Method for producing carbon monoxide, carbon dioxide reduction electrode, carbon dioxide reduction device, and modified metal complex

Abstract

Provided are: a method for producing carbon monoxide, which has excellent reduction efficiency of carbon dioxide; a carbon dioxide reduction electrode; a carbon dioxide reduction device; and a modified metal complex.　This method for producing carbon monoxide includes reacting carbon dioxide with water in the presence of a modified metal complex which is obtained from a mixture that contains a polynuclear metal complex represented by formula (1) and a conductive material. In the formula (1), R, P, Q1, Q2, M, a, X, b, and O are as defined in the description.

Description

Method for producing carbon monoxide, carbon dioxide reduction electrode, carbon dioxide reduction apparatus, and modified metal complex

[0001] This disclosure relates to a method for producing carbon monoxide, a carbon dioxide reduction electrode, a carbon dioxide reduction apparatus, and a modified metal complex.

[0002] Metal complexes are used as catalysts. For example, Patent Document 1 discloses the use of a binuclear complex represented by a specific structural formula and a metal complex obtained by thermally modifying it as an electrode catalyst for fuel cells.

[0003] Furthermore, metal complexes are also known to be used as carbon dioxide reduction catalysts in methods for producing carbon monoxide by reducing carbon dioxide. For example, Patent Document 2 discloses the use of a porous electrode containing a heat-modified mononuclear metal complex in a carbon dioxide reduction apparatus. Non-Patent Document 1 describes the use of a nickel-containing binuclear complex for the reduction of carbon dioxide.

[0004] Japanese Patent Publication No. 2009-173627, International Publication No. 2019 / 065258

[0005] Y. Xiao et al., "Bioinspired Binickel Catalyst for Carbon Dioxide Reduction: The Importance of Metal-ligand Cooperation", JACS Au 2024, 4, 1207-1218

[0006] However, knowledge of catalysts with superior reduction efficiency in methods for producing carbon monoxide by reducing carbon dioxide has been limited. For example, Patent Document 1 only relates to a dinuclear complex represented by a specific structural formula and does not specifically disclose a method for producing carbon monoxide by reducing carbon dioxide. The mononuclear metal complex described in Patent Document 2 had low carbon dioxide reduction efficiency even after modification treatment and was not sufficient. The dinuclear complex described in Non-Patent Document 1 tended to have improved reduction efficiency compared to the mononuclear metal complex, but its carbon dioxide reduction efficiency was not sufficient.

[0007] This disclosure is made in view of the above, and relates to a method for producing carbon monoxide with excellent carbon dioxide reduction efficiency, a carbon dioxide reduction electrode, a carbon dioxide reduction apparatus, and a modified metal complex.

[0008] This disclosure includes the following aspects: <1> A method for producing carbon monoxide, comprising reacting carbon dioxide with water in the presence of a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (1) and a conductive material.

[0009] (In formula (1), R represents a hydrogen atom or substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, and P represents a divalent group containing one or more aromatic rings, Q 1 and Q 2 Q represents a monovalent group containing one or more aromatic rings. 1 and Q 2 ) The members 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 from 2 to 4, and the multiple M members may be the same or different, X is a counterion or a neutral molecule, b is an integer of 0 or more, and if there are multiple X members, the multiple X members may be the same or different, and O is an oxygen atom that bonds with at least one M.) <2> The method for producing carbon monoxide according to <1>, wherein the modified metal complex is obtained by heat treatment, radiation treatment, or discharge treatment of the mixture. <3> The method for producing carbon monoxide according to <2>, wherein the heat treatment, radiation treatment, or discharge treatment is performed such that the mass reduction rate calculated by the following formula (A) is 1% to 90%. Mass reduction rate (%) = [(Total mass of polynuclear metal complex and conductive material before treatment) - (Total mass of polynuclear metal complex and conductive material after treatment) / (Total mass of polynuclear metal complex and conductive material before treatment)] × 100 ... (A) <4> In formula (1) above, P is given by the following formula (P a ), formula (P b ), or formula (P c A method for producing carbon monoxide, which is a divalent group represented by <1> to <3>, as described in any one of <1> to <3>.

[0010] (In formula (P a ), R 1 and R 2 represent a hydrogen atom or a substituent, and multiple R 1 and R 2 may be the same or different from each other, and two adjacent R 1 and two adjacent R 2 may be bonded to each other to form a ring structure. In formula (P b ), R 3 and R 4 represent a hydrogen atom or a substituent, and multiple R 3 may be the same or different from each other, and two adjacent R 3 as well as two adjacent R 3 and R 4 may be bonded to each other to form a ring structure. In formula (P c ), R 5 represents a hydrogen atom or a substituent, and multiple R 5 may be the same or different from each other, Y represents the following formula (P c1 ), formula (P c2 ), or formula (P c3 ), and multiple Y may be the same or different from each other. Z represents an alkylene group or an arylene group. In formula (P a ) to formula (P c ), * represents a bond.)

[0011] (In formula (P c1 ) to formula (P c3 ), R p represents a hydrogen atom or a substituent, and * represents a bond.) <5> The method for producing carbon monoxide according to any one of <1> to <3>, wherein the polynuclear metal complex is a compound represented by the following formula (2).

[0012] (In formula (2), R 6 to R 8 represent a hydrogen atom or a substituent, and multiple R 6 to R 8 may be the same or different from each other, and two adjacent R 6 , two adjacent R 7Two Rs that are adjacent to each other 8 They may bond to each other to form a ring structure, Q 3 and Q 4 Q represents a monovalent group containing one or more aromatic rings. 3 and Q 4 The atoms 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 from 2 to 4, and the multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, the multiple X atoms may be the same or different, and O is an oxygen atom that bonds with at least one M.) <6> In the above formula (1), P is the following formula (P a ) or formula (P b It is a divalent group represented by Q 1 and Q 2 The formula is as follows (Q a ) or formula (Q b A method for producing carbon monoxide according to any one of <1> to <3>, which is a monovalent group represented by ).

[0013] (Formula (P a ) Medium, R 1 and R 2 R represents a hydrogen atom or substituent, and there are multiple R 1 and R 2 These can be the same or different, and the two adjacent Rs 1 Two Rs that are adjacent to each other 2 These elements may bond to each other to form a ring structure. Formula (P b ) Medium, R 3 and R 4 R represents a hydrogen atom or substituent, and there are multiple R 3 These can be the same or different, and the two adjacent Rs 3 R adjacent to each other 3 and R 4 These may bond to each other to form a ring structure. Formula (P a ) and formula (P b (In the above, * represents a combination.)

[0014] (Formula (Q a) and (Q b ) Medium, R q R represents a hydrogen atom or substituent, and there are multiple R q These can be the same or different, and the two adjacent Rs q The elements may bond to each other to form a ring structure, and * represents a bond.) <7> The method for producing carbon monoxide according to any one of <1> to <3>, wherein the polynuclear metal complex is a compound represented by the following formula (3).

[0015] (In formula (3), R 9 ~R 13 R represents a hydrogen atom, substituent, or divalent group, and there are multiple R 9 ~R 12 These can be the same or different, and the two adjacent Rs 9 Two adjacent Rs 10 Two adjacent Rs 11 Two adjacent Rs 12 R, both adjacent to each other 12 and R 13 They may bond to each other to form a ring structure, R 13 If is a divalent group, the divalent group may combine with other compounds represented by formula (3) above to form a dimer, where M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, where X is a counterion or a neutral molecule, where b is an integer of 0 or more, and if there are multiple Xs, multiple Xs may be the same or different.) <8> The method for producing carbon monoxide according to any one of <1> to <3>, wherein the polynuclear metal complex is a compound represented by the following formula (4).

[0016] (In formula (4), R 14 ~R 16 R represents a hydrogen atom or substituent, and there are multiple R 14 ~R 16 These can be the same or different, and the two adjacent Rs 14 Two adjacent Rs 15 R, both adjacent to each other 15 and R 16They may combine with each other to form a ring structure. M represents a cobalt atom, a nickel atom, or a zinc atom. The plurality of Ms may be the same or different from each other. X is a counter ion or a neutral molecule. b is an integer of 0 or more. When there are a plurality of Xs, the plurality of Xs may be the same or different from each other. ) <9> The method for producing carbon monoxide according to any one of <1> to <3>, wherein the polynuclear metal complex is a compound represented by the following formula (5).

[0017] (In formula (5), R 17 ~R 21 represents a hydrogen atom or a substituent. The plurality of Rs 17 ~R 21 may be the same or different from each other. Two adjacent Rs 17 to each other, two adjacent Rs 18 to each other, two adjacent Rs 19 to each other, two adjacent Rs 20 to each other, and two adjacent Rs 21 to each other may combine with each other to form a ring structure. M represents a cobalt atom, a nickel atom, or a zinc atom. X is a counter ion or a neutral molecule. b is an integer of 0 or more. When there are a plurality of Xs, the plurality of Xs may be the same or different from each other. ) <10> The method for producing carbon monoxide according to any one of <1> to <3>, wherein the polynuclear metal complex is a compound represented by the following formula (6).

[0018] (In formula (6), R 22 ~R 26 represents a hydrogen atom or a substituent. The plurality of Rs 22 ~R 26 may be the same or different from each other. Two adjacent Rs 22 to each other, two adjacent Rs 23 to each other, two adjacent Rs 24 to each other, two adjacent Rs 26 to each other, and adjacent Rs 25 and R 26The elements may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X is a counterion or a neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, multiple Xs may be the same or different.) <11> The method for producing carbon monoxide according to any one of <1> to <3>, wherein the polynuclear metal complex is a compound represented by the following formula (7).

[0019] (In formula (7), R 27 ~R 34 R represents a hydrogen atom or substituent, and there are multiple R 27 ~R 34 These can be the same or different, and the two adjacent Rs 27 Two adjacent Rs 28 Two adjacent Rs 29 Two adjacent Rs 30 Two adjacent Rs 31 Two adjacent Rs 32 Two adjacent Rs 33 Two Rs that are adjacent to each other 34 The elements may bond to each other to form a ring structure, Ar represents a divalent aromatic group which may have substituents, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer from 2 to 4, and any multiple Ms may be the same or different, X is a counterion or a neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, any multiple Xs may be the same or different, and O is an oxygen atom which is bonded to at least one M.) <12> The method for producing carbon monoxide according to any one of <1> to <3>, wherein the polynuclear metal complex is a compound represented by the following formula (8).

[0020] (In formula (8), Z represents an alkylene group or an arylene group, and the multiple Zs may be the same or different, R 35 R represents a hydrogen atom or substituent, and there are multiple R 35 These can be the same or different, and the two adjacent Rs 35They may bond to each other to form a ring structure, and Y is given by the following formula (P c1 ), formula (P c2 ), or formula (P c3 ) represents a cobalt atom, nickel atom, or zinc atom, and multiple Ys may be the same or different. X is a counterion or neutral molecule, and b is a non-negative integer. If there are multiple Xs, they may be the same or different.

[0021] (Formula (P c1 ) ~ formula (P c3 ) Medium, R p ∫ represents a hydrogen atom or substituent, and * represents a bond.) <13> A carbon dioxide reduction electrode comprising a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (1) and a conductive material.

[0022] (In formula (1), R represents a hydrogen atom or substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, and P represents a divalent group containing one or more aromatic rings, Q 1 and Q 2 Q represents a monovalent group containing one or more aromatic rings. 1 and Q 2) <14> The carbon dioxide reduction electrode according to <13>, further comprising a support for supporting the modified metal complex. <15> The carbon dioxide reduction electrode according to <13> or <14>, further comprising an ion conductor. <16> A carbon dioxide reduction apparatus comprising an oxidation electrode, a carbon dioxide reduction electrode according to any one of <13> to <15>, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode, an electrolyte, and a power supply connected to the oxidation electrode and the carbon dioxide reduction electrode. <17> A modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (6).

[0023] (In formula (6), R 22 ~R 26 R represents a hydrogen atom or substituent, and there are multiple R 22 ~R 26 These can be the same or different, and the two adjacent Rs 22 Two adjacent Rs 23 Two adjacent Rs 24 Two adjacent Rs 26 R, both adjacent to each other 25 and R 26 The atoms may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X is a counterion or a neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, the multiple Xs may be the same or different.) <18> The modified metal complex according to <17>, wherein the mixture further comprises a conductive material. <19> A modified metal complex obtained from a mixture comprising a polynuclear metal complex represented by the following formula (10).

[0024] (In formula (10), R represents a hydrogen atom or a substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, R 3 and R 4 R represents a hydrogen atom or substituent, and there are multiple R 3 These can be the same or different, and the two adjacent Rs 3 R adjacent to each other 3 and R 4 They may bond to each other to form a ring structure, Q 1 and Q 2 The formula is as follows (Q a ) or formula (Q b ) represents a monovalent group, where M represents a cobalt atom, nickel atom, or zinc atom, a is an integer from 2 to 4, and multiple Ms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, each X may be the same or different, and O is an oxygen atom that is bonded to at least one M.

