Method for producing carbon monoxide, carbon dioxide reduction electrode, and carbon dioxide reduction device

Abstract

Provided are a method for producing carbon monoxide having high carbon monoxide selectivity, a carbon dioxide reduction electrode, and a carbon dioxide reduction device.　A method for producing carbon monoxide according to the present invention includes a step for reacting carbon dioxide and water in the presence of a carbon dioxide reduction catalyst represented by formula (1). In formula (1): R1 represents a hydrogen atom or a substituent; P1 represents a divalent group including one or more aromatic rings; Q1 and Q2 represent monovalent groups including one or more aromatic rings; M represents a cobalt atom, a nickel atom, or a zinc atom; a represents an integer of 2 to 4; the M, of which there are a plurality, may be the same or different as each other; X represents a counter ion or a neutral molecule; b represents an integer of 0 or greater; and O represents an oxygen atom and is bonded to at least one M.

Description

Carbon monoxide production method, carbon dioxide reduction electrode and carbon dioxide reduction device

[0001] The present disclosure relates to a method for producing carbon monoxide, a carbon dioxide reduction electrode, and a carbon dioxide reduction device.

[0002] In methods for producing carbon monoxide by reducing carbon dioxide, precious metals such as gold and silver are sometimes used as carbon dioxide reduction catalysts. For example, Patent Document 1 and Patent Document 2 disclose examples of using gold nanoparticles as catalysts. Meanwhile, complex catalysts in which a nitrogen-containing compound is coordinated to a base metal have recently attracted attention. Non-Patent Document 1 describes a method for converting carbon dioxide to carbon monoxide using cobalt phthalocyanine as a catalyst. Non-Patent Document 2 describes a method for converting carbon dioxide to carbon monoxide using a complex having two nickel cyclams in the same molecule as a catalyst.

[0003] Nature, 2019, 575, 640Green Chem., 2018, 20, 798-803

[0004] Japanese Patent Application Publication No. 2021-147677

[0005] The noble metal catalysts described in Patent Documents 1 and 2 are expensive and there are concerns about increased costs. On the other hand, in the carbon monoxide production methods using complexes containing base metals as carbon dioxide reduction catalysts as described in Non-Patent Documents 1 and 2, a large amount of by-products is likely to be generated and the carbon monoxide selectivity tends to be low.

[0006] An object of one embodiment of the present disclosure is to provide a method for producing carbon monoxide with high carbon monoxide selectivity using a base metal complex as a catalyst.An object of another embodiment of the present disclosure is to provide a carbon dioxide reduction electrode with high carbon monoxide selectivity.An object of another embodiment of the present disclosure is to provide a carbon dioxide reduction device with high carbon monoxide selectivity.

[0007] Means for solving the above problems include the following means: <1> A method for producing carbon monoxide, comprising a step of reacting carbon dioxide with water in the presence of a carbon dioxide reduction catalyst represented by the following formula (1):

[0008] (In formula (1), R １ represents a hydrogen atom or a substituent, and a plurality of R １ may be the same or different, and two adjacent R １ may be bonded to each other to form a ring, P １ represents a divalent group containing one or more aromatic rings, and Q １ and Q ２ represents a monovalent group containing one or more aromatic rings, and Q １ and Q ２ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0009] <2> The P １ is expressed by the following formula (P ａ ), the following formula (P ｂ ) or the following formula (P ｃ 2. The method for producing carbon monoxide according to claim 1, wherein R is a divalent group represented by the formula (1).

[0010] (Formula (P ａ ) ~ formula (P ｃ In the above, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, the multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring, Y represents any of the groups shown below, and the multiple Ys may be the same or different, Z represents an alkylene group or an arylene group, and * represents a bond.

[0011] (In the formula, R ａ represents a hydrogen atom or a substituent.

[0012] <3> The method for producing carbon monoxide according to <1>, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (2):

[0013] (In formula (2), R ６ ~R ８ represents a hydrogen atom or a substituent, and two adjacent R ６ Two adjacent Rs ７ Each other and two adjacent R ８ may be bonded to each other to form a ring structure, and multiple R ６ ~R ８ may be the same or different, and Q ３ and Q ４ represents a monovalent group containing one or more aromatic rings, and Q ３ and Q ４ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0014] <4> The method for producing carbon monoxide according to <1>, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (3):

[0015] (In formula (3), R ９ ~R １３ represents a hydrogen atom, a substituent, or a divalent group, and two adjacent R ９ Two adjacent Rs １０ Two adjacent Rs １１ Two adjacent Rs １２ R １２ and R １３ may be bonded to each other to form a ring structure, and multiple R ９ ~R １３ may be the same or different, R １３is a divalent group, the divalent group may form a bond with another compound represented by formula (3) to form a dimer, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

[0016] <5> The method for producing carbon monoxide according to <1>, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (4):

[0017] (In formula (4), R １４ ~R １６ represents a hydrogen atom or a substituent, and two adjacent R １４ Two adjacent Rs １５ R １５ and R １６ may be linked to each other to form a ring, and multiple R １４ ~R １６ may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and a plurality of M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are a plurality of X's, they may be the same or different.

[0018] <6> The method for producing carbon monoxide according to <1>, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (5):

[0019] (In formula (5), R １７ ~R ２１ represents a hydrogen atom or a substituent, and two adjacent R １７ Two adjacent Rs １８ Two adjacent Rs １９ Two adjacent Rs ２１ R ２０ and R ２１ may be bonded to each other to form a ring structure, and multiple R １７ ~R ２１may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

[0020] <7> A carbon dioxide reduction electrode comprising a carbon dioxide reduction catalyst represented by the following formula (1) or a conductive material supporting the carbon dioxide reduction catalyst represented by the following formula (1):

[0021] (In formula (1), R １ represents a hydrogen atom or a substituent, and a plurality of R １ may be the same or different, and two adjacent R １ may be bonded to each other to form a ring, P １ represents a divalent group containing one or more aromatic rings, and Q １ and Q ２ represents a monovalent group containing one or more aromatic rings, and Q １ and Q ２ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0022] <8> The carbon dioxide reduction electrode according to <7>, comprising a conductive material on which the carbon dioxide reduction catalyst represented by formula (1) is supported, and further comprising a support for supporting the conductive material. <9> The carbon dioxide reduction electrode according to <7> or <8>, further comprising an ion conductor. <10> A carbon dioxide reduction device comprising: an oxidation electrode, the carbon dioxide reduction electrode according to any one of <7> to <9>, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode, an electrolyte, and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode.

[0023] According to one embodiment of the present disclosure, there is provided a method for producing carbon monoxide with high carbon monoxide selectivity. According to another embodiment of the present disclosure, there is provided a carbon dioxide reduction electrode with high carbon monoxide selectivity. According to another embodiment of the present disclosure, there is provided a carbon dioxide reduction device with high carbon monoxide selectivity.

[0024] 1 is a schematic cross-sectional view showing an example of a carbon dioxide reduction electrode according to the present disclosure, and FIG. 2 is a schematic cross-sectional view showing an example of a carbon dioxide reduction device according to the present disclosure.

[0025] Hereinafter, an embodiment that is an example of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiments and do not limit the scope of the invention. In the numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in an example.

