Carbon dioxide adsorbent and carbon dioxide adsorption-desorption device

Abstract

To provide an adsorbent capable of realizing a carbon dioxide adsorption-desorption device that can efficiently adsorb and desorb carbon dioxide, as well as a carbon dioxide adsorption-desorption device that includes the adsorbent.SOLUTION: According to one embodiment, a carbon dioxide adsorbent is provided. The carbon dioxide adsorbent is capable of adsorbing and desorbing carbon dioxide and has a fused heteroaromatic ring structure that includes one or more quinone structures.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE The present invention relates to a carbon dioxide adsorbent and a carbon dioxide absorption and release device. [Background technology]

[0002] The technology of absorbing carbon dioxide (CO2) into absorbents such as amines is used in CCS (Carbon dioxide Capture and Storage) plants such as thermal power plants, and is considered to be the leading candidate for a technology to prevent global warming. The absorbent that absorbed the carbon dioxide is generally heated in a regeneration tower and regenerated by releasing the carbon dioxide, and is then used repeatedly. The typical temperature at this time is about 140°C, which consumes a large amount of energy. The heat and energy required for regeneration are also called heat duty or energy penalty. If the heating temperature can be lowered to efficiently release carbon dioxide, energy can be reduced, and the spread of this technology as a global warming prevention technology can be promoted.

[0003] One energy-saving regeneration method is to replace the adsorbed carbon dioxide with water vapor. Carbon dioxide is released from the adsorbent through a replacement reaction between the adsorbed carbon dioxide and water vapor. This method allows the heating temperature to be lowered to below 100°C, but the released gas contains water vapor in addition to carbon dioxide. Therefore, a process is added in the later stage to cool the released gas and condense the water vapor to separate it from the carbon dioxide. Therefore, although this method can be more energy-efficient than thermal desorption, it is difficult to say that it is the optimal method for regenerating absorbents.

[0004] On the other hand, technology is being investigated that uses molecules or polymers that contain electroresponsive active groups to separate carbon dioxide by switching the electric potential instead of heating. This method is expected to have an energy-saving effect because it allows carbon dioxide to be released without heating. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2014 / 0271434 [Patent Document 2] Patent Publication No. 2022-25699 [Patent Document 3] Special Publication No. 2022-546697 [Non-patent literature]

[0006] [Non-Patent Document 1] J. Am. Chem. Soc., 2013, 135, 16821-16824 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the embodiments is to provide an adsorbent that can realize a carbon dioxide absorption / release device that can efficiently absorb and release carbon dioxide, and a carbon dioxide absorption / release device that includes the adsorbent. [Means for solving the problem]

[0008] According to an embodiment, a carbon dioxide adsorbent is provided, which is capable of adsorbing and releasing carbon dioxide and has a fused heteroaromatic ring structure, the fused heteroaromatic ring structure including one or more quinone structures. [Brief description of the drawings]

[0009] [Figure 1] An example of a CO2 adsorption / desorption scheme using a redox molecule with a condensed heteroaromatic ring structure containing a quinone structure. [Diagram 2] Another example of a CO2 adsorption / desorption scheme using a redox molecule having a condensed heteroaromatic ring structure including a quinone structure. [Diagram 3] FIG. 1 is a list showing examples of structural formulas of redox molecules having a condensed heteroaromatic ring structure containing a quinone structure. [Figure 4] FIG. 13 is a list showing structural formulas of other examples of redox molecules having a condensed heteroaromatic ring structure containing a quinone structure. [Diagram 5] FIG. 13 is a list showing structural formulas of other examples of redox molecules having a condensed heteroaromatic ring structure containing a quinone structure. [Figure 6] Plot showing CO2 binding energy at reactive sites for an example redox molecule and the predominance of CO2 adsorption at reactive sites compared to active oxygen conversion. [Figure 7] FIG. 1 is a cross-sectional view illustrating an example of a carbon dioxide absorption and release device according to an embodiment. [Figure 8] FIG. 13 is a cross-sectional view illustrating an electrochemical cell that can be included in another example of a carbon dioxide absorption and release device according to an embodiment. [Figure 9] Graph showing cyclic voltammetry curves measured in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described with reference to the drawings as appropriate. Note that the same reference numerals are used to designate common components throughout the embodiments, and duplicated descriptions will be omitted. Also, each figure is a schematic diagram for explaining the embodiments and for facilitating understanding thereof, and the shapes, dimensions, ratios, etc. may differ from those of the actual device, but these can be appropriately modified in design by taking into consideration the following explanation and known techniques.

[0011] The following embodiments relate to an adsorbent and a device for separating carbon dioxide (CO2) from a gas containing carbon dioxide by an electrochemical process. The adsorbent is an adsorbent that can realize an electrically responsive device that efficiently absorbs and releases carbon dioxide.

[0012] (Carbon dioxide adsorbent) The carbon dioxide adsorbent according to the embodiment has a condensed heteroaromatic ring structure when it is electrically neutral. The condensed heteroaromatic ring structure contains one or more quinone structures. The carbon dioxide adsorbent contains a quinone structure, and thus can adsorb and release carbon dioxide. Hereinafter, the carbon dioxide adsorbent may be simply referred to as an "adsorbent." Compounds or materials having a condensed heteroaromatic ring structure containing a quinone structure can be produced by appropriately applying known methods.

[0013] According to embodiments, an adsorbent for electro-swing adsorption devices is provided. The electrochemical swing process involves maintaining a specific potential in the forward direction and then cycling to a different potential in the reverse direction. In this manner, the affinity for the target adsorbent can be tuned by using redox-active groups that can be reduced at one potential and oxidized at a different potential. According to such embodiments, energy is efficiently delivered to drive the electrochemical reaction that results in the capture of the target substance (e.g., CO2).

[0014] In such an adsorbent, the quinone structure exhibits an oxidation-reduction response. That is, the quinone structure functions as an oxidation-reduction active moiety. In the adsorbent, the quinone structure exhibits an oxidation-reduction response, thereby adsorbing and releasing carbon dioxide. In detail, the quinone structure is capable of adsorbing carbon dioxide in a reduced state, and the carbon dioxide adsorbed in the quinone structure is capable of releasing the carbon dioxide in an oxidized state.

[0015] It has been reported that typical adsorbents that respond to oxidation and reduction compete with the oxidation and reduction reaction of oxygen depending on the environment in which they are used. In an environment in which oxygen is present, active oxygen species may be generated by the oxidation and reduction reaction of oxygen, and it is known that these active oxygen species deteriorate the adsorbent. Therefore, it is desirable that the adsorbent can give and receive electrons preferentially even in the presence of oxygen, that is, the adsorbent has a more noble oxidation and reduction potential than oxygen.