[0025] (Formula (Q a ) and (Q b ) Medium, R q R represents a hydrogen atom or substituent, and there are multiple R q These can be the same or different, and the two adjacent Rs q ) The elements may bond to each other to form a ring structure, and * represents a bond.) <20> The modified metal complex according to <19>, wherein the mixture further comprises a conductive material. <21> A method for producing carbon monoxide, comprising reacting carbon dioxide and water in the presence of a modified metal complex obtained from a mixture comprising a polynuclear metal complex and a conductive material, wherein the polynuclear metal complex comprises at least one metal atom selected from the group consisting of cobalt atoms, nickel atoms, and zinc atoms, and the distance between the metal atoms calculated by density functional theory is less than 3.18 Å. <22> The method for producing carbon monoxide according to <21>, wherein the polynuclear metal complex is a polynuclear metal complex in which one of the metal atoms and two oxygen atoms are coordinately bonded.

[0026] According to this disclosure, a method for producing carbon monoxide with excellent carbon dioxide reduction efficiency, a carbon dioxide reduction electrode, a carbon dioxide reduction apparatus, and a modified metal complex are provided.

[0027] Figure 1 is a schematic cross-sectional view showing an example of a carbon dioxide reduction electrode according to the present disclosure. Figure 2 is a schematic cross-sectional view showing an example of a carbon dioxide reduction apparatus according to the present disclosure.

[0028] The following describes an example embodiment of this disclosure. These descriptions and examples are illustrative and do not limit the scope of the invention. In numerical ranges described stepwise in this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Also, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the value shown in the example.

[0029] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if multiple types of the substance corresponding to each component are present in the composition, unless otherwise specified, it means the total amount of those multiple types of substances present in the composition. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended function of that process is achieved.

[0030] Examples of "substituents" include halogen atoms, alkyl groups (including cycloalkyl groups), alkenyl groups, alkynyl groups, alkoxy groups, alkylthio groups, aryl groups, aryloxy groups, divalent oxo groups, arylthio groups, monovalent heterocyclic groups, substituted amino groups, acyl groups, imine residues, amide groups, acidimide groups, substituted oxycarbonyl groups, cyano groups, alkylsulfonyl groups, and nitro groups. In this specification, when referring to the number of carbon atoms, the number of carbon atoms of substituents is usually not included.

[0031] An "aromatic hydrocarbon ring group" refers to the group of atoms remaining after removing one or more hydrogen atoms that are directly bonded to the carbon atoms constituting an aromatic hydrocarbon ring, which may be unsubstituted or substituted, and which may consist of two or more fused rings.

[0032] An "aromatic heterocyclic group" refers to the group of atoms remaining after removing one or more hydrogen atoms directly bonded to a carbon or heteroatom that constitutes an aromatic heterocyclic ring, which may be unsubstituted or substituted, and in which two or more rings are fused.

[0033] In compound names, "t-" means tertiary, "n-" means normal, and "p-" means para. In chemical structural formulas, dotted lines represent parts that may be single or double bonds.

[0034] <<Method A for Producing Carbon Monoxide>> Method A for producing carbon monoxide according to the present disclosure (hereinafter also referred to as "Method A") includes reacting carbon dioxide with water in the presence of a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (1) and a conductive material.

[0035]

[0036] In formula (1), R represents a hydrogen atom or substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, P represents a divalent group containing one or more aromatic rings, Q 1 and Q 2 Q represents a monovalent group containing one or more aromatic rings. 1 and Q 2 The atoms 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 from 2 to 4, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, multiple X atoms may be the same or different, and O is an oxygen atom that is bonded to at least one M atom.

[0037] According to manufacturing method A of the present disclosure, the reduction efficiency of carbon dioxide is excellent. Manufacturing method A of the present disclosure uses a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by formula (1) and a conductive material as a catalyst. Here, although the detailed mechanism is unknown, it is presumed that the polynuclear metal complex represented by formula (1) has a binuclear structure in which the central metals are adjacent to each other, and the coordination environment to the central metal by the macrocyclic ligand suppresses the generation of hydrogen and promotes the generation of carbon monoxide by the reduction of carbon dioxide, thereby increasing the selectivity for carbon monoxide. The polynuclear metal complex represented by formula (1) becomes a modified metal complex having a structure in which the nitrogen and metal atoms of the polynuclear metal complex are immobilized in the conductive material while maintaining a part of the structure of the complex. It is presumed that carbon dioxide is reduced by coordinating with the cobalt atom, nickel atom, and / or zinc atom of the modified metal complex, and that carbon monoxide is further generated with high selectivity. In other words, since the modified metal complex of this disclosure is a modified metal complex obtained by modifying a polynuclear metal complex having a specific chemical structure and metal atoms represented by formula (1), it is presumed that the structure of the central metal and the coordination environment to the central metal in the modified metal complex are optimized, and the reduction reaction of carbon dioxide proceeds rapidly.

[0038] <Polynuclear metal complex represented by formula (1)> The manufacturing method A of the present disclosure uses a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (1) and a conductive material.

[0039]

[0040] In formula (1), R represents a hydrogen atom or substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, P represents a divalent group containing one or more aromatic rings, Q 1 and Q 2 Q represents a monovalent group containing one or more aromatic rings. 1 and Q 2The atoms 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 from 2 to 4, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, multiple X atoms may be the same or different, and O is an oxygen atom that is bonded to at least one M atom.

[0041] [R] In formula (1), R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. If R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms (also called "carbon number"), and even more preferably a t-butyl group. If 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. In formula (1), from the viewpoint of reduction efficiency, the R at the para position with respect to the bonded position of the oxygen atom is preferably an alkyl group or an alkoxy group. Also, in formula (1), from the viewpoint of reduction efficiency, it is preferable that both R at the meta positions with respect to the bonded position of the oxygen atom are hydrogen atoms.

[0042] [M] a From the viewpoint of reduction efficiency, M is preferably a nickel atom or a cobalt atom, and more preferably a nickel atom. Furthermore, from the viewpoint of reduction efficiency, M is preferably a divalent nickel atom or a divalent cobalt atom, and more preferably a divalent nickel atom. The polynuclear metal complex may be a heterogeneous metal 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.

[0043] a is preferably 2 or 4, and more preferably 2. That is, the polynuclear metal complex is preferably a dinuclear complex (also called a "multinuclear complex").

[0044] [X] bThe counterion represented by X is preferably an anion, and more preferably at least one anion selected from the group consisting of fluoride ions, chloride ions, bromide ions, iodide ions, sulfide ions, oxide ions, hydroxide ions, hydride ions, sulfite ions, phosphate ions, cyanide ions, acetate ions, 2-ethylhexanoate ions, carbonate ions, sulfate ions, nitrate ions, bicarbonate ions, trifluoroacetate ions, thiocyanide ions, trifluoromethanesulfonate ions, acetylacetonate, tetrafluoroborate ions, hexafluorophosphate ions, and tetraphenylborate ions. 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.

[0045] b is preferably an integer between 0 and 8, and more preferably between 0 and 4.

[0046] [O] In formula (1) above, O is preferably bonded with two M.

[0047] [P] In formula (1) above, the aromatic rings that P contains include aromatic hydrocarbon ring groups and aromatic heterocyclic groups. From the viewpoint of reduction efficiency, 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 an aromatic heterocyclic group of a five-membered ring or a six-membered ring containing a nitrogen atom. Furthermore, from the viewpoint of reduction efficiency, P is preferably a divalent group containing two or more aromatic rings, and more preferably a divalent group containing two aromatic rings. Furthermore, from the viewpoint of reduction efficiency, P is preferably a divalent group containing two or more aromatic rings. a ), formula (P b ), or formula (P c It is preferable that the group is a divalent group represented by ).

[0048]

[0049] Formula (P a ) Medium, R 1 and R 2 R represents a hydrogen atom or substituent, and there are multiple R 1 and R 2 These can be the same or different, and the two adjacent Rs 1 Two Rs that are adjacent to each other 2 These elements may bond to each other to form a ring structure. Formula (P b ) Medium, R 3 and R 4 R represents a hydrogen atom or substituent, and there are multiple R 3 These can be the same or different, and the two adjacent Rs 3 R adjacent to each other 3 and R 4 These may bond to each other to form a ring structure. Formula (P c ) Medium, R 5 R represents a hydrogen atom or substituent, and there are multiple R 5 These can be the same or different, and Y is given by the following formula (P c1 ), formula (P c2 ), or formula (P c3 The formula (Pa ) ~ formula (P c In the above, * represents a combination.

[0050]

[0051] Formula (P c1 ) ~ formula (P c3 ) Medium, R p * represents a hydrogen atom or substituent, and * represents a bond.

[0052] (Formula (P a )) The above formula (P a ) Medium, R 1 It is preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom or an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably a hydrogen atom or an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 1 It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 1 The ring structure formed by the bonding of these elements is preferably a benzene ring. a ) Medium, R 2 It is preferable that it is a hydrogen atom.

[0053] (Formula (P b )) The above formula (P b ) Medium, R 3 It is preferable that is a hydrogen atom. The above formula (P b ) Medium, R 4The ring group is preferably an aromatic hydrocarbon ring group, more preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or fewer carbon atoms, even 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 particularly preferably an unsubstituted or substituted phenyl group. Specific examples of substituents include halogen atoms such as fluorine, chlorine, bromine, and iodine, hydroxyl groups, carboxyl groups, ester groups, mercapto groups, sulfonic acid groups, nitro groups, phosphonic acid groups, silyl groups having C1-C4 alkyl groups, 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, norbonyl groups, nonyl groups, cyclononyl groups, and decyl groups. Examples include monovalent monovalent saturated hydrocarbon groups with approximately 1 to 50 carbon atoms, such as 3,7-dimethyloctyl group, adamantyl group, dodecyl group, cyclododecyl group, pentadecyl group, octadecyl group, and docosyl group; and monovalent monovalent alkoxy groups with approximately 1 to 50 carbon atoms, such as alkenyl group, alkynyl group, methoxy group, ethoxy group, propiooxy group, butoxy group, pentyloxy group, cyclohexyloxy group, norbonyloxy group, decyloxy group, and dodecyloxy group. The number of substituents can be any number that is substituted, such as 1 to 5 for phenyl groups, 1 to 7 for naphthyl groups, and 1 to 9 each for anthryl and pyrenyl groups.

[0054] (Formula (P c )) The above formula (P c ) Medium, R 5 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. 5 If R is an alkyl group, 5 It 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. 5If R is an aryl group, 5 It is preferably an aryl group having 6 to 14 carbon atoms, and more preferably a phenyl group. 5 If R is an alkoxy group, 5 It 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. 5 If R is an alkylthio group, 5 The group 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. The formula (P c In the formula (P c1 ) or formula (P c2 ) is more preferable, formula (P c1 ) is even more preferable. Formula (P c2 ) Medium, R p It is preferable that is a hydrogen atom. The above formula (P c In the above, 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. 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, pyridinediyl group, tetrafluorophenylene group, naphthalenediyl group, thiophenediyl group, dimethylphenylene group, or phenanthrenediyl group, more preferably a 1,2-phenylene group, 3,4-pyridinediyl group, 3,4,5,6-tetrafluoro-1,2-phenylene group, 2,3-naphthalenediyl group, 3,4-thiophenediyl group, 3,4-dimethyl-1,2-phenylene group, or 9,10-phenanthrenediyl group, and particularly preferably a 1,2-phenylene group.

[0055] [Q 1 Q 2In the above formula (1), Q 1 and Q 2 Examples of aromatic rings contained in the monovalent group represented by include aromatic hydrocarbon ring groups and aromatic heterocyclic ring groups. 1 and Q 2 The aromatic heterocyclic group contained in the monovalent group represented by is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom. 1 and Q 2 When these atoms are bonded to each other to form a ring structure, it is preferable that this ring structure is, for example, the remaining atomic group after removing two hydrogen atoms from phenanthroline.

[0056] Q 1 and Q 2 The formula is as follows (Q a ) or formula (Q b It is preferable that the group is a monovalent group represented by ).

[0057]

[0058] Formula (Q a ) and (Q b ) Medium, R q R represents a hydrogen atom or substituent, and there are multiple R q These can be the same or different, and the two adjacent Rs q These elements may be bonded to each other to form a ring structure, and * represents a bonding hand.

[0059] Formula (Q a ) and (Q b ) Medium, R q It is preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom or an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably a hydrogen atom. Two adjacent R q They may be bonded to each other to form a ring structure, and two adjacent R q The ring structure formed by the bonding of these elements is preferably a benzene ring.

[0060] Furthermore, from the viewpoint of reduction efficiency, in equation (1), P is given by equation (P a ) or formula (P b It is a divalent group represented by Q1 and Q 2 is equation (Q a ) or formula (Q b A combination of monovalent groups represented by ) is preferred.

[0061] <Polynuclear metal complex represented by formula (2)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (2).

[0062]

[0063] In formula (2), R 6 ~R 8 R represents a hydrogen atom or substituent, and there are multiple R 6 ~R 8 These can be the same or different, and the two adjacent Rs 6 Two adjacent Rs 7 Two Rs that are adjacent to each other 8 They may bond to each other to form a ring structure, Q 3 and Q 4 Q represents a monovalent group containing one or more aromatic rings. 3 and Q 4 The atoms 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 from 2 to 4, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, multiple X atoms may be the same or different, and O is an oxygen atom that is bonded to at least one M atom.

[0064] [R 6 ~R 8 In the above formula (2), R 6 R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 6 If it 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. 6 If is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. Also, in formula (2), from the viewpoint of reduction efficiency, the two R groups at the para position relative to the bond position of the oxygen atom6 It is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in formula (2), from the viewpoint of reduction efficiency, the four R groups at the meta position relative to the bonded position of the oxygen atom 6 R is preferably a hydrogen atom. In formula (2) above, 7 It is preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom or an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably a hydrogen atom or an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 7 It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 7 The ring structure formed by the bonding of these elements is preferably a benzene ring. In formula (2), R 8 It is preferable that it is a hydrogen atom.