[0026] Each component may contain multiple corresponding substances. When referring to the amount of each component in a composition, if multiple substances corresponding to each component are present in the composition, the total amount of those multiple substances present in the composition is meant unless otherwise specified. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0027] Examples of the "substituent" include a halogen atom, an alkyl group (including a cycloalkyl group), an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, a divalent oxo group, an arylthio group, a monovalent heterocyclic group, a substituted amino group, an acyl group, an imine residue, an amide group, an acid imide group, a substituted oxycarbonyl group, a cyano group, an alkylsulfonyl group, and a nitro group. In this specification, when referring to the number of carbon atoms, the number of carbon atoms does not usually include the number of carbon atoms of the substituent A.

[0028] The term "aromatic hydrocarbon ring group" refers to an atomic group remaining after removing one or more hydrogen atoms directly bonded to carbon atoms constituting an aromatic hydrocarbon ring, which may be unsubstituted or substituted, and which may be condensed with two or more rings.

[0029] The term "aromatic heterocyclic group" refers to an atomic group remaining after removing one or more hydrogen atoms directly bonded to carbon atoms or heteroatoms constituting an aromatic heterocyclic ring, which may be unsubstituted or substituted and may be condensed with two or more rings.

[0030] In the compound names, "t-" means tertiary, "n-" means normal, and "p-" means para. The dotted lines in the chemical structural formulas represent moieties that may be either single or double bonds.

[0031] <Method for Producing Carbon Monoxide> The method for producing carbon monoxide according to the present disclosure includes a step of reacting carbon dioxide with water in the presence of a carbon dioxide reduction catalyst represented by the following formula (1).

[0032] (In formula (1), R １ represents a hydrogen atom or a substituent, and a plurality of R １ may be the same or different, and two adjacent R １ may be bonded to each other to form a ring, P １ represents a divalent group containing one or more aromatic rings, and Q １ and Q ２ represents a monovalent group containing one or more aromatic rings, and Q １ and Q ２ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0033] The carbon monoxide production method according to one embodiment of the present disclosure has the above-described configuration, and is therefore a carbon monoxide production method with high carbon monoxide selectivity. The reason for this is presumed to be as follows.

[0034] It is presumed that the production of carbon monoxide using a polynuclear metal proceeds by using a polynuclear metal complex having a polynuclear structure in which central metals are adjacent to each other, whereby carbon dioxide coordinates to the cobalt atom, nickel atom, and / or zinc atom of the polynuclear metal complex, and the coordinated carbon dioxide reacts with water to produce carbon monoxide. Here, it is presumed that a carbon monoxide production method according to an embodiment of the present disclosure uses a carbon dioxide reduction catalyst represented by formula (1) above, and although the detailed mechanism is unknown, it is presumed that the polynuclear structure in which central metals are adjacent to each other and the coordination environment of the central metal by the macrocyclic ligand suppress the generation of hydrogen and promote the production of carbon monoxide by the reduction of carbon dioxide, resulting in a carbon monoxide production method with high carbon monoxide selectivity.

[0035] (Carbon dioxide reduction catalyst represented by formula (1)) The carbon dioxide reduction catalyst represented by formula (1) used in the carbon monoxide production method according to the present disclosure will be described.

[0036] In the formula (1), R １ is preferably a hydrogen atom, an alkyl group, or an alkoxy group. １ When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms (also referred to as "carbon atom number"), and even more preferably a t-butyl group. １ When R is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. １ In addition, in the formula (1), from the viewpoint of carbon monoxide selectivity, it is preferable that R １ In the formula (1), it is preferable that all of Q are hydrogen atoms. １ and Q ２ Examples of the aromatic ring contained in the monovalent group represented by the formula Q include an aromatic hydrocarbon ring group and an aromatic heterocyclic group. １ and Q ２The aromatic heterocyclic group as the aromatic ring contained in the monovalent group represented by the formula (I) is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom. １ and Q ２are bonded to each other to form a ring structure, the ring structure is preferably an atomic group remaining after removing two hydrogen atoms from phenanthroline, for example. M represents a cobalt atom, a nickel atom, or a zinc atom, and is preferably a nickel atom from the viewpoint of carbon monoxide selectivity. Furthermore, M is preferably a divalent cobalt atom or a divalent nickel atom from the viewpoint of carbon monoxide selectivity. The carbon dioxide reduction catalyst represented by formula (1) may be a heterometal complex. From the viewpoint of reduction efficiency, M is also preferably a combination of a nickel atom and a zinc atom, or a combination of a cobalt atom and a zinc atom. Among these, the metal atom contained in the carbon dioxide reduction catalyst represented by formula (1) is preferably a nickel atom from the viewpoint of carbon monoxide selectivity. a is preferably 2. The counter ion represented by X is preferably an anion, and more preferably at least one anion selected from the group consisting of a fluoride ion, a chloride ion, a bromide ion, an iodide ion, a sulfide ion, an oxide ion, a hydroxide ion, a hydride ion, a sulfite ion, a phosphate ion, a cyanide ion, an acetate ion, a 2-ethylhexanoate ion, a carbonate ion, a sulfate ion, a nitrate ion, a hydrogen carbonate ion, a trifluoroacetate ion, a thiocyanide ion, a trifluoromethanesulfonate ion, an acetylacetonate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a tetraphenylborate ion. The neutral molecule represented by X is preferably at least one neutral molecule selected from the group consisting of water, methanol, ethanol, n-propanol, isopropyl alcohol, 2-methoxyethanol, 1,1-dimethylethanol, ethylene glycol, N,N'-dimethylformamide, N,N'-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, acetone, chloroform, acetonitrile, benzonitrile, triethylamine, pyridine, pyrazine, diazabicyclo[2.2.2]octane, 4,4'-bipyridine, tetrahydrofuran, diethyl ether, dimethoxyethane, methyl ethyl ether, 1,4-dioxane, acetic acid, propionic acid, and 2-ethylhexanoic acid.b is preferably an integer of 0 or more and 8 or less, and more preferably an integer of 0 or more and 4 or less.

[0037] In the formula (1), P １ Examples of the aromatic ring contained in include an aromatic hydrocarbon ring group and an aromatic heterocyclic group. From the viewpoint of carbon monoxide selectivity, the aromatic heterocyclic group is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom, more preferably an aromatic heterocyclic group containing a nitrogen atom, and particularly preferably a five- or six-membered aromatic heterocyclic group containing a nitrogen atom. １ From the viewpoint of carbon monoxide selectivity, P is preferably a divalent group containing two or more aromatic rings, and more preferably a divalent group containing two aromatic rings. １ is expressed by the following formula (P ａ ), the following formula (P ｂ ), or the following formula (P ｃ ) is preferably a divalent group represented by the formula:

[0038] (Formula (P ａ ) ~ formula (P ｃ In the formula, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, the multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring, Y represents any of the groups shown below, and the multiple Ys may be the same or different, Z represents an alkylene group or an arylene group, and * represents a bond.

[0039] (In the formula, R ａ represents a hydrogen atom or a substituent.

[0040] The formula (P ａIn the formula (P), R at the ortho position relative to the bonding position of the pyridine rings of the bipyridyl structure is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. It is preferable that the two Rs at the ortho positions are bonded to each other to form a ring structure, and the ring structure formed by bonding the two Rs at the ortho positions to each other is preferably a benzene ring. ａ In the above, R at the meta and para positions of the bonding positions between the pyridine rings of the bipyridyl structure is preferably a hydrogen atom.