[0016] As a result of intensive research, we found that the redox potential of molecules having a condensed heteroaromatic ring structure containing a quinone structure tends to be more noble than the redox potential of oxygen. Figures 1 and 2 show examples of carbon dioxide adsorption and desorption schemes using molecules having such structures. Figure 1 shows a scheme when 4,7-phenanthroline-5,6-dione (CAS No. 84-12-8) is used. Figure 2 shows a scheme when benzo[1,2-b:4,5-b']bisthiophene-4,8-dione (CAS No. 32281-36-0) is used. Figures 1 and 2 show examples of redox molecules containing an ortho-quinone structure and a para-quinone structure, respectively. A quinone structure (diketone structure) takes in two electrons when a reduction potential is applied, and the oxygen of the ketone, which is negatively charged due to the localization of the electrons, binds to CO2. Conversely, by applying an oxidizing potential, the bond with CO2 is broken and the quinone structure is formed again. The above chemical reaction proceeds reversibly.

[0017] Unsubstituted quinone compounds such as 1,4-benzoquinone and substituted quinone compounds with halogen or other substituents have been reported as electrochemically active species that can bind to gases in systems that electrochemically separate gases such as CO2. Molecules with condensed heteroaromatic ring structures that contain a quinone structure have superior oxygen dominance during reduction and CO2 adsorption properties compared to the unsubstituted quinone compounds and substituted quinone compounds that have been used conventionally. Therefore, adsorbents that contain condensed heteroaromatic ring structures can provide electrically responsive carbon dioxide absorption and desorption devices that can efficiently absorb and desorb carbon dioxide.

[0018] The condensed heteroaromatic ring structure preferably has one or more selected from the group consisting of a benzene-based heteroaromatic ring structure, a naphthalene-based heteroaromatic ring structure, an anthracene-based heteroaromatic ring structure, and a phenanthrene-based heteroaromatic ring structure. That is, the condensed heteroaromatic ring structure preferably has a skeleton structure similar to a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring. The condensed heteroaromatic ring structure may be a derivative of a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring. The heteroatom contained in the condensed heteroaromatic ring structure may be, for example, one or more selected from the group consisting of nitrogen, oxygen, and sulfur. In addition to nitrogen (N), oxygen (O), and sulfur (S), examples of heteroatoms include phosphorus (P), selenium (Se), and boron (B). The molecule containing the condensed heteroaromatic ring structure may have functional groups such as halogen groups, amino groups, nitro groups, imide groups, imine bonds, aldehyde groups, etc. Examples are shown in Figures 3 to 5.

[0019] 3 to 5 are diagrams showing structural formulas of molecules having a condensed heteroaromatic ring structure containing an example of a quinone structure. FIG. 3 shows a condensed heteroaromatic ring structure containing S as a heteroatom, such as a thiophene-based structure. FIG. 4 shows a condensed heteroaromatic ring structure containing O as a heteroatom, such as a furan-based structure. FIG. 5 shows an example of a molecule having a condensed heteroaromatic ring structure containing N as a heteroatom, such as a pyridine-based or pyrrole-based structure. The condensed heteroaromatic ring quinone molecule that can function as an adsorbent is not limited to the examples shown in the figures. In addition, the condensed heteroaromatic ring structure containing a quinone structure that the adsorbent may contain is not limited to the structure of the molecule shown in the figures.

[0020] In Fig. 3, examples of thiophene-based molecules having a naphthalene-based heteroaromatic ring structure are shown in the left column. Similarly, in Fig. 4, examples of furan-based molecules having a naphthalene-based heteroaromatic ring structure are shown in the left column. In Fig. 5, four examples of pyridine-based molecules having a naphthalene-based heteroaromatic ring structure are shown in the top two rows of the two left columns, and three examples of pyrrole-based molecules having a naphthalene-based heteroaromatic ring structure are shown in the bottom two rows of the right column and the bottom row of the center right column. These molecules having a naphthalene-based heteroaromatic ring structure can also be said to have a condensed heteroaromatic ring structure based on naphthoquinone.

[0021] The central column of Figure 3 shows an example of a thiophene-based molecule having an anthracene-based heteroaromatic ring structure, the central column of Figure 4 shows an example of a furan-based molecule having an anthracene-based heteroaromatic ring structure, and the top row on the right edge of Figure 5 shows an example of a pyrrole-based molecule having an anthracene-based heteroaromatic ring structure, and the top row on the left of the central right column shows an example of a pyridine-based molecule having an anthracene-based heteroaromatic ring structure. These molecules having an anthracene-based heteroaromatic ring structure can also be said to have a condensed heteroaromatic ring structure based on anthraquinone.

[0022] The right column of Figure 3 shows examples of thiophene-based molecules having a phenanthrene-based heteroaromatic ring structure, the right column of Figure 4 shows examples of furan-based molecules having a phenanthrene-based heteroaromatic ring structure, and the bottom two rows of the left two columns of Figure 5 show two examples of pyridine-based molecules having a phenanthrene-based heteroaromatic ring structure, and the middle row of the center right column shows one example of a pyrrole-based molecule having a phenanthrene-based heteroaromatic ring structure. These molecules having a phenanthrene-based heteroaromatic ring structure can also be said to be molecules having a condensed heteroaromatic ring structure based on phenanthrenequinone.

[0023] It is preferable that the redox active site contained in the adsorbent is reduced preferentially to oxygen even in the presence of oxygen, and can adsorb CO2. Since not only competition with the redox reaction of oxygen but also deterioration of the adsorbent due to active oxygen species is avoided, it becomes possible to select the application environment of the adsorbent and the gas to be treated without worrying about the presence or absence of oxygen. If the material has a high bond energy with CO2 and the highest occupied molecular orbital (HOMO) of the reduced state molecule is lower than oxygen, it can be reduced preferentially in the presence of oxygen and adsorb CO2. Therefore, it is possible to estimate molecules that are advantageous as redox active sites in the presence of oxygen by evaluating two evaluation parameters, namely, the advantage in generating active oxygen species and the CO2 binding energy, using first-principles calculations.

[0024] The quinone structure (diketone structure) is formed by two-electron reduction, where the oxygen of the two ketones (R2C=O) becomes anion (R2C-O - ), each -O - CO2 is bonded to the group, resulting in two R2C-O-CO2 - On the other hand, when oxygen molecule O2 is reduced by one electron, reactive oxygen species O2 - (superoxide). So, two molecules of O2 are converted to two molecules of O2 - The difference between the stabilization energy when oxygen is generated and the stabilization energy when electrons are localized in the quinone structure and oxygen is ionized is defined as the advantage parameter for the generation of reactive oxygen species. The stabilization energy when oxygen in the quinone structure is ionized and bonds with CO2 is defined as the other parameter, the CO2 bond energy. An example is shown below.

