Carbon dioxide capture methods

Abstract

One aspect of the present invention provides a means for highly selectively carrying out the carboxylation of unsaturated organic compounds as a method of carbon dioxide recovery using an organic catalyst that does not contain transition metals. [Solution] One aspect of the present invention relates to a method for recovering carbon dioxide, wherein carbon dioxide is recovered as a carboxylic acid of an unsaturated organic compound or a salt thereof by irradiating a solution containing carbon dioxide, an unsaturated organic compound, a solvent, and one or more photosensitizers selected from a carbazole catalyst with light.

Description

[Technical Field]

[0001] One aspect of the present invention relates to a method for recovering carbon dioxide. [Background technology]

[0002] Photochemical carboxylation of unsaturated compounds is a known process.

[0003] For example, Non-Patent Document 1 discloses carboxylation of various heterocyclic compounds.

[0004] Non-patent document 2 discloses the synthesis of salicylic acid analogs from phenol analogs using a polymer catalyst.

[0005] Patent document 1 and non-patent document 3 disclose carboxylation of pyridine analogs using a thiol catalyst. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 117247351 Specification [Non-patent literature]

[0007] [Non-Patent Document 1] Matthias Schmalzbauer et al., "Redox-Neutral Photocatalytic CH Carboxylation of Arenes and Styrenes with CO2," Chem, 6, Cell Press, October 8, 2020, pp. 2658-2672. [Non-Patent Document 2] T. Kawai et al., "Photocatalytic Fixation of Carbon Dioxide with Conducting Polymer", Journal of the Chemical Society, Faraday Transactions, 88, pp. 2041-2046, 1992 [Non-Patent Document 3] Yuan-Xu Jiang et al., “Visible-light-driven synthesis of N-heteroaromatic carboxylic acids by thiolate-catalysed carboxylation of C(sp2)-H bonds using CO2,” Nature Synthesis, 3, Springer Science and Business Media LLC, pp. 394-405, 2024 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, conventional technology had the following problems: • Requires a large amount of catalyst. • Requires a reaction temperature higher than room temperature. Only specific compounds can be used as substrates.

[0009] Therefore, one aspect of the present invention aims to provide a means for highly selectively carrying out the carboxylation of unsaturated organic compounds as a method of carbon dioxide recovery using an organic catalyst that does not contain transition metals. [Means for solving the problem]

[0010] The inventors have investigated various means to solve the above-mentioned problems. The inventors have found that when a carbazole catalyst is used as a photosensitizer in the carboxylation of unsaturated organic compounds in the presence of carbon dioxide and, optionally, a base, even at room temperature and atmospheric pressure, the carboxylic acid or salt thereof can be synthesized from the unsaturated organic compound by irradiation with light (LED). Based on the above findings, the inventors have completed one aspect of the present invention.

[0011] In other words, one aspect of the present invention encompasses the following aspects and embodiments. (Embodiment 1) A method for recovering carbon dioxide, comprising irradiating a solution containing carbon dioxide, an unsaturated organic compound, a solvent, and one or more photosensitizers selected from a carbazole catalyst with light to recover carbon dioxide as a carboxylic acid of an unsaturated organic compound or a salt thereof. (Embodiment 2) The recovery method according to Embodiment 1, wherein the unsaturated organic compound is an aromatic organic compound. (Embodiment 3) The recovery method according to Embodiment 2, wherein the aromatic organic compound is one or more compounds selected from the group consisting of benzene and its derivatives, naphthalene and its derivatives, anthracene and its derivatives, furan and its derivatives, thiophene and its derivatives, and pyrrole and its derivatives. (Embodiment 4) An aromatic organic compound is a compound of formula I [ka] I [In formula I, X is O, S or NY, Y is hydrogen or a protecting group, R 1 This includes hydrogen, halogens, alkyl groups having 1 to 6 carbon atoms (the alkyl group may be unsubstituted or substituted with OH), CN, trimethylsilyl (TMS), and COOR. 4 , or an aryl having 6 to 18 carbon atoms (the aryl may be unsubstituted or substituted with 1 to 3 substituents independently selected from the group consisting of aryls having 6 to 18 carbon atoms, alkoxys having 1 to 6 carbon atoms, and CN), R 2is hydrogen or an alkyl having 1 to 6 carbon atoms (the alkyl may be unsubstituted or substituted by OH), R 3 is hydrogen, an alkyl having 1 to 6 carbon atoms (the alkyl may be unsubstituted or substituted by COOR 4 ), heteroaryl having 3 to 10 ring members, COOR 4 , COR 4 , aryl having 6 to 18 carbon atoms, CN, or TMS, or R 2 and R 3 together with the carbon atom to which they are attached form an aryl having 6 to 18 carbon atoms or heteroaryl having 3 to 10 ring members (the aryl or heteroaryl may be unsubstituted or substituted by 1 to 3 substituents independently selected from the group consisting of aryl having 6 to 18 carbon atoms and alkoxy having 1 to 6 carbon atoms), and R 4 is an alkyl having 1 to 6 carbon atoms.] The recovery method according to Embodiment 2, which is one or more compounds selected from the group consisting of compounds represented by . (Embodiment 5) The aromatic organic compound is of formula I