[0041] The formula (P ｂ In the formula (P), it is preferable that the four Rs on the aromatic heterocycle are hydrogen atoms. ｂIn the above, R in the bridging portion connecting the two aromatic heterocycles is preferably an aromatic hydrocarbon ring group, and is preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or less carbon atoms, more preferably an unsubstituted or substituted phenyl group, an unsubstituted or substituted naphthyl group, an unsubstituted or substituted anthryl group, or an unsubstituted or substituted pyrenyl group, and even more preferably an unsubstituted or substituted phenyl group. Specific examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom, hydroxy group, carboxyl group, ester group, mercapto group, sulfonic acid group, nitro group, phosphonic acid group, silyl group having an alkyl group having 1 to 4 carbon atoms, linear, branched, or cyclic monovalent saturated hydrocarbon groups having a total of 1 to 50 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, norbornyl group, nonyl group, cyclononyl group, decyl group, 3,7-dimethyloctyl group, adamantyl group, dodecyl group, cyclododecyl group, pentadecyl group, octadecyl group, and docosyl group, alkenyl group, alkynyl group, methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group, cyclohexyloxy group, and the like. Examples of the substituents include linear, branched, or cyclic alkoxy groups having a total carbon number of about 1 to 50, such as an oxy group, a norbornyloxy group, a decyloxy group, and a dodecyloxy group. The number of substituents may be any number that allows substitution, and is 1 to 5 for a phenyl group, 1 to 7 for a naphthyl group, and 1 to 9 for each of an anthryl group and a pyrenyl group.

[0042] The formula (P ｃIn the above formula (1), Z is preferably an alkylene group having 2 to 6 carbon atoms or an arylene group having 4 to 14 carbon atoms, more preferably an arylene group having 4 to 14 carbon atoms, and even more preferably an arylene group having 6 to 10 carbon atoms, from the viewpoint of carbon monoxide selectivity. When Z is an alkylene group, Z is preferably a 1,3-propylene group. The arylene group in Z may be a divalent hydrocarbon aromatic group or a divalent heteroaromatic group. When Z is an arylene group, Z is preferably a phenylene group, a pyridinediyl group, a tetrafluorophenylene group, a naphthalenediyl group, a thiophenediyl group, a dimethylphenylene group, or a phenanthrenediyl group, more preferably a 1,2-phenylene group, a 3,4-pyridinediyl group, a 3,4,5,6-tetrafluoro-1,2-phenylene group, a 2,3-naphthalenediyl group, a 3,4-thiophenediyl group, a 3,4-dimethyl-1,2-phenylene group, or a 9,10-phenanthrenediyl group, and particularly preferably a 1,2-phenylene group.

[0043] The formula (P ｃ In the formula (I), R is preferably a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, or an alkylthio group, and more preferably a hydrogen atom or an alkyl group, from the viewpoint of carbon monoxide selectivity. When R is an alkyl group, R is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably a methyl group or a t-butyl group. When R is an aryl group, R is preferably an aryl group having 6 to 14 carbon atoms, and more preferably a phenyl group. When R is an alkoxy group, R is preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms, and even more preferably a methoxy group. When R is an alkylthio group, R is preferably an alkylthio group having 1 to 10 carbon atoms, more preferably an alkylthio group having 1 to 4 carbon atoms, and even more preferably a methylthio group.

[0044] The formula (P ｃIn terms of carbon monoxide selectivity, Y in each of the above formulas is preferably the same group, and more preferably the group shown below.

[0045]

[0046] R in the above formula ａ is preferably a hydrogen atom from the viewpoint of carbon monoxide selectivity.

[0047] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (2):

[0048] (In formula (2), R ６ ~R ８ represents a hydrogen atom or a substituent, and two adjacent R ６ Two adjacent Rs ７ Each other and two adjacent R ８ may be bonded to each other to form a ring structure, and multiple R ６ ~R ８ may be the same or different, and Q ３ and Q ４ represents a monovalent group containing one or more aromatic rings, and Q ３ and Q ４ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0049] In the formula (2), R ６ is preferably a hydrogen atom, an alkyl group, or an alkoxy group. ６ When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. ６When R is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. ６ is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (2), from the viewpoint of carbon monoxide selectivity, the four R ６ is preferably a hydrogen atom. ７ is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. ７ Preferably, two adjacent R ７ The ring structure formed by bonding together is preferably a benzene ring. ８ In the formula (2), Q is preferably a hydrogen atom. ３ and Q ４ Examples of the aromatic ring contained in the monovalent group represented by the formula Q include an aromatic hydrocarbon ring group and an aromatic heterocyclic group. ３ and Q ４ The aromatic heterocyclic group as the aromatic ring contained in the monovalent group represented by the formula (I) is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom. ３ and Q ４ In the case where M, a, X, and b are bonded to each other to form a ring structure, the ring structure is preferably an atomic group remaining after removing two hydrogen atoms from phenanthroline. In the formula (2), preferred embodiments of M, a, X, and b are the same as preferred embodiments of M, a, X, and b in the formula (1).

[0050] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (3):

[0051] (In formula (3), R ９~R １３ represents a hydrogen atom, a substituent, or a divalent group, and two adjacent R ９ Two adjacent Rs １０ Two adjacent Rs １１ Two adjacent Rs １２ R １２ and R １３ may be bonded to each other to form a ring structure, and multiple R ９ ~R １３ may be the same or different, R １３ is a divalent group, the divalent group may form a bond with another compound represented by formula (3) to form a dimer, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

[0052] In the formula (3), R ９ is preferably a hydrogen atom, an alkyl group, or an alkoxy group. ９ When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. ９ When R is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. ９ is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (3), from the viewpoint of carbon monoxide selectivity, the four R ９ is preferably a hydrogen atom. １０ is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. １０Preferably, two adjacent R １０ The ring structure formed by bonding together is preferably a benzene ring. １１ is preferably a hydrogen atom. １２ is preferably a hydrogen atom. １３ is preferably an aromatic hydrocarbon ring group, preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or less carbon atoms, more preferably an unsubstituted or substituted phenyl group, an unsubstituted or substituted naphthyl group, an unsubstituted or substituted anthryl group, or an unsubstituted or substituted pyrenyl group, and even more preferably an unsubstituted or substituted phenyl group. Specific examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, a hydroxy group, a carboxyl group, an ester group, a mercapto group, a sulfonic acid group, a nitro group, a phosphonic acid group, a silyl group having an alkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a norbornyl group, a nonyl group, a cyclononyl group, and a decyl group. Examples of the substituents include linear, branched, or cyclic saturated monovalent hydrocarbon groups having a total carbon number of about 1 to about 50, such as 3,7-dimethyloctyl, adamantyl, dodecyl, cyclododecyl, pentadecyl, octadecyl, and docosyl; and linear, branched, or cyclic alkoxy groups having a total carbon number of about 1 to about 50, such as alkenyl, alkynyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy, cyclohexyloxy, norbornyloxy, decyloxy, and dodecyloxy. The number of substituents may be any number that allows substitution, and is 1 to 5 for phenyl groups, 1 to 7 for naphthyl groups, and 1 to 9 for anthryl and pyrenyl groups, respectively. In formula (3), preferred embodiments of M, X, and b are the same as preferred embodiments of M, X, and b in formula (1).