[0025] The structures and energies of various redox-responsive molecules and their interactions and adsorption reaction systems with CO2 were calculated using density functional theory (DFT) with B3LYP functional. The basis set used was 6-31++G(d,p). The molecular structures were optimized using the energy gradient method in the dielectric field of acetonitrile, and the structures obtained by normal mode analysis were confirmed to be equilibrium structures. For calculations in a dielectric field, a dielectric model (polarizable continuum (PCM) model) that takes into account the solvent effect was used. All calculations were performed using the molecular orbital calculation program Gaussian 16 (Hulinks Co., Ltd.).

[0026] If the CO2 bond energy is small, it is equivalent to CO2 floating around the molecule. Therefore, the larger this energy is, the more stable the bond between the molecule and CO2 can be maintained. Also, the smaller the advantage parameter is, the more unclear the difference between achieving a reduced state of the molecule and generating reactive oxygen species becomes. Therefore, the larger this energy difference is, the more preferable it is.

[0027] The calculation results for examples of molecules having a condensed heteroaromatic ring structure containing a quinone structure are shown in Tables 1 to 4. Table 1 shows the results for thiophene-based molecules, Table 2 shows the results for furan-based molecules, Table 3 shows the results for pyridine-based molecules, and Table 4 shows the results for pyrrole-based molecules.

[0028] [Table 1]

[0029] [Table 2]

[0030] [Table 3]

[0031] [Table 4]

[0032] Some of the results shown in Tables 1 to 4 are summarized in Figure 6. Figure 6 is a distribution diagram plotting the advantage against reactive oxygen species generation on the horizontal axis and the binding energy between molecules and CO2 on the vertical axis. Molecules with higher CO2 adsorptivity compared to reactive oxygen are more likely to bind with CO2 even in the presence of oxygen, and molecules with higher binding energy with CO2 are more likely to bind with CO2.

[0033] The heteroatom introduced into the heteroaromatic ring is electron donating. Therefore, although there may be some variation depending on the positional relationship between the heteroatom and the quinone due to the conjugation effect (resonance effect), it is expected that in quinone compounds containing heteroaromatic rings, the electron density of the quinone O atom increases somewhat, decreasing its dominance against active oxygen. However, the above calculation results suggest that the dominance against active oxygen is high, and that in molecules having a condensed heteroaromatic ring structure containing a quinone structure, electrons are attracted to the heteroatom, decreasing the number of quinone O atoms. In other words, contrary to the expectation that electron donating heteroatoms are unfavorable to the oxidation and reduction of quinones, the introduction of heteroatoms is advantageous.

[0034] In condensed heteroaromatic quinones, electrons are attracted to the heteroatom introduced compared to non-heterocyclic quinones with a diketone in the aromatic ring of the carbon skeleton, and this reduces the degree of electron localization on the O atom of the quinone. On the one hand, the heteroatom attracts electrons, which reduces the binding energy to CO2. On the other hand, the reduced electron localization on the O atom of the quinone makes the quinone more likely to bind to CO2 than to convert environmental oxygen into active oxygen. In detail, when the electron density decreases, the redox potential shifts to a more noble potential, so the reaction proceeds in preference to active oxygen conversion. As a result, the heteroaromatic ring is more dominant.

[0035] Even when a halogen substituent is introduced, the electron density of the O atom of the quinone decreases because the inductive effect of the halogen (I effect) attracts electrons. This reduces the bond energy with CO2, but it is more effective than active oxygenation. Since the I effect is not included in the conjugated system of the aromatic ring, the effect of introducing the halogen is the I effect alone. Condensed heteroaromatic ring quinones show better oxygen dominance and CO2 adsorption than quinones that are not heterocyclic and substituted with halogens. Therefore, condensed heteroaromatic ring structures containing a quinone structure are suitable as carbon dioxide adsorbents.

[0036] The adsorbent may be a porous material containing a condensed heteroaromatic ring structure including a quinone structure as an oxidation-reduction active site, or an oligomer or polymer containing a molecule including the condensed heteroaromatic ring structure as a unit structure.

[0037] The porous body, which is one of the forms that the carbon dioxide adsorbent can take, includes a porous material having a large number of pores. The pores preferably have a pore size of 5 nm or less. Specifically, the porous body is preferably a sub-nanoporous material or nanoporous material having pores of angstrom size (1 nm or less) to nanometer size, more specifically, 0.5 nm to 5 nm.

[0038] The porous body includes a redox active moiety, i.e., the above-mentioned quinone structure, which reduces a diketone structure in response to an electric current and bonds with carbon dioxide, and then oxidizes the diketone structure in response to an electric current, releasing the bond with carbon dioxide, and reforms the diketone structure. The redox active moiety may be included as a functional group in the molecular structure that constitutes the porous body. The redox active moiety is not limited to the molecules and compounds of the above-mentioned examples, and may also be a derivative of the above-mentioned molecules and compounds having a condensed heteroaromatic ring structure containing a quinone structure.

[0039] The content of molecules having a condensed heteroaromatic ring structure including a quinone structure that exhibits redox activity through electrical response in the porous body is preferably 10% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 75% by mass or less, based on the total mass of the porous body.

[0040] In general, the greater the amount of active groups contained in the adsorbent, the greater the amount of carbon dioxide absorbed and desorbed per unit volume of the adsorbent. Therefore, from the standpoints of energy consumption, plant equipment size, and treatment efficiency, a larger amount of active groups is desirable.

[0041] The content of the molecules having a condensed heteroaromatic ring structure including a quinone structure that shows redox activity by electrical response is preferably 90% by mass or less based on the total mass of the porous body. This content allows the amount of redox active sites per unit volume of the porous body to be appropriate, so that the redox active groups are not too close to each other and the pores can be maintained. In addition, the active groups can be fully utilized because carbon dioxide can easily access them. The content of the molecules having a condensed heteroaromatic ring structure including a quinone structure is more preferably 75% by mass or less.

[0042] By setting the content of redox active sites to 10 mass% or more, sufficient carbon dioxide adsorption amount and adsorption rate can be obtained, and excellent treatment efficiency can be obtained. Therefore, a porous body having a content of redox active sites within the above range is advantageous in that it not only has a high carbon dioxide absorption amount and carbon dioxide absorption rate in carbon dioxide recovery applications, but also has a large carbon dioxide desorption amount from the porous body and a high carbon dioxide desorption rate (reaction rate), allowing efficient carbon dioxide recovery.

[0043] Specific examples of molecules having a condensed heteroaromatic ring structure containing a quinone structure that can function as an oxidation-reduction active site in a porous body include those having an amino group or an aldehyde group as the functional group R or R', as shown in Figures 3 to 5. Molecules having an amino group or an aldehyde group as the functional group R or R' that is present at symmetrical positions on the ring as shown in the figures can be suitably incorporated into the molecular structure of a porous body.

