (9.99 mmol) and 0.325 g DVB (2.02 mmol DVB and 0.47 mmol EVB) (both passed through inhibitor removal resin) with 0.162 g PVP-10K in 25 mL DMSO, and 0.165 g (1.0 mmol) AIBN / 5 mL DMSO; 90 °C, 42 h. Polymer precipitation was observed. A 50 mL portion of isopropanol was added to the polymerization flask. The slurry was stirred for 1 h and the white solid polymer was collected, then washed with an additional 20 mL isopropanol. The collected solidpolymer was again stirred in 50 mL isopropanol for 66 h at RT. A spot of the final extractate was put onto a TLC plate into an iodine chamber; no yellow staining (that would indicate PVP in the extractate) was observed. Collected solids were finally washed with an additional 30 mL isopropanol to remove PVP-10K. The final solid was split into two portions; one was not dried (0.6 g, 36%); the other was dried at 60 °C for 18 h in a vacuum oven (0.45 g, 27%). (Overall yield 63%, total volume 31.84 mL, [Mon]o 0.39 M, 80:16:4 VBA:DVB:EVB, M:I 6.2:1, Mn (calc lin.)820 g / mol, Mnbetween crosslinks 750 g / mol).

[0187] The sorbents of Examples 9A-I, 10A-F, and 11A-H are summarized in Table 10. Sorbents that were not evaluated beyond synthesis previously described are not included. The information in the Thermal Stability column (Col.3) summarizes per cent weight losses over given temperature ranges under nitrogen and / or air. “Stab.” denotes stability (as evidenced by little or no weight loss); a “plateau” also denotes a temperature region of little or no weight loss. Information noted as “rpt” indicates a repeat analysis. The last temperature listed in each entry denotes the temperature at which the onset of major decomposition occurs. These experiments were conducted similarly to previously described TGA thermal stability experiments (some trials experienced an erroneous 30 minute hold at 200 °C, which did not affect evaluation). Surface area and pore measurements were conducted as previously described. Unless otherwise indicated, surface area and pore measurement sample pre-treatment for the results in Column 2 was performed at 90 °C under vacuum for 4.2-4.4 hours. Table 10. Compositions and Properties of Sorbents in Examples 9A-I, 10A-F, and 11A-H. Ex. No., Composition BET Surf. Area (m2 / g) Thermal stability under N2 and air (TGA) to70:30 PSA:DVB 0.02 5.0 . : C, : b. °C C80:20 GVBA:m-DV- GVBA 20 % C, 0 ) < C, ) <11E-2 9.40 (0) N2: drying loss <120 °C ~10%, 2% 130-215 °C, little plateau 80:20 m-VBA:DVB 0.012 emeasurement (adsorption) taken at P / Po > 0.99. The two pore diameter measurements (BJH 4V / A) are, listed in order, from the adsorption and desorption isotherm branches.

[0188] Table 11 presents dry CO2sorption data for the Sorbents in Examples 9A-I, 10A-F, and 11A-H as well as one sorbent prepared in earlier Examples. Experimentation and data analyses are similar to those previously described. Pre-treatment conditions are shown in parentheses. RT denotes room temperature (25 – 27.5 °C). For isobaric TGA data taken under a constant 1 atm CO2 (Col. 4), two temperatures are listed as a range, for example RT – 120 °C. These samples represent the temperatures of CO2 sorption (the lower temperature) and desorption (the higher temperature). The sample was first dried (pre-treated) under nitrogen at the temperature listed in parentheses, which is typically the same as the higher temperature of the range. It was then cooled to the lower temperature, 1 atm dry CO2was introduced and the sample was held at that temperature for 6 hours. The sample was then heated to the upper temperature to effect desorption and held for 1 hour. The first number listed is CO2sorption capacity calculated from the end of the drying step (temperature listed in parentheses) to the maximum of the weightgain in the sorption step (lower temperature). The second number listed is isobaric cycle capacity and represents the CO2 calculated from the maximum weight of the sorption step to the minimum weight point of the desorption step. Table 11. Dry CO2 Sorption Properties of Sorbents in Table 10. Ex. No., Composition Autosorb 30 °C at 1.0, Multicycle TGA 30 °C Isobaric TGA (1 atm CO2) 0.04 atm CO2(if 3rd 1 atm, 4% CO2 / 120 °C Initial Uptake, Cycle10B Not tested Not tested Not tested 80:20 VBA:Di-PZ- 0 RT11D-2 0.81, 0.35 N / A, 1.34 (140 °C, 3 h) 0.82, 0.32 – 0.35, RT - 90 °C 80:20 GVBA:DVB (90 °C 4.2 h) (90 °C 2 h) iedAuthority.bA single sample was pre-treated 3 times in sequence for isotherms at 3 different temperatures.