[0065] [Q 3 Q 4 In the above formula (2), Q 3 and Q 4 Examples of aromatic rings contained in the monovalent group represented by include aromatic hydrocarbon ring groups and aromatic heterocyclic ring groups. 3 and Q 4 The aromatic heterocyclic group contained in the monovalent group represented by is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom. 3 and Q 4 When these atoms are bonded to each other to form a ring structure, it is preferable that this ring structure is, for example, the remaining atomic group after removing two hydrogen atoms from phenanthroline.

[0066] Q 3 and Q 4 The formula is as follows (Q a ) or formula (Q b It is preferable that the group is a monovalent group represented by ).

[0067]

[0068] Formula (Q a ) and (Q b ) Medium, R qR represents a hydrogen atom or substituent, and there are multiple R q These can be the same or different, and the two adjacent Rs q These elements may be bonded to each other to form a ring structure, and * represents a bonding hand.

[0069] Formula (Q a ) and (Q b ) Medium, R q It is preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom or an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably a hydrogen atom. Two adjacent R q They may be bonded to each other to form a ring structure, and two adjacent R q The ring structure formed by the bonding of these elements is preferably a benzene ring.

[0070] [M] a [X] b , O] In the above formula (2), [M] a [X] b A preferred embodiment of , and O is [M] in formula (1) a [X] b , and are identical to the preferred embodiment of O.

[0071] <Polynuclear metal complex represented by formula (3)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (3).

[0072]

[0073] In formula (3), R 9 ~R 13 R represents a hydrogen atom, substituent, or divalent group, and there are multiple R 9 ~R 12 These can be the same or different, and the two adjacent Rs 9 Two adjacent Rs 10 Two adjacent Rs 11 Two adjacent Rs 12 R, both adjacent to each other 12 and R 13 They may bond to each other to form a ring structure, R 13If is a divalent group, the divalent group may combine with other compounds represented by formula (3) above 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 is a counterion or a neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, multiple Xs may be the same or different.

[0074] [R 9 ~R 13 In the above formula (3), R 9 R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 9 If it 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 If is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. Also, in formula (3), from the viewpoint of reduction efficiency, the two R groups at the para position relative to the bond position of the oxygen atom 9 It is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in formula (3), from the viewpoint of reduction efficiency, the four R groups at the meta position relative to the bonded position of the oxygen atom 9 It is preferably a hydrogen atom. In formula (3) above, R 10 It is preferably a hydrocarbon group, more preferably an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 10 It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 10 The ring structure formed by the bonding of these elements is preferably a benzene ring. In formula (3), R 11 It is preferable that is a hydrogen atom. In formula (3) above, R 12 It is preferable that is a hydrogen atom. In formula (3) above, R 13The ring group is preferably an aromatic hydrocarbon ring group, more preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or fewer carbon atoms, even 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 particularly preferably an unsubstituted or substituted phenyl group. Specific examples of substituents include halogen atoms such as fluorine, chlorine, bromine, and iodine, hydroxyl groups, carboxyl groups, ester groups, mercapto groups, sulfonic acid groups, nitro groups, phosphonic acid groups, silyl groups having C1-C4 alkyl groups, 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, norbonyl groups, nonyl groups, cyclononyl groups, and decyl groups. Examples include monovalent monovalent saturated hydrocarbon groups with approximately 1 to 50 carbon atoms, such as 3,7-dimethyloctyl group, adamantyl group, dodecyl group, cyclododecyl group, pentadecyl group, octadecyl group, and docosyl group; and monovalent monovalent alkoxy groups with approximately 1 to 50 carbon atoms, such as alkenyl group, alkynyl group, methoxy group, ethoxy group, propiooxy group, butoxy group, pentyloxy group, cyclohexyloxy group, norvonyloxy group, decyloxy group, and dodecyloxy group. The number of substituents can be any number that is substituted, such as 1 to 5 for phenyl groups, 1 to 7 for naphthyl groups, and 1 to 9 each for anthryl and pyrenyl groups. In addition, in formula (3) above, R 13 If the group is divalent, the divalent group may combine with another compound molecule, which is a compound represented by formula (3) and is different from the compound molecule containing the divalent group, to form a dimer.

[0075] [M, [X] b ] In the formula (3), M and [X] b A preferred embodiment of the formula is M and [X] in formula (1) b This is identical to the preferred embodiment.

[0076] <Polynuclear metal complex represented by formula (4)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (4).

[0077]

[0078] In formula (4), R 14 ~R 16 R represents a hydrogen atom or substituent, and there are multiple R 14 ~R 16 These can be the same or different, and the two adjacent Rs 14 Two adjacent Rs 15 R, both adjacent to each other 15 and R 16 The atoms may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M atoms may be the same or different, X is a counterion or a neutral molecule, b is a non-negative integer, and if there are multiple X atoms, multiple X atoms may be the same or different.

[0079] [R 14 ~R 16 In the above formula (4), R 14 R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 14 If it 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 If is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. Also, in formula (4), from the viewpoint of reduction efficiency, the two R at the para position relative to the bond position of the oxygen atom 14 It is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in formula (4), from the viewpoint of reduction efficiency, the four R groups at the meta position relative to the bonded position of the oxygen atom 14 It is preferably a hydrogen atom. In formula (4) above, R 15 It is preferable that is a hydrogen atom. In formula (4) above, R 16The ring group is preferably an aromatic hydrocarbon ring group, more preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or fewer carbon atoms, even 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 particularly preferably an unsubstituted or substituted phenyl group. Specific examples of substituents include halogen atoms such as fluorine, chlorine, bromine, and iodine, hydroxyl groups, carboxyl groups, ester groups, mercapto groups, sulfonic acid groups, nitro groups, phosphonic acid groups, silyl groups having C1-C4 alkyl groups, 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, norbonyl groups, nonyl groups, cyclononyl groups, and decyl groups. Examples include monovalent monovalent saturated hydrocarbon groups with approximately 1 to 50 carbon atoms, such as 3,7-dimethyloctyl group, adamantyl group, dodecyl group, cyclododecyl group, pentadecyl group, octadecyl group, and docosyl group; and monovalent monovalent alkoxy groups with approximately 1 to 50 carbon atoms, such as alkenyl group, alkynyl group, methoxy group, ethoxy group, propiooxy group, butoxy group, pentyloxy group, cyclohexyloxy group, norbonyloxy group, decyloxy group, and dodecyloxy group. The number of substituents can be any number that is substituted, such as 1 to 5 for phenyl groups, 1 to 7 for naphthyl groups, and 1 to 9 each for anthryl and pyrenyl groups.

[0080] [M, [X] b ] In the formula (4), M and [X] b A preferred embodiment of the formula is M and [X] in formula (1) b This is identical to the preferred embodiment.

[0081] <Polynuclear metal complex represented by formula (5)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (5).

[0082]

[0083] In formula (5), R17 ~R 21 R represents a hydrogen atom or substituent, and there are multiple R 17 ~R 21 These can be the same or different, and the two adjacent Rs 17 Two adjacent Rs 18 Two adjacent Rs 19 Two adjacent Rs 20 Two Rs that are adjacent to each other 21 The elements may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, X is a counterion or a neutral molecule, b is a non-negative integer, and if there are multiple X elements, each X element may be the same or different.

[0084] [R 17 ~R 21 In the above formula (5), R 17 R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 17 If it 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 If 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. In formula (5), R 18 It is preferably a hydrocarbon group, more preferably an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 18 It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 18 The ring structure formed by the bonding of these elements is preferably a benzene ring. In formula (5), R 19 It is preferable that is a hydrogen atom. In formula (5) above, R 20 It is preferably a hydrocarbon group, more preferably an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 20It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 20 The ring structure formed by the bonding of these elements is preferably a benzene ring. In formula (5), R 21 It is preferable that it is a hydrogen atom.

[0085] [M, [X] b ] In the formula (5), M and [X] b A preferred embodiment of the formula is M and [X] in formula (1) b This is identical to the preferred embodiment.

[0086] <Polynuclear metal complex represented by formula (6)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (6).

[0087]

[0088] In formula (6), R 22 ~R 26 R represents a hydrogen atom or substituent, and there are multiple R 22 ~R 26 These can be the same or different, and the two adjacent Rs 22 Two adjacent Rs 23 Two adjacent Rs 24 Two adjacent Rs 26 R, both adjacent to each other 25 and R 26 The atoms may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M atoms may be the same or different, X is a counterion or a neutral molecule, b is a non-negative integer, and if there are multiple X atoms, multiple X atoms may be the same or different.

[0089] [R 22 ~R 26 In the above formula (6), R 22 R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 22 If it 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. 22If 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. In formula (6), R 23 It is preferably a hydrocarbon group, more preferably an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 23 It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 23 The ring structure formed by the bonding of these elements is preferably a benzene ring. In formula (6), R 24 and R 25 It is preferable that is a hydrogen atom. In formula (6), R 26 It is preferably a hydrocarbon group, more preferably an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 26 It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 26 The ring structure formed by the bonding of these elements is preferably a benzene ring.

[0090] [M, [X] b ] In the formula (6), M and [X] b A preferred embodiment of the formula is M and [X] in formula (1) b This is identical to the preferred embodiment.

[0091] <Polynuclear metal complex represented by formula (7)> ​​From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (7).

[0092]

[0093] In formula (7), R 27 ~R 34 R represents a hydrogen atom or substituent, and there are multiple R 27 ~R 34 These can be the same or different, and the two adjacent Rs 27 Two adjacent Rs 28 Two adjacent Rs 29Two adjacent Rs 30 Two adjacent Rs 31 Two adjacent Rs 32 Two adjacent Rs 33 Two Rs that are adjacent to each other 34 The elements may bond to each other to form a ring structure, Ar represents a divalent aromatic group which may have substituents, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer from 2 to 4, and multiple Ms may be the same or different, X is a counterion or a neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, multiple Xs may be the same or different, and O is an oxygen atom which is bonded to at least one M.

[0094] [R 27 ~R 34 In the above formula (7), R 27 and R 31 R is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 27 and R 31 If it 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. 27 and R 31 If 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. In formula (7), R 28 It is preferably a hydrocarbon group, more preferably an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 28 It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 28 The ring structure formed by the bonding of these elements is preferably a benzene ring. In formula (7), R 32 It is preferably a hydrocarbon group, more preferably an alkyl group or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. Two adjacent R 32It is preferable that the two adjacent Rs are bonded to each other to form a ring structure. 32 The ring structure formed by the bonding of these elements is preferably a benzene ring. In formula (7), R 29 and R 33 It is preferable that is a hydrogen atom. In formula (7) above, R 30 and R 34 It is preferable that it is a hydrogen atom.

[0095] [M] a In formula (7), the preferred embodiment of M is the same as the preferred embodiment of M in formula (1). In formula (7), a is preferably 4.

[0096] [X] b , O] In the above formula (7), [X] b A preferred embodiment of O is [X] in formula (1) b And is identical to the preferred embodiment of O.

[0097] [Ar] In formula (7), Ar can be an aromatic hydrocarbon ring group or an aromatic heterocyclic group. From the viewpoint of reduction efficiency, 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-membered or six-membered aromatic heterocyclic group containing a nitrogen atom. Furthermore, from the viewpoint of reduction efficiency, Ar is preferably a divalent group containing one or more aromatic rings, and more preferably a divalent group containing one aromatic ring.

[0098] <Polynuclear metal complex represented by formula (8)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (8).

[0099]

[0100] In formula (8), Z represents an alkylene group or an arylene group, and the multiple Zs may be the same or different, R 35 R represents a hydrogen atom or substituent, and there are multiple R 35 These can be the same or different, and the two adjacent Rs35 They may bond to each other to form a ring structure, and Y is given by the following formula (P c1 ), formula (P c2 ), or formula (P c3 ) represents a cobalt atom, nickel atom, or zinc atom, and multiple Ms may be the same or different. X is a counterion or neutral molecule, b is a non-negative integer, and if there are multiple Xs, multiple Xs may be the same or different.

[0101]

[0102] Formula (P c1 ) ~ formula (P c3 ) Medium, R p * represents a hydrogen atom or substituent, and * represents a bond.

[0103] [Z] In formula (8) above, Z is preferably a C2-C6 alkylene group or a C4-C4 arylene group, more preferably a C4-C4 arylene group, and even more preferably a C6-C10 arylene group, from the viewpoint of reduction efficiency. 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, pyridinediyl group, tetrafluorophenylene group, naphthalenediyl group, thiophenediyl group, dimethylphenylene group, or phenanthrenediyl group, more preferably a 1,2-phenylene group, 3,4-pyridinediyl group, 3,4,5,6-tetrafluoro-1,2-phenylene group, 2,3-naphthalenediyl group, 3,4-thiophenediyl group, 3,4-dimethyl-1,2-phenylene group, or 9,10-phenanthrenediyl group, and particularly preferably a 1,2-phenylene group.

[0104] [R 35 In the above formula (8), R 35From the viewpoint of reduction efficiency, it 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. 35 If R is an alkyl group, 35 It 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. 35 If R is an aryl group, 35 It is preferably an aryl group having 6 to 14 carbon atoms, and more preferably a phenyl group. 35 If R is an alkoxy group, 35 It 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. 35 If R is an alkylthio group, 35 It 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.