Chemical formula

[0012] According to one aspect of the present invention, it is possible to provide a means for highly selectively carrying out the carboxylation of unsaturated organic compounds as a method of carbon dioxide recovery using an organic catalyst that does not contain transition metals. [Modes for carrying out the invention]

[0013] A preferred embodiment of one aspect of the present invention will be described in detail below.

[0014] In one embodiment of the present invention, the unsaturated organic compound is not limited. In one embodiment of the present invention, the unsaturated organic compound may be a mixture of two or more compounds. In one embodiment of the present invention, the unsaturated organic compound is, for example, an aromatic organic compound.

[0015] The aromatic organic compounds are not limited. Examples of aromatic organic compounds include benzene-based aromatic compounds and heteroaromatic compounds, each of which includes fused ring aromatic compounds. More specifically, examples of aromatic organic compounds include benzene and its derivatives, naphthalene and its derivatives, anthracene and its derivatives, furan and its derivatives, thiophene and its derivatives, pyrrole and its derivatives, etc. For example, examples of furan and its derivatives include furan, benzofuran, and compounds in which one or more hydrogen atoms, excluding the hydrogen bonded to the carbon atom at position 2 of furan or benzofuran, are substituted by substituents. Here, the hydrogen bonded to the carbon atom at position 2 of furan or benzofuran, in one embodiment, is the hydrogen that is substituted with a carboxyl group derived from carbon dioxide by the reaction according to one aspect of the present invention. Examples of thiophene and its derivatives include thiophene, benzothiophene, and compounds in which one or more hydrogen atoms, excluding the hydrogen bonded to the carbon atom at position 2 of thiophene or benzothiophene, are substituted by substituents. Here, any carbon atom of thiophene or benzothiophene that reacts with carbon dioxide, in one embodiment, the hydrogen bonded to the carbon at position 2, is hydrogen that is substituted with a carboxyl group derived from carbon dioxide by the reaction according to one aspect of the present invention. Examples of pyrrole and its derivatives include pyrrole, indole, compounds in which the hydrogen bonded to the nitrogen of pyrrole or indole is substituted with a protecting group, such as tert-butoxycarbonyl (Boc) or benzyloxycarbonyl (Cbz), and compounds in which one or more hydrogen atoms, excluding the hydrogen bonded to the carbon at position 2 in one embodiment, that react with carbon dioxide of pyrrole or indole, are substituted with substituents. Here, any carbon atom of pyrrole or indole that reacts with carbon dioxide, in one embodiment, the hydrogen bonded to the carbon at position 2, is hydrogen that is substituted with a carboxyl group derived from carbon dioxide by the reaction according to one aspect of the present invention.The substituents are not limited, but include, for example, halogens (e.g., fluorine, chlorine, bromine, or iodine), and alkyl groups having 1 to 6 carbon atoms (e.g., alkyl groups having 1 to 3 carbon atoms) (the alkyl group may be unsubstituted or in an OH or COOR configuration). 4 (may be substituted by), CN, trimethylsilyl (TMS), COOR 4 aryls with 6 to 18 carbon atoms (for example, aryls with 6 to 12 carbon atoms), heteroaryls with 3 to 10 ring members, and COR 4 One or more selected from the group consisting of R. 4 This is an alkyl group having 1 to 6 carbon atoms (for example, an alkyl group having 1 to 3 carbon atoms). Furthermore, the aryl or heteroaryl group may be unsubstituted, or it may be substituted with 1 to 3 substituents independently selected from the group consisting of aryl groups having 6 to 18 carbon atoms (for example, aryl groups having 6 to 12 carbon atoms), alkoxy groups having 1 to 6 carbon atoms (for example, alkoxy groups having 1 to 3 carbon atoms), and CN.

[0016] In one aspect of the present invention, an aromatic organic compound is of formula I [ka] I It is represented as follows.

[0017] One embodiment of each substituent in formula I is as follows:

[0018] In one aspect of the present invention, X is O, S, or NY, and Y is hydrogen or a protecting group. Examples of protecting groups include tert-butoxycarbonyl (Boc) and benzyloxycarbonyl (Cbz). In one aspect of the present invention, X is O. In one aspect of the present invention, X is S. In one aspect of the present invention, X is NY, and Y is hydrogen or a protecting group, for example, tert-butoxycarbonyl (Boc).