[0189] Table 12 presents humidified CO2sorption data for the Sorbents in Examples 9A-I, 10A-F, and 11A and one previous example. Although this data is tabulated in slightly different form, protocols are similar to those described in conjunction with Table 9. Table 12. Humidified CO2 Sorption Properties of Sorbents in Table 10 (RH = Relative Humidity) Ex. No., CompositionTGA 4% CO2 (4%)TGA DAC CO2(400 ppm) Water Isotherm ll l l * ll l l *9A 1.67, 1.65 0.92, 1.61 N / A 80:20 m-VBA:DVB 2.05 7.42weight differential for the entire cycle (water pre-saturation, CO2sorption, and waterdesorption with dry CO2feed); the second number is taken from the dry CO2sorption step only.

[0190] Table 13 presents humid CO2sorption data for representative sorbents using a breakthrough unit under conditions that mimic those relevant to Direct Air Capture. In these experiments, the sorbent sample (typically pelleted and sized through a molecular sieve to ensure consistent particle size) is tightly packed in a cylindrical reactor. The reactor is sealed, weighed, and a flow of inert gas is passed through the cylinder and packed sorbent at elevated temperature to dry the sorbent. The sorbent dry weight is then recorded. The sample is cooled to room temperature and then optionally pre-saturated with a humidified, CO2-free gas stream. A gas stream (typically inert, such as N2) containing ~400 ppm CO2 and humidified to an appropriate relative humidity, is then passed over the sample for a specified length of time. The amount of CO2sorbed by the sample is plotted over time and total gas sorbed is calculated using the CO2 entry flow rate and the amount of CO2detected (or not detected) at the reactor exit. After the sample has reached maximum CO2 uptake, it is then heated at a set rate to a set elevated temperature under dry inert gas flow, and CO2(and water) released from the sorbent and exiting the packed column are quantified if desired. The post-experiment weight of the sample may also be recorded. A sample breakthrough curve for CO2sorption is shown in FIG.15 (Sample 9H-2, in Table 14).

[0191] In Table 13, three sorbents are subjected to the above-described experimental protocol. The samples were pre-treated at 90 °C for 6 hours under inert gas flow, and then subjected to 22 °C (room temperature) sorption under a 370 ppm CO2 in N2 feed gas containing varying relative humidities (110 sccm gas flow) for 6 hours. Desorption was then performed in two steps: (1) purging the sorbent with inert gas for 2 hours at room temperature; then (2) heating the sorbent under inert gas flow to 90 °C over a two hour period. Sorbed CO2 was quantified using the adsorption step; sorbed water was quantified using the amount of water that was desorbed in the desorption step.

[0192] Material 5C was pelleted at 2000 lbs of pressure and sized through #40 / 60 mesh before packing in the ¼” bore breakthrough column (wet sample weight: 0.1923 g; dry sample weight: 0.1680 g; dry sample weight after cycles: 0.1686 g). Material 11D-1 was sieved through #40 / 60 mesh with no pressing. Wet sample weight: 0.1390 g; dry sample weight: 0.1200 g; dry sample weight after cycles: 0.1148 g. Material 11F waspartially pelleted at 2000 lbs of pressure and sized through #40 / 60 mesh. Wet sample weight: 0.1079 g; dry sample weight: mg; dry sample weight after cycles: 0.0117 g. Table 13. Room Temperature Breakthrough CO2 and Water Uptakes (370 ppm CO2 in N2 Feed Gas) for Representative Sorbents at Varying Relative Humidities Approx. CO2 uptake / water uptake (mmol / g) RH (%) exact relative humidity (RH) (%)

