ATMOSPHERIC CARBON DIOXIDE SORBENT

A sorbent for direct air capture of CO2 includes a porous amine-functionalized polymeric material including a backbone and a plurality of side chains having amine groups branching from the backbone, the backbone including a rigid crosslinker having crosslinker groups, a ratio of the crosslinker groups to a total number of monomer repeating units in the polymeric material is about 0.1 to 0.4 such that the polymeric material's internal surface area is about 10 to 500 m2/g.

TECHNICAL FIELD

The present disclosure relates to a sorbent for capture of atmospheric carbon dioxide (CO2) and a method of making and using the same.

BACKGROUND

Carbon dioxide is a notorious greenhouse gas whose emissions have been sharply on the rise since the Industrial Revolution began in the 18th century. Since then, the CO2 emissions have been a confirmed culprit in the climate change around the world. Recent findings of the International Panel on Climate Change have proposed that the CO2 emissions should be halved by 2030 to avoid further negative impact on the planet. Various technologies have been developed to capture atmospheric CO2, but their drawbacks prevent realization of more widespread CO2 sequestration from air.

SUMMARY

In one embodiment, a sorbent for direct air capture of CO2 is disclosed. The sorbent may include a porous amine-functionalized polymeric material including a backbone and a plurality of side chains having amine groups branching from the backbone. The backbone may include a rigid crosslinker having crosslinker groups. A ratio of the crosslinker groups to a total number of monomer repeating units in the polymeric material may be about 0.1 to 0.4 such that the polymeric material's internal surface area is about 10 to 500 m2/g. An average micropore size of the sorbent may be about 5 to 20 Å. The crosslinker may retain an end-to-end distance of at least about 70% of its predetermined molecular geometry. The polymeric material may be polyallylamine. The polymeric material may be polystyrene. The crosslinker may include a conjugated benzene. The conjugated benzene may include anthracene. The crosslinker may include a polyphenyl compound directly bound to a side chain of the polymeric sorbent.

In another embodiment, a sorbent for direct air capture of CO2 is disclosed. The sorbent may include a porous amine-functionalized polymeric material having an internal surface area of about 10 to 1500 m2/g at crosslinker fraction of about 20 to 60 mol %, based on a total molar number of monomers in the polymeric sorbent. The crosslinker may include at least two benzene rings. The crosslinker may be a rigid crosslinker which maintains an end-to-end distance of a least 70% of predetermined molecular geometry. An average micropore size of the sorbent may be about 5 to 20 A. The crosslinker may include a conjugated benzene compound. The crosslinker may include anthracene. The crosslinker may include a polyphenyl directly bound to a side chain of the polymeric sorbent.

In an alternative embodiment, a system for direct air capture of CO2 is disclosed. The system may include a compartment housing a porous amine-functionalized polymeric sorbent including a rigid crosslinker configured to maintain a distance between amine groups of the sorbent. The crosslinker may be included in an amount of about 20 to 60 mol %, based on a total molar number of monomers in the polymeric sorbent, and have at least one benzene ring. The system may further include a first conduit structured to bring air into the compartment and a second conduit structured to lead CO2-free air from the compartment. The crosslinker may be a rigid crosslinker which maintains an end-to-end distance of a least 70% of its predetermined molecular geometry. An average micropore size of the sorbent may be about 5 to 20 A. The crosslinker may include a conjugated benzene. The crosslinker may include a polyphenyl directly bound to a side chain of the polymeric sorbent. The crosslinker may include anthracene.

DETAILED DESCRIPTION

The first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.

As used herein, the term “substantially,” “generally,” or “about” means that the amount or value in question may be the specific value designated or some other value in its neighborhood. Generally, the term “about” denoting a certain value is intended to denote a range within +/−5% of the value. As one example, the phrase “about 100” denotes a range of 100+/−5, i.e. the range from 95 to 105. Generally, when the term “about” is used, it can be expected that similar results or effects according to the disclosure can be obtained within a range of +/−5% of the indicated value. The term “substantially” may modify a value or relative characteristic disclosed or claimed in the present disclosure. In such instances, “substantially” may signify that the value or relative characteristic it modifies is within +0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative characteristic.