[0019] In one aspect of the present invention, R 1This includes hydrogen, halogens (e.g., fluorine, chlorine, bromine, or iodine), alkyl groups having 1 to 6 carbon atoms (e.g., alkyl groups having 1 to 3 carbon atoms) (the alkyl group may be unsubstituted or substituted with OH), CN, trimethylsilyl (TMS), COOR 4 , or aryls having 6 to 18 carbon atoms (for example, aryls having 6 to 12 carbon atoms) (the aryl may be unsubstituted, or may be substituted with 1 to 3 substituents independently selected from the group consisting of aryls having 6 to 18 carbon atoms (for example, aryls having 6 to 12 carbon atoms), alkoxys having 1 to 6 carbon atoms (for example, alkoxys having 1 to 3 carbon atoms), and CN). Here, R 4 is an alkyl group having 1 to 6 carbon atoms (for example, an alkyl group having 1 to 3 carbon atoms). In one aspect of the present invention, R 1 is hydrogen, methyl (also represented as "Me" or "CH3") (the methyl may be unsubstituted or substituted with an OH group), CN, trimethylsilyl, COOCH3, or phenyl (also represented as "Ph"), wherein the phenyl may be unsubstituted or substituted with one to three substituents independently selected from the group consisting of phenyl and methoxy (also represented as "OMe" or "OCH3").

[0020] In one aspect of the present invention, R 2 is hydrogen or an alkyl group having 1 to 6 carbon atoms (for example, an alkyl group having 1 to 3 carbon atoms) (the alkyl group may be unsubstituted or substituted with an OH group). In one aspect of the present invention, R 2 It is hydrogen.

[0021] In one aspect of the present invention, R 3 This includes hydrogen and alkyl groups having 1 to 6 carbon atoms (for example, alkyl groups having 1 to 3 carbon atoms) (the alkyl group is unsubstituted or COOR). 4 (may be substituted by), heteroaryls with 3 to 10 ring members (for example, heteroaryls with 3 to 6 ring members), COOR 4 COR 4, aryl with 6 to 18 carbon atoms (for example, aryl with 6 to 12 carbon atoms), CN, or trimethylsilyl (TMS). Here, R 4 is an alkyl group having 1 to 6 carbon atoms (for example, an alkyl group having 1 to 3 carbon atoms). In one aspect of the present invention, R 3 The ions are hydrogen, CH2COOCH3, 2-thienyl, 2-furyl, COOC2H5, phenyl, CN, or TMS.

[0022] In one aspect of the present invention, R 2 and R 3 These, together with the carbon atoms to which they are bonded, form an aryl group having 6 to 18 carbon atoms (for example, an aryl group having 6 to 12 carbon atoms) or a heteroaryl group having 3 to 10 ring members (for example, a heteroaryl group having 3 to 6 ring members). The aryl or heteroaryl group may be unsubstituted, or it may be substituted with 1 to 3 substituents independently selected from the group consisting of aryl groups having 6 to 18 carbon atoms and alkoxy groups having 1 to 6 carbon atoms (for example, alkoxy groups having 1 to 3 carbon atoms). In one aspect of the present invention, R 2 and R 3 These, together with the carbon atoms to which they are bonded, form a benzene ring or a naphthalene ring. In one aspect of the present invention, R 2 and R 3 These atoms, together with the carbon atoms to which they are bonded, form a benzene ring, which may be unsubstituted or substituted with phenyl.

[0023] In one aspect of the present invention, X is S and R 1 R is hydrogen, CN, COOCH3, or phenyl, and the phenyl may be substituted with 1 to 3 substituents independently selected from the group consisting of unsubstituted or methoxy. 2 is hydrogen, and R 3 is hydrogen, CH2COOCH3, 2-thienyl, 3-thienyl, phenyl, CN, or TMS, or R 2 and R 3These atoms, together with the carbon atoms to which they are bonded, form a benzene ring.

[0024] In one aspect of the present invention, X is NY, Y is Boc, and R 1 is hydrogen, CN, or COOCH3, and R 2 and R 3 These atoms, together with the carbon atoms to which they are bonded, form a benzene ring.

[0025] In one aspect of the present invention, X is O and R 1 R is hydrogen, methyl (which may be unsubstituted or substituted with OH), CN, trimethylsilyl, COOCH3, or phenyl, which may be unsubstituted or substituted with 1 to 3 substituents independently selected from the group consisting of phenyl and methoxy, 2 is hydrogen, and R 3 is hydrogen, 2-furyl, COOC2H5, phenyl, or CN, or R 2 and R 3 These atoms, together with the carbon atoms to which they are bonded, form a benzene ring or a naphthalene ring, and the benzene ring may be unsubstituted or substituted with phenyl.