[0193] Table 14 presents further breakthrough experiment evaluation of sorbent CO2capture under Direct Air Capture relevant conditions (~400 ppm CO2in inert gasflow, 60% relative humidity, room temperature). Multiple values for CO2sorption indicate multiple sorption cycles Table 14. Room Temperature Breakthrough CO2 Uptakes (~400 ppm CO2 in 60% Relative Humidity N2 Feed Gas) for Additional Sorbents Sample Breakthrough Testing Test Description CO2 Adsorption (mmol / g) and (see Footnotes)11D-2 0.41, 0.49 1st data is B 8020 GVBA DVB 052 052 053 2ndd 3 d C

[0194] In Table 14, A = standard conditions are the same as for the breakthrough unit described in association with Table 13. B = standard conditions are 25 °C, 400 ppm CO2feed gas, pre-saturation with 60% relative humidity inert gas, pre-treatment at 90 °C for 4 h; sorption with ~400 ppm CO2inert gas at 60% relative humidity, followed by desorption with dry N2 at 25 °C for 2 h, then at 90 °C for 6 h. C = standard sorption conditions are 400 ppm CO2, 21 °C, 60% relative humidity, 110 sccm gas flow (other parameters not recorded). Pre-treat and desorption not recorded but most likely at 90 °C. Additional Embodiments

[0195] Embodiment 1. A method for synthesizing a cross-linked polymer from vinyl-aromatic monomers that have an amino-containing substituent comprising: exposing a plurality of vinyl-aromatic monomers having at least one amino-containing substituent to CO2, to convert at least a portion of the at least one amino-containing substituent to a protected form, the at least one amino-containing substituent comprising1 to 14 carbon atoms, the at least one amino-containing substituent being bonded to an aromatic ring of the vinyl-aromatic via one or more carbon atoms in the amino-containing substituent; reacting at least a portion of the vinyl-aromatic monomers having the protected amino-containing substituents under polymerization conditions with a plurality of copolymerizing cross-linkers and an initiator in a solvent to form a cross-linked polyvinyl-aromatic that comprises at least a portion of the protected amino- containing substituents; and desorbing CO2from the cross-linked polyvinyl-aromatic to convert at least a portion of the protected amino-containing substituents into amino- containing substituents.

[0196] Embodiment 2. The method of Embodiment 1, wherein the reacting at least a portion of the vinyl aromatic monomers having the protected amino- containing substituents comprises reacting a mixture containing 65 mol% or more of vinyl-aromatic monomers having at least one amino-containing substituent and 3.0 mol% or more of the plurality of co-polymerizing cross-linkers, the 65 mol% or more of vinyl- aromatic monomers having at least one amino-containing substituent comprising the at least a portion of vinyl-aromatic monomers having the protected amino-containing substituents.

[0197] Embodiment 3. The method of Embodiment 2, wherein the mixture contains 10 mol% to 30 mol% of the plurality of copolymerizing cross-linkers, or wherein the mixture contains 2 mol% to 20 mol% of vinyl-aromatic monomers that do not have an amino-containing substituent, or a combination thereof.

[0198] Embodiment 4. The method of any of the above embodiments, wherein the plurality of vinyl-aromatic monomers having at least one amino-containing substituent comprises a mixture of first vinyl-aromatic monomers and second vinyl- aromatic monomers, a molar ratio of the first vinyl-aromatic monomers to the second vinyl-aromatic monomers being from 5 : 95 to 95 : 5.

[0199] Embodiment 5. The method of any of the above embodiments, wherein the at least one amino-containing substituent comprises a non-benzylic amine, or wherein the at least one amino-containing substituent is attached to a single-ring aromatic in a para position relative to a vinyl group, or a combination thereof.

[0200] Embodiment 6. The method of any of the above embodiments, wherein the plurality of vinyl-aromatic monomers is a plurality of vinyl-benzylaminemonomers, or wherein the plurality of copolymerizing cross-linkers is a plurality of divinylbenzene cross-linkers, or a thereof.