[0105] [Y] In formula (8) above, Y is preferably the same group from the viewpoint of reduction efficiency, and formula (P c1 It is more preferable that Y is given by equation (P c2 ) If R p From the viewpoint of reduction efficiency, it is preferable that it be a hydrogen atom.

[0106] [M, [X] b In formula (8), preferred embodiments of M and X are the same as preferred embodiments of M and X in formula (1). In formula (8), b is preferably an integer between 0 and 4, more preferably an integer between 0 and 2, and particularly preferably 2.

[0107] <Polynuclear metal complex represented by formula (11)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (11).

[0108]

[0109] In formula (11), Ar 1 and Ar 2 Each of these independently represents an arylene group, R 35 R represents a hydrogen atom or substituent, and there are multiple R 35 These can be the same or different, and the two adjacent Rs 35 They may bond to each other to form a ring structure, and Y is given by the following formula (P c1 ), formula (P c2 ), or formula (P c3 ) represents a θ such that any multiple Ys may be the same or different, X is a counterion or neutral molecule, b is a non-negative integer, and if there are multiple Xs, any multiple Xs may be the same or different.

[0110]

[0111] Formula (P c1 ) ~ formula (P c3 ) Medium, R p * represents a hydrogen atom or substituent, and * represents a bond.

[0112] [Ar 1 Ar 2 Ar in equation (11) 1 and Ar 2 From the viewpoint of ease of synthesis and reduction efficiency, it is preferable that the groups are the same. Also, Ar in formula (11) 1 and Ar 2 Each of these groups is preferably an arylene group having 4 to 14 carbon atoms, and more preferably an arylene group having 6 to 10 carbon atoms, from the viewpoint of reduction efficiency. 1 and Ar 2 The arylene group in this compound may be a divalent hydrocarbon aromatic group or a divalent heteroaromatic group. 1 and Ar 2Specifically, preferred groups include phenylene, pyridinediyl, tetrafluorophenylene, naphthalenediyl, thiophenediyl, dimethylphenylene, and phenanthrenediyl; more preferred groups include 1,2-phenylene, 3,4-pyridinediyl, 3,4,5,6-tetrafluoro-1,2-phenylene, 2,3-naphthalenediyl, 3,4-thiophenediyl, 3,4-dimethyl-1,2-phenylene, and 9,10-phenanthrenediyl; and particularly preferred is the 1,2-phenylene group.

[0113] [R 35 , M, [X] b , Y] In formula (11), R 35 , M, [X] b A preferred embodiment of Y is R in formula (8). 35 , M, [X] b , and is identical to the preferred embodiment of Y.

[0114] <Polynuclear metal complex represented by formula (12)> From the viewpoint of reduction efficiency, the polynuclear metal complex is preferably a compound represented by the following formula (12).

[0115]

[0116] In formula (12), Ar 1 and Ar 2 Each of these is an independently independent arylene group, R 36 R represents a hydrogen atom, alkyl group, alkoxy group, or alkylthio group, and there are multiple R 36 These may be the same or different, R 37 R represents a hydrogen atom, alkyl group, or aryl group, and there are multiple R 37 These may be the same or different, R 38 R represents a hydrogen atom, alkyl group, or aryl group, and there are multiple R 38 Each of the elements may be the same or different, X is a counterion or neutral molecule, b is a non-negative integer, and if there are multiple X's, each of the multiple X's may be the same or different.

[0117] [R 36 ~R 38The two R's in equation (12) 36 From the viewpoint of ease of synthesis and reduction efficiency, it is preferable that the groups are the same. Also, R in formula (12) 36 From the viewpoint of reduction efficiency, it is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, even more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and particularly preferably a hydrogen atom or a t-butyl group. The four R in formula (12) 37 From the viewpoint of ease of synthesis and reduction efficiency, it is preferable that the groups are the same. Also, R in formula (12) 37 From the viewpoint of reduction efficiency, the R is preferably a hydrogen atom, an alkyl group, or an aryl group, more preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, even more preferably a hydrogen atom, a methyl group, or a phenyl group, and particularly preferably a hydrogen atom. The four R in formula (12) 38 From the viewpoint of ease of synthesis and reduction efficiency, it is preferable that the groups are the same. Also, R in formula (12) 38 From the viewpoint of reduction efficiency, it is preferably a hydrogen atom, an alkyl group, or an aryl group; more preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms; even more preferably a hydrogen atom, a methyl group, or a phenyl group; and particularly preferably a hydrogen atom.

[0118] [Ar 1 Ar 2 , M, [X] b , Y] Ar in equation (12) 1 and Ar 2 A preferred embodiment is Ar in formula (11) 1 and Ar 2 This is identical to the preferred embodiment of [M, X] in formula (12). b A preferred embodiment of Y is M, [X] in formula (8). b , and is identical to the preferred embodiment of Y.

[0119] <Specific structural formula of the polynuclear metal complex represented by formula (1)> Below are specific structural formulas of the polynuclear metal complex represented by formula (1), but are not limited to these. In the following structural formulas, "Me" represents a methyl group, "Et" represents an ethyl group, "t-Bu" means a t-butyl group, "TMS" represents a trimethylsilyl group, and "i-Pr" means an isopropyl group. - "OAc" means acetate anion, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, and the valence of M is divalent (M 2+ )

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148] <Modified Metal Complex> In Production Method A of the present disclosure, the modified metal complex is obtained from a mixture containing a polynuclear metal complex represented by formula (1) and a conductive material. The modified metal complex is preferably obtained by subjecting a mixture containing a polynuclear metal complex represented by formula (1) and a conductive material to a modification treatment. By subjecting the mixture to a modification treatment, the polynuclear metal complex represented by formula (1) is also modified. That is, the modified metal complex is a polynuclear metal complex with enhanced carbon dioxide reduction efficiency by the modification treatment.

[0149] The modified metal complex is considered to condense with low molecular weight detachment by causing mass reduction with low molecular weight detachment and reacting ligands with each other and ligands with the conductive material during the modification treatment. Among the modified products of the ligands formed by condensation, those in which the metal atoms maintain substantially the same spatial arrangement as the polynuclear metal complex before modification and the coordination structure is stable are considered.

[0150] Here, it is preferable that the modified ligand is in a state of condensation and linkage in a graphene-like structure, as this further enhances its stability against acids and alkalis, as well as its thermal stability. A "graphene-like structure" refers to a two-dimensional carbon hexagonal network structure in which carbon atoms are chemically bonded by sp2 hybrid orbitals, and some of the carbon atoms constituting the graphene-like structure may be replaced with heteroatoms such as nitrogen. Alternatively, the modified ligand may take the form of a graphite-like structure in which the aforementioned graphene-like structures are stacked.

[0151] A processed product containing a modified metal complex obtained from a mixture of a polynuclear metal complex represented by formula (1) and a conductive material may contain unreacted polynuclear metal complexes or metal nanoparticles or metal oxides generated by the decomposition of the polynuclear metal complex after the modification treatment. In such cases, the modified metal complex is obtained by removing the metal nanoparticles or metal oxides by acid treatment or the like, but the processed product obtained by the modification treatment can be used as a catalyst as is, as long as it does not impair the function of the modified metal complex.

[0152] Furthermore, the cobalt, nickel, and zinc atoms that may be included in the modified metal complex may be uncharged or charged ions, but from the viewpoint of catalytic activity, they are preferably divalent cobalt, divalent nickel, and divalent zinc atoms, more preferably divalent cobalt and divalent nickel atoms, and even more preferably divalent nickel atoms.

[0153] [Mixture] (Polynuclear metal complex represented by formula (1)) The polynuclear metal complex represented by formula (1) included in the mixture is as described above, and only one type of polynuclear metal complex may be used, or two or more types of polynuclear metal complexes may be used.

[0154] (Conductive Material) As for the conductive material included in the mixture, any known material can be used without particular limitation, as long as it is capable of supporting the polynuclear metal complex. The conductive material may be a flat plate or rod-shaped carbonaceous material or metallic material, or a porous carbonaceous material or metallic material such as carbon paper or metal mesh. The conductive material may also be a powder material such as carbon black (C.B.) or metal particles. Only one type of conductive material may be used, or two or more types of conductive materials may be used.

[0155] There are no particular restrictions on the conductive material, but a porous carbon material is preferred. Examples of conductive materials include carbon particles such as Norlit, Ketjenblack, Vulcan, Black Pearl, and Acetylene Black; fullerenes such as C60 and C70; carbon nanotubes; carbon nanohorns; carbon fibers; graphene; graphene oxide; reduced graphene oxide; Knobel; and graphene mesosponges.

[0156] A mixture containing a polynuclear metal complex represented by formula (1) and a conductive material may be a mixture in which the polynuclear metal complex represented by formula (1) is supported on a conductive material. The method of support is not particularly limited, and any known method can be arbitrarily applied. Examples include a method of vacuum deposition of the polynuclear metal complex represented by formula (1) onto a conductive material (also called a conductive carrier), a method of immersing a conductive material in a solution in which the polynuclear metal complex represented by formula (1) is dissolved or dispersed in a solvent, ultrasonically treating it, and drying it, a method of coating a conductive material with a solution in which the polynuclear metal complex represented by formula (1) is dissolved or dispersed in a solvent, adding a powdered conductive material to a solution in which the polynuclear metal complex represented by formula (1) is dissolved or dispersed in a solvent, adsorbing the polynuclear metal complex represented by formula (1) onto the surface of the powder, concentrating or filtering, and then drying it.

[0157] Alternatively, a mixture may be obtained by molding a mixture in which the polynuclear metal complex represented by formula (1) is supported on a powdered conductive material by compression or concentration to dryness. Or, a mixture in which the polynuclear metal complex represented by formula (1) is supported on a powdered conductive material may be immobilized on a support such as a flat plate, rod, grid, or porous carbonaceous material or metallic material.

[0158] The amount of the polynuclear metal complex represented by formula (1) in the mixture is preferably such that the total mass of cobalt atoms, nickel atoms, and 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 1% by mass or more and 10% by mass or less.

[0159] In the mixture, the mass of the polynuclear metal complex represented by formula (1) is preferably 1% by mass or more and 100% by mass or less relative to the mass of the conductive material, and more preferably 5% by mass or more and 50% by mass or less.

[0160] The mass of metal atoms (cobalt, nickel, and zinc atoms) relative to the mass of the conductive material is measured using a thermomass-differential thermal analyzer (TG-DTA). The measurement method is as follows: Using a thermomass-differential thermal analyzer, the temperature is increased from below 25°C to 900°C in air at a heating rate of 10°C / min, and the TG-DTA curve is measured.

[0161] The mixture may contain components other than the polynuclear metal complex represented by formula (1) and the conductive material. Examples of other components include solvents, ligands for the polynuclear metal complex represented by formula (1), mononuclear metal complexes, polynuclear metal complexes other than the polynuclear metal complex represented by formula (1), organic compounds with a boiling or melting point of 200°C or higher, and organic compounds with a thermal polymerization initiation temperature of 250°C or lower.

[0162] Examples of solvents include chloroform, methanol, ethanol, and mixtures thereof.

[0163] Examples of organic compounds having a boiling or melting point of 200°C or higher include perylene-3,4,9,10-tetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic diimide, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic diimide, 1,4,5,8-naphthalenetetracarboxylic acid, pyromellitic acid, and aromatic compound carboxylic acid derivatives such as pyromellitic dianhydride. The structural formulas of these compounds are as described in paragraphs

[0115] to

[0116] of Japanese Patent Application Publication No. 2009-173627.

[0164] Here, the boiling point or melting point can be measured using known methods and selected from the measured values, but it can also be selected using values ​​described in literature, etc. Furthermore, the boiling point or melting point may also be a calculated value obtained through computer simulation, for example, a calculated boiling point or melting point registered in SciFinder (version 2007.2), software provided by Chemical Abstract Service, may be used.

[0165] Organic compounds with a thermal polymerization initiation temperature of 250°C or lower are organic compounds that have double or triple bonds in addition to aromatic rings. Examples include organic compounds such as acenaphthylene and vinylnaphthalene described in paragraph

[0118] of Japanese Patent Publication No. 2009-173627. The thermal polymerization initiation temperature is described in "Fundamentals of Carbonization Engineering" (1st edition, 2nd printing, 1982, Ohmsha).

[0166] [Pretreatment] It is particularly preferable to pretreat the mixture by drying it for 6 hours or more at a temperature of 15°C to 200°C under a reduced pressure of 1 kPa or less. A vacuum dryer or the like can be used for this pretreatment.

[0167] [Modification Treatment] The modification treatment of the mixture is preferably carried out in the presence of a reducing atmosphere such as hydrogen or carbon monoxide, an oxidizing atmosphere such as oxygen, carbon dioxide, or water vapor, an inert gas atmosphere such as nitrogen, helium, neon, argon, krypton, or xenon, or a nitrogen-containing compound gas or vapor such as ammonia or acetonitrile, or a mixture thereof. More preferably, in a reducing atmosphere, hydrogen and a mixture of hydrogen and the aforementioned inert gas are used; in an oxidizing atmosphere, oxygen and a mixture of oxygen and the aforementioned inert gas are used; and in an inert gas atmosphere, nitrogen, neon, argon, and a mixture thereof are used. The pressure used in the heat treatment is not particularly limited, but is preferably around atmospheric pressure of about 0.5 to 1.5 atmospheres. The pressure used in the modification treatment can be appropriately changed in the selected modification treatment.