[0026] In one embodiment of the present invention, the aromatic organic compound is the following compound.

[0027] [ka] TIFF2026105955000007.tif240167TIFF2026105955000008.tif33167

[0028] In one aspect of the present invention, the content of the unsaturated organic compound is not limited as long as it is soluble in the solvent, but is typically in the range of 0.05 mol / L (M) to 10 M relative to the total amount of the reaction solution (reaction mixture), 0.1 mol / L (M) to 10 M in one embodiment, 1 M to 8 M in one embodiment, and 2 M to 6 M in another embodiment. By carrying out this method using the amount of unsaturated organic compound within the ranges exemplified above, carboxylation can be carried out with high efficiency and carbon dioxide can be recovered efficiently.

[0029] In one embodiment of the present invention, the photosensitizer is one or more compounds selected from the group consisting of carbazole catalysts. In one embodiment of the present invention, the photosensitizer may be a mixture of two or more compounds.

[0030] In one embodiment of the present invention, the carbazole catalyst is not limited. The carbazole catalyst may be, for example, the following formula II: [ka] II It is represented as follows.

[0031] One embodiment of each substituent in Equation II is as follows:

[0032] In one embodiment of the present invention, R 5 R is hydrogen, an alkyl group having 1 to 6 carbon atoms (for example, an alkyl group having 1 to 3 carbon atoms), or an aryl group having 6 to 18 carbon atoms (for example, an aryl group having 6 to 12 carbon atoms). In one embodiment of the present invention, R 5 is hydrogen, ethyl, or phenyl.

[0033] In one embodiment of the present invention, R 6 , R 6’ , R 7 , and R 7’ These are, independently of each other, hydrogen, an alkyl group having 1 to 6 carbon atoms (for example, an alkyl group having 1 to 3 carbon atoms), and NR 8 R 8’, an alkoxy having 1 to 6 carbon atoms (for example, an alkoxy having 1 to 3 carbon atoms), or OH. In one aspect of the present invention, R 8 and R 8’ are, independently of each other, an alkyl having 1 to 6 carbon atoms (for example, an alkyl having 1 to 3 carbon atoms) or an aryl having 6 to 18 carbon atoms (for example, an aryl having 6 to 12 carbon atoms). In one aspect of the present invention, R 8 and R 8’ together with the nitrogen atom to which they are attached form a heterocyclic ring having 3 to 10 ring members (for example, a heterocyclic ring having 3 to 7 ring members).

[0034] In one aspect of the present invention, R 6 and R 6’ are, independently of each other, hydrogen, NR 8 R 8’ , methoxy, or OH. In one aspect of the present invention, R 7 and R 7’ are, independently of each other, methyl, NR 8 R 8’ , methoxy, or OH. In one aspect of the present invention, R 8 and R 8’ are methyl. In one aspect of the present invention, R 8 and R 8’ together with the nitrogen atom to which they are attached form aziridinyl or azetidinyl.

[0035] In one aspect of the present invention, R 6 and R 6’ are the same group. In one aspect of the present invention, R 6 and R 6’ are the same group, R 6 and R 6’ are hydrogen, NR 8 R 8’ , OCH3, or OH, and R 8 and R 8’ are methyl, or together with the nitrogen atom to which they are attached form aziridinyl or azetidinyl. In one aspect of the present invention, R 6 and R6’ These are different groups. In one embodiment of the present invention, R 6 and R 6’ These are different groups, R 6 is hydrogen, R 6’ , NR 8 R 8’ , OCH3, or OH, R 8 and R 8’ These atoms are either methyl or, together with the nitrogen atom to which they are bonded, form azilidinyl or azetidinyl.

[0036] In one embodiment of the present invention, R 7 and R 7’ These are the same group. In one embodiment of the present invention, R 7 and R 7’ These are the same group, R 7 and R 7’ is methyl, NR 8 R 8’ , OCH3, or OH, R 8 and R 8’ R is either methyl or, together with the nitrogen atom to which it is bonded, forms azilidinyl or azetidinyl. In one embodiment of the present invention, R 7 and R 7’ These are different groups. In one embodiment of the present invention, R 7 and R 7’ These are different groups, R 7 OH is R 7’ This is OCH3.

[0037] In one embodiment of the present invention, the carbazole catalyst is the following compound. [ka] TIFF2026105955000011.tif174169

[0038] In one embodiment of the present invention, a resonance effect can be further obtained by arranging electron-donating groups at one or more locations selected from the group consisting of the 1st, 3rd, 6th, and 8th positions of the carbazole, and in one embodiment, two or more locations, for example, two, three, or four.