[0201] Embodiment 7. The method of any of the above embodiments, wherein the at least one amino-containing substituent is selected from the group consisting of methanamine, ethanamine, N-methyl methanamine, guanidinyl, amidinyl, alkyl-substituted guanidinyl, aminoguanidinyl, biguanide, linear alkylamine, branched alkylamine, cyclic alkylamine, or a combination thereof, the at least one amino- containing substituent optionally being a multi-amine comprising at least one of a primary amine and a secondary amine.

[0202] Embodiment 8. The method of any of the above embodiments, wherein the vinyl-aromatic monomer comprises vinylbenzylamine, methylvinylbenzylamine, meta,meta-di(aminomethyl)styrene, para- (aminoethyl)styrene, guanidinylated vinylbenzylamine, a methyl guanidinylated vinylbenzylamine, a dimethyl guanindinylated vinylbenzylamine, trimethyl guanidinylated vinylbenzylamine, or a combination thereof.

[0203] Embodiment 9. The method of any of the above embodiments, wherein the vinyl-aromatic monomer comprises meta-vinylbenzylamine, meta,meta,para-tri-(aminomethyl)styrene, para-(aminopropyl)styrene, para-(3-amino- 2,2-dimethyl-propyl)styrene, (N-aminopropyl)-vinylbenzylamine, N,N-di- (aminopropyl)-vinylbenzylamine, N-(3-amino-2,2-dimethyl-propyl)-vinylbenzylamine, N,N-di-(3-amino-2,2-dimethyl-propyl)-vinylbenzylamine, para-(piperazinyl- methyl)styrene, or a combination thereof.

[0204] Embodiment 10. The method of any of the above embodiments, wherein the plurality of copolymerizing cross-linkers comprises a plurality of divinyl aromatic cross-linkers, the plurality of divinyl aromatic cross-linkers being a plurality of single-ring divinyl aromatic cross-linkers, a plurality of multi-ring divinyl aromatic cross-linkers, or a combination thereof, the plurality of divinyl aromatic cross-linkers optionally further comprising a portion of divinyl aromatic cross-linkers having one or more amino-containing substituents.

[0205] Embodiment 11. The method of any of the above embodiments, wherein the one or more co-polymerizing cross-linkers are selected from the group consisting of divinylbenzene, 4,4’-divinyl-p-biphenyl, bis (4-vinylbenzyl)amine, 1-aminomethyl-3,5-divinylbenzene, 1-(guanidinylated aminomethyl)-3,5-divinylbenzene, 1,3-di(4- vinylbenzyl)guanidine, 4,4’-divinyl- (aminomethyl)-p-biphenyl, 3,3’-divinyl- 2,2’-di(aminomethyl)-p-biphenyl, or a combination thereof.

[0206] Embodiment 12. The method of any of the above embodiments, wherein 30 mol% to 80 mol% of the vinyl-aromatic monomers having at least one amino- containing substituent comprise guanidinylated vinylbenzylamine, alkyl-substituted guanidinylated vinylbenzylamine, or a combination thereof.

[0207] Embodiment 13. The method of any of the above embodiments, wherein reacting at least a portion of the vinyl-aromatic monomers having the protected amino-containing substituents under polymerization conditions with a plurality of copolymerizing cross-linkers and an initiator comprises reacting the at least a portion of the vinyl aromatic monomers having the protected amino-containing substituents under polymerization conditions with a plurality copolymerizing cross-linkers, an initiator, and at least at least one additional co-monomer that does not have an amino-containing substituent, a molar ratio of the one or more copolymerizing cross-linkers to the at least one additional co-monomer being from 1 : 10 to 50 : 1, the at least one additional co- monomer optionally being styrene, ethylvinylbenzene, or a combination thereof.

[0208] Embodiment 14. The method of any of the above embodiments, i) wherein 10 mol% or less of the protected amino-containing substituents comprise bicarbonate salts; ii) wherein, prior to the desorbing, at least 10 mol% of the repeat units in the cross-linked polyvinyl-aromatic have a protected amino-containing substituent; or iii) a combination of i) and ii).