[0168] When a mixture containing a conductive material supported with a polynuclear metal complex represented by formula (1) is subjected to a modification treatment, a conductive material supported with a modified metal complex is obtained.

[0169] Modified metal complexes are preferably obtained by heat treatment, radiation treatment, or electrical discharge treatment of the mixture.

[0170] (Heat Treatment) When heat-treating the mixture, the treatment temperature should be a temperature that sufficiently denatures the polynuclear metal complex to achieve excellent reduction efficiency while maintaining the complex structure. Preferably, it is 250°C or higher, more preferably 300°C or higher, even more preferably 400°C or higher, and may be 500°C or higher or 600°C or higher. The heat treatment temperature is preferably 1200°C or lower, more preferably 1000°C or lower, even more preferably 800°C or lower, and may be 700°C or lower or 600°C or lower. For example, the heat treatment temperature is 250°C to 1200°C. The heat treatment temperature may be set depending on the type of polynuclear metal complex.

[0171] The heat treatment time can be appropriately set according to the gas used, temperature, etc. above. However, in the state where the gas is sealed or ventilated, the temperature can be gradually increased from room temperature, and after reaching the target temperature, the temperature can be decreased immediately. Among these, it is preferable to maintain the temperature after reaching the target temperature, so that the mixture can be gradually heated, which can further improve the durability. The holding time after reaching the target temperature is preferably 0.5 hours to 100 hours, more preferably 0.5 hours to 40 hours, still more preferably 1 hour to 10 hours, and particularly preferably 1 to 5 hours.

[0172] Examples of the apparatus for performing the heat treatment include a tubular furnace, an oven, a furnace, and an IH hot plate.

[0173] (Radiation irradiation treatment, discharge treatment) As the modification treatment alternative to the heat treatment, it is possible to select any radiation irradiation treatment that irradiates radiation such as electromagnetic waves or particle beams selected from α-rays, β-rays, neutron rays, electron rays, γ-rays, X-rays, vacuum ultraviolet rays, ultraviolet rays, visible light rays, infrared rays, microwaves, radio waves, and lasers, and discharge treatments such as corona discharge treatment, glow discharge treatment, and plasma treatment (including low-temperature plasma treatment). Among these, preferable modification treatments include radiation irradiation treatments that irradiate radiation selected from X-rays, electron rays, ultraviolet rays, visible light rays, infrared rays, microwaves, and lasers, and low-temperature plasma treatment. More preferably, it is a radiation irradiation treatment that irradiates radiation selected from ultraviolet rays, visible light rays, infrared rays, microwaves, and lasers. These methods can be carried out according to the equipment and treatment methods usually used for the surface modification treatment of polymer films. For example, the methods described in the literature (edited by the Adhesion Society of Japan, "Chemistry of Surface Analysis and Modification", published by Nikkan Kogyo Shimbun, Inc., on December 19, 2003) can be used.

[0174] (Mass Loss Rate) From the viewpoint of sufficiently modifying the polynuclear metal complex to achieve excellent reduction efficiency while maintaining the complex structure, the modification treatment (e.g., heat treatment, radiation treatment, or discharge treatment) is preferably performed under conditions arbitrarily set so that the mass loss rate calculated by the following formula (A) is 1% to 90%, more preferably 1% to 80%, even more preferably 1% to 50%, particularly preferably 2% to 30%, and most preferably 2% to 15%. Mass loss rate (%) = [(Total mass of polynuclear metal complex and conductive material before treatment) - (Total mass of polynuclear metal complex and conductive material after treatment) / (Total mass of polynuclear metal complex and conductive material before treatment)] × 100 …(A)

[0175] By processing the material so that the mass loss rate falls within the above range, the catalytic activity of the polynuclear metal complex can be stabilized and further enhanced, similar to that of the polynuclear metal complex before modification. The mass loss due to modification is mainly due to the elimination of low-molecular-weight molecules from the polynuclear metal complex or conductive material. This elimination of low-molecular-weight molecules can be confirmed by using a mass spectrometer or similar device to analyze the gaseous components generated during the modification process.

[0176] (Carbon Content) Modification treatment (e.g., heat treatment, radiation treatment, or electrical discharge treatment) is preferably performed so that the carbon content of the modified metal complex is 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, particularly preferably 30% by mass or more, and most preferably 40% by mass or more. The upper limit of the carbon content is 100% by mass. The higher the carbon content, the more stable the complex structure becomes, and the greater the degree of accumulation of metal atoms in the modified metal complex. The carbon content of the modified metal complex can be measured by elemental analysis.

[0177] The distance between coordinating heteroatoms and metal atoms, as well as the distance between metal atoms in a modified metal complex, can be confirmed using broad-field X-ray absorption fine structure (EXAFS) analysis. Here, heteroatoms refer to oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, selenium atoms, arsenic atoms, and halogen atoms, more preferably oxygen atoms, nitrogen atoms, sulfur atoms, and phosphorus atoms, even more preferably oxygen atoms, nitrogen atoms, and sulfur atoms, and particularly preferably oxygen atoms and nitrogen atoms. Furthermore, the metal atoms included in the modified metal complex are synonymous with the metal atoms described above. In the EXAFS radial distribution function of the central metal, heteroatoms coordinated to the central metal are observed as peaks originating from the first nearest neighbor atom, and are usually observed in the range of 1.0 Å to 2.5 Å. The lower limit of the range in which the peak originating from the first nearest neighbor atom is observed is more preferably 1.1 Å or more, and even more preferably 1.2 Å or more. The upper limit is more preferably 2.2 Å or less, even more preferably 1.8 Å or less, and particularly preferably 1.6 Å or less. Furthermore, the peak originating from the distance between metal atoms in the modified metal complex is observed in the range of 1.8 Å to 2.9 Å. The lower limit of the range in which the peak originating from the distance between metal atoms in the modified metal complex is observed is more preferably 1.9 Å or more, and even more preferably 2.0 Å or more. The upper limit is more preferably 2.8 Å or less, and even more preferably 2.7 Å or less. The peak originating from the distance between metal atoms in the modified metal complex is observed as a separate peak from the peak originating from the metal foil used as a standard, and is observed as a peak with a longer distance between metal atoms.

[0178] <Reaction of carbon dioxide with water> The manufacturing method A of the present disclosure includes reacting carbon dioxide with water in the presence of a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by formula (1) and a conductive material. The reaction is not particularly limited as long as carbon dioxide and water can be reacted in the presence of a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by formula (1) and a conductive material. From the viewpoint of carbon monoxide selectivity, the reaction is preferably carried out using a carbon dioxide reduction apparatus comprising an oxidizing electrode, a carbon dioxide reduction electrode of the present disclosure described later, a membrane separating the oxidizing electrode and the carbon dioxide reduction electrode, an electrolyte, and a power supply connected to the oxidizing electrode and the carbon dioxide reduction electrode. Details of the carbon dioxide reduction electrode and the carbon dioxide reduction apparatus will be described later.

[0179] One method for reacting carbon dioxide with water using a carbon dioxide reduction device is to pass an electric current through the oxidation electrode and the carbon dioxide reduction electrode, to flow carbon dioxide into the device so that it comes into contact with the carbon dioxide reduction electrode, and to react the water contained in the electrolyte of the carbon dioxide reduction device with the carbon dioxide on the carbon dioxide reduction electrode.

[0180] <<Carbon Dioxide Reduction Electrode>> The carbon dioxide reduction electrode of this disclosure includes a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (1) and a conductive material.

[0181]

[0182] In formula (1), R represents a hydrogen atom or substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, P represents a divalent group containing one or more aromatic rings, Q 1 and Q 2 Q represents a monovalent group containing one or more aromatic rings. 1 and Q 2The atoms 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 from 2 to 4, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, multiple X atoms may be the same or different, and O is an oxygen atom that is bonded to at least one M atom.

[0183] (Modified Metal Complex) The preferred embodiment of the modified metal complex in the carbon dioxide reduction electrode of this disclosure is the same as the preferred embodiment of the modified metal complex in manufacturing method A of this disclosure.

[0184] (Support) The carbon dioxide reduction electrode of the present disclosure preferably further comprises a support for the modified metal complex. The support is preferably conductive and includes, for example, carbon nanotubes, graphene, carbon black, carbon cloth, carbon paper, glassy carbon, graphite, and tantalum (Ta).

[0185] (Ionic Conductor) The carbon dioxide reduction electrode of this disclosure preferably further includes an ionic conductor. Known ionic conductors can be used and are not particularly limited, but an electrolyte solution obtained by dissolving an ionic substance in a solvent such as water may be used, or an ion exchange resin may be used. The ionic conductor used between the reduction electrode and the membrane and the ionic conductor used between the oxidation electrode and the membrane may be the same or different, and both an electrolyte solution and an ion exchange resin may be used as ionic conductors. Examples of ionic conductors include ionsomers. An ionomer is a polymer neutralized by ions. Preferably, the ionomer is a polymer neutralized by a cation such as a metal (cationic ionomer) or a polymer neutralized by an anion (anionic ionomer). Examples of anionic ionomers include Sustainion from Dioxide Materials, AEMION from Ionomer Innovations, Fumasep from FumaTech, Orion from Orion, NEOSEPTA from ASTOM, and SELEMIN from AGC.

[0186] The ion conductor is preferably 10% by mass or more and 200% by mass or less relative to the mass of the conductive material on which the modified metal complex is supported.

[0187] (Other Components) The carbon dioxide reduction electrode of this disclosure may contain other components besides the modified metal complex, conductive material, support, and ion conductor. Examples of other components include water-repellent materials. Examples of water-repellent materials include fluorine-containing resins, silicon-containing resins, silane coupling agents, and waxes, but fluorine-containing resins are preferred from the viewpoint of water-repellent effect, and polytetrafluoroethylene is an example of a fluorine-containing resin.

[0188] (Method for manufacturing a carbon dioxide reduction electrode) The carbon dioxide reduction electrode of this disclosure is preferably manufactured by preparing an electrode ink in which the modified metal complex or a conductive material on which the modified metal complex is supported, an ionic conductor, and other components are dispersed in a solvent, and then applying the electrode ink to a support and drying it.

[0189] (Example of a carbon dioxide reduction electrode) Figure 1 shows an example of a carbon dioxide reduction electrode of the present disclosure. Figure 1 is a schematic cross-sectional view of the carbon dioxide reduction electrode of the present disclosure. In Figure 1, the carbon dioxide reduction electrode 10 has a layer 1 on a support 2 that includes a conductive material on which the modified metal complex is supported. If the carbon dioxide reduction electrode includes components other than the ion conductor, these components are included in the layer 1 that includes the conductive material on which the modified metal complex is supported.

[0190] <<Carbon Dioxide Reduction Device>> The carbon dioxide reduction device of this disclosure comprises an oxidation electrode, a carbon dioxide reduction electrode of this disclosure, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode, an electrolyte, and a power supply connected to the oxidation electrode and the carbon dioxide reduction electrode.

[0191] (Example of a 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 includes 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 supply 14 connected to the oxidation electrode 11 and the carbon dioxide reduction electrode 10. The carbon dioxide reduction device 100 also includes an electrolytic cell 15 equipped with these components and a reaction vessel 16. Here, it is preferable that the carbon dioxide reduction electrode 10 is installed so that the conductive material on which the modified metal complex is supported is in contact with the electrolyte 13.

[0192] The carbon dioxide reduction device 100 is applicable to a reaction that reduces carbon dioxide and produces carbon monoxide. When used in this reaction, it is preferable to use the power supply 14 to pass current from the carbon dioxide reduction electrode 10 towards the oxidation electrode 11. It is also preferable to flow carbon dioxide into the reaction vessel 16 in the direction of arrow A. The carbon dioxide flowing into the reaction vessel 16 comes into contact with the modified metal complex in the carbon dioxide reduction electrode 10. As a result, the reaction represented by the following reaction equation 1 proceeds on the carbon dioxide reduction electrode 10 side, and the reaction represented by the following reaction equation 2 proceeds on the oxidation electrode 11 side. Reaction equation 1: CO2 + H2O + 2e - →CO + 2OH - Reaction equation 2: 2OH - →1 / 2O2+H2O+2e - The generated carbon monoxide then flows out of the reaction vessel 16 in the direction of arrow B.

[0193] The carbon dioxide reduction electrode will be described in detail below. Note that symbols will be omitted.

[0194] (Oxidation Electrode) Any known oxidizing electrode can be used, and is not particularly limited, but an electrode that oxidizes water or hydroxide ions to generate oxygen is preferred. Examples include, but are not particularly limited to, metallic materials such as titanium or nickel, or porous materials made of carbonaceous materials such as carbon paper. The oxidizing electrode may contain metals such as platinum, palladium, or nickel, or metal oxides such as nickel oxide, iridium oxide, or ruthenium oxide, in order to promote the generation of oxygen.

[0195] (Carbon dioxide reduction electrode) The carbon dioxide reduction electrode described above in this disclosure is applicable.

[0196] (Membrane) A known membrane can be used to separate the carbon dioxide reduction electrode and the oxidation electrode, and is not particularly limited, but any material having ion conductivity can be used. For example, porous polymer membranes such as PTFE or porous membranes such as glass filters, cation exchange membranes such as Nafion or FLEMION, or anion exchange membranes such as Sustainion, NEOSEPTA, or SELEMINION can be used. Although not particularly limited to these, an ion exchange membrane is preferred. As an ion exchange membrane, an anion exchange membrane is more preferred.