[0039] In one aspect of the present invention, the content of the photosensitizer is not limited, but is typically in the range of 5 mol% to 30 mol% relative to the number of moles of the aromatic organic compound used as a raw material, in one embodiment in the range of 8 mol% to 25 mol%, and in another embodiment in the range of 10 mol% to 20 mol%. By carrying out this method using the amount of photosensitizer within the ranges exemplified above, carbon dioxide can be recovered in high yield.

[0040] In one embodiment of the present invention, the photosensitizer can be reused while maintaining a high yield of carbon dioxide recovery.

[0041] In one aspect of the present invention, the solution may further contain a base. Here, the base is not limited. In one aspect of the present invention, the base may be a mixture of two or more types. Examples of bases include alkali metal hydroxides, such as potassium hydroxide; alkaline earth metal hydroxides, such as magnesium hydroxide; alkali metal alkoxides, such as potassium tert-butoxide; phosphates, such as tripotassium phosphate (K3PO4); and carbonates. From the viewpoint of producing fewer by-products and carrying out carboxylation with high selectivity, carbonates are preferred as the base. The carbonate is not limited. Examples of carbonates include alkali metal carbonates, such as lithium carbonate, sodium carbonate, potassium carbonate, and cesium carbonate; alkali metal bicarbonates, such as lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, and cesium bicarbonate; alkaline earth metal salts, such as magnesium carbonate and calcium carbonate; and ammonium carbonate. In one aspect of the present invention, the carbonate is one or more salts selected from the group consisting of alkali metal carbonates and alkali metal bicarbonates. In one embodiment of the present invention, the carbonate is one or more salts selected from the group consisting of alkali metal carbonates. By carrying out this method using a carbonate as the base, carbon dioxide can be recovered in high yield.

[0042] In one aspect of the present invention, the base content is not limited. In one aspect of the present invention, the base content is typically in the range of 0.8 equivalents to 5 equivalents relative to the raw material aromatic organic compound, in one embodiment in the range of 1 equivalent to 4 equivalents, and in one embodiment in the range of 1.1 equivalents to 3.5 equivalents. By carrying out this method using the amount of base within the ranges exemplified above, carbon dioxide can be recovered in high yield.

[0043] In one embodiment of the present invention, the solvent is not limited. Examples of solvents include water (purified water, tap water, seawater, mixtures of two or more of these, etc.), organic solvents (for example, alcohols (ethyl alcohol, isopropyl alcohol, t-butyl alcohol, 1-methoxy-2-propyl alcohol, 2,2,2-trifluoroethyl alcohol, mixtures of two or more of these, etc.), acetonitrile, diglyme, N,N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), hexamethylphosphoric triamide (HMPA), N,N'-dimethylpropylene urea (DMPU), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), 1,4-dioxane, mixtures of two or more of these, etc.), and mixed solvents of water and organic solvents. In one embodiment of the present invention, the solvent is DMSO.

[0044] In one embodiment of the present invention, the environment in which the carbon dioxide recovery method is carried out is not limited. In one embodiment of the present invention, the carbon dioxide recovery method can be carried out at room temperature and atmospheric pressure. In "room temperature and atmospheric pressure," room temperature usually means a temperature of 15°C to 40°C, in one embodiment 15°C to 25°C, and in another embodiment 20°C to 40°C, and atmospheric pressure usually means atmospheric pressure. In one embodiment of the present invention, the carbon dioxide pressure is 1 atm.

[0045] In one embodiment of the present invention, the reaction time between the unsaturated organic compound and carbon dioxide in the carbon dioxide recovery method is not limited. In one embodiment of the present invention, the reaction time is usually in the range of 1 hour to 48 hours, and in one embodiment, in the range of 10 hours to 24 hours. By carrying out the method with a reaction time within the range exemplified above, carbon dioxide can be recovered in high yield.

[0046] In one embodiment of the present invention, the light is not limited as long as it has a wavelength that can normally be absorbed by a photosensitizer. Examples of light include LED light and sunlight, where the maximum emission wavelength is typically in the range of 350 nm to 500 nm, for example, 400 nm. By carrying out this method using light having wavelengths within the range exemplified above, carbon dioxide can be recovered in high yield.