[0044] As in the above example, the quinone structure, which is the active site in the porous material, absorbs CO2 and then releases CO2 to be regenerated and reused. For this reason, it is preferable that the condensed heteroaromatic ring structure containing the quinone structure has high chemical stability.

[0045] The porous body preferably contains one or more porous materials selected from the group consisting of a covalent-organic framework (COF) having an electric response activity, a metal-organic framework (MOF), a porous carbon material, a zeolite, a porous silica, and a porous alumina. For example, the porous body may contain a COF having an electric response. Alternatively, the porous body may contain a MOF having an electric response.

[0046] The presence or absence of a quinone structure is 1 H NMR (Nuclear Magnetic Resonance) and 13 Based on C NMR measurements, it is possible to predict the formation of a condensed heteroaromatic ring structure containing a quinone structure. -1 - 1800 cm -1 If the carbonyl stretching vibration absorption is observed at 1060 cm, it can be determined that the compound contains a ketone structure. For heteroaromatic ring structures, for example, if the compound contains a sulfur atom, it can be determined that the compound contains a ketone structure at 1060 cm based on Raman spectroscopy. -1 - 1100 cm -1It can be determined that the material contains a heteroaromatic ring structure by observing strong luminescence due to the stretching vibration of the aromatic S-C bond. The same is true for heteroaromatic rings containing nitrogen or oxygen. In this way, a combination of infrared spectroscopy, Raman spectroscopy, and NMR measurements can be used to confirm that the carbon dioxide adsorbent contains a condensed heteroaromatic ring structure that contains a quinone structure.

[0047] The carbon dioxide adsorbent described above includes a condensed heteroaromatic ring structure containing one or more quinone structures, and is capable of efficiently adsorbing and releasing carbon dioxide even in an oxygen-containing environment.

[0048] (Carbon dioxide absorption and release device) The carbon dioxide absorption and release device according to the embodiment includes the carbon dioxide adsorbing material according to the embodiment described above.

[0049] As explained above, such an adsorbent can exhibit redox activity through electrical response. Therefore, the carbon dioxide absorption / release device can adsorb and release carbon dioxide at the redox active site (quinone structure; ketone group) of the adsorbent through a change in the electric potential applied to the device. A device using an adsorbent that absorbs and releases carbon dioxide at such an electrically responsive redox active site can absorb and release carbon dioxide at room temperature. Therefore, the device can absorb and release carbon dioxide with low energy.

[0050] The device can preferably absorb carbon dioxide as described above, and can be preferably applied to a device for recovering carbon dioxide contained in factory exhaust gases and the atmosphere. For example, a carbon dioxide recovery system can be constructed using the carbon dioxide absorption and release device.

[0051] Such a device may include an electrode for applying an electric charge to the redox active site of the adsorbent having the above-mentioned condensed heteroaromatic ring structure containing a quinone structure. In the device, the adsorbent may be included in an electrode (working electrode). The electrode is preferably porous, such as a mesh shape, so that more adsorbents can receive and give electrons. The adsorbent may also be dispersed in a porous electrode. The adsorbent may be dispersed in a solution within the device. The solution containing the adsorbent and the electrode may be arranged in the device so that the solution and the electrode are in electrical contact with each other.

[0052] The electrode may further include a current collector. For example, the adsorbent may be in the form of the porous body described above, dispersed in another porous structure, or modified into a conductive member and supported on the current collector and included in the electrode. For example, the porous body may be formed on the surface of the current collector.

[0053] The current collector can act as a conductor to transfer charge to the adsorbent and electrically activate the redox-active sites. By changing the potential of the current collector, the adsorbent contains redox-active sites that can be oxidized and reduced, allowing the adsorbent to adsorb and release carbon dioxide at the sites.

[0054] A porous composite can also be formed by combining a porous body with a conductive member, for example, by mixing the porous body with the conductive member or by modifying (coating) the surface of the conductive member with the porous body.

[0055] In the porous composite, it is preferable that the redox active site contained in the adsorbent is in close proximity to or in contact with a nearby conductive member. Therefore, it is preferable that the adsorbent covers at least a part of the surface of the conductive member or that the adsorbent is attached to the conductive member. For example, the above-mentioned COF or MOF can be included in the porous composite so as to cover the conductive member.

[0056] The electrode may further include a binder. The electrode may or may not include a binder. The binder can, for example, bind the current collector, the porous body, and the conductive member, or the current collector and the porous composite. Examples of the binder that can be used include polyvinylidene fluoride (PVdF), polymethyl methacrylate (PMMA), and polyimide (PI).

[0057] Such a carbon dioxide absorption / release device may further include an electrolyte (e.g., an electrolyte solution). An adsorbent may be dispersed in the electrolyte solution. Alternatively, an electrolyte may be held in a porous body by an electrode having a porous body or a porous composite. The electrolyte may be contained, for example, in the pores of the porous body. By containing an electrolyte, electrical conductivity is improved, and the ability to absorb and release CO2 is increased.

[0058] The device includes an electrode containing the adsorbent or an electrode in electrical contact with a solution in which the adsorbent is dispersed, which is used as a working electrode. A potential is applied to the working electrode to apply a charge to the redox active sites contained in the adsorbent. In other words, the redox state of the adsorbent is switched between an oxidized state and a reduced state by controlling the potential of the electrode. The adsorbent is capable of adsorbing carbon dioxide in a reduced state and releasing carbon dioxide in an oxidized state.

[0059] For example, a potential can be applied to the working electrode by using a counter electrode for the working electrode and applying a voltage between the two electrodes. For example, the carbon dioxide absorption / release device may include a counter electrode for the electrode included in the device. In other words, the carbon dioxide absorption / release device may be configured as an electrochemical cell using the working electrode and counter electrode. The embodiment of the device is not limited to an electrochemical cell. A specific example of an electrochemical cell may be a three-electrode cell including a reference electrode in addition to the working electrode and counter electrode.

[0060] A specific example of the carbon dioxide absorption and release device according to the embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a schematic cross-sectional view showing an example of the carbon dioxide absorption and release device according to the embodiment. Fig. 8 is a schematic cross-sectional view showing an electrochemical cell that can be included in another example of the device.

[0061] The carbon dioxide absorption / release device 100 shown in FIG. 7 includes an electrochemical cell 110 and a potentiostat 10. The electrochemical cell 110 includes an electrolytic cell 1 including cells 1a and 1b, a working electrode 2, a counter electrode 3, a reference electrode 4, a separator 6, a nozzle 8 for introducing gas, a nozzle 18 for collecting released carbon dioxide, and a lid 9. The cell 1a contains an electrolytic solution 5a and a rotor 7 for stirring the electrolytic solution 5a. The carbon dioxide adsorbent may be contained in the electrochemical cell 110 in a state dispersed in the electrolytic solution 5a. The cell 1b contains an electrolytic solution 5b. In one example, the electrolytic solution 5b does not contain a carbon dioxide adsorbent. A lid 9 for preventing the intrusion of outside air into the cells 1a and 1b is provided at the opening of each cell, and a gas containing carbon dioxide can be introduced into the electrolytic solution 5a through a nozzle 8 penetrating the lid 9. In the example shown in the figure, the working electrode 2 and the counter electrode 3 are located separately in the cells 1a and 1b, respectively. The arrangement of the electrodes is not limited to this example, and for example, the counter electrode and the working electrode may be integrated with a separator interposed therebetween. A specific example is an electrochemical cell 120 shown in FIG.