[0209] Embodiment 15. The method of any of the above embodiments, a) wherein the solvent is selected from the group consisting of dimethylsulfoxide, toluene, 1,2-dichloroethane, or a mixture thereof; b) wherein the initiator is 2,2’-azobis(2- methylpropionitrile); or c) a combination of a) and b).

[0210] Embodiment 16. A cross-linked polymer composition made according to the method of any of the above embodiments.

[0211] Embodiment 17. The composition of Embodiment 16, wherein the composition comprises 65 mol% or more of primary repeat units based on vinyl-aromatic monomers having at least one amino-containing substituent, the at least one amino- containing substituent comprising 1 to 14 carbon atoms, the at least one amino-containing substituent being bonded to an aromatic ring of the vinyl-aromatic monomer via one or more carbon atoms in the at one amino-containing substituent; and 3.0 mol% or more of cross-linker repeat units based on copolymerizing cross-linkers, counting the entire mass of a cross-linker repeat unit as one unit; and wherein at least 30% of the primary repeat units, relative to the number of primary repeat units, comprise an amino-containing substituent that is different from methanamine.

[0212] Embodiment 18. The composition of any of Embodiments 16 to 17, wherein the composition comprises a pore volume of 0.02 cm3 / g or more, a BET surface area of 5.0 m2 / g or higher, or a combination thereof.

[0213] Embodiment 19. A method of adsorbing CO2, comprising exposing a composition according to any of Embodiments 15 to 18 to a gas phase environment comprising CO2.

[0214] Embodiment 20. The method of adsorbing CO2 of Embodiment 19, wherein the composition is exposed to a gas phase environment comprising 6.0 vol% or less of CO2, or wherein the composition is exposed to air under direct air capture conditions.

[0215] Additional Embodiment A. The method of any of Embodiments 1 to 15, wherein exposing the plurality of vinyl-aromatic monomers to CO2comprises bubbling CO2 through a solution comprising the plurality of vinyl-aromatic monomers, the one or more copolymerizing cross-linkers, and the solvent; or wherein reacting at least a portion of the vinyl-aromatic monomers under polymerization conditions in a solvent comprises bubbling CO2 through the solvent during the reacting; or a combination thereof.

[0216] Additional Embodiment B. The method of any of Embodiments 1 to 15 or Additional Embodiment A, wherein the cross-linked polyvinyl-aromatic is substantially free of chlorine; or wherein the cross-linked polyvinyl-aromatic is substantially free of alkali metals; or wherein the cross-linked polyvinyl-aromatic is substantially free of formates; or wherein the cross-linked polyvinyl-aromatic is substantially free of sulfates; or a combination thereof.

[0217] Additional Embodiment C. The composition of any of Embodiments 16 to 18, wherein at least 50% of the primary repeat units comprise amino-containing substituents different from methanamine.

[0218] Additional Embodiment D. The composition of Embodiment 16 to 18 or additional Embodiment C, wherein the does not have an observable glass transition.

[0219] Additional Embodiment E. The method of adsorbing CO2 of Embodiment 19 or 20, wherein exposing the composition to the gas phase environment forms a sorption- enriched polymer comprising sorbed CO2, the method further comprising exposing the sorption-enriched polymer under the same gas phase environment to a higher temperature than a temperature during the exposing the composition to form a CO2- depleted composition.

[0220] All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

[0221] While the present invention has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the invention lends itself to variations not necessarily illustrated herein. For this reason, then, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A method for synthesizing a cross-linked polymer from vinyl- aromatic monomers that have an amino-containing substituent comprising: exposing a plurality of vinyl-aromatic monomers having at least one amino-containing substituent to CO2, to convert at least a portion of the at least one amino-containing substituent to a protected form, the at least one amino-containing substituent comprising 1 to 14 carbon atoms, the at least one amino-containing substituent being bonded to an aromatic ring of the vinyl-aromatic monomers via one or more carbon atoms in the amino-containing substituent; reacting at least a portion of the vinyl-aromatic monomers having the protected amino-containing substituents under polymerization conditions with a plurality of copolymerizing cross-linkers and an initiator in a solvent to form a cross-linked polyvinyl-aromatic that comprises at least a portion of the protected amino-containing substituents; and desorbing CO2from the cross-linked polyvinyl-aromatic to convert at least a portion of the protected amino-containing substituents into amino-containing substituents.