[0053] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (4):

[0054] (In formula (4), R １４ ~R １６ represents a hydrogen atom or a substituent, and two adjacent R １４ Two adjacent Rs １５ R １５ and R １６ may be linked to each other to form a ring, and multiple R １４ ~R １６ may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and a plurality of M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are a plurality of X's, they may be the same or different.

[0055] In the formula (4), R １４ is preferably a hydrogen atom, an alkyl group, or an alkoxy group. １４ When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. １４ When R is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. １４ is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (4), from the viewpoint of carbon monoxide selectivity, the four R １４ is preferably a hydrogen atom. １５ is preferably a hydrogen atom. １６is preferably an aromatic hydrocarbon ring group, preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or less carbon atoms, more preferably an unsubstituted or substituted phenyl group, an unsubstituted or substituted naphthyl group, an unsubstituted or substituted anthryl group, or an unsubstituted or substituted pyrenyl group, and even more preferably an unsubstituted or substituted phenyl group. Specific examples of the substituent include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, hydroxy groups, carboxyl groups, ester groups, mercapto groups, sulfonic acid groups, nitro groups, phosphonic acid groups, silyl groups having an alkyl group having 1 to 4 carbon atoms, methyl groups, ethyl groups, propyl groups, isopropyl groups, cyclopropyl groups, butyl groups, isobutyl groups, tert-butyl groups, pentyl groups, cyclopentyl groups, hexyl groups, cyclohexyl groups, norbornyl groups, nonyl groups, cyclononyl groups, and decyl groups. Examples of the substituents include linear, branched, or cyclic monovalent saturated hydrocarbon groups having a total carbon number of about 1 to about 50, such as 3,7-dimethyloctyl, adamantyl, dodecyl, cyclododecyl, pentadecyl, octadecyl, and docosyl; and linear, branched, or cyclic alkoxy groups having a total carbon number of about 1 to about 50, such as alkenyl, alkynyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy, cyclohexyloxy, norbornyloxy, decyloxy, and dodecyloxy. The number of substituents may be any number that allows substitution, and is 1 to 5 for phenyl groups, 1 to 7 for naphthyl groups, and 1 to 9 for anthryl and pyrenyl groups, respectively. In formula (4), preferred embodiments of M, X, and b are the same as preferred embodiments of M, X, and b in formula (1).

[0056] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (5):

[0057] (In formula (5), R １７ ~R ２１ represents a hydrogen atom or a substituent, and two adjacent R １７ Two adjacent Rs １８ Two adjacent Rs１９ Two adjacent Rs ２１ R ２０ and R ２１ may be bonded to each other to form a ring structure, and multiple R １７ ~R ２１ may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and a plurality of M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are a plurality of X's, they may be the same or different.

[0058] In the formula (5), R １７ is preferably a hydrogen atom, an alkyl group, or an alkoxy group. １７ When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. １７ When R is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. １７ is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (5), from the viewpoint of carbon monoxide selectivity, the four R １７ is preferably a hydrogen atom. １８ is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. １８ Preferably, two adjacent R １８ The ring structure formed by bonding together is preferably a benzene ring. １９ and R ２０ is preferably a hydrogen atom. ２１is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. ２１ Preferably, two adjacent R ２１ The ring structure formed by bonding together is preferably a benzene ring. In the formula (5), preferred embodiments of M, X, and b are the same as preferred embodiments of M, X, and b in the formula (1).

[0059] Specific structural formulas of the carbon dioxide reduction catalyst represented by the formula (1) are shown below, but the catalyst is not limited thereto. In the structural formulas below, "t-Bu" means a t-butyl group, "i-Pr" means an isopropyl group, "Et" means an ethyl group, "Me" means a methyl group, "TMS" means a trimethylsilyl group, and － "OAc" means acetate ion, M represents Ni or Co, and the valence of Ni is divalent (Ni ２＋ ), and the valence of Co is divalent (Co ２＋ )

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] (Step of reacting carbon dioxide and water) The method for producing carbon monoxide according to the present disclosure includes a step of reacting carbon dioxide and water in the presence of a carbon dioxide reduction catalyst represented by formula (1). This step is not particularly limited as long as it is a step that can react carbon dioxide and water in the presence of a carbon dioxide reduction catalyst represented by formula (1). From the viewpoint of carbon monoxide selectivity, however, it is preferable to carry out this step using a carbon dioxide reduction device that includes an oxidation electrode, a carbon dioxide reduction electrode according to the present disclosure, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode, an electrolyte, and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode. Details of the carbon dioxide reduction device will be described later.

[0075] A method for reacting carbon dioxide with water using a carbon dioxide reduction device includes passing a current through an oxidation electrode and a carbon dioxide reduction electrode, flowing carbon dioxide into the device so that it comes into contact with the carbon dioxide reduction electrode, and reacting the water contained in the electrolyte of the carbon dioxide reduction device with carbon dioxide on the carbon dioxide reduction electrode.

[0076] <Carbon Dioxide Reduction Electrode> The carbon dioxide reduction electrode according to the present disclosure contains the carbon dioxide reduction catalyst represented by the formula (1) above or a conductive material on which the carbon dioxide reduction catalyst represented by the formula (1) above is supported.

[0077] (Carbon dioxide reduction catalyst represented by formula (1)) The cobalt atom, nickel atom, or zinc atom contained in the carbon dioxide reduction catalyst represented by formula (1) may be an uncharged or charged ion, but from the viewpoint of catalytic activity, it is preferably a divalent cobalt atom or a divalent nickel atom. The carbon dioxide reduction catalyst represented by formula (1) may be a heterometal complex. From the viewpoint of reduction efficiency, it is also preferable that M is a combination of nickel atoms and zinc atoms, or a combination of cobalt atoms and zinc atoms. Among these, the metal atom contained in the carbon dioxide reduction catalyst represented by formula (1) is preferably a nickel atom from the viewpoint of carbon monoxide selectivity.

[0078] (Conductive Material) Any known conductive material can be used without any particular limitation, as long as it is capable of supporting the carbon dioxide reduction catalyst represented by formula (1). The carbon dioxide reduction catalyst represented by formula (1) may be supported on a flat or rod-shaped carbonaceous material, metal material, or the like. Alternatively, the carbon dioxide reduction catalyst represented by formula (1) may be supported on a porous carbonaceous material, metal material, or the like, such as carbon paper or a metal mesh. The carbon dioxide reduction catalyst represented by formula (1) may also be supported on a powder material such as carbon black (CB) or metal particles. That is, the carbon dioxide reduction catalyst represented by formula (1) can be used as a composite material supported on a conductive material. Furthermore, a composite material in which the carbon dioxide reduction catalyst represented by formula (1) is supported on a powder material may be molded by compression or the like. Alternatively, a powder material in which the carbon dioxide reduction catalyst represented by formula (1) is supported on a powder material may be immobilized on a support such as a flat, rod-shaped, lattice-shaped, or porous carbonaceous material, metal material, or the like.

[0079] The conductive material is not particularly limited, but is preferably a porous carbon material, and examples of the conductive material include carbon particles such as Norit, Ketjen Black, Vulcan, Black Pearl, and acetylene black, fullerenes such as C60 and C70, carbon nanotubes, carbon nanohorns, carbon fibers, graphene, graphene oxide, reduced graphene oxide, and graphene meso sponge.