In the examples set forth herein, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 50 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In a refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 30 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In another refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 10 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples.

As used herein, the term “and/or” means that either all or only one of the elements of said group may be present. For example, “A and/or B” means “only A, or only B, or both A and B”. In the case of “only A,” the term also covers the possibility that B is absent, i.e. “only A, but not B”.

It is also to be understood that this disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present disclosure and is not intended to be limiting in any way.

The term “comprising” is synonymous with “including,” “having,” “containing,” or “characterized by.” These terms are inclusive and open-ended and do not exclude additional, unrecited elements or method steps. The term “including” or “includes” may encompass the phrases “comprise,” “consist of,” or “essentially consist of.”

With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed subject matter can include the use of either of the other two terms.

The term “one or more” means “at least one” and the term “at least one” means “one or more.” The terms “one or more” and “at least one” include “plurality” as a subset.

The description of a group or class of materials as suitable for a given purpose in connection with one or more embodiments implies that mixtures of any two or more of the members of the group or class are suitable. Also, the description of a group or class of materials as suitable for a given purpose in connection with one or more embodiments implies that the group or class of materials can “comprise,” “consist of,” and/or “consist essentially of” any member or the entirety of that group or class of materials. First definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.

Carbon dioxide or CO2 is a primary greenhouse gas accounting for about 80% of all U.S. annual greenhouse gas emissions from human activities. The CO2 emissions are a well-recognized global problem. Greenhouse gasses are gasses that trap heat in the atmosphere. The heat trapping causes changes in the radiative balance of the Earth that alter climate and weather patterns at global and regional scales. CO2 is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. CO2 is found in the gas state at ambient temperature. In the air, CO2 is transparent to visible light but absorbs infrared radiation, thereby acting as a greenhouse gas. CO2 enters the atmosphere through burning of fossil fuels such as coal, natural gas, and oil, solid waste, trees, and other biological materials. CO2 further enters the atmosphere as a result of certain chemical reactions such as manufacturing of cement or aluminum. Additionally, when methane enters the atmosphere, it combines with oxygen to form CO2.

Because of its negative impact on the global climate, efforts have been made to reduce CO2 emissions, mostly by capture of CO2 at the source of release such as from smokestacks of power plants, cement plants, or aluminum plants. Yet, much of the man-made CO2 emissions cannot be captured at the source such as those originating from cars or airplanes. Additionally, capture of the already released CO2, so called legacy CO2, is highly desirable to reduce the overall climate impact of the CO2 greenhouse gas.

Hence, the extraction of CO2 from ambient air is a potential route for the mitigation of greenhouse gas emissions and associated climate change. The direct extraction of CO2 from air via a sorbent, typically termed direct air capture (DAC), is the gold-standard technology for this objective.

A typical sorbent technology in DAC includes a porous support material functionalized with amine-containing molecules or polymers. For example, a porous silica or cellulose support material may be functionalized with amine-containing molecules or polyethyleneimine (PEI). In this type of sorbent, the amines react spontaneously with CO2 to separate the CO2 from the air while the porous support material provides a high surface area for the amine/air interface, ensures thar the air can flow through the sorbent, and anchors the amines in the solid sorbent, preventing their volatilization.

A non-limiting example DAC sorption system/process includes two steps, shown schematically in FIG. 1. As can be seen in FIG. 1, in the first stage or step 1, a sorbent 20 chosen to selectively absorb CO2 is exposed to air until it reaches a desired saturation point. In the first step of FIG. 1, air is passed over an amine-functionalized sorbent 20, which separates CO2 from the incoming gas stream, denoted as air. In the second stage or step 2, the sorbent is regenerated by stripping the absorbed CO2 from the sorbent 20 and storing the captured CO2 at high pressure and purity for later utilization or sequestration, marked as B. In the second step, the CO2 bound to the solid sorbent 20 is detached using a change in temperature, pressure, humidity level, or other stimulus, marked as A, regenerating the sorbent to its pristine state and releasing the CO2 for storage or utilization. The process can then be repeated. In the schematic, the line connecting “amine” to “porous support” denotes that the amines are chemically bonded to the support.