[0197] (Electrolyte) Any known electrolyte can be used and is not particularly limited, but examples include those containing a cation such as sodium ions or potassium ions, anions such as bicarbonate ions, carbonate ions, hydroxide ions, sulfate ions, phosphate ions, or borate ions, and water.

[0198] 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.

[0199] (Power supply) The power supply is connected to the oxidation electrode and the carbon dioxide reduction electrode. The power supply is not particularly limited as long as it is capable of supplying current between the carbon dioxide reduction electrode and the oxidation electrode. For example, an electrochemical analyzer 1140D manufactured by BAS Corporation can be used as a power supply.

[0200] <<An Embodiment A of the Modified Metal Complex>> An embodiment A of the modified metal complex of the present disclosure is obtained from a mixture containing a polynuclear metal complex represented by the following formula (6).

[0201]

[0202] In formula (6), R 22 ~R 26 R represents a hydrogen atom or substituent, and there are multiple R 22 ~R 26 These can be the same or different, and the two adjacent Rs 22 Two adjacent Rs 23 Two adjacent Rs 24 Two adjacent Rs 26 R, both adjacent to each other 25 and R 26 The atoms may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M atoms may be the same or different, X is a counterion or a neutral molecule, b is a non-negative integer, and if there are multiple X atoms, multiple X atoms may be the same or different.

[0203] In one embodiment A of the modified metal complex of the present disclosure, the preferred embodiment of the modified metal complex obtained from a mixture containing a multinuclear metal complex represented by formula (6) is the same as the preferred embodiment of the modified metal complex obtained from a mixture containing a multinuclear metal complex represented by formula (6) in the manufacturing method A of the present disclosure described above.

[0204] In one embodiment A of the modified metal complex of the present disclosure, the mixture preferably further comprises a conductive material. Preferred embodiments of the conductive material are as described above.

[0205] <<An Embodiment B of the Modified Metal Complex>> An embodiment B of the modified metal complex of the present disclosure is obtained from a mixture containing a polynuclear metal complex represented by the following formula (10).

[0206]

[0207] In formula (10), R represents a hydrogen atom or a substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, 3 and R 4 R represents a hydrogen atom or substituent, and there are multiple R 3 These can be the same or different, and the two adjacent Rs 3 R adjacent to each other 3 and R 4 They may bond to each other to form a ring structure, Q 1 and Q 2 The formula is as follows (Q a ) or formula (Q b ) represents a monovalent group, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer from 2 to 4, and multiple Ms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, multiple Xs may be the same or different, and O is an oxygen atom that is bonded to at least one M.

[0208]

[0209] Formula (Q a ) and (Q b ) Medium, R q R represents a hydrogen atom or substituent, and there are multiple R q These can be the same or different, and the two adjacent Rs q These elements may be bonded to each other to form a ring structure, and * represents a bonding hand.

[0210] A preferred embodiment of the modified metal complex obtained from a mixture containing a polynuclear metal complex represented by formula (10) in one embodiment B of the modified metal complex of the present disclosure is, among the modified metal complex obtained from a mixture containing a polynuclear metal complex represented by formula (1) in the above-described manufacturing method A of the present disclosure, wherein in formula (1), P is of formula (P b It is a divalent group represented by Q 1 and Q 2 is equation (Q a ) or formula (Q b This is the same as the preferred embodiment when representing a monovalent group represented by ).

[0211] In one embodiment B of the modified metal complex of the present disclosure, the mixture preferably further comprises a conductive material. Preferred embodiments of the conductive material are as described above.

[0212] <<Method B for Producing Carbon Monoxide>> Method B for producing carbon monoxide according to the present disclosure (hereinafter also referred to as "Method B") comprises reacting carbon dioxide with water in the presence of a modified metal complex obtained from a mixture containing a polynuclear metal complex and a conductive material, wherein the polynuclear metal complex contains at least one metal atom selected from the group consisting of cobalt atoms, nickel atoms, and zinc atoms, and the distance between the metal atoms calculated by density functional theory is less than 3.18 Å.

[0213] A preferred embodiment of manufacturing method B of the present disclosure is identical to a preferred embodiment of manufacturing method A of the present disclosure, except that the polynuclear metal complex contains at least one metal atom selected from the group consisting of cobalt atoms, nickel atoms, and zinc atoms, and the distance between the metal atoms calculated by density functional theory is less than 3.18 Å. In other words, the polynuclear metal complex in manufacturing method B of the present disclosure is not limited to the polynuclear metal complex represented by formula (1) in manufacturing method A of the present disclosure.

[0214] <Distance between metal atoms> In manufacturing method B of this disclosure, by using a modified metal complex having a binuclear structure with adjacent central metals and a coordination environment to the central metal by macrocyclic ligands, it is presumed that hydrogen generation is suppressed and carbon monoxide production by reduction of carbon dioxide is promoted, resulting in a carbon monoxide production method with high carbon monoxide selectivity. To improve reduction efficiency, it is thought that increasing the interaction between metal atoms in the coordination environment to the central metal by ligands is effective, and for this purpose, it is presumed that shortening the distance between metal atoms is effective. Here, manufacturing method B of this disclosure uses a modified metal complex obtained from a multinuclear metal complex in which the distance between metal atoms calculated by density functional theory is less than 3.18 Å. By making the distance between metal atoms in the multinuclear metal complex calculated by density functional theory less than 3.18 Å, the interaction between metal atoms can be increased even in the modified metal complex. Therefore, it is presumed that this will be a carbon monoxide production method with high reduction efficiency.

[0215] In the manufacturing method B of this disclosure, the distance between metal atoms of the multinuclear metal complex, calculated by density functional theory, is less than 3.18 Å, preferably 2.20 Å or more and less than 3.18 Å, more preferably 2.40 Å or more and 3.15 Å or less, even more preferably 2.60 Å or more and 3.13 Å or less, and particularly preferably 2.70 Å or more and 3.10 Å or less. The reason why a distance between metal atoms of 2.20 Å or more is preferable is that, due to the structure of the multinuclear metal complex, it is difficult to make the distance between metal atoms less than 2.20 Å.

[0216] The distance between metal atoms in a multinuclear metal complex is calculated using a quantum chemistry calculation program. For example, Gaussian 16 from Gaussian GmbH can be used as a quantum chemistry calculation program. The structure optimization calculation of the multinuclear metal complex for which the distance between metal atoms is to be calculated is performed using density functional theory (B3LYP / def2svp, sdd for Co, Ni, Zn) to calculate the distance between metal atoms. If the SCF (self-consistent field) solution of the structure optimization calculation is an unstable solution, the structure optimization calculation is performed again to derive a stable solution. Note that the distance between metal atoms refers to the distance between the central metal atoms in the multinuclear metal complex. If the multinuclear metal complex contains three or more central metal atoms in one molecule, the distance between the closest central metal atoms is used as the distance between metal atoms in the manufacturing method B of this disclosure.

[0217] From the viewpoint of carbon monoxide selectivity, the polynuclear metal complex is preferably one in which at least one oxygen atom is coordinately bonded to one metal atom, and more preferably one in which one metal atom and two oxygen atoms are coordinately bonded.

[0218] Furthermore, it is preferable that the above-described manufacturing method A of the present disclosure also satisfies manufacturing method B of the present disclosure. That is, it is preferable that the distance between metal atoms M calculated by density functional theory in manufacturing method A of the present disclosure is less than 3.18 Å. On the other hand, it is also preferable that the above-described manufacturing method B of the present disclosure also satisfies manufacturing method A of the present disclosure. That is, it is preferable that the multinuclear metal complex in manufacturing method B of the present disclosure is a multinuclear metal complex represented by formula (1).

[0219] The present disclosure will be described in more detail below with reference to examples, 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, proportions, processing content, 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. The various manufacturing conditions and evaluation result values ​​in the following examples are meant as preferred upper or lower limits in the embodiments of the present disclosure, and the preferred range is meant as a preferred value for the aforementioned upper or lower limit, and the preferred range may be defined by a combination of the aforementioned upper or lower limit value and the values ​​of the following examples or values ​​between examples. In the following description, unless otherwise specified, "parts" and "%" are all based on mass.

[0220] The performance of the carbon dioxide reduction electrodes prepared by the method described in the Examples or Comparative Examples was evaluated using the carbon dioxide reduction apparatus 100 shown in Figure 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, Inc.) was used as the membrane 12. A 1.0 M (= 1.0 mol / L) aqueous potassium hydroxide solution was used as the electrolyte 13. An electrochemical measuring device (electrochemical analyzer 1140D, manufactured by BAS Corporation) was used as the power supply 14. Furthermore, an Hg / HgO reference electrode (manufactured by EC Frontier Corporation) was placed in the electrolyte 13 between the membrane 12 and the reduction electrode 10 as a reference electrode. Carbon dioxide gas set to 15 mL / min was flowed in the direction of arrow A in the reaction vessel 16, and electrochemical measurements were performed by applying a potential to the reduction electrode 10 using the electrochemical measuring device. Using a gas-tight syringe, 50 μL of the outlet gas (gas flowing out of reaction vessel 16 in the direction of arrow B) was collected, and the products contained in the gas were quantitatively analyzed using a gas chromatograph (GC-2010 / BID detector, Shimadzu Corporation). The current density (mA / cm²) obtained when the potential was applied was measured. 2A higher value of ) indicates a faster reaction rate. The Faraday efficiency (%) of carbon monoxide (CO) was calculated as the proportion of the charge used to produce observed carbon monoxide out of the total charge used in the reaction. A higher value of the Faraday efficiency of carbon monoxide indicates that carbon monoxide is being produced selectively, meaning high carbon monoxide selectivity. Partial current density of carbon monoxide (CO) (mA / cm²) 2 The partial current density of carbon monoxide was calculated using the following formula. A higher value for the partial current density of carbon monoxide indicates that carbon dioxide is being converted to carbon monoxide more efficiently. Partial current density (mA / cm²) 2 ) = current density (mA / cm 2 ) × Faraday efficiency of carbon monoxide (%) … (B)

[0221] For MALDI-MS measurements, a JEOL JMS S-3000 was used.

[0222] A Shimadzu UV-2400PC was used for ultraviolet-visible absorption spectrum measurements.

[0223] (Mass Loss Rate) The total mass of the polynuclear metal complex and conductive material was measured before and after treatment, and the mass loss rate was calculated using the following formula (A). Mass loss rate (%) = [(Total mass of polynuclear metal complex and conductive material before treatment) - (Total amount of polynuclear metal complex and conductive material after treatment) / (Total mass of polynuclear metal complex and conductive material before treatment)] × 100 … (A)

[0224] <Synthesis Example 1> (Synthesis of Polynuclear Metal Complex 1) Using compound 1 synthesized by the method described in Japanese Patent No. 5422159, polynuclear metal complex 1 was synthesized according to the reaction formula shown below.

[0225]

[0226] After creating a nitrogen gas atmosphere in the reaction vessel, 7.18 g (28.87 mmol) of nickel acetate tetrahydrate (Ni(OAc)2・4H2O) was suspended in 72.8 g of pre-degassed methanol (MeOH). 148 g of chloroform (HCl3) was added to this, and the temperature was raised to 50°C to obtain a nickel acetate solution. In another reaction vessel, after creating a nitrogen gas atmosphere, a suspension consisting of 8.00 g (11.55 mmol) of compound 1 and 180 g of chloroform was prepared. This suspension was added dropwise to the above 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 1. After cooling this reaction solution to room temperature, it was filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain polynuclear metal complex 1 in a yield of 8.60 g and 93%. The identification data for the obtained polynuclear metal complex 1 is shown below. The results of MALDI-MS measurement were confirmed as follows. MALDI-MS [M-OAc] + : m / z = 807.2

[0227] The interatomic distances in polynuclear metal complex 1 were 2.92 Å.

[0228] <Synthesis Example 2> (Synthesis of Compound 2) Compound 2 was synthesized using Compound 1, which was synthesized by the method described in Patent No. 5422159, according to the reaction formula shown below.

[0229]

[0230] After creating a nitrogen gas atmosphere in the reaction vessel, 10.00 g (14.43 mmol) of compound 1 was added to 370 g of chloroform (HCl3) and suspended, then the temperature was raised to 50°C. In another reaction vessel, after creating a nitrogen gas atmosphere, a suspension consisting of 2.65 g (14.43 mmol) of zinc acetate (Zn(OAc)2) and 90 g of methanol (MeOH) was prepared. The zinc acetate suspension was added dropwise to the suspension of compound 1, and the temperature was raised to 55°C, with reflux and stirring for 1 hour to obtain a reaction solution containing compound 2. After cooling this reaction solution to room temperature, water was added and the mixture was stirred for a while to wash and remove the aqueous phase. Heptane was added to the obtained organic phase, and after concentration, the mixture was filtered. Compound 2 was obtained in a yield of 10.9 g and 100% by vacuum drying of the obtained crystals. The identification data for the obtained compound 2 is shown below. The results of MALDI-MS measurement were confirmed as follows: MALDI-MS [M+H] + :m / z=756.23

[0231] <Synthesis Example 3> (Synthesis of Multinuclear Metal Complex 2) Multinuclear metal complex 2 was synthesized according to the reaction equation shown below.