[0080] The method of loading is not particularly limited, and any known method can be applied, including a method of vacuum-depositing the carbon dioxide reduction catalyst represented by the formula (1) onto a conductive support (conductive material), a method of immersing a conductive support in a dispersion liquid obtained by dispersing the carbon dioxide reduction catalyst represented by the formula (1) in a solvent and drying it, a method of coating a dispersion liquid obtained by dispersing the carbon dioxide reduction catalyst represented by the formula (1) in a solvent onto a conductive support, and a method of adding a powdered conductive support to a dispersion liquid obtained by dispersing the carbon dioxide reduction catalyst represented by the formula (1) in a solvent and adsorbing the carbon dioxide reduction catalyst represented by the formula (1) onto the surface of the powder.

[0081] The amount of the carbon dioxide reduction catalyst represented by formula (1) supported on the conductive material is preferably an amount such that the mass of cobalt atoms, nickel atoms, or zinc atoms relative to the mass of the conductive material is 1% by mass or more and 50% by mass or less, and more preferably an amount such that the mass of cobalt atoms, nickel atoms, or zinc atoms is 2% by mass or more and 10% by mass or less.

[0082] The amount of the carbon dioxide reduction catalyst represented by formula (1) supported on the conductive material is preferably an amount such that the mass of the carbon dioxide reduction catalyst represented by formula (1) relative to the mass of the conductive material is 1 mass% or more and 100 mass% or less, and more preferably an amount such that the mass of the carbon dioxide reduction catalyst represented by formula (1) is 5 mass% or more and 50 mass% or less.

[0083] The mass of metal atoms (cobalt atoms, nickel atoms, or zinc atoms) relative to the mass of the conductive material is measured using a thermogravimetric differential thermal analyzer (TG-DTA). The measurement method is as follows: Using the thermogravimetric differential thermal analyzer, the temperature is increased from 25°C or lower to 900°C at a rate of 10°C / min in the atmosphere, and the TG-DTA curve is measured.

[0084] The carbon dioxide reduction electrode according to the present disclosure preferably includes a conductive material supporting the carbon dioxide reduction catalyst represented by formula (1), and further includes a support supporting the conductive material. The support is preferably conductive, and examples thereof include carbon nanotubes, graphene, carbon black, carbon cloth, carbon paper, glassy carbon, graphite, and tantalum (Ta).

[0085] (Ion Conductor) The carbon dioxide reduction electrode according to the present disclosure preferably includes an ion conductor. Known ion conductors can be used as the ion conductor, and are not particularly limited. An electrolyte solution in which an ionic substance is dissolved in a solvent such as water may be used, or an ion exchange resin may be used. The ion conductor used between the reduction electrode and the membrane and the ion conductor used between the oxidation electrode and the membrane may be the same or different, and both the electrolyte solution and the ion exchange resin may be used as the ion conductor. Examples of ion conductors include ionomers. An ionomer is a polymer neutralized with ions. The ionomer is preferably a polymer neutralized with cations such as metals (cationic ionomers) or a polymer neutralized with anions (anionic ionomers). Examples of anionic ionomers include Sustainion manufactured by Dioxide Materials, AEMION manufactured by Ionomer Innovations, Fumasep manufactured by FumaTech, and Orion manufactured by Orion.

[0086] The ion conductor preferably accounts for 10% by mass or more and 200% by mass or less of the mass of the conductive material on which the carbon dioxide reduction catalyst represented by the formula (1) is supported.

[0087] (Other Components) The carbon dioxide reduction electrode according to the present disclosure may contain other components in addition to the conductive material, support, and ion conductor. Examples of other components include a water-repellent material. Examples of water-repellent materials include fluorine-containing resins, silicon-containing resins, silane coupling agents, and waxes. From the viewpoint of water-repellent effect, fluorine-containing resins are preferred, and examples of fluorine-containing resins include polytetrafluoroethylene.

[0088] (Method for manufacturing carbon dioxide reduction electrode) The carbon dioxide reduction electrode according to the present disclosure is preferably manufactured by preparing an electrode ink in which the carbon dioxide reduction catalyst represented by formula (1) or a conductive material supporting the carbon dioxide reduction catalyst represented by formula (1), an ionic conductor as needed, and other components are dispersed in a solvent, and then applying the electrode ink to a support and drying it.

[0089] (Example of Carbon Dioxide Reduction Electrode) Figure 1 shows an example of a carbon dioxide reduction electrode according to the present disclosure. Figure 1 is a schematic cross-sectional view of a carbon dioxide reduction electrode according to the present disclosure. In Figure 1, the carbon dioxide reduction electrode 10 has, on a support 2, a layer 1 containing a conductive material on which a carbon dioxide reduction catalyst represented by formula (1) is supported. When components other than the ion conductor are contained, these components are contained in layer 1 containing a conductive material on which a carbon dioxide reduction catalyst represented by formula (1) is supported.

[0090] <Carbon dioxide reduction device> The carbon dioxide reduction device according to the present disclosure includes an oxidation electrode, a carbon dioxide reduction electrode according to the present disclosure, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode, an electrolyte, and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode.

[0091] (Example of Carbon Dioxide Reduction Device) Figure 2 shows an example of a carbon dioxide reduction device according to the present disclosure. In Figure 2, the carbon dioxide reduction device 100 comprises an oxidation electrode 11, a carbon dioxide reduction electrode 10, a membrane 12 separating the oxidation electrode 11 and the carbon dioxide reduction electrode 10, an electrolyte 13, and a power source 14 connected to the oxidation electrode 11 and the carbon dioxide reduction electrode 10. The carbon dioxide reduction device 100 also has an electrolytic cell 15 comprising these components, and a reaction cell 16. Here, the carbon dioxide reduction electrode 10 is preferably installed so that a conductive material carrying the carbon dioxide reduction catalyst represented by formula (1) above is in contact with the electrolyte 13.

[0092] The carbon dioxide reduction device 100 is applicable to a reaction in which carbon dioxide is reduced to produce carbon monoxide. When used in this reaction, it is preferable to use a power source 14 to pass a current from the carbon dioxide reduction electrode 10 to the oxidation electrode 11. It is then preferable to pass carbon dioxide into the reaction vessel 16 in the direction of arrow A. The carbon dioxide that has flowed into the reaction vessel 16 comes into contact with the carbon dioxide reduction catalyst represented by the above formula (1) in the carbon dioxide reduction electrode 10. This causes the reaction represented by the following reaction formula 1 to proceed on the carbon dioxide reduction electrode 10 side, and the reaction represented by the following reaction formula 2 to proceed on the oxidation electrode 11 side. Reaction formula 1: CO ２ +H ２ O + 2e － →CO + 2OH － Reaction Scheme 2: 2OH － →1 / 2O ２ +H ２ O + 2e － The produced carbon monoxide then flows out of the reaction tank 16 in the direction of arrow B.

[0093] The carbon dioxide reduction electrode will be described in detail below, with the reference numerals omitted.

[0094] (Oxidation Electrode) Known oxidation electrodes can be used without particular limitation, but an electrode that generates oxygen by oxidizing water or hydroxide ions is preferred. Examples include, but are not limited to, porous materials made of metal materials such as titanium and nickel, and carbonaceous materials such as carbon paper. The oxidation electrode may contain a metal such as platinum, palladium, or nickel, or a metal oxide such as nickel oxide, iridium oxide, or ruthenium oxide to promote oxygen generation.

[0095] (Carbon dioxide reduction electrode) The carbon dioxide reduction electrode according to the present disclosure described above is applied as the carbon dioxide reduction electrode.