[0062] The electrochemical cell 120 shown in FIG. 8 includes a cell 121, a working electrode 122, a counter electrode 123, and a separator 126. The cell 121 is divided into two chambers, an upper chamber and an lower chamber, with a separator 126 sandwiched therebetween, and a working electrode 122 and a counter electrode 123 are provided on the upper and lower main surfaces of the separator 126, respectively. An electrolyte 125 is contained in the lower chamber of the cell 121, and the counter electrode 123 is in contact with the electrolyte 125. The counter electrode 123 may be immersed in the electrolyte 125. The working electrode 122 is located in the upper chamber of the cell 121. The working electrode 122 contains a carbon dioxide adsorbent, and may include, for example, the above-mentioned porous composite. The electrolyte 125 contained in the lower chamber does not contain an adsorbent. The upper chamber in which the working electrode 122 is located can function as a gas flow path 128, and by ventilating a gas containing carbon dioxide, the contained carbon dioxide can be adsorbed by the adsorbent in the working electrode 122.

[0063] In order to improve the current flow to the working electrode 122, a porous collector 124 may be laminated on the outside of the working electrode 122, and a porous support 127 for fixing the working electrode 122 and the porous collector 124 as a whole may be laminated on the outside of the porous collector 124. A porous support 127 may also be laminated on the outside of the counter electrode 123. The end of the laminate of the porous collector 124, working electrode 122, separator 126, and counter electrode 123 sandwiched between the supports 127 thus prepared may be fixed with a fixture 129. Since the working electrode 122 is porous, the porous collector 124 may be omitted as necessary. In addition, if the mechanical strength of the working electrode 122 and the counter electrode 123 is sufficient, the porous support 127 may be omitted.

[0064] The current collector, the conductive member, and the electrolyte will be described in detail below.

[0065] Current collector A member made of carbon or metal can be used as the current collector. The better the conductivity of the current collector and the larger the surface area, the more redox active sites the charge can be transferred to. Examples of carbon members include glassy carbon, graphite sheet, carbon felt, carbon cloth, carbon mesh, carbon paper, and carbon sheet with gas diffusion layer. Examples of metal members include copper plate, copper sheet, copper mesh, aluminum plate, aluminum sheet, aluminum mesh, nickel plate, nickel sheet, and nickel mesh. The carbon members and metal members are not limited to the above.

[0066] Conductive Materials The conductive member may be, for example, a carbon material having good electrical conductivity. The conductive member may include, for example, one or more selected from the group consisting of carbon nanotubes, graphite, graphene, carbon nanofibers, and Ketjen black. The conductive member may have a linear or planar shape to increase the contact probability, and may preferably be in the form of a rod, tube, fiber, sheet, or flake.

[0067] electrolyte The electrolyte may be, for example, a liquid electrolyte (electrolyte). The electrolyte may include, for example, an ionically bonded salt. Specifically, the ionically bonded salt is preferably one or more selected from the group consisting of an alkali metal salt, an alkaline earth metal salt, a transition metal salt, an amphoteric metal salt, an ammonium salt, an imidazolium salt, a pyridinium salt, and a phosphonium salt. The ionically bonded salt may be in the form of a solid or liquid, and an example of the liquid may include, for example, an ionic liquid.

[0068] The cations of the ionic salts are alkali metals such as Li, Na, K, Rb, and Cs; alkaline earth metals such as Mg, Ca, Sr, and Ba; transition metals such as Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Pd, and Ag; amphoteric metals such as Al, Ga, and Sn; ammonium ions and ammonium ions substituted with lower hydrocarbons of C1 to C5 (N(C n H2n+1 )4 + , n=1-5); imidazolium ion or imidazolium ion having one to three substituents; pyridinium ion or pyridinium ion having one to three substituents; piperidinium ion or piperidinium ion having one to three substituents; pyrrolidinium ion or pyrrolidinium ion having one to three substituents; and phosphonium ion having four substituents PR4 + (R: hydrocarbon group), one or more selected from the group consisting of these may be used, and one of the above may be used alone or a combination of two or more may be used.

[0069] The anion of the ionic salt is Cl. - , Br - , and I - Halogens such as nitrate ions (NO3 - ), PF6 - , BF4 - , CF3SO3 - , N(SO2F2)2 - , N(SO2CF3)2 - , CH3COO - , CF3COO - , and ClO4 - One or more selected from the group consisting of the above may be used, and one of the above may be used alone or a combination of a plurality of them may be used.

[0070] As the ion-conductive polymer, it is preferable to use, for example, one or more selected from the group consisting of polyethylene oxide (PEO), polypropyl oxide (PPO), polyacrylonitrile (PAN), polyvinyl chloride (PVC), ionic liquid polymer, polyaniline, and polythiophene (PEDOT).

[0071] The electrolyte may contain a solvent. The solvent of the electrolyte may be, for example, water or an organic solvent. When the electrolyte is an ionic liquid, the solvent may be used or may be omitted. As the organic solvent, it is desirable to use one or more selected from the group consisting of acetonitrile, propylene carbonate, ethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, succinic anhydride, cyclohexylbenzene, thiophene, toluene, fluorobenzene, and hexafluorobenzene.

[0072] <Manufacturing method> Such a carbon dioxide absorbing and releasing device can be manufactured, for example, as follows.

[0073] First, a carbon dioxide adsorbent is prepared. For example, the adsorbent is obtained by synthesis.

[0074] To obtain a device containing the adsorbent in a solution state, the prepared adsorbent is added to an electrolyte solution, and the electrodes are placed in contact with the resulting solution.

[0075] When integrating an adsorbent with an electrode, for example, a porous body containing an adsorbent is synthesized, and a paste containing the obtained porous body is applied to a current collector to obtain an electrode containing an adsorbent. Specifically, the synthesized porous body is mixed with an appropriate conductive material, a binder, a solvent, etc. to prepare a paste. The paste is applied to a current collector to obtain an electrode.

[0076] The above is merely an example, and the paste does not necessarily need to contain a binder. Depending on the properties of the conductive material, it may be possible to heat and dry the paste to form a self-supporting electrode. In other words, it is possible to obtain an electrode that includes, for example, a porous body containing an adsorbent alone, without using a current collector.