While the first stage of this process is spontaneous, as the sorbent chemistry is chosen to react favorably with CO2, the regeneration stage requires energy input to desorb the captured CO2. The energy may come in the form of heat, changes in external pressure, changes in humidity, changes in potential, or washing with an exchange or transfer fluid having a component with preferential affinity towards CO2, as was described in U.S. patent application Ser. No. 18/162,326, which is hereby incorporated in its entirety by reference.

The energy cost of the DAC process, as well as the useful life of the sorbent material, are largely determined by the efficiency of the regeneration stage, making it an important design component of any DAC process. The cost of the DAC process is dependent on the amount of CO2 which the sorbent can take up in a set amount of time as well as the energy input required to release the captured CO2 during the regeneration stage.

Amine-functionalized solid sorbents are generally hydrophilic and absorb water alongside CO2 with the amount and structure of absorbed water dependent on ambient conditions such as humidity and temperature, as well as the type of sorbent material used. Some water is absorbed in the bulk of the polymer at low humidity, but most of the water absorption occurs by capillary condensation in the micropores at medium-to-high humidity. The exact humidity value for condensation depends on the size of the micropores, with larger micropores more resistant to capillary condensation.

The porous sorbents used for CO2 capture typically have a multiscale porosity schematically shown in FIG. 2. This structure may include a small number of macropores (20-200 nm diameter) and a larger number of micropores (0.5-2 nm diameter). In FIG. 2, the sorbent 20 includes macropores 22 and micropores 24. Since porosity influences the amount of CO2 capture, it would be desirable to increase porosity to increase efficiency of CO2 capture.

In one of more embodiments, a solid sorbent for CO2 capture is disclosed. The sorbent may be porous. The sorbent may be a 3D structure having a solid portion and a porous portion. The porous portion may be distributed throughout the solid portion. The solid portion and the porous portion may form an internal volume of the sorbent. The sorbent may be formed into a variety of shapes, sizes, and configurations. The internal volume of the sorbent may be defined by an increased surface area compared to typical CO2 sorbents.

The sorbent may have multiple porosity including macropores (20-200 nm diameter), micropores (0.5-2 nm diameter), and mesopores (2-20 nm). The macropores may be configured to facilitate long-range diffusion of CO2. The micropores and mesopores may form an interpenetrating network structured to facilitate CO2 access to the interior volume of the sorbent.

The sorbent may include one or more polymeric compounds, resins, or materials. The polymeric material may include a backbone structure with side chains facilitating chemisorption of CO2. The side chains may be amine-functionalized. The polymeric compound may thus be amine-functionalized. A typical example of a backbone may be amine functionalized polystyrene, polyethyleneimine, polypropyleneimine, and polyallylamine. The backbone may be linear or branched. The repeating monomer unit may be homogenous or heterogenous.

The polymeric compounds may also include a rigid crosslinker molecule incorporated into the backbone, locking the backbone chains in place and preventing the chain compaction, thereby creating a permanent porosity in the material.

Traditional crosslinkers may include divinylbenzene (DVB) or diphenylmethane crosslinked by the Friedel-Crafts reaction. Formulas of DVB and diphenylmethane are shown in FIGS. 4A and 4B, respectively.

Typically, the solid portion of the sorbent is free of pores, including for example long-chained polymeric compounds. Porosity is caused, for example, by inclusion of one or more chemical groups (spacers, crosslinkers) between the chains. The chemical groups may push the chains apart, thus causing porosity in the otherwise solid material. The increased porosity may be observed as increased surface area of the sorbent internal volume. The more pores are present, the greater surface area is observed. Yet, including too many chains via a crosslinker may be counterproductive as the amount, proximity, and availability of amine groups which facilitate the capture may be then limited. To illustrate the principle, FIG. 3 is provided herein.