[0232]

[0233] After creating a nitrogen gas atmosphere in the reaction vessel, 2.00 g (2.65 mmol) of compound 2 was added to 200 g of chloroform (HCl3) and suspended, then the temperature was raised to 50°C. In another reaction vessel, after creating a nitrogen gas atmosphere, a suspension consisting of 0.66 g (2.65 mmol) of nickel acetate tetrahydrate (Ni(OAc)2・4H2O) and 40 g of methanol (MeOH) was prepared. The nickel acetate suspension was added dropwise to the suspension of compound 2, and the temperature was raised to 55°C, with reflux and stirring for 1.5 hours to obtain a reaction solution containing the polynuclear metal complex 2. After cooling this reaction solution to room temperature, it was filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain the polynuclear metal complex 2 in a yield of 1.91 g and 83%. The identification data for the obtained polynuclear metal complex 2 is shown below. The results of MALDI-MS measurement were confirmed as follows: MALDI-MS [M-OAc] + m / z = 813.9

[0234] The interatomic distances in polynuclear metal complex 2 were 2.90 Å.

[0235] <Synthesis Example 4> (Synthesis of Polynuclear Metal Complex 3) Using compound 3 synthesized by the method described in Japanese Patent No. 5422159, polynuclear metal complex 3 was synthesized according to the reaction formula shown below.

[0236]

[0237] After creating a nitrogen gas atmosphere in the reaction vessel, 0.74 g (1.19 mmol) of nickel acetate tetrahydrate was added to 12 g of pre-degassed methanol (MeOH) and suspended. 44 g of chloroform (HCl3) was added to this, and the temperature was raised to 50°C to obtain a nickel acetate solution. In another reaction vessel, after creating a nitrogen gas atmosphere, a suspension was prepared consisting of 0.87 g (2.97 mmol) of compound 3 and 44 mL of chloroform. This suspension was added dropwise to the above 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 the polynuclear metal complex 3. After cooling this reaction solution to room temperature, it was filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain the polynuclear metal complex 3 in a yield of 0.85 g and 85%. The identification data for the obtained polynuclear metal complex 3 is shown below. The results of MALDI-MS measurement were confirmed as follows: MALDI-MS [M+H] + m / z = 847.3

[0238] The interatomic distances in the polynuclear metal complex 3 were 3.05 Å.

[0239] <Synthesis Example 5> (Synthesis of Polynuclear Metal Complex 4) Polynuclear metal complex 4 was synthesized according to the reaction equation shown below.

[0240]

[0241] After creating a nitrogen atmosphere in the reaction vessel, 1.49 g (6.00 mmol) of nickel acetate tetrahydrate was added to 10 mL of methanol (MeOH) and suspended. To this nickel acetate suspension, 4 mL of methanol solution containing 0.65 g (6.00 mmol) of 1,2-phenylenediamine was added with stirring, and the temperature was raised to reflux. Subsequently, 42 mL of methanol solution containing 0.90 g (6.00 mmol) of 2,6-diformylphenol was gradually added, and reflux was maintained for 3 hours. After concentrating the solution using an evaporator, it was cooled to room temperature and filtered. The obtained crystals were washed with acetone and dried under reduced pressure to obtain polynuclear metal complex 4 in a yield of 1.52 g and 75%. The identification data for the obtained polynuclear metal complex 4 is shown below. The results of MALDI-MS measurement were confirmed as follows. MALDI-MS [M] + : m / z = 558.0

[0242] The interatomic distances in the polynuclear metal complex 4 were 2.83 Å.

[0243] <Synthesis Example 6> (Synthesis of Polynuclear Metal Complex 5) Using compound 4 synthesized by the method described in Tetrahedron, 1999, 55, 8377, polynuclear metal complex 5 was synthesized according to the reaction formula shown below.

[0244]

[0245] After creating a nitrogen atmosphere in the reaction vessel, 1.75 g (7.04 mmol) of nickel acetate tetrahydrate was suspended in 10 mL of methanol (MeOH) and 5 mL of chloroform (HCl3). To this nickel acetate suspension, 101 mL of chloroform solution containing 1.50 g (2.82 mmol) of compound 4 was added while stirring, and the mixture was heated to reflux temperature. Subsequently, 10 mL of chloroform solution containing 0.30 g (2.82 mmol) of 1,2-phenylenediamine was gradually added, and reflux was maintained for 3 hours. After concentrating the solution using an evaporator, acetone was added, the mixture cooled to room temperature, and the solution was filtered. The obtained crystals were washed with acetone and dried under reduced pressure to obtain polynuclear metal complex 5 in a yield of 1.68 g and 71%. The identification data for the obtained polynuclear metal complex 5 is shown below. The results of MALDI-MS measurement were confirmed as follows: MALDI-MS [M]+ :m / z=718.14

[0246] The interatomic distances in the polynuclear metal complex 5 were 2.79 Å.

[0247] <Synthesis Example 7> (Synthesis of Polynuclear Metal Complex 6) Using compound 5 synthesized by the method described in Japanese Patent No. 5396031, polynuclear metal complex 6 was synthesized according to the reaction formula shown below.

[0248]

[0249] After creating a nitrogen gas atmosphere in the reaction vessel, 0.90 g (3.63 mmol) of nickel acetate tetrahydrate was added to 15 g of pre-degassed methanol (MeOH), and the temperature was raised to 55°C to obtain a nickel acetate solution. In another reaction vessel, after creating a nitrogen gas atmosphere, a suspension consisting of 1.00 g (1.65 mmol) of compound 5 and 20 g of chloroform (HCl3) was prepared. This suspension was added dropwise to the above nickel acetate solution, and the mixture was stirred under reflux for 1 hour to obtain a reaction solution containing the polynuclear metal complex 6. After cooling the reaction solution to room temperature, it was filtered. The obtained crystals were washed with methanol to obtain the polynuclear metal complex 6 in a yield of 0.35 g and 25%. The identification data for the obtained polynuclear metal complex 6 is shown below. The results of MALDI-MS measurement were confirmed as follows: MALDI-MS [M-OAc] + :m / z=720.15

[0250] The interatomic distances in the polynuclear metal complex 6 were 2.98 Å.

[0251] <Synthesis Example 8> (For comparison: Synthesis of polynuclear metal complex 7) Polynuclear metal complex 7 was synthesized according to the reaction shown below, using the method described in J. Phys. Chem. B 2005, 109, 2836.

[0252]

[0253] After creating a nitrogen gas atmosphere in the reaction vessel, 0.45 g (1.10 mmol) of tris(2-benzimidazolylmethyl)amine was added to 9 g of pre-degassed ethanol, and the mixture was heated to 78°C to dissolve. In another reaction vessel, after creating a nitrogen gas atmosphere, 0.24 g (1.10 mmol) of nickel bromide was added to 9 g of pre-degassed ethanol and dissolved. This nickel bromide solution was added dropwise to the above tris(2-benzimidazolylmethyl)amine solution, and the mixture was stirred under reflux for 5 hours to obtain a reaction solution containing the polynuclear metal complex 7. After concentrating this reaction solution, it was cooled to room temperature and filtered to obtain the polynuclear metal complex 9 in a yield of 0.64 g and 93%. The identification data for the obtained polynuclear metal complex 7 is shown below. The results of the ultraviolet-visible absorption spectrum measurement were confirmed as follows. The methanol solution of the polynuclear metal complex 7 had peak wavelengths at 394 nm and 632 nm.

[0254] The interatomic distances in the polynuclear metal complex 7 were 3.18 Å.

[0255] <Synthesis Example 9> (Synthesis of Multinuclear Metal Complex 8) Multinuclear metal complex 8 was synthesized according to the reaction equation shown below.

[0256]

[0257] After creating a nitrogen gas atmosphere in the reaction vessel, 2.00 g (2.65 mmol) of compound 2 was added to 200 g of chloroform (HCl3) and suspended, then the temperature was raised to 50°C. In another reaction vessel, after creating a nitrogen gas atmosphere, a suspension consisting of 0.66 g (2.65 mmol) of cobalt acetate tetrahydrate (Co(OAc)2・4H2O) and 40 g of methanol (MeOH) was prepared. The nickel acetate suspension was added dropwise to the suspension of compound 2, and the temperature was raised to 55°C and stirred under reflux for 2 hours to obtain a reaction solution containing the 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 the polynuclear metal complex 8 in a yield of 1.55 g and 67%. The identification data for the obtained polynuclear metal complex 8 is shown below. The results of MALDI-MS measurement were confirmed as follows. MALDI-MS [M-OAc] +: m / z = 812.1

[0258] The interatomic distances in the polynuclear metal complex 8 were 2.93 Å.

[0259] <Synthesis Example 10> (Synthesis of Polynuclear Metal Complex 9) Polynuclear metal complex 9 was synthesized according to the method described in Japanese Patent No. 5422159, following the reaction formula shown below.

[0260]

[0261] After creating a nitrogen gas atmosphere in the reaction vessel, a suspension consisting of 5.00 g (6.82 mmol) of compound 3 and 45 g of chloroform was prepared. In another reaction vessel, after creating a nitrogen gas atmosphere, 4.25 g (17.05 mmol) of cobalt acetate tetrahydrate was added to 15 g of pre-degassed methanol to prepare a cobalt acetate solution. This cobalt acetate solution was added dropwise to the compound 3 suspension, and the mixture was heated to 55°C and stirred under reflux for 3 hours to obtain a reaction solution containing the polynuclear metal complex 9. After cooling the reaction solution to room temperature, it was filtered. The obtained crystals were washed with methanol and water to obtain the polynuclear metal complex 9 in a yield of 5.07 g and 88%. The identification data for the obtained polynuclear metal complex 9 is shown below. The results of MALDI-MS measurement were confirmed as follows: MALDI-MS [M] + : m / z = 846.1

[0262] The interatomic distances in the polynuclear metal complex 9 were 2.96 Å.

[0263] <Mononuclear Metal Complexes> For comparison, the following mononuclear metal complexes were purchased.

[0264]

[0265] Nickel(II) tetraphenylporphyrin (Ni(TPP)) was purchased from Sigma-Aldrich.

[0266]

[0267] Nickel(II) phthalocyanine (Ni(Pc)) was purchased from Sigma-Aldrich.

[0268] Nickel(II) acetate tetrahydrate (Ni(OAc)2) was purchased from Tokyo Chemical Industry Co., Ltd.

[0269]

[0270] Cobalt(II) tetraphenylporphyrin (Co(TPP)) was purchased from Tokyo Chemical Industries.

[0271]

[0272] Cobalt(II) phthalocyanine (Co(Pc)) was purchased from Tokyo Chemical Industries.

[0273] <Examples 1 to 16 and Comparative Examples 1 to 20> (Preparation of Mixtures 1 to 14) 1 g of carbon black (Ketjen Black EC600JD, manufactured by Lion Specialty Chemicals, Inc.) was weighed into a reaction vessel as the conductive material. A metal complex was weighed into another reaction vessel so that the mass of metal atoms was 5% by mass relative to the carbon black. After confirming that a solution of the metal complex had been formed by adding a solvent, the solution was transferred to the reaction vessel from which the conductive material had been weighed to obtain a dispersion. By irradiating this dispersion with ultrasound, a suspension was obtained in which the conductive material supported by the metal complex was uniformly dispersed. After obtaining a wet cake (WC) of the mixture by filtration of the suspension using a filter or concentration to dryness using an evaporator, the mixture was dried under reduced pressure at 80°C to obtain Mixtures 1 to 14 containing the conductive material supported by the metal complex. Table 1 shows the metal complex, solvent, and WC acquisition method used in the preparation of Mixtures 1 to 14.

[0274]

[0275] -TGA Measurement- The mass change (TGA) of the mixture during heat treatment was measured using a thermomass / differential thermal analyzer (Bruker TG-DTA 2010SA). The measurement was performed under the same conditions as when preparing the modified metal complex. A sample consisting of the above mixture was placed in a platinum dish and heated under a nitrogen atmosphere with a heating rate of 10°C / min, followed by heating at 60°C for 1 hour, then at 300°C for 1 hour, and finally at the highest temperature reached for 1 hour.

[0276] (Modification treatment of the mixture: Preparation of modified metal complexes 1A-14A and 1B-14B) Based on the findings obtained from the TGA measurement results above, the metal complexes were modified (heat-treated) so that the mass loss rate during the heat treatment of the mixture was 1% to 15% by mass. The heat treatment was performed using a tubular furnace (Isuzu Manufacturing Co., Ltd. program-controlled open / closed tubular furnace EPKRO-14R) under a nitrogen atmosphere, with a program of 60°C for 1 hour, followed by 300°C for 1 hour, followed by the highest temperature reached for 1 hour. Table 3 shows the mixtures used to prepare modified metal complexes 1A-14A and modified metal complexes 1B-14B, the metal complexes contained in each mixture, the highest temperature reached during the heat treatment, the mass loss rate after the heat treatment, and the resulting modified metal complexes.

[0277] (Preparation of carbon dioxide reduction electrodes (1) to (16) and (1') to (20')) 20.0 mg of the aforementioned mixture or a modified metal complex powder obtained from the aforementioned mixture, 2.50 mL of ethanol, and 100 mg of a 5% solution of Nafion (manufactured by WAKO) as a cationic ionomer, which is an ion conductor, were added to a screw tube to form a dispersion. Ultrasound was irradiated onto this dispersion to obtain an ink. Carbon paper (25 mm in diameter) was used as a support, and 250 mg of the obtained ink was applied to the carbon paper and then dried to obtain carbon dioxide reduction electrodes (1) to (16) and (1') to (20'), respectively. The mixtures or modified metal complexes used in the preparation of the carbon dioxide reduction electrodes in Examples 1 to 16 and Comparative Examples 1 to 20 are shown in Tables 2 and 3.