[0096] (Membrane) As the membrane separating the carbon dioxide reduction electrode and the oxidation electrode, a known material can be used, and is not particularly limited, but a material having ion conductivity can be used. For example, a porous polymer membrane such as PTFE, a porous membrane such as a glass filter, a cation exchange membrane such as Nafion, an anion exchange membrane such as Sustenion, Neosepta, or Selemion can be used. Although not particularly limited, an ion exchange membrane is preferred. As the ion exchange membrane, an anion exchange membrane is more preferred.

[0097] (Electrolyte) Any known electrolyte can be used as the electrolyte, and is not particularly limited. Examples of the electrolyte include an electrolyte containing a cation such as a sodium ion or a potassium ion, an anion such as a hydrogen carbonate ion, a carbonate ion, a hydroxide ion, a sulfate ion, a phosphate ion, or a borate ion, and water.

[0098] The ion concentration of the electrolyte is preferably 0.01 mol / L or more and 5.0 mol / L or less, and more preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0099] (Power supply) A power supply is connected to the oxidation electrode and the carbon dioxide reduction electrode. There are no particular limitations on the power supply as long as it can pass a current between the carbon dioxide reduction electrode and the oxidation electrode. For example, an electrochemical analyzer 701C manufactured by BAS Corporation can be used as the power supply.

[0100] The present disclosure will be described in more detail below using examples, etc., but these are illustrative and the present disclosure is not limited thereto. That is, those skilled in the art can implement the present disclosure by making various modifications to the examples shown below. For example, the materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be modified as appropriate as long as they do not deviate from the spirit of the present disclosure. Note that the values ​​of various manufacturing conditions and evaluation results in the following examples represent preferred upper or lower limit values ​​in the embodiments of the present disclosure, and preferred ranges represent preferred values ​​of the above-mentioned upper or lower limit values. The preferred range may be a range defined by a combination of the above-mentioned upper or lower limit values ​​and the values ​​of the following examples or values ​​between examples. Note that in the following description, unless otherwise specified, all "parts" and "%" are based on mass.

[0101] The performance of the carbon dioxide reduction electrodes prepared by the methods described in the Examples and Comparative Examples was evaluated using a carbon dioxide reduction device 100 shown in FIG. 2 . A platinum mesh was used as the oxidation electrode 11. A carbon dioxide reduction electrode was used as the reduction electrode 10. An anion exchange membrane (Sustainion, manufactured by Dioxide Materials) was used as the membrane 12. A 1.0 M (=1.0 mol / L) potassium hydroxide aqueous solution was used as the electrolyte 13. An electrochemical measurement device (Electrochemical Analyzer 701C, manufactured by BAS Corporation) was used as the power source 14. Furthermore, a Hg / HgO reference electrode (manufactured by EC Frontier Co., Ltd.) was installed in the electrolyte 13 between the membrane 12 and the reduction electrode 10 as a reference electrode. Carbon dioxide gas set at 15 mL / min was circulated in the direction of arrow A in the reaction chamber 16, and a constant potential was applied to the reduction electrode 10 using the electrochemical measurement device to perform electrochemical measurements. 50 μL of the outlet gas (gas flowing out of the reaction vessel 16 in the direction of arrow B) was collected using a gas-tight syringe, and the products contained in the gas were quantitatively analyzed using a gas chromatograph (Shimadzu Corporation, GC-2010 / BID detector). The Faraday efficiency of each product was calculated as the ratio of the charge used to generate each observed product to the total charge used in the reaction. A higher value for the Faraday efficiency of carbon monoxide indicates that carbon monoxide is produced selectively, which means that the selectivity for carbon monoxide is high.

[0102] Synthesis Example 1 Polynuclear metal complex 1 was synthesized according to the method described in JP-A-2009-173627 in accordance with the reaction formula shown below.

[0103]

[0104] Synthesis Example 2 Polynuclear metal complex 2 was synthesized according to the method described in JP-A-2009-173627 in accordance with the reaction formula shown below.

[0105]

[0106] Synthesis Example 3 Synthesis of Compound 3 Compound 3 was synthesized according to the reaction formula shown below.

[0107]

[0108] Under a nitrogen atmosphere, 92 mL of dehydrated toluene and N,N-dimethylanilinium tetrakispentafluorophenylborate (PhNH ＋ Me ２ B (C ６ F ５ ) ４ － 231 mg (0.29 mmol) of pyrene-1-carbaldehyde was added, and the resulting solution was heated to 80°C with stirring using a rotor. A mixture of 2.09 g (9.06 mmol) of pyrene-1-carbaldehyde, 5.0 g (8.24 mmol) of compound 2, and 12 mL of toluene was added dropwise to this solution. After stirring for 3 hours, the reaction solution was allowed to cool, and the temperature was gradually adjusted to room temperature.

[0109] To the reaction solution, a solution prepared by dissolving 0.98 g (9.06 mmol) of benzoquinone in 11 mL of tetrahydrofuran (THF) was added dropwise. After confirming the completion of the reaction, the resulting reaction solution was filtered to obtain the target compound 3 in an amount of 5.89 g and a yield of 99%. The identification data for the obtained compound 3 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M+H] ＋ : m / z = 817.4

[0110] Synthesis Example 4 Synthesis of Polynuclear Metal Complex 3 Polynuclear Metal Complex 3 was synthesized according to the reaction formula shown below.

[0111]

[0112] After the reaction vessel was filled with nitrogen gas, nickel acetate tetrahydrate (Ni(OAc) ２ ・4H ２ 0.34 g (1.35 mmol) of chloroform (CHCl 3 ) was added to 10 mL of degassed methanol (MeOH) and suspended. ３) was added and the temperature was raised to 50°C to prepare a nickel acetate solution. A nitrogen gas atmosphere was placed in another reaction vessel, and a suspension consisting of 0.5 g (0.61 mmol) of compound 3 and 30 mL of chloroform was prepared. This suspension was added dropwise to the nickel acetate solution, and the temperature was raised to 55°C and the mixture was stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 3. This reaction solution was cooled to room temperature and then filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain 0.22 g of polynuclear metal complex 3 in a yield of 35%. The identification data for the obtained polynuclear metal complex 3 are shown below. The results of ESI-MS measurement were confirmed as follows: ESI-MS [M-OAc] ＋ : m / z = 929.3

[0113] Synthesis Example 5 Synthesis of Polynuclear Metal Complex 4 Polynuclear metal complex 4 was synthesized according to the reaction formula shown below.

[0114]

[0115] After the inside of the reaction vessel was filled with nitrogen gas, cobalt acetate tetrahydrate (Co(OAc) ２ ・4H ２ 0.34 g (1.35 mmol) of cobalt acetate (C10) was added to 10 mL of degassed methanol and suspended therein. 10 mL of chloroform was added thereto and the temperature was raised to 50°C to prepare a cobalt acetate solution. A nitrogen gas atmosphere was placed in another reaction vessel, and a suspension consisting of 0.5 g (0.61 mmol) of compound 3 and 30 mL of chloroform was prepared. This suspension was added dropwise to the cobalt acetate solution, and the temperature was raised to 55°C and the mixture was stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 4. This reaction solution was cooled to room temperature and then filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain polynuclear metal complex 4 in an amount of 0.29 g and a yield of 48%. Identification data for the obtained polynuclear metal complex 4 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M] ＋ : m / z = 931.2

[0116] Synthesis Example 6 Compound 4 was synthesized according to the reaction formula shown below.