2. The method of claim 1, wherein the reacting at least a portion of the vinyl aromatic monomers having the protected amino-containing substituents comprises reacting a mixture containing 65 mol% or more of vinyl-aromatic monomers having at least one amino-containing substituent and 3.0 mol% or more of the plurality of co-polymerizing cross-linkers, the 65 mol% or more of vinyl-aromatic monomers having at least one amino- containing substituent comprising the at least a portion of vinyl-aromatic monomers having the protected amino-containing substituents.

3. The method of claim 2, wherein the mixture contains 10 mol% to 30 mol% of the plurality of copolymerizing cross-linkers, or wherein the mixture contains 2 mol% to 20 mol% of vinyl-aromatic monomers that do not have an amino-containing substituent, or a combination thereof.

4. The method of any of the above claims, wherein the plurality of vinyl-aromatic monomers having at least one amino-containing substituent comprises a mixture of first vinyl-aromatic monomers and second vinyl-aromatic monomers, a molar ratio of the first vinyl-aromatic monomers to the second vinyl-aromatic monomers being from 5 : 95 to 95 : 5.

5. The method of any of the above claims, wherein the at least one amino-containing substituent comprises a non-benzylic amine, or wherein the at least one amino-containing substituent is attached to a single-ring aromatic in a para position relative to a vinyl group, or a combination thereof.

6. The method of any of the above claims, wherein the plurality of vinyl-aromatic monomers is a plurality of vinyl-benzylamine monomers, or wherein the plurality of copolymerizing cross-linkers is a plurality of divinylbenzene cross-linkers, or a combination thereof.

7. The method of any of the above claims, wherein the at least one amino-containing substituent is selected from the group consisting of methanamine, ethanamine, N-methyl methanamine, guanidinyl, amidinyl, alkyl-substituted guanidinyl, aminoguanidinyl, biguanide, linear alkylamine, branched alkylamine, cyclic alkylamine, or a combination thereof, the at least one amino-containing substituent optionally being a multi- amine comprising at least one of a primary amine and a secondary amine.

8. The method of any of the above claims, wherein the vinyl- aromatic monomer comprises vinylbenzylamine, methylvinylbenzylamine, meta,meta- di(aminomethyl)styrene, para-(aminoethyl)styrene, guanidinylated vinylbenzylamine, a methyl guanidinylated vinylbenzylamine, a dimethyl guanindinylated vinylbenzylamine, trimethyl guanidinylated vinylbenzylamine, or a combination thereof.

9. The method of any of the above claims, wherein the vinyl- aromatic monomer comprises meta-vinylbenzylamine, meta,meta,para-tri- (aminomethyl)styrene, para-(aminopropyl)styrene, para-(3-amino-2,2-dimethyl- propyl)styrene, (N-aminopropyl)-vinylbenzylamine, N,N-di-(aminopropyl)- vinylbenzylamine, N-(3-amino-2,2-dimethyl-propyl)-vinylbenzylamine, N,N-di-(3-amino- 2,2-dimethyl-propyl)-vinylbenzylamine, para-(piperazinyl-methyl)styrene, or a combination thereof.

10. The method of any of the above claims, wherein the plurality of copolymerizing cross-linkers comprises a plurality of divinyl aromatic cross-linkers, the plurality of divinyl aromatic cross-linkers being a plurality of single-ring divinyl aromatic cross-linkers, a plurality of multi-ring divinyl aromatic cross-linkers, or a combination thereof, the plurality of divinyl aromatic cross-linkers optionally further comprising a portion of divinyl aromatic cross-linkers having one or more amino-containing substituents.