[0278] (Evaluation results of carbon dioxide reduction efficiency) Electrochemical measurements were performed using the carbon dioxide reduction electrodes obtained in Examples 1 to 16 and Comparative Examples 1 to 20, according to the method described above. The results are shown in Tables 2 and 3.

[0279]

[0280]

[0281] - Comparison of Multinuclear Metal Complexes and Mononuclear Metal Complexes - From Tables 2 and 3, when modified metal complexes using multinuclear metal complexes (Examples 1-16) were used, the partial current density of carbon monoxide was higher than when modified metal complexes using mononuclear metal complexes (Comparative Examples 9-14 and 17-20), indicating more efficient conversion of carbon dioxide to carbon monoxide.

[0282] - Comparison of the mixture before heat treatment and the modified metal complex obtained by heat treatment - From Tables 2 and 3, when the modified metal complex obtained by heat treatment was used (Examples 1 to 16), the partial current density of carbon monoxide was higher than when the mixture before heat treatment was used (Comparative Examples 1 to 6 and Comparative Examples 15 to 16), indicating that carbon dioxide was efficiently converted to carbon monoxide.

[0283] - Comparison based on distance between metal atoms - From Tables 2 and 3, when multinuclear metal complexes with a distance between metal atoms of less than 3.18 Å were used (Examples 1-12), the partial current density of carbon monoxide was higher than when multinuclear metal complexes with a distance of 3.18 Å or more were used (Comparative Examples 7-8), indicating that carbon dioxide was efficiently converted to carbon monoxide.

[0284] From the above results, it can be seen that manufacturing methods A and B of this disclosure showed higher partial current densities of carbon monoxide and higher reduction efficiency of carbon dioxide to carbon monoxide compared to the comparative example.

[0285] 1: Layer containing a conductive material on which a modified metal complex is supported; 2: Support; 10: Carbon dioxide reduction electrode; 11: Oxidation electrode; 12: Film; 13: Electrolyte; 14: Power supply; 15: Electrolytic cell; 16: Reaction vessel; 100: Carbon dioxide reduction device

Claims

1. A method for producing carbon monoxide, comprising reacting carbon dioxide with water in the presence of a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (1) and a conductive material. (In formula (1), R represents a hydrogen atom or substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, and P represents a divalent group containing one or more aromatic rings, Q 1 and Q 2 Q represents a monovalent group containing one or more aromatic rings. 1 and Q 2 The atoms 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 from 2 to 4, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, multiple X atoms may be the same or different, and O is an oxygen atom that bonds to at least one M atom.

2. The method for producing carbon monoxide according to claim 1, wherein the modified metal complex is obtained by heat treatment, radiation treatment, or electrical discharge treatment of the mixture.

3. The method for producing carbon monoxide according to claim 2, wherein the heat treatment, radiation treatment, or discharge treatment is performed such that the mass reduction rate calculated by the following formula (A) is between 1% and 90%. Mass reduction rate (%) = [(Total mass of the polynuclear metal complex and conductive material before treatment) - (Total mass of the polynuclear metal complex and conductive material after treatment) / (Total mass of the polynuclear metal complex and conductive material before treatment)] × 100 … (A) 4. In the above formula (1), P is a divalent group represented by the following formula (P a ), formula (P b ), or formula (P c ). The method for producing carbon monoxide according to claim 1 or claim 2. (In formula (P a ), R 1 and R 2 represent a hydrogen atom or a substituent. A plurality of R 1 and R 2 may be the same or different from each other, and two adjacent R 1 s and two adjacent R 2 s may combine with each other to form a ring structure. In formula (P b ), R 3 and R 4 represent a hydrogen atom or a substituent. A plurality of R 3 may be the same or different from each other, and two adjacent R 3 s, as well as adjacent R 3 and R 4 may combine with each other to form a ring structure. In formula (P c ), R 5 represents a hydrogen atom or a substituent. A plurality of R 5 may be the same or different from each other. Y represents the following formula (P c1 ), formula (P c2 ), or formula (P c3 ). A plurality of Y may be the same or different from each other. Z represents an alkylene group or an arylene group. In formula (P a ) to formula (P c ), * represents a bond. ) (In formula (P c1 ) to formula (P c3 ), R p represents a hydrogen atom or a substituent, and * represents a bond. ) 5. The method for producing carbon monoxide according to claim 1 or claim 2, wherein the polynuclear metal complex is a compound represented by the following formula (2). (In formula (2), R 6 ~R 8 R represents a hydrogen atom or substituent, and there are multiple R 6 ~R 8 These can be the same or different, and the two adjacent Rs 6 Two adjacent Rs 7 Two Rs that are adjacent to each other 8 They may bond to each other to form a ring structure, Q 3 and Q 4 Q represents a monovalent group containing one or more aromatic rings. 3 and Q 4 The atoms 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 from 2 to 4, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, multiple X atoms may be the same or different, and O is an oxygen atom that bonds to at least one M atom.

6. In the above formula (1), P is the following formula (P a ) or formula (P b It is a divalent group represented by Q 1 and Q 2 The formula is as follows (Q a ) or formula (Q b A method for producing carbon monoxide according to claim 1 or claim 2, wherein the monovalent group is represented by ). (Formula (P a ) Medium, R 1 and R 2 R represents a hydrogen atom or substituent, and there are multiple R 1 and R 2 These can be the same or different, and the two adjacent Rs 1 Two Rs that are adjacent to each other 2 These elements may bond to each other to form a ring structure. Formula (P b ) Medium, R 3 and R 4 R represents a hydrogen atom or substituent, and there are multiple R 3 These can be the same or different, and the two adjacent Rs 3 R adjacent to each other 3 and R 4 These may bond to each other to form a ring structure. Formula (P a ) and formula (P b (In the above, * represents a combination.) (Formula (Q a ) and (Q b ) Medium, R q R represents a hydrogen atom or substituent, and there are multiple R q These can be the same or different, and the two adjacent Rs q These elements may bond to each other to form a ring structure, and * represents a bonding hand.

7. The method for producing carbon monoxide according to claim 1 or claim 2, wherein the polynuclear metal complex is a compound represented by the following formula (3). (In formula (3), R 9 ~R 13 R represents a hydrogen atom, substituent, or divalent group, and there are multiple R 9 ~R 12 These can be the same or different, and the two adjacent Rs 9 Two adjacent Rs 10 Two adjacent Rs 11 Two adjacent Rs 12 R, both adjacent to each other 12 and R 13 They may bond to each other to form a ring structure, R 13 If is a divalent group, the divalent group may combine with other compounds represented by formula (3) to form a dimer, where M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, where X is a counterion or a neutral molecule, where b is an integer of 0 or more, and if there are multiple Xs, multiple Xs may be the same or different.

8. The method for producing carbon monoxide according to claim 1 or claim 2, wherein the polynuclear metal complex is a compound represented by the following formula (4). (In formula (4), R 14 ~R 16 R represents a hydrogen atom or substituent, and there are multiple R 14 ~R 16 These can be the same or different, and the two adjacent Rs 14 Two adjacent Rs 15 R, both adjacent to each other 15 and R 16 The atoms may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is a non-negative integer, and if there are multiple X atoms, each X atom may be the same or different.

9. The method for producing carbon monoxide according to claim 1 or claim 2, wherein the polynuclear metal complex is a compound represented by the following formula (5). (In formula (5), R 17 ~R 21 represents a hydrogen atom or a substituent, and a plurality of R 17 ~R 21 may be the same or different from each other, and two adjacent R 17 s, two adjacent R 18 s, two adjacent R 19 s, two adjacent R 20 s, and two adjacent R 21 s may be bonded to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are a plurality of Xs, the plurality of Xs may be the same or different from each other.) 10. The method for producing carbon monoxide according to claim 1 or claim 2, wherein the polynuclear metal complex is a compound represented by the following formula (6). (In formula (6), R 22 ~R 26 R represents a hydrogen atom or substituent, and there are multiple R 22 ~R 26 These can be the same or different, and the two adjacent Rs 22 Two adjacent Rs 23 Two adjacent Rs 24 Two adjacent Rs 26 R, both adjacent to each other 25 and R 26 The atoms may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is a non-negative integer, and if there are multiple X atoms, each X atom may be the same or different.

11. The method for producing carbon monoxide according to claim 1 or claim 2, wherein the polynuclear metal complex is a compound represented by the following formula (7). (In formula (7), R 27 ~R 34 R represents a hydrogen atom or substituent, and there are multiple R 27 ~R 34 These can be the same or different, and the two adjacent Rs 27 Two adjacent Rs 28 Two adjacent Rs 29 Two adjacent Rs 30 Two adjacent Rs 31 Two adjacent Rs 32 Two adjacent Rs 33 Two Rs that are adjacent to each other 34 The elements may bond to each other to form a ring structure; Ar represents a divalent aromatic group which may have substituents; M represents a cobalt atom, a nickel atom, or a zinc atom; a is an integer from 2 to 4, and multiple Ms may be the same or different; X is a counterion or a neutral molecule; b is an integer of 0 or more, and if there are multiple Xs, multiple Xs may be the same or different; O is an oxygen atom which is bonded to at least one M.

12. The method for producing carbon monoxide according to claim 1 or claim 2, wherein the polynuclear metal complex is a compound represented by the following formula (8). (In formula (8), Z represents an alkylene group or an arylene group, and the multiple Zs may be the same or different, R 35 R represents a hydrogen atom or substituent, and there are multiple R 35 These can be the same or different, and the two adjacent Rs 35 They may bond to each other to form a ring structure, and Y is given by the following formula (P c1 ), formula (P c2 ), or formula (P c3 ) represents a cobalt atom, nickel atom, or zinc atom, and multiple Ys may be the same or different. X is a counterion or neutral molecule, and b is a non-negative integer. If there are multiple Xs, they may be the same or different. (Formula (P c1 ) ~ formula (P c3 ) Medium, R p (where * represents a hydrogen atom or substituent, and * represents a bond.) 13. A carbon dioxide reduction electrode comprising a modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (1) and a conductive material. (In formula (1), R represents a hydrogen atom or substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, and P represents a divalent group containing one or more aromatic rings, Q 1 and Q 2 Q represents a monovalent group containing one or more aromatic rings. 1 and Q 2 The atoms 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 from 2 to 4, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple X atoms, multiple X atoms may be the same or different, and O is an oxygen atom that bonds to at least one M atom.

14. The carbon dioxide reduction electrode according to claim 13, further comprising a support for the modified metal complex.

15. The carbon dioxide reduction electrode according to claim 14, further comprising an ion conductor.

16. A carbon dioxide reduction device comprising: an oxidation electrode; a carbon dioxide reduction electrode according to any one of claims 13 to 15; a membrane separating the oxidation electrode and the carbon dioxide reduction electrode; an electrolyte; and a power supply connected to the oxidation electrode and the carbon dioxide reduction electrode.

17. Modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (6). (In formula (6), R 22 ~R 26 R represents a hydrogen atom or substituent, and there are multiple R 22 ~R 26 These can be the same or different, and the two adjacent Rs 22 Two adjacent Rs 23 Two adjacent Rs 24 Two adjacent Rs 26 R, both adjacent to each other 25 and R 26 The atoms may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M atoms may be the same or different, X is a counterion or neutral molecule, b is a non-negative integer, and if there are multiple X atoms, each X atom may be the same or different.

18. The modified metal complex according to claim 17, wherein the mixture further comprises a conductive material.

19. Modified metal complex obtained from a mixture containing a polynuclear metal complex represented by the following formula (10). (In formula (10), R represents a hydrogen atom or a substituent, and any multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring structure, R 3 and R 4 R represents a hydrogen atom or substituent, and there are multiple R 3 These can be the same or different, and the two adjacent Rs 3 R adjacent to each other 3 and R 4 They may bond to each other to form a ring structure, Q 1 and Q 2 The formula is as follows (Q a ) or formula (Q b ) represents a monovalent group, where M represents a cobalt atom, nickel atom, or zinc atom, a is an integer from 2 to 4, and multiple Ms may be the same or different, X is a counterion or neutral molecule, b is an integer of 0 or more, and if there are multiple Xs, each X may be the same or different, and O is an oxygen atom that is bonded to at least one M. (Formula (Q a ) and (Q b ) Medium, R q R represents a hydrogen atom or substituent, and there are multiple R q These can be the same or different, and the two adjacent Rs q These elements may bond to each other to form a ring structure, and * represents a bonding hand.

20. The modified metal complex according to claim 19, wherein the mixture further comprises a conductive material.

21. A method for producing carbon monoxide, comprising reacting carbon dioxide with water in the presence of a modified metal complex obtained from a mixture containing a polynuclear metal complex and a conductive material, wherein the polynuclear metal complex contains at least one metal atom selected from the group consisting of cobalt atoms, nickel atoms, and zinc atoms, and the distance between the metal atoms calculated by density functional theory is less than 3.18 Å.

22. The method for producing carbon monoxide according to claim 21, wherein the polynuclear metal complex is a polynuclear metal complex in which one metal atom and two oxygen atoms are coordinately bonded.

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