A method for producing formic acid or its salts from a carbonic acid source, and a phosphorus-containing reducing agent or photocatalyst for use therein.

Abstract

This disclosure aims to provide a method for producing formic acid or a salt thereof from a carbon dioxide source selected from carbon dioxide compounds under light irradiation, without using hydrogen molecules. [Solution] A method for producing formic acid or a salt thereof, comprising a reaction step of reacting at least one carbon dioxide source selected from the group consisting of carbon dioxide and carbonate compounds with a reducing agent under light irradiation to obtain formic acid or a salt thereof, wherein the reducing agent is a phosphorus-containing reducing agent.

Claims

1. A method for producing formic acid or a salt thereof, comprising a reaction step of reacting at least one carbonic acid source selected from the group consisting of carbon dioxide and carbonate compounds with a reducing agent under light irradiation to obtain formic acid or a salt thereof, A method for producing formic acid or a salt thereof, wherein the reducing agent is a phosphorus-containing reducing agent.

2. The method for producing formic acid or a salt thereof according to claim 1, wherein the phosphorus-containing reducing agent is at least one reducing agent selected from the group consisting of phosphates, hypophosphates, and phosphine compounds.

3. A method for producing formic acid or a salt thereof according to claim 1, further comprising a photocatalyst in the reaction step.

4. The method for producing formic acid or a salt thereof according to claim 3, wherein the photocatalyst is at least one compound selected from the group consisting of carbazole compounds, dibenzothiophene compounds, and transition metal complex compounds.

5. The aforementioned photocatalyst is a carbazole compound, The carbazole compound is General formula (3-1): 【Chemistry 1】 (In the formula, R １ This represents a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted aryl group. R ２ 、 R ３ 、 R ４ 、 R ５ 、 R ６ 、 R ７ 、 R ８ 、 and, R ９ are, the same or different, a hydrogen atom, NR １０ R １１ 、 or, OR １２ represents. R １０ , R １１ , and R １２ This represents, either identically or differently, a hydrogen atom, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted aryl group. Alternatively, R １０ and R １１ These atoms, together with the nitrogen atoms to which they are bonded, form a 3- to 10-membered heterocycle, and the 3- to 10-membered heterocycle may have substituents. A method for producing formic acid or a salt thereof according to claim 4, wherein the compound is represented by [the compound name].

6. The aforementioned photocatalyst is a dibenzothiophene compound. The aforementioned dibenzothiophene compound General formula (3-2): 【Chemistry 2】 (In the formula, R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , and R ９ are identical or different, hydrogen atoms, NR １０ R １１ OR １２ This indicates. R １０ , R １１ , and R １２ This represents, either identically or differently, a hydrogen atom, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted aryl group. Alternatively, R １０ and R １１ These atoms, together with the nitrogen atoms to which they are bonded, form a 3- to 10-membered heterocycle, and the 3- to 10-membered heterocycle may have substituents. A method for producing formic acid or a salt thereof according to claim 4, wherein the compound is represented by [the compound name].

7. The aforementioned photocatalyst is a transition metal complex compound, The aforementioned transition metal complex compound General formula (3-3): 【Transformation 3】 (In the formula, M １ This indicates a transition metal atom. R １８ , R １９ , R ２０ , R ２１ , R ２２ , R ２３ , R ２４ , R ２５ , R ２６ , R ２７ , R ２８ , R ２９ , R ３０ , R ３１ , R ３２ , R ３３ , R ３４ , R ３５ , R ３６ , R ３７ , R ３８ , R ３９ , R ４０ , and R ４１ This represents, either identically or differently, a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, or an optionally substituted aryl group. Alternatively, R ２１ and R ２２ These may bond to each other to form a -CH=CH- group, and each of the H atoms in the -CH=CH- group may be independently substituted with any substituent. R ２９ and R ３０ These may bond to each other to form a -CH=CH- group, and each of the H atoms in the -CH=CH- group may be independently substituted with any substituent. R ３７ and R ３８ These may bond to each other to form a -CH=CH- group, and each of the H atoms in the -CH=CH- group may be independently substituted with any substituent. A １ A ２ , and A ３ A represents a carbon atom or a nitrogen atom, either identical or different. １ A ２ , and A ３ (If the atom is a nitrogen atom, the transition metal complex may have a counter anion.) A method for producing formic acid or a salt thereof according to claim 4, wherein the compound is represented by [the compound name].

8. A method for producing formic acid or a salt thereof according to claim 3, further comprising a hydrogen atom transfer catalyst in the reaction step.

9. The method for producing formic acid or a salt thereof according to claim 8, wherein the hydrogen atom transfer catalyst comprises at least one compound selected from the group consisting of thiol compounds and benzimidazole compounds.

10. A phosphorus-containing reducing agent for use in a method for producing formic acid or a salt thereof according to any one of claims 1 to 9.

11. It contains at least one compound selected from the group consisting of carbazole compounds, dibenzothiophene compounds, and transition metal complex compounds. A photocatalyst for use in a method for producing formic acid or a salt thereof according to any one of claims 1 to 9.

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