[0047] In one embodiment of the present invention, an aromatic organic compound reacts with carbon dioxide at any of the carbon atoms in the ring structure, in one embodiment, the carbon adjacent to the heteroatom, i.e., the carbon at position 2, and is carboxylated. Therefore, in one embodiment of the present invention, by reacting carbon dioxide with the aromatic organic compound described above, carbon dioxide can be efficiently recovered as the carboxylic acid of the aromatic organic compound or a salt thereof. The carboxylic acid of the aromatic organic compound is given by the following chemical formula [ka] (In the formula, X, R 1 , R 2 and R 3 (As stated above.) The salts of aromatic organic compounds with carboxylic acids have the following characteristics: In the above chemical formula, the hydrogen of the carboxyl group is a cation, for example, alkali metal ions, for example lithium ions, sodium ions, potassium ions, cesium ions, etc.; alkaline earth metal ions, for example magnesium ions, calcium ions, etc.; ammonium cations, for example NH4 + These are compounds substituted with primary to quaternary ammonium cations, etc.

[0048] One aspect of the present invention can be represented by the following reaction scheme. [ka] (In the formula, R 1 , R 2 , R 3 , R 5 , R 6 , R 6’ , R 7 , R7’ , and X are as described above.

[0049] As described in detail above, the method of this embodiment allows for the highly efficient recovery of carbon dioxide through the reaction of carbon dioxide with an unsaturated organic compound. Furthermore, if the carbonylated unsaturated organic compound obtained by the method of this embodiment is a salt of a carboxylic acid, the carboxylic acid of the unsaturated organic compound can be obtained by subsequent acid treatment, such as with hydrochloric acid, nitric acid, or sulfuric acid. The carboxylic acid obtained by the method of this embodiment is expected to serve as a raw material for useful compounds. Therefore, the method of this embodiment can provide a raw material for these useful compounds. [Examples]

[0050] The present invention will be described in more detail below using examples. However, the technical scope of the present invention is not limited to these examples.

[0051] [Experiment 1: Investigation of photosensitizers in the organic photocatalytic carboxylation of benzothiophene] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing benzothiophene (0.5 mmol) as an unsaturated organic compound, carbon dioxide (1 atm: bubbling), potassium tert butoxide (KOt-Bu) as a base (3.0 equivalents relative to benzothiophene), and DMSO (5 mL) as a solvent was added. A carbazole catalyst (20 mol%) relative to benzothiophene, as shown in the reaction formula below or in Table 1, was then irradiated with LED light (hν, λmax = 400 nm) for 21 hours (h) at room temperature and atmospheric pressure (room temperature (rt) (25°C), 1 atm), and then an aqueous solution of hydrochloric acid (HCl) (2M) was added. Table 1 shows the yield of the obtained carboxylic acid along with the photosensitizer used.

[0052] [ka]

[0053] [Table 1]

[0054] [Experiment 2: Investigation of organic photocatalytic carboxylation of benzothiophene or thiophene derivatives 1] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing benzothiophene or a thiophene derivative (0.5 mmol) as an unsaturated organic compound (compound with a hydrogen carboxyl group in Table 2), carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to benzothiophene or thiophene derivative), and DMSO (5 mL) as a solvent was added. A carbazole catalyst shown in the following reaction formula was added as a photosensitizer (10 mol%) relative to benzothiophene or thiophene derivative. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. Table 2 shows the yields of the obtained carboxylic acids of the unsaturated organic compounds.

[0055] [ka]

[0056] [Table 2]

[0057] [Experiment 3: Investigation of organic photocatalytic carboxylation of thiophene derivatives, Part 2] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing a thiophene derivative shown in the following formula (0.5 mmol) as an unsaturated organic compound, carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to the thiophene derivative), and DMSO (5 mL) as a solvent was added. A carbazole catalyst shown in the following reaction formula (10 mol%) relative to the thiophene derivative was then added as a photosensitizer. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. The yield of the obtained unsaturated organic compound, along with its carboxylic acid, is shown in the following formula.

[0058] [ka]

[0059] [Experiment 4: Investigation of organic photocatalytic carboxylation of indole derivatives] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing an indole derivative (0.5 mmol) as an unsaturated organic compound (compound with a hydrogen carboxyl group in Table 3), carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to the indole derivative), and DMSO (5 mL) as a solvent was added. A carbazole catalyst (10 mol%) relative to the indole derivative, as shown in the following reaction equation, was added as a photosensitizer. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. Table 3 shows the yield of the obtained carboxylic acid along with the photosensitizer used.

[0060] [ka]

[0061] [Table 3]

[0062] [Experiment 5: Investigation of photosensitizers in the organic photocatalytic carboxylation of benzofurans] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing benzofuran (0.5 mmol) as an unsaturated organic compound, carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to benzofuran), and DMSO (5 mL) as a solvent was added. A carbazole catalyst (10 mol%) relative to benzofuran, as shown in the reaction formula below or in Table 4, was then irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), after which an aqueous solution of hydrochloric acid (HCl) (2 M) was added. Table 4 shows the yield of the obtained carboxylic acid along with the photosensitizer used. Note that no carboxylic acid was obtained when no photosensitizer was added.