[0077] When the electrode is to be impregnated with an electrolyte, for example, an electrolyte solution is prepared, the prepared solution is cast on the surface of the electrode, and then vacuum impregnation is performed, whereby the electrolyte can be impregnated in the electrode.

[0078] The carbon dioxide absorption / release device described above includes a carbon dioxide adsorbent having a condensed heteroaromatic ring structure. The condensed heteroaromatic ring structure contains one or more quinone structures. Such a device is a carbon dioxide absorption / release device that can absorb and release carbon dioxide efficiently with low energy.

[0079] (Carbon dioxide separation method) The carbon dioxide separation method according to the embodiment includes removing carbon dioxide from a gas containing carbon dioxide by adsorbing carbon dioxide onto an adsorbent using the carbon dioxide absorption and release device, and desorbing carbon dioxide from the adsorbent to regenerate the adsorbent. Adsorbing carbon dioxide onto the adsorbent includes passing a current through the adsorbent at the reduction potential of the adsorbent, and contacting the gas containing carbon dioxide with the adsorbent while maintaining the potential flowing through the adsorbent at the reduction potential. Desorbing carbon dioxide from the adsorbent to regenerate the adsorbent includes switching the potential flowing through the adsorbent that has adsorbed carbon dioxide to the oxidation potential of the adsorbent. The regenerated adsorbent can be reused.

[0080] By setting the device after the carbon dioxide has been separated from the adsorbent back to the reduction potential, the carbon dioxide adsorption process can be carried out again. In this way, the device can be used repeatedly by switching the potential of the current passed through the adsorbent between the reduction potential and the oxidation potential.

[0081] The method of contacting the gas containing carbon dioxide with the adsorbent is not particularly limited. For example, in a carbon dioxide absorption / release device containing an electrolyte, a method of bubbling a gas containing carbon dioxide in the electrolyte to adsorb carbon dioxide in the electrolyte can be mentioned. As another example, a method of configuring a carbon dioxide absorption / release device so that the adsorbent is exposed to a gas stream containing carbon dioxide can be mentioned.

[0082] The concentration of carbon dioxide to be contacted with the adsorbent is not particularly limited, but can accommodate a wide range of CO2 concentrations, from atmospheric levels to concentrations emitted from thermal power plants, etc. Specifically, the carbon dioxide concentration is preferably 0.01 vol% or more, and more preferably 0.04 vol% or more and 50 vol% or less.

[0083] The environmental temperature during the carbon dioxide absorption / release treatment is usually preferably 0°C or higher and 60°C or lower. A more preferable temperature is 50°C or lower, and an especially preferable temperature is 10°C or higher and 45°C or lower. The lower the temperature at which absorption is performed, the greater the amount of carbon dioxide adsorbed. The lower limit of the treatment temperature can be determined based on the gas temperature in the process, the heat recovery target, etc. The carbon dioxide adsorption pressure is usually approximately equal to atmospheric pressure. It can also be pressurized to a higher pressure to improve the absorption performance.

[0084] A method for absorbing and releasing carbon dioxide using such a carbon dioxide absorption and release device may include, for example, the following steps: passing an electric current at a reduction potential through a site containing the adsorbent; adsorbing carbon dioxide onto an adsorbent; changing the potential to an oxidation potential and passing a current; The process in which carbon dioxide is desorbed from the adsorbent.

[0085] The carbon dioxide separation method described above includes adsorbing carbon dioxide to an adsorbent contained in a carbon dioxide absorption / release device, desorbing and separating carbon dioxide from the adsorbent to which the carbon dioxide has been adsorbed, and regenerating the adsorbent. Carbon dioxide is adsorbed into the adsorbent while a current flowing through the adsorbent is maintained at a reduction potential. The current flowing through the adsorbent is switched to an oxidation potential, and carbon dioxide is desorbed while the oxidation potential is maintained. According to this separation method, carbon dioxide can be efficiently absorbed and released. EXAMPLES

[0086] Hereinafter, an embodiment of a carbon dioxide absorbing and releasing device using a carbon dioxide adsorbent will be described.

[0087] (Example 1) <Synthesis of Phenanthrene-dithiophene (PDT)> Commercially available phenanthrene-dithiophene (PDT) was prepared and used as it was.

[0088] <Fabrication of Device> The PDT obtained above and tetrabutylammonium tetrafluoroborate (TBABF4) as an electrolyte were added to propylene carbonate (PC) at 0.2 mol / L and 0.75 mol / L respectively, and heated and mixed (about 80 °C) to obtain a pale yellow transparent solution. The obtained solution was set in an electrolytic cell as an electrolyte to obtain the device of Example 1. Other details of the device will be described later.

[0089] (Example 2) <Synthesis of 2,6-diaminobenzo[1,2-b:4,5-b']dithiophene-4,8-dione (2NH2-BDTD)> Commercially available 2,6-diaminobenzo[1,2-b:4,5-b']dithiophene-4,8-dione (2NH2-BDTD) was prepared and used as it was.

[0090] <Fabrication of Device> The 2NH2-BDTD and TBABF4 obtained above were added to PC and adjusted to 0.2 mol / L and 0.75 mol / L respectively to obtain an electrolyte. The obtained electrolyte was set in an electrolytic cell to obtain the device of Example 2. Other details of the device will be described later.

[0091] (Example 3) <Synthesis of 2NH2-BDTD-TFP-COF Composite Electrode> Referencing Non-Patent Document 1 (J. Am. Chem. Soc., 2013, 135, 16821-16824), 2NH2-BDTD and 1,3,5-triformylphloroglucinol (TFP) were placed in a heat-resistant container in a molar ratio of 1:3 and heated at 120 °C for 2 days in a dioxane solvent. The obtained crude crystals were washed and filtered with a dimethylacetamide (DMA) solvent and dried under reduced pressure to obtain 2NH2-BDD-TFP-COF. The obtained 2NH2-BDTD-TFP-COF was mixed with carbon nanofibers (CNF) and polyvinylidene fluoride (PVdF) in a mass ratio of 6:3:1 under an N-methylformaldehyde solvent (NMF solvent), and coated on a carbon felt to obtain an electrode as a composite containing a porous body.

[0092] <Fabrication of Device> The composite electrode obtained above was set in an electrolytic cell, and an electrolytic solution prepared by dissolving TBABF4 in PC at 0.75 mol / L was used to obtain the device of Example 3. Other details of the device will be described later.

[0093] (Example 4) <Synthesis of 5,8-Quinolinediol (QD)> Commercially available 5,8-quinolinediol (QD) was prepared and used as it was.

[0094] <Fabrication of Device> QD and TBABF4 obtained above were added to PC and adjusted to 0.2 mol / L and 0.75 mol / L respectively to obtain an electrolytic solution. The obtained electrolytic solution was set in an electrolytic cell to obtain the device of Example 4.