[0117]

[0118] Under a nitrogen atmosphere, 37 mL of dehydrated toluene and 264 mg (0.33 mmol) of N,N-dimethylanilinium tetrakispentafluorophenylborate were added, and the resulting solution was heated to 80°C with stirring using a rotor. To this solution was added dropwise a mixture of 0.60 g (3.63 mmol) of 2,5-dimethoxybenzaldehyde, 2.0 g (3.30 mmol) of compound 2, and 5 mL of toluene. After stirring for 3 hours, the mixture was allowed to cool, and the temperature of the reaction solution was gradually adjusted to room temperature.

[0119] To the reaction solution, a solution prepared by dissolving 0.39 g (3.63 mmol) of benzoquinone in 5 mL of THF was added dropwise. After confirming the completion of the reaction, the resulting reaction solution was filtered to obtain the target compound 4 in an amount of 2.27 g and a yield of 91%. The identification data for the resulting compound 4 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M+H] ＋ : m / z = 753.3

[0120] Synthesis Example 7 Synthesis of Polynuclear Metal Complex 5 Polynuclear Metal Complex 5 was synthesized according to the reaction formula shown below.

[0121]

[0122] After creating a nitrogen gas atmosphere inside the reaction vessel, 0.22 g (0.88 mmol) of nickel acetate tetrahydrate was added to 10 mL of pre-degassed methanol and suspended. 10 mL of chloroform was added to this suspension and heated to 50°C to prepare a nickel acetate solution. Another reaction vessel was then created under a nitrogen gas atmosphere, and a suspension consisting of 0.3 g (0.40 mmol) of compound 4 and 30 mL of chloroform was prepared. This suspension was added dropwise to the nickel acetate solution, then heated to 55°C and stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 5. This reaction solution was cooled to room temperature and then filtered. The filtrate was concentrated to dryness and washed with acetone to obtain polynuclear metal complex 5 in a yield of 0.27 g and 72%. Identification data for the obtained polynuclear metal complex 5 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M-OAc] ＋ : m / z = 865.3

[0123] Synthesis Example 8 Using Compound 5 synthesized by the method described in JP-A-2009-173627, Polynuclear Metal Complex 6 was synthesized according to the reaction formula shown below.

[0124]

[0125] After creating a nitrogen gas atmosphere inside the reaction vessel, 0.25 g (1.00 mmol) of nickel acetate tetrahydrate was added to 10 mL of pre-degassed methanol and suspended. 10 mL of chloroform was added to this suspension and heated to 50°C to prepare a nickel acetate solution. Another reaction vessel was then created under a nitrogen gas atmosphere, and a suspension consisting of 0.3 g (0.40 mmol) of compound 5 and 30 mL of chloroform was prepared. This suspension was added dropwise to the nickel acetate solution, then heated to 55°C and stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 6. This reaction solution was cooled to room temperature and then filtered. The filtrate was concentrated to dryness and washed with methanol to obtain polynuclear metal complex 6 in a yield of 0.28 g and 84%. Identification data for the obtained polynuclear metal complex 6 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M+H] ＋ : m / z = 847.3

[0126] Synthesis Example 9 Polynuclear metal complex 7 was synthesized according to the method described in JP-A-2009-173627 in accordance with the reaction formula shown below.

[0127]

[0128] Synthesis Example 10 Compound 6 was synthesized according to the reaction scheme shown below using Compound 1 synthesized by the method described in JP-A-2009-173627.

[0129]

[0130] After the inside of the reaction vessel was filled with nitrogen gas, 10.00 g (14.43 mmol) of Compound 1 was dissolved in chloroform (CHCl ３ After 370 g of zinc acetate (Zn(OAc)) was added and suspended, the temperature was raised to 50° C. Another reaction vessel was conditioned under nitrogen gas, and zinc acetate (Zn(OAc)) was added. ２A suspension consisting of 2.65 g (14.43 mmol) of zinc acetate and 90 g of methanol (MeOH) was prepared. A suspension of zinc acetate was added dropwise to the suspension of compound 1, and the mixture was heated to 55°C and stirred under reflux for 1 hour to obtain a reaction solution containing compound 2. This reaction solution was cooled to room temperature, and water was added, stirred for a while, and washed, and the aqueous phase was removed. Heptane was added to the obtained organic phase, which was then concentrated and filtered. The obtained crystals were dried under reduced pressure to obtain compound 6 in a yield of 10.9 g and 100%. The identification data for the obtained compound 2 are shown below. The results of MALDI-MS measurement were confirmed as follows. MALDI-MS [M+H] ＋ :m / z=756.23

[0131] Synthesis Example 11 Polynuclear metal complex 8 was synthesized according to the reaction formula shown below.

[0132]

[0133] After the inside of the reaction vessel was filled with nitrogen gas, 2.00 g (2.65 mmol) of Compound 6 was dissolved in chloroform (CHCl ３ After 200 g of nickel acetate tetrahydrate (Ni(OAc) ２ ・4H ２ A suspension consisting of 0.66 g (2.65 mmol) of nickel acetate (M-OAc) and 40 g of methanol (MeOH) was prepared. A suspension of nickel acetate was added dropwise to the suspension of compound 2, and the mixture was heated to 55°C and stirred under reflux for 1.5 hours to obtain a reaction solution containing polynuclear metal complex 2. This reaction solution was cooled to room temperature and then filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain 1.91 g of polynuclear metal complex 2 in a yield of 83%. The identification data for the obtained polynuclear metal complex 8 are shown below. The results of MALDI-MS measurement were confirmed as follows. MALDI-MS [M-OAc] ＋ : m / z = 813.9

[0134] Synthesis Example 12 Polynuclear metal complex 9 was synthesized according to the reaction formula shown below.

[0135]

[0136] After the inside of the reaction vessel was filled with nitrogen gas, 2.00 g (2.65 mmol) of Compound 6 was dissolved in chloroform (CHCl ３ After 200 g of cobalt acetate tetrahydrate (Co(OAc) ２ ・4H ２ A suspension consisting of 0.66 g (2.65 mmol) of cobalt acetate and 40 g of methanol (MeOH) was prepared. A suspension of cobalt acetate was added dropwise to the suspension of compound 2, and the mixture was heated to 55°C and stirred under reflux for 2 hours to obtain a reaction solution containing polynuclear metal complex 8. After cooling this reaction solution to room temperature, 40 g of methanol containing 0.27 g (2.65 mmol) of triethylamine was added and the mixture was filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain polynuclear metal complex 8 in an amount of 1.55 g and a yield of 67%. The identification data for the obtained polynuclear metal complex 8 are shown below. The results of MALDI-MS measurement were confirmed as follows. MALDI-MS [M-OAc] ＋ : m / z = 812.1

[0137] Synthesis Example 13 Using compound 7 synthesized by the method described in Tetrahedron, 1999, 55, 8377, polynuclear metal complex 10 was synthesized according to the reaction formula shown below.