[0063] [ka]

[0064] [Table 4] TIFF2026105955000023.tif140166

[0065] [Experiment 6: Investigation of bases in the organic photocatalytic carboxylation of benzofuran] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing benzofuran (0.5 mmol) as an unsaturated organic compound, carbon dioxide (1 atm: bubbling), the compound listed in Table 5 as a base (3.0 equivalents relative to benzofuran), and DMSO (5 mL) as a solvent was added. A carbazole catalyst shown in the following reaction equation was added as a photosensitizer (10 mol%) relative to benzofuran, and the solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and atmospheric pressure (room temperature (25°C), 1 atm). Subsequently, an aqueous solution of hydrochloric acid (HCl) (2 M) was added. Table 5 shows the yield of the obtained carboxylic acid along with the solvent used.

[0066] [ka]

[0067] [Table 5]

[0068] [Experiment 7: Investigation of solvents in the organic photocatalytic carboxylation of benzofuran] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing benzofuran (0.5 mmol) as an unsaturated organic compound, carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to benzofuran), and the compounds listed in Table 6 as a solvent (5 mL) was added. A carbazole catalyst (10 mol%) relative to benzofuran, as shown in the following reaction equation, was added as a photosensitizer. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. Table 6 shows the yield of the obtained carboxylic acid along with the base used.

[0069] [ka]

[0070] [Table 6]

[0071] Table 6 shows that in one embodiment of the present invention, a wide range of solvents can be used as solvents, including polar solvents such as DMSO, DMF, HMPA, DMPU, NMP, and THF.

[0072] [Experiment 8: Investigation of organic photocatalytic carboxylation of benzofuran or its derivatives 1] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing benzofuran or its derivative (0.5 mmol) as an unsaturated organic compound (compound with hydrogen in the carboxyl group in Table 7), carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to benzofuran or its derivative), and DMSO (5 mL) as a solvent was added. A carbazole catalyst shown in the following reaction formula was added as a photosensitizer (10 mol%) relative to benzofuran or its derivative. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. Table 7 shows the yields of the obtained carboxylic acids.

[0073] [ka]

[0074] [Table 7]

[0075] [Experiment 9: Investigation of organic photocatalytic carboxylation of benzofuran or its derivatives 2] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing benzofuran or its derivative (0.5 mmol) as an unsaturated organic compound (compound with hydrogen in the carboxyl group in Table 8), carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to benzofuran or its derivative), and DMSO (5 mL) as a solvent was added as a photosensitizer, with 10 mol% of the carbazole catalyst shown in the following reaction formula relative to benzofuran or its derivative being added. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. Table 8 shows the yields of the obtained carboxylic acids.

[0076] [ka]

[0077] [Table 8]

[0078] [Experiment 10: Investigation of organic photocatalytic carboxylation of furan derivatives 1] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing a furan derivative (0.5 mmol) as an unsaturated organic compound (compound with a hydrogen carboxyl group in Table 9), carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to the furan derivative), and DMSO (5 mL) as a solvent was added. A carbazole catalyst (10 mol%) relative to the furan derivative, as shown in the following reaction equation, was added as a photosensitizer. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. Table 9 shows the yields of the obtained carboxylic acids.

[0079] [ka]

[0080] [Table 9]

[0081] [Experiment 11: Investigation of organic photocatalytic carboxylation of furan derivatives 2] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing a furan derivative (0.5 mmol) as an unsaturated organic compound (compound with a hydrogen carboxyl group in Table 10), carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to the furan derivative), and DMSO (5 mL) as a solvent was added. A carbazole catalyst (10 mol%) relative to the furan derivative, as shown in the following reaction equation, was added as a photosensitizer. The solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm), and then an aqueous hydrochloric acid (HCl) solution (2 M) was added. Table 10 shows the yields of the obtained carboxylic acids.

[0082] [ka]

[0083] [Table 10]

[0084] [Experiment 12: Investigation of organic photocatalytic carboxylation of naphthalene or its derivatives] In a Schlenk tube equipped with a balloon filled with carbon dioxide, a solution containing naphthalene or its derivative (0.5 mmol) as an unsaturated organic compound (compound with hydrogen in the carboxyl group in Table 11), carbon dioxide (1 atm: bubbling), cesium carbonate (Cs2CO3) as a base (3.0 equivalents relative to naphthalene), and DMSO (5 mL) as a solvent was added. A carbazole catalyst shown in the following reaction formula was added as a photosensitizer (10 mol%) relative to naphthalene, and the solution was irradiated with LED light (λmax = 400 nm) for 21 hours at room temperature and pressure (room temperature (25°C), 1 atm). Subsequently, an aqueous solution of hydrochloric acid (HCl) (2 M) was added. Table 11 shows the yields of the obtained carboxylic acids.