FIG. 3 shows schematically two examples of simulated polymer resins. Example A is a simulated crosslinked polymer resin based on amine-functionalized polystyrene crosslinked with DVB. Example B is a simulated crosslinked polymer resin based on polyallylamine crosslinked with DVB. FIG. 3 shows non-limiting examples of increasing a molar fraction of DVB crosslinker in an amine-functionalized polystyrene and polyallylamine sorbents, respectively.

Each example is shown as a line in the graph and the structure of each example is also shown with a repeating backbone monomer unit of each example. The crosslinker is represented by the ring connecting the individual chains terminating with NH2 groups. FIG. 3 shows a plot of the polymeric material surface area in relationship to the crosslinker fraction. In the plot of FIG. 3, axis x shows the crosslinker fraction which may be defined as the ratio of crosslinker groups to the total number of monomers in the polymer chain. Monomers, that are not the crosslinker, are predominantly functionalized by NH2 groups. The y axis shows the surface area of the internal volume of the polymer resins.

In general, crosslinkers typically increase porosity, but sacrifice amine content. As can be observed from FIG. 3, the internal surface area of polymer sorbents increases with crosslinker fraction, reflecting an increase in porosity. However, by definition, an increase in the crosslinker fraction leads to a decrease in the amine fraction, decreasing the maximum possible CO2 binding capacity of the sorbent. Example B requires a smaller crosslinker fraction than Example A to achieve the same internal surface area and porosity, meaning that this polymer type can maintain a larger amine content and CO2 binding capacity at a given level of porosity. Alternatively, at the same crosslinker fraction and CO2 binding capacity, Example B has a higher porosity than Example A, meaning it allows for more robust gas permeation throughout the sorbent material. Overall, Example B is a more desirable sorbent than Example A because its internal surface area, which serves as a measure of porosity, can be higher without excessively increasing crosslinker fraction and sacrificing amine content, which is necessary for binding of CO2. In other words, Example B requires fewer crosslinkers to achieve a set value of porosity, meaning there are more amines left in the polymeric material to bind CO2. At a given crosslinker fraction and amine content, Example B has higher porosity than Example A, meaning it will be easier for CO2 to permeate the material to reach the binding sites.

It was discovered that the porosity may be tuned by controlling the following: (a) the type of monomer backbone of the polymer resin, (b) the amount of the crosslinker or molar fraction of the crosslinker, and (c) the type of crosslinker. Adjusting (a), (b), (c), or their combination may thus result in a polymeric compound tailored for the sorbent application, resulting in an increased capacity of CO2 capture. To maximize the capacity of the CO2 capture of the sorbent, it was discovered that it is desirable to maximize the surface area of the internal volume of the sorbent at the smallest crosslinker molar fraction. The crosslinker molar fraction relates to a ratio of crosslinker groups to the total number of monomer repeating units, where the majority of non-crosslinker monomers are functionalized by NH2 groups. Tuning of (a), (b), (c), or their combination may thus yield an optimized sorbent with (I) maximum internal surface area and (II) maximally large pore diameters with (III) a minimum molar fraction of crosslinker.

The herein-disclosed crosslinker may include, comprise, consist essentially of, or consist of at least two benzene rings. The two benzene rings may be connected. The crosslinker may include, comprise, consist essentially of, or consist of a polyphenyl such as biphenyl, terphenyl or diphenylbenzene, tetraphenyl, benzerythrene, pentaphenyl, etc., or their combination with ortho, meta, and/or para substitutions patterns. The crosslinker may thus include, comprise, consist essentially of, or consist of a benzene ring substituted with at least one phenyl group or phenyl ring. The benzene ring may be central to the substituted phenyl rings surrounding the central ring.

Alternatively, or in addition, the herein-disclosed crosslinker may include, comprise, consist essentially of, or consist of a compound with conjugated benzene rings, polycyclic aromatic hydrocarbons, arenes, cyclic unsaturated compounds, or their combination. The compound may be directly connected to the one or more side chains stemming from the backbone. The crosslinker may be free of branching, functionalization, substitution, or additional moieties stemming from the compound. The compound may be free of a vinyl, vinylidene, aliphatic, alkyl, alkane, aryl, or another linking moiety. In other words, the backbone may be free of any side chains within the backbone, thus being attached only to the amine-functionalized side chains the backbone is configured to keep apart. The compound may include nitrogen substitution or amine functionalization as is described below.