11. The method of any of the above claims, wherein the one or more co-polymerizing cross-linkers are selected from the group consisting of divinylbenzene, 4,4’- divinyl-p-biphenyl, bis (4-vinylbenzyl)amine, 1-aminomethyl-3,5-divinylbenzene, 1- (guanidinylated aminomethyl)-3,5-divinylbenzene, 1,3-di(4-vinylbenzyl)guanidine, 4,4’- divinyl-2,2’-di(aminomethyl)-p-biphenyl, 3,3’-divinyl-2,2’-di(aminomethyl)-p-biphenyl, or a combination thereof.

12. The method of any of the above claims, wherein 30 mol% to 80 mol% of the vinyl-aromatic monomers having at least one amino-containing substituent comprise guanidinylated vinylbenzylamine, alkyl-substituted guanidinylated vinylbenzylamine, or a combination thereof.

13. The method of any of the above claims, wherein reacting at least a portion of the vinyl-aromatic monomers having the protected amino-containing substituents under polymerization conditions with a plurality of copolymerizing cross-linkers and an initiator comprises reacting the at least a portion of the vinyl aromatic monomers having the protected amino-containing substituents under polymerization conditions with a plurality copolymerizing cross-linkers, an initiator, and at least at least one additional co-monomer that does not have an amino-containing substituent, a molar ratio of the one or more copolymerizing cross-linkers to the at least one additional co-monomer being from 1 : 10 to 50 : 1, the at least one additional co-monomer optionally being styrene, ethylvinylbenzene, or a combination thereof.

14. The method of any of the above claims, i) wherein 10 mol% or less of the protected amino-containing substituents comprise bicarbonate salts; ii) wherein, prior to the desorbing, at least 10 mol% of the repeat units in the cross-linked polyvinyl- aromatic have a protected amino-containing substituent; or iii) a combination of i) and ii).

15. The method of any of the above claims, a) wherein the solvent is selected from the group consisting of dimethylsulfoxide, toluene, 1,2-dichloroethane, or a mixture thereof; b) wherein the initiator is 2,2’-azobis(2-methylpropionitrile); or c) a combination of a) and b).

16. A cross-linked polymer composition made according to the method of any of the above claims.

17. The composition of claim 16, wherein the composition comprises 65 mol% or more of primary repeat units based on vinyl-aromatic monomers having at least one amino-containing substituent, the at least one amino-containing substituent comprising 1 to 14 carbon atoms, the at least one amino-containing substituent being bonded to an aromatic ring of the vinyl-aromatic monomer via one or more carbon atoms in the at least one amino-containing substituent; and 3.0 mol% or more of cross-linker repeat units based on copolymerizing cross-linkers, counting the entire mass of a cross-linker repeat unit as one unit; and wherein at least 30% of the primary repeat units, relative to the number of primary repeat units, comprise an amino-containing substituent that is different from methanamine.

18. The composition of any of claims 16 to 17, wherein the composition comprises a pore volume of 0.02 cm3 / g or more, a BET surface area of 5.0 m2 / g or higher, or a combination thereof.

19. A method of adsorbing CO2, comprising exposing a composition according to any of claims 15 to 18 to a gas phase environment comprising CO2.

20. The method of adsorbing CO2of claim 19, wherein the composition is exposed to a gas phase environment comprising 6.0 vol% or less of CO2, or wherein the composition is exposed to air under direct air capture conditions.

21. The method of any of claims 1 to 15, wherein exposing the plurality of vinyl-aromatic monomers to CO2 comprises bubbling CO2 through a solution comprising the plurality of vinyl-aromatic monomers, the one or more copolymerizing cross- linkers, and the solvent; or wherein reacting at least a portion of the vinyl-aromatic monomers under polymerization conditions in a solvent comprises bubbling CO2through the solvent during the reacting; or a combination thereof.

22. The method of any of claims 1 to 15 or 21, wherein the cross- linked polyvinyl-aromatic is substantially free of chlorine; or wherein the cross-linked polyvinyl-aromatic is substantially free of alkali metals; or wherein the cross-linked polyvinyl- aromatic is substantially free of formates; or wherein the cross-linked polyvinyl-aromatic is substantially free of sulfates; or a combination thereof.

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