[0085] [ka]

[0086] [Table 11]

[0087] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. In addition, it is possible to add, delete, and / or replace some of the configurations in each embodiment with other configurations.

Claims

1. A method for recovering carbon dioxide, comprising irradiating a solution containing carbon dioxide, an unsaturated organic compound, a solvent, and one or more photosensitizers selected from a carbazole catalyst with light to recover carbon dioxide as a carboxylic acid of the unsaturated organic compound or a salt thereof.

2. The unsaturated organic compound is an aromatic organic compound, and the aromatic organic compound is benzene and its derivatives, naphthalene and its derivatives, anthracene and its derivatives, and formula I 【Chemistry 1】 I [In formula I, X is O, S or NY, Y is hydrogen or a protecting group, and R １ is hydrogen, halogen, alkyl having 1 to 6 carbon atoms (the alkyl may be unsubstituted or substituted by OH), CN, trimethylsilyl, COOR ４ , or aryl having 6 to 18 carbon atoms (the aryl may be unsubstituted or substituted by 1 to 3 substituents independently selected from the group consisting of aryl having 6 to 18 carbon atoms, alkoxy having 1 to 6 carbon atoms, and CN), R ４ is alkyl having 1 to 6 carbon atoms, R ２ is hydrogen or alkyl having 1 to 6 carbon atoms (the alkyl may be unsubstituted or substituted by OH), R ３ is hydrogen, alkyl having 1 to 6 carbon atoms (the alkyl may be unsubstituted or substituted by COOR ４ ), heteroaryl having 3 to 10 ring members, COOR ４ , COR ４ , aryl having 6 to 18 carbon atoms, CN, or TMS, or R ２ and R ３ together with the carbon atom to which they are attached form aryl having 6 to 18 carbon atoms or heteroaryl having 3 to 10 ring members (the aryl or heteroaryl may be unsubstituted or substituted by 1 to 3 substituents independently selected from the group consisting of aryl having 6 to 18 carbon atoms and alkoxy having 1 to 6 carbon atoms).] The recovery method according to claim 1, wherein the compound is one or more compounds selected from the group consisting of compounds represented by .

3. Aromatic organic compounds, Formula I 【Chemistry 2】 I [In formula I, X is O, S or NY, Y is Boc, R １ This includes hydrogen, methyl (which may be unsubstituted or substituted with OH), CN, trimethylsilyl, and COOCH. ３ , or phenyl (the phenyl may be unsubstituted or substituted with one to three substituents independently selected from the group consisting of phenyl and methoxy), R ２ is hydrogen, and R ３ Hydrogen, CH ２ COOCH ３ , 2-Thenyl, 2-Frill, COOC ２ H ５ , phenyl, CN, or trimethylsilyl, or R ２ and R ３ These atoms, together with the carbon atoms to which they are bonded, form a benzene ring or a naphthalene ring (the benzene ring may be unsubstituted or substituted with phenyl). The recovery method according to claim 2, wherein the compound is one or more compounds selected from the group consisting of compounds represented by .

4. The carbazole catalyst is, Formula II 【Transformation 3】 II [In formula II, R ５ R is hydrogen, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 18 carbon atoms. ６ , R ６’ , R ７ , and R ７’ These are, independently of each other, hydrogen, alkyl with 1 to 6 carbon atoms, and NR ８ R ８’ , an alkoxy having 1 to 6 carbon atoms, or an OH group, R ８ and R ８’ These are, independently of each other, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 18 carbon atoms, or R ８ and R ８’ These atoms, together with the nitrogen atoms to which they are bonded, form a heterocycle with a ring membership of 3 to 10. The recovery method according to any one of claims 1 to 3, wherein the compound is one or more compounds selected from the group consisting of compounds represented by .

5. The carbazole catalyst is, Formula II 【Chemistry 4】 II [In formula II, R ５ is hydrogen, ethyl, or phenyl, and R ６ and R ６’ These are, independently of each other, hydrogen, NR ８ R ８’ , methoxy, or OH, R ７ and R ７’ These are methyl and NR, independently of each other. ８ R ８’ , methoxy, or OH, R ８ and R ８’ is methyl, or R ８ and R ８’ These, together with the nitrogen atom to which they are bonded, form azilidinyl or azetidinyl. The recovery method according to claim 4, wherein the compound is one or more compounds selected from the group consisting of compounds represented by .

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