[0095] (Example 5) <Synthesis of Benzo[1,2-b:4,5-b']difuran-4,8-dione (BDFD)> Commercially available benzo[1,2-b:4,5-b']difuran-4,8-dione (BDFD) was prepared and used as it was.

[0096] <Fabrication of the Device> BDFD and TBABF4 obtained above were added into PC and adjusted to 0.2 mol / L and 0.75 mol / L respectively to obtain an electrolyte. The obtained electrolyte was set in an electrolytic cell to obtain the device of Example 5.

[0097] (Example 6) <Synthesis of 1H-Indole-4,5-dione (ID)> Commercially available 1H-indole-4,5-dione (ID) was prepared and used as it was.

[0098] <Fabrication of the Device> ID and TBABF4 obtained above were added into PC and adjusted to 0.2 mol / L and 0.75 mol / L respectively to obtain an electrolyte. The obtained electrolyte was set in an electrolytic cell to obtain the device of Example 6.

[0099] (Example 7) <Synthesis of Benzo[b]selenophene-4,7-dione (BSD)> Commercially available benzo[b]selenophene-4,7-dione (BSD) was prepared and used as it was.

[0100] <Fabrication of the Device> BSD and TBABF4 obtained above were added into PC and adjusted to 0.2 mol / L and 0.75 mol / L respectively to obtain an electrolyte. The obtained electrolyte was set in an electrolytic cell to obtain the device of Example 7.

[0101] (Comparative Example 1) <Preparation of 1,8-diaminoanthraquinone (2NH2-AQ)> Commercially available 1,8-diaminoanthraquinone (1,8-diaminoanthraquinone; 2NH2-AQ) was prepared and used as it was.

[0102] <Fabrication of Device> A device of Comparative Example 1 was obtained in the same manner as in Example 1 except that 2NH2-AQ was used instead of PDT.

[0103] (Comparative Example 2) <Synthesis of Naphthazarin (NZ)> Naphthazarin (NZ) was obtained.

[0104] <Fabrication of Device> A device of Comparative Example 2 was obtained in the same manner as in Example 1 except that NZ was used instead of PDT.

[0105] (Evaluation) <Infrared Spectroscopy Measurement> Infrared spectroscopy measurement was performed on the PDT prepared in Example 1. The infrared spectroscopy measurement was carried out as follows. Using an infrared spectroscopy apparatus (FT-IR6100 manufactured by JASCO Corporation), the measurement range was 400 cm -1 - 4000 cm -1 , and the measurement was performed at a measurement speed of 40 cm -1 / sec. Absorption derived from the stretching vibration of the aromatic S-C bond was observed near 1100 cm -1 , absorption derived from the stretching vibration of the aromatic ring was observed at 1400 cm -1 - 1600 cm -1 , and a strong absorption derived from the stretching vibration of the C=O bond was observed near 1600 cm -1 - 1850 cm -1 . From this, it was confirmed that it is a heteroaromatic ring structure containing S having a quinone structure. <Raman Spectroscopy Measurement> Raman spectroscopy measurement was performed on the PDT prepared in Example 1.

[0106] Raman spectroscopic measurement was carried out as follows. Using a Raman spectrometer (LabRAM Evolution manufactured by HORIBA), measurements were performed with an excitation laser wavelength of 532 nm and a measurement range of 200 cm -1 - 3300 cm -1 A strong emission derived from the stretching vibration of the aromatic S-C bond was observed at 1060 cm -1 - 1100 cm -1 and a strong emission derived from the stretching vibration of the aromatic ring was observed at 1400 cm -1 - 1600 cm -1 From this, it was confirmed that there is a heteroaromatic ring structure containing S in the molecular structure.

[0107] <NMR Measurement> For the PDT prepared in Example 1, 1 1H and 13 13C NMR measurements were performed. The measurement conditions and the peaks confirmed in the measurement spectra were as follows.

[0108] 1 1H NMR (CD2Cl2, 400 MHz, δ in ppm): 7.62 (dd, 2H), 7.44 (dd, 2H). 13 13C NMR (DMSO, 100 MHz, δ in ppm): 127.0, 135.0, 138.2, 149.5, 177.0. <Electrochemical Measurement> For each device fabricated in Examples 1 to 6 and Comparative Examples 1 to 2, the electrochemical performance was evaluated. Specifically, test devices using each fabricated device were constructed, and cyclic voltammetry (CV) measurements were performed.

[0109] For Examples 1, 2, and 4 to 6, and Comparative Examples 1 and 2, a three-electrode electrochemical cell configuration similar to that of the carbon dioxide absorption and release device 100 shown in Fig. 7 was used for the test device. In the test device, a glassy carbon rod with a diameter of 3 mm was used as the working electrode 2, an electrolyte containing the adsorbent prepared in Examples 1, 2, and 4 to 6, and Comparative Examples 1 and 2 was used as the working electrode side electrolyte (5a), a platinum mesh electrode was used as the counter electrode 3, a 0.75 mol / L TBABF4 electrolyte containing 0.01 mol / L ferrocene was used as the counter electrode side electrolyte (5b), and an Ag / Ag + An electrode (acetonitrile / 0.1M (M:mol / L) tetrabutylammonium perchlorate solution / 0.01M AgNO3) was used.

[0110] Before the measurement, argon (Ar) gas was passed through the nozzle 8 into the electrolyte 5a in the cell 1a for about 30 minutes, and a CV measurement was performed using the potentiostat 10. Next, 100% carbon dioxide gas was passed through the nozzle 8 for about 30 minutes, and a CV measurement was performed again.

[0111] For Example 3, since the adsorbent was integrated with the electrode, measurements were carried out using a test device with an electrochemical cell having the configuration shown in FIG. 8. The fabricated composite electrode was used as the working electrode 122 and laminated with a platinum mesh electrode as the counter electrode 123 via a separator 126. In order to improve the energization of the composite electrode, a porous current collector 124 was laminated outside the working electrode 122, and a support 127 of a porous material for fixing the entire electrode was further laminated outside thereof. A support 127 of a porous material was similarly laminated outside the counter electrode 123, and the ends were fixed with a fixture 129. An electrolytic solution 125 (a 0.75 mol / L TBABF4 solution containing 0.01 mol / L ferrocene not containing an adsorbent) was placed in one chamber of the cell 121 having two communicating chambers, the communication between the two chambers was blocked, and a laminate including the working electrode 122 and the counter electrode 123 was set in the cell 121 so that the counter electrode 123 was immersed in the electrolytic solution 125. The chamber without the electrolytic solution 125 was used as a gas flow path 128 through which Ar gas and carbon dioxide gas were passed. Note that a separator 126 having a structure in which the electrolytic solution 125 penetrates through the separator 126 to the working electrode 122 was used. CV measurement was performed in the same manner as in Example 1 except that such an electrochemical cell 120 was used.