The crosslinker may include, comprise, consist essentially of, or consist of compounds such as naphthalene, anthracene, tetracene, pentacene, phenalene, phenantrene, triphenylene, pyrene, chrysene, naphtacene (tetracene), picene, perylene, etc. The crosslinker may thus include at least one compound including at least two aromatic rings. The aromatic rings may be benzene rings. At least two aromatic rings may share at least some of the adjacent atoms. The aromatic rings may be fused or condensed. The fusion may be linear or non-linear.

The crosslinker may include at least one cyclic compound with at least two unsaturated fused rings. The cyclic compound may include at least two fused rings, each ring having 4, 5, 6, 7 carbons, or their combination. The crosslinker may include pentalene, indene, azulene, heptalene, biphenylene, as-indacene, s-indacene, acenaphthylene, fluorene, fluoranthene, acephenanthrylene, aceanthrylene, pleiadene, or a combination thereof, or in a combination with at least one compound named above. Cyclic compounds with saturated rings are also contemplated.

In a non-limiting example, the cross-linker may include anthracene, terphenyl, or their combination.

The crosslinker molecule may have sufficient rigidity to maintain a relatively large distance between the side chains, NH2 groups, end-groups of the sorbent, or a combination thereof. The distance may be constant or relatively constant. The crosslinker may be thus rigid enough to prevent compression of the polymer and elimination of the pores. The rigidity of a crosslinker molecule may be defined by considering the variation in its end-to-end distance, where the ends of the crosslinker are the chemical bonds connecting the crosslinker to the polymer backbone. A structurally rigid crosslinker may be defined as one whose end-to-end distance remains at least about 70, 75, 80, 85, 90, or 95% of its geometry at all temperatures, pressures, and chemical environments encountered or experienced by the sorbent material. The geometry may be a predetermined geometry of a desirable value, ideal relaxed geometry, or initial geometry.

The crosslinker fraction or the ratio of crosslinker groups to total number of monomers in the polymer chain of the sorbent may be about 0.05-0.6, 0.1-0.4, or 0.2-0.3. The fraction may be about, at least about, or at most about 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, or 0.6.

The disclosed crosslinker was observed to increase porosity, resulting in a sorbent with a greater number of pores, pores of a larger diameter, and increased internal surface area compared to the traditional crosslinkers named herein. Furthermore, the disclosed crosslinker was observed to reduce the crosslinker fraction required to achieve a desired porosity, resulting in a sorbent with a higher non-crosslinker fraction and thus higher amine content and CO2 binding capacity.

Additionally, the sorbent material may be tailored to increase the amount of capturable CO2. The amount of CO2 that can be absorbed by a sorbent material is determined by the amine loading and amine efficiency. Amine loading may be defined as the amount of accessible primary and secondary amines in the material. Amine efficiency may be defined as the number of CO2 molecules that can be captured per amine.

Due to various factors, amine loading may be constrained. For example, the accessible amines may be sterically blocked or otherwise prevented from chemisorption of CO2 due to the amount of structural support in the sorbent (polymer backbone, crosslinkers) necessary to maintain the porosity of the sorbent.

The amine efficiency is dictated by the chemical mechanism responsible for CO2 binding and is typically limited to about 0.3 in state-of-the-art sorbents. Under dry conditions, CO2 is absorbed by the carbamate mechanism shown in FIG. 9, where two amines are necessary to bind a single CO2 molecule. In this case, the amine efficiency cannot exceed a value of 0.5, and is in practice limited to 0.3 by the electrostatic repulsion between the bound carbamates.

Under wet/humid conditions, CO2 can be absorbed by a carbamic acid mechanism shown in FIG. 10, where CO2 can be bound to a single amine, releasing a solvated hydronium ion into the sorbent. While the mechanism shown in FIG. 10 suggests the possibility of improving the amine efficiency beyond 0.5, in practice the hydronium ion binds to another amine in the material, once again leading to two amines being used to absorb a single CO2 molecule.