[0138]

[0139] After the inside of the reaction vessel was filled with nitrogen gas, 1.75 g (7.04 mmol) of nickel acetate tetrahydrate was dissolved in 10 mL of methanol (MeOH) and chloroform (CHCl ３) was added and suspended. 101 mL of a chloroform solution containing 1.50 g (2.82 mmol) of compound 7 was added to this nickel acetate suspension with stirring, and the temperature was raised to reflux. Subsequently, 10 mL of a chloroform solution containing 0.30 g (2.82 mmol) of 1,2-phenylenediamine was gradually added, and the mixture was refluxed for 3 hours. After concentrating the solution using an evaporator, acetone was added, cooled to room temperature, and filtered. The obtained crystals were washed with acetone and dried under reduced pressure to obtain polynuclear metal complex 9 in a weight of 1.68 g and a yield of 71%. The identification data for the obtained polynuclear metal complex 10 are shown below. The results of MALDI-MS measurement were confirmed as follows. MALDI-MS [M] ＋ :m / z=718.14

[0140] Example 1 - Preparation of Carbon Dioxide Reduction Electrode (1) - 250 mg of carbon black (KetjenBlack EC600JD, manufactured by Lion Specialty Chemicals Co., Ltd.) was weighed out as a conductive material into a reaction vessel. Polynuclear metal complex 1 was weighed out into a separate reaction vessel so that the mass of nickel atoms was 5 mass% relative to the mass of carbon black, and chloroform was added to confirm that a solution of polynuclear metal complex 1 had been formed. After that, the solution was transferred to the reaction vessel into which the conductive material had been weighed out to form a dispersion. Ultrasonic irradiation of this dispersion yielded a suspension in which the conductive material carrying a carbon dioxide reduction catalyst was uniformly dispersed. This suspension was filtered using a filter and then dried under reduced pressure to obtain conductive material 1 carrying a carbon dioxide reduction catalyst.

[0141] A dispersion was prepared by adding 20.0 mg of the powder of the conductive material 1, 2.50 mL of ethanol, and 400 mg of a 5% ethanol solution of Sustainion (manufactured by Dioxide Materials) as an anionic ionomer, which is an ion conductor, to a screw tube. Ultrasonic waves were applied to this dispersion to obtain an ink. Carbon paper (25 mm diameter) was used as a support, and 250 mg of the ink obtained above was applied to the carbon paper, which was then dried to obtain a carbon dioxide reduction electrode (1).

[0142] <Examples 2, 3, Comparative Examples 1 and 2> - Preparation of carbon dioxide reduction electrodes (2), (3), (1'), and (2') - Carbon dioxide reduction electrodes (2), (3), (1'), and (2') were obtained in the same manner as in Example 1, except that the metal complexes, conductive materials, ion conductors, and supports were used in the combinations shown in Table 1 below.

[0143] Example 4 - Preparation of Carbon Dioxide Reduction Electrode (4) - A carbon dioxide reduction electrode (4) was obtained in the same manner as in Example 1, except that 100 mg of a 5% solution of Nafion (manufactured by ALDRICH) was used as the ion conductor cationic ionomer.

[0144] Examples 5 to 11 and Comparative Example 3 Preparation of Carbon Dioxide Reduction Electrodes (5) to (11) and (3′) Carbon dioxide reduction electrodes (5) to (11) and (3′) were obtained in the same manner as in Example 4, except that the metal complexes, conductive materials, ion conductors, and supports were used in the combinations shown in Table 1 below.

[0145]

[0146] <Evaluation Results> Electrochemical measurements were carried out by the method described above using the carbon dioxide reduction electrodes obtained in Examples 1 to 11 and Comparative Examples 1 to 3. The results are shown in Table 2.

[0147]

[0148] From the above results, it can be seen that the carbon oxide production method of this example has higher carbon monoxide selectivity than the comparative example.

[0149] 1: Layer containing a conductive material carrying a carbon dioxide reduction catalyst, 2: Support, 10: Carbon dioxide reduction electrode, 11: Oxidation electrode, 12: Membrane, 13: Electrolyte, 14: Power source, 15: Electrolytic cell, 16: Reactor, 100: Carbon dioxide reduction device

Claims

1. A method for producing carbon monoxide, comprising a step of reacting carbon dioxide with water in the presence of a carbon dioxide reduction catalyst represented by the following formula (1): (In formula (1), R １ represents a hydrogen atom or a substituent, and a plurality of R １ may be the same or different, and two adjacent R １ may be bonded to each other to form a ring, P １ represents a divalent group containing one or more aromatic rings, and Q １ and Q ２ represents a monovalent group containing one or more aromatic rings, and Q １ and Q ２ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

2. The above P １ is expressed by the following formula (P ａ ), the following formula (P ｂ ) or the following formula (P ｃ 2. The method for producing carbon monoxide according to claim 1, wherein R is a divalent group represented by the formula (I). (Formula (P ａ ) ~ formula (P ｃ In the formula (I), R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, the multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring, Y represents any of the groups shown below, and the multiple Ys may be the same or different, Z represents an alkylene group or an arylene group, and * represents a bond. (In the formula, R ａ represents a hydrogen atom or a substituent.

3. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (2): (In formula (2), R ６ ~R ８ represents a hydrogen atom or a substituent, and two adjacent R ６ Two adjacent Rs ７ Each other and two adjacent R ８ may be bonded to each other to form a ring structure, and multiple R ６ ~R ８ may be the same or different, and Q ３ and Q ４ represents a monovalent group containing one or more aromatic rings, and Q ３ and Q ４ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

4. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (3): (In formula (3), R ９ ~R １３ represents a hydrogen atom, a substituent, or a divalent group, and two adjacent R ９ Two adjacent Rs １０ Two adjacent Rs １１ Two adjacent Rs １２ R １２ and R １３ may be bonded to each other to form a ring structure, and multiple R ９ ~R １３ may be the same or different, R １３ is a divalent group, the divalent group may form a bond with another compound represented by formula (3) to form a dimer, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

5. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (4): (In formula (4), R １４ ~R １６ represents a hydrogen atom or a substituent, and two adjacent R １４ Two adjacent Rs １５ R １５ and R １６ may be linked to each other to form a ring, and multiple R １４ ~R １６ may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or greater, and when there are multiple X's, they may be the same or different.

6. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (5): (In formula (5), R １７ ~R ２１ represents a hydrogen atom or a substituent, and two adjacent R １７ Two adjacent Rs １８ Two adjacent Rs １９ Two adjacent Rs ２１ R ２０ and R ２１ may be bonded to each other to form a ring structure, and multiple R １７ ~R ２１ may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and a plurality of M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are a plurality of X's, they may be the same or different.

7. A carbon dioxide reduction electrode comprising a carbon dioxide reduction catalyst represented by the following formula (1) or a conductive material carrying a carbon dioxide reduction catalyst represented by the following formula (1): (In formula (1), R １ represents a hydrogen atom or a substituent, and a plurality of R １ may be the same or different, and two adjacent R １ may be bonded to each other to form a ring, P １ represents a divalent group containing one or more aromatic rings, and Q １ and Q ２ represents a monovalent group containing one or more aromatic rings, and Q １ and Q ２ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

8. The carbon dioxide reduction electrode according to claim 7, comprising a conductive material on which the carbon dioxide reduction catalyst represented by formula (1) is supported, and further comprising a support for supporting the conductive material.

9. The carbon dioxide reduction electrode according to claim 7 or 8, further comprising an ionic conductor.

10. A carbon dioxide reduction device comprising: an oxidation electrode; the carbon dioxide reduction electrode according to claim 7 or 8; a membrane separating the oxidation electrode and the carbon dioxide reduction electrode; an electrolyte; and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode.

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