[0112] As an example, the CV measurement results of PDT obtained by the device of Example 1 are shown in FIG. 9. In the graph shown in FIG. 9, the curve in the CV measurement under a CO2 atmosphere is shown by a solid line. As shown in the graph, a reduction peak was observed around -0.8 V (vs. Ag / Ag + ) and an oxidation peak was observed around -0.66 V (vs. Ag / Ag + ). Therefore, as predicted by the calculation, it was confirmed that the redox reaction was carried out at a potential nobler than the redox potential of oxygen.

[0113] <CO2 Adsorption and Desorption Test> A carbon dioxide absorption / release test was carried out using the devices prepared in Examples 1 to 6 and Comparative Examples 1 to 2. The basic operation of this test was the same as that of the CV evaluation. First, an inert gas was introduced into the electrolyte, and bubbling was carried out for about 30 minutes. Argon gas was used as the inert gas. Then, while the carbon dioxide gas was being bubbled, a potential slightly exceeding the reduction potential of each adsorbent was applied for a certain period of time to adsorb carbon dioxide to the adsorbent. Then, the space above the electrolyte was replaced with an inert gas, and a tube for recovering CO2 was connected to the cell. With everything except the CO2 recovery tube sealed, a potential slightly exceeding the oxidation potential of each adsorbent was applied for a certain period of time to desorb carbon dioxide from the adsorbent. The desorbed carbon dioxide accumulates in the space above the electrolyte. After the application of the potential for desorbing carbon dioxide was stopped, sampling was carried out on the space above the electrolyte. Quantitative analysis was carried out by gas chromatography (GC) using the collected gas to determine the amount of carbon dioxide that could be adsorbed and recovered by the adsorbent. The amount of CO2 recovered by each adsorbent is shown in Table 5 below. The abbreviation and chemical structure of each adsorbent are also shown in Table 5. However, for Example 3, the chemical structure is shown below Table 5 due to its size.

[0114] [Table 5]

[0115] [ka]

[0116] From the results of Examples 1 to 6 and Comparative Examples 1 and 2 shown in Table 5, it can be seen that it is advantageous not only to introduce a substituent to the periphery of the condensed ring but also to replace some of the carbons constituting the ring to form a heterocycle. Moreover, from Examples 1, 2, and 3, it can be seen that the performance of the adsorbent having a condensed heteroaromatic ring structure does not differ significantly depending on the heteroatom introduced into the ring. Furthermore, from Examples 2 and 3, since the COF is on the electrode, the transfer of electrons is easier than in the solution type, and the amount of CO2 is slightly increased.

[0117] According to one or more of the embodiments and examples described above, a carbon dioxide adsorbent and a carbon dioxide absorption / release device using the same are provided. The adsorbent has a condensed heteroaromatic ring structure containing one or more quinone structures, and can efficiently absorb and release carbon dioxide. As a result, the device can efficiently absorb and release carbon dioxide, and can efficiently recover carbon dioxide.

[0118] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0119] Several embodiments according to the present invention will be described below. [1] A carbon dioxide adsorbent that can adsorb and release carbon dioxide and has a condensed heteroaromatic ring structure containing one or more quinone structures. [2] The carbon dioxide adsorbent according to [1], which is capable of adsorbing carbon dioxide to the quinone structure in a reduced state and releasing carbon dioxide from the quinone structure in an oxidized state. [3] The carbon dioxide adsorbent according to [1] or [2], which is capable of performing oxidation-reduction through an electrical response. [4] The carbon dioxide adsorbing material according to any one of [1] to [3], wherein the condensed heteroaromatic ring structure has one or more selected from the group consisting of a benzene-based heteroaromatic ring structure, a naphthalene-based heteroaromatic ring structure, an anthracene-based heteroaromatic ring structure, and a phenanthrene-based heteroaromatic ring structure. [5] The carbon dioxide adsorbing material according to any one of [1] to [4], wherein the condensed heteroaromatic ring structure contains one or more elements selected from the group consisting of nitrogen, oxygen, and sulfur. [6] The carbon dioxide adsorbent according to any one of [1] to [5], which is a porous metal-organic framework. [7] The carbon dioxide adsorbent according to any one of [1] to [5], which is a porous covalent organic framework. [8] The carbon dioxide adsorbing material according to any one of [1] to [5], which is an oligomer or polymer having a molecule containing the condensed heteroaromatic ring structure as a unit structure. [9] The carbon dioxide adsorbent according to any one of [1] to [8], which exhibits an oxidation-reduction potential higher than the oxidation-reduction potential of oxygen.

[10] A carbon dioxide absorption and release device comprising the carbon dioxide adsorbent material described in any one of [1] to [9]. [Explanation of symbols]

[0120] 1...electrolytic cell, 1a...cell, 1b...cell, 2...working electrode, 3...counter electrode, 4...reference electrode, 5a...electrolyte, 5b...electrolyte, 6...separator, 7...rotor, 8...nozzle, 9...lid, 10...potentiostat, 18...nozzle, 100...carbon dioxide absorption and release device, 110...electrochemical cell, 120...electrochemical cell, 121...cell, 122...working electrode, 123...counter electrode, 125...electrolyte, 126...separator, 128...gas flow path.

Claims

1. A carbon dioxide adsorbent capable of adsorbing and releasing carbon dioxide, which has a condensed heteroaromatic ring structure containing one or more quinone structures.

2. 2. The carbon dioxide adsorbing material according to claim 1, which is capable of adsorbing carbon dioxide to the quinone structure in a reduced state and releasing carbon dioxide from the quinone structure in an oxidized state.

3. The carbon dioxide adsorbing material according to claim 1 or 2, which is capable of performing oxidation / reduction in response to an electric current.

4. The carbon dioxide adsorbing material according to claim 3, wherein the condensed heteroaromatic ring structure has one or more selected from the group consisting of a benzene-based heteroaromatic ring structure, a naphthalene-based heteroaromatic ring structure, an anthracene-based heteroaromatic ring structure, and a phenanthrene-based heteroaromatic ring structure.

5. The carbon dioxide adsorbing material according to claim 3 , wherein the condensed heteroaromatic ring structure contains one or more atoms selected from the group consisting of nitrogen, oxygen, and sulfur.

6. The carbon dioxide adsorbing material according to claim 1 or 2, which is a porous metal-organic framework.

7. The carbon dioxide adsorbing material according to claim 1 or 2, which is a porous covalent organic framework.

8. The carbon dioxide adsorbing material according to claim 1 or 2, which is an oligomer or polymer containing, as a unit structure, a molecule containing the condensed heteroaromatic ring structure.

9. The carbon dioxide adsorbing material according to claim 1 or 2, which exhibits an oxidation-reduction potential higher than the oxidation-reduction potential of oxygen.

10. A carbon dioxide absorbing and releasing device comprising the carbon dioxide adsorbent material according to claim 1.

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