It would be thus desirable to improve amine efficiency of the sorbent.

Traditionally, the crosslinker only serves structural purposes, maintaining the porosity of the sorbent, but does not contribute to the CO2 binding chemistry.

In one or more embodiments, the crosslinker described herein is modified to include one or more proton binding sites configured to enable proton binding to the crosslinker units in the sorbent. The crosslinker may include, comprise, consist essentially of, or consist of one or more tertiary amines capable of chemisorption of CO2 molecules. The crosslinker molecule may include, comprise, consist essentially of, or consist of at least one, more than one, two, three, four, five, six, or more proton binding sites per crosslinker molecule. The proton binding sites may include tertiary amines. The amine proton binding sites improve the amine efficiency of the sorbent under wet conditions as the added proton binding sites create additional binding sites for the hydronium ion released during the carbamic acid formation, allowing more of the primary and secondary amines in the material to bind CO2.

The crosslinker may include, comprise, consist essentially of, or consist of one or more pyridine rings, pyrazine rings, of their combination. The rings may be fused, linear, non-linear, include substitutions, or their combination. In a non-limiting example, the crosslinker may include pyrazine, phenazine, pyridazine, pyrimidine, and/or other tertiary-amine-containing ring. Non-limiting example compounds may be the compounds depicted in FIGS. 5A-5D and 6A-6K with at least one tertiary amine incorporated in at least one of the rings. Each ring may include one or two tertiary amines. At least some of the rings may include one or two tertiary amines.

A non-limiting example crosslinker disclosed herein may include divinylpyrazine, shown in FIG. 11A in comparison with traditional DVB. Additional non-limiting examples are shown in FIGS. 11B and 11C.

As a result, amine efficiency of the sorbent may be greater than 0.3, 0.4, or 0.5. The sorbent may thus include a polymeric material having amine-functionalized side chains and amine-functionalized backbone structured to maintain a distance between the side chains.

It was also discovered that the amine should ideally be a tertiary amine as opposed to primary or secondary amines to maintain rigidity sufficient to maintain distance between the side chains resulting in desired porosity. Inclusion of at least some secondary amines in the proton binding sites is contemplated, for example in combination with tertiary amines.

Primary and secondary amine (to a lesser degree) incorporation in the crosslinker compound was shown to result in folding and collapse of the porous structure of the sorbent material. Primary amines do not provide structural support and are not depicted.

FIG. 12 depicts the internal surface area of three systems: a baseline system that does not have amines in the crosslinker, and two systems containing secondary and tertiary amines in the crosslinker. The data was derived from an atomistically simulated representative structure of the amorphous polymer resins. The internal surface area was used as a measure of the porosity of the sorbent. While both tertiary and secondary amines decreased the porosity compared to the baseline case, the secondary amine scenario resulted in a larger loss of porosity. This data illustrates a tradeoff between the improved CO2 binding capacity (amine content) of the sorbent, and its porosity.

To mitigate the loss of porosity with amine incorporation into the crosslinker, some crosslinker molecules may remain free of proton binding sites while other crosslinker molecules may include at least one tertiary amine. The sorbent may thus include a mixture of crosslinkers disclosed herein, a first portion of crosslinkers configured for structural purposes such as added surface area and porosity, a second portion of crosslinkers configured to improve amine efficiency.

A method of forming a sorbent for DAC of CO2 capture is disclosed herein. The method may include forming a porous sorbent including a functional group configured to capture or bind CO2 from air and immobilizing the functional group on a support material which includes pores. The method may include polymerization, crosslinking of base components using one or more crosslinkers disclosed herein, or both to form a porous support material.

A method of using the herein-disclosed sorbent is disclosed herein. The method may include providing the sorbent in a DAC system. The method may include sorbing CO2 within the sorbent until a predetermined CO2 saturation point, value, or range. The method may include regenerating the sorbent by using an exchange fluid with affinity to CO2, thermally, or otherwise.

The sorbent disclosed herein may be part of a system structured to sequester CO2 from dilute sources. The system may be a DAC system. The system is arranged to capture CO2 from air, atmosphere. The capture may be direct capture. The CO2 may be anthropogenic CO2, legacy CO2, naturally produced CO2, CO2 from various sources such as decomposition CO2, ocean release CO2, respiration CO2, industrial sources CO2, deforestation CO2, fossil fuel burning CO2, transportation CO2, fuel combustion CO2, exhaust CO2, the like, or their combination.

The system includes several components which cooperate mechanically, physically, chemically, fluidly, or a combination thereof. The system may include one more compartments housing the porous sorbent, one or more mechanisms configured to regenerate the sorbent, one or more apparati for storage of the captured CO2, one or more components for release of the outgoing air having a lower concentration of CO2 than the incoming air, the like, or a combination thereof. The compartment may be a tank, vessel, container, canister, capsule, tub, chamber, cistern, flask, receptacle, or the like. The container may be a closed, enclosable, openable, scalable, and/or resealable container.

The compartments may include one or more air inputs structured as resealable or enclosable openings, one or more conduits connecting one or more portions of the system and arranged to lead one or more fluids between various portions of the system. The fluids may be air, exchange liquid(s), electrolyte(s), etc. The compartment may include one or more conduits to lead CO2-free air from the compartment.

The system may utilize the solid porous sorbent in combination with a liquid exchange of transfer fluid having a chemical with preferential affinity for CO2, configured to regenerate the sorbent after CO2 is bound to the sorbent to a predetermined saturation point. The regeneration may be realized by mediated transport of CO2 from the sorbent by removing, desorbing, stripping, or displacing CO2 absorbed onto the sorbent, and binding the CO2. Alternatively, the system may use heat, changes in external pressure, changes in RH to regenerate the porous sorbent. The system may thus include a heat source, pressure regulator(s), humidity control system, or the like.

The system may further include one or more controllers, sensors, or both, receiving or providing inputs and outputs to trigger binding of CO2, release of CO2 from the sorbent, regeneration of the sorbent, or a combination thereof. The controller(s) may thus monitor, adjust, initiate, terminate, or contribute to binding and/or release of the sorbent, for example by controlling, adjusting, monitoring RH of the system, subsystem, or cell which the sorbent is present in. Alternatively, controlled flooding may be secured by the structural features of the sorbent disclosed herein and may not need a controller's assistance. Non-limiting examples of a controller 90 and sensor 92 are schematically depicted in the system shown in FIG. 1. The placement and configuration is just schematical and may differ from that depicted in FIG. 1.

Example 1, 2, and Comparative Example A

Simulated crosslinked polymer resins were prepared using polyallylamine crosslinked with DVB (Comparative Example A), terphenyl (Example 1), and anthracene (Example 2). The repeating monomer units with the rigid crosslinkers are shown in FIGS. 7A-7C. Two plots were prepared showing the increase in surface area (FIG. 8A) and average or typical pore size (FIG. 8B) depending on the crosslinker fraction of each Example and Comparative Example.

As can be observed from FIG. 8A, an average pore size increased sharply for Example 1 at a low crosslinker fraction of about 0.25. While the average pore size with Comparative Example at 0.25 crosslinker fraction was below 5 A, Example 1 reached 7.5 A. At 0.3 crosslinker fraction, Example 1 had average pore size of about 10 A, Example 2 about 8 A, while Comparative Example A about 6 A. A dramatic increase of average pore size was observed from Example 2 between 0.4 and 0.5 crosslinker fraction. In conclusion, a greater average pore size is achievable with a relatively low molar crosslinker fraction for Examples 1 and 2 in comparison to Comparative Example A.

As can be seen in FIG. 8B, a greater surface area of the resin may be obtained at a lower crosslinker fraction for both Examples 1 and 2 in comparison to Comparative Example A. Specifically, at about 0.325 crosslinker fraction, Examples 1 and 2 had visibly greater surface area than Comparative Example A. Example 2 surface area increased dramatically between 0.42 and 0.6 crosslinker fraction, reaching beyond 1500 m2/g while comparative Example A's maximum was at 1000 m2/g.