Metal complex nanosheet and method for producing same

Abstract

To provide a metal complex nanosheet having novel properties.SOLUTION: A metal complex nanosheet includes a metal organic structure layer in which metal cores and organic ligands are coordinated so as to develop in a surface direction, where the metal organic structure layer includes a region in which structural units expressed by formula (I) (in formula (I), M denotes, each independently, at least one kind selected from the group consisting of Cu, Ni and Co, X1 to X6, each independently, are -NH- or -NH2-, a dash line denotes a bond to a ligand group in another constitutional unit) develop in a surface direction. In XPS spectrum of N1s of the metal complex nanosheet, a ratio (SNA / SNI) of an area SNA of an amine structure-derived peak which appears near 398.8 eV to an area SNI of an imine structure-derived peak which appears near 397.4 eV is 0.6 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a metal complex nanosheet and a method for producing the same. [Background technology]

[0002] Nanosheets based on graphene, transition metal chalcogenides, metal oxides, metal hydroxides, etc. have attracted attention in recent years. Nanosheets are anisotropic materials, with nanometer-order thicknesses and in-plane domain sizes hundreds of times larger. These nanosheets exhibit unique physical and chemical properties not observed in bulk due to their nanometer-order thickness. While all of the nanosheets mentioned above are classified as inorganic two-dimensional nanosheets, organic two-dimensional nanosheets, which are composed of organic molecules, have also been actively studied in recent years. One of the greatest features of organic two-dimensional nanosheets is their wide variety. By bottom-up synthesis using appropriately designed organic molecules, nanosheets with a wide variety of chemical structures can be constructed. Metal complex nanosheets, one type of organic two-dimensional nanosheet, have a metal complex as their main backbone. By combining countless metal ions and organic ligands, they can be flexibly configured into various chemical and geometric structures, and the complex moieties can be enhanced with electronic, magnetic, optical, and catalytic properties. Furthermore, since complex formation reactions generally proceed under mild conditions, metal complex nanosheets have the advantage that they can be synthesized using simple equipment.

[0003] Non-Patent Documents 1 to 5 disclose metal complex nanosheets consisting of metal ions such as nickel or copper and hexaaminobenzene, i.e., bis(diimino)metal complex nanosheets. Bis(diimino)metal complex nanosheets have a periodic chemical structure and are known to exhibit semiconducting electrical conduction properties. Because they have a large surface area due to their two-dimensional structure, they are also expected to be used as electrode materials for supercapacitors, lithium-ion batteries, and the like.

[0004] Patent Document 1 also discloses a two-dimensional metal complex having a ligand having three or more bidentate coordination sites, at least one of the bidentates being NH; and a metal core M (M is at least one selected from the group consisting of Ni, Co, Cu, Pt, Pd, Fe, Mn, Re, Ru, Os, Rh, Ir, Ag, and Au), in which substantially all atoms of the ligand that substantially form the metal complex and the metal core are present on approximately the same plane. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-2623 [Non-patent literature]

[0006] [Non-Patent Document 1] "Hexaaminobenzene as a building block for a Family of 2D Coordination Polymers", Nabajit Lahiri et al., J. Am. Chem. Soc. 2017, 139, 19-22 [Non-patent document 2] "Signature of Metallic Behavior in the Metal-Organic Frameworks M3(hexaiminobenzene)2(M = Ni, Cu)", Jin-Hu Dou et al., J. Am. Chem. Soc. 2017, 139, 13608-13611 [Non-patent document 3] "Oxidation-promoted Interfacial Synthesis of Redox-active Bis(diimino)nickel Nanosheet", Eunice JH Phua et al., Chem. Lett. 2018, 47, 126-129 [Non-patent document 4] "Stabilization of Hexaaminobenzene in a 2D Conductive Metal-Organic Framework for High Power Sodium Storage", Jihye Park et al., J. Am. Chem. Soc. 2018, 140, 10315-10323 [Non-Patent Document 5] "Air-Stability and Carrier Type in Conductive M3(Hexaaminobenzene)2, (M = Co, Ni, Cu)", Allison C. Hinckley et al., J. Am. Chem. Soc. 2020, 142, 11123-11130 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, Patent Document 1 and Non-Patent Documents 1 to 5 disclose bis(diimino)metal complex nanosheets, which have electrical conductivity and are expected to be used as electrode materials for capacitors, lithium-ion batteries, and the like.

[0008] On the other hand, metal complex nanosheets may have different structures even when using the same metal and ligands, and metal complex nanosheets with different structures can lead to the creation of nanosheets with new properties, which can be expected to lead to new technological developments.

[0009] Therefore, an object of the present disclosure is to provide a metal complex nanosheet having new properties. [Means for solving the problem]

[0010] The present inventors have studied a method for producing a metal complex nanosheet composed of a metal such as nickel or copper and hexaaminobenzene, and have discovered that by setting the concentration of the base agent used in synthesis at a liquid-liquid two-phase interface to a lower concentration than conventionally used, a metal complex nanosheet with a new structure can be obtained, leading to the present disclosure. Analysis of this metal complex nanosheet has confirmed that it has a structure different from conventional bis(diimino) metal complex nanosheets in that it contains a large number of amine structures, and further, surprisingly, it has been confirmed that it has proton conductivity not observed in conventional bis(diimino) metal complex nanosheets.

[0011] An example of this embodiment is as follows.

[0012] (1) A metal complex nanosheet including a metal-organic framework layer in which metal nuclei and organic ligands are coordinated so as to extend in the plane direction, The metal organic framework layer is a compound represented by the following formula (I): [ka] (In formula (I), each M is independently at least one selected from the group consisting of Cu, Ni, and Co; each of X1 to X6 is independently -NH- or -NH2-; and the dashed line represents a bond to a coordinating group in another structural unit.) The structural unit represented by the formula (1) is expanded in the plane direction. In the N1s XPS spectrum of the metal complex nanosheet, the area S of the peak due to the imine structure that appears around 397.4 eV NI The area S of the peak due to the amine structure that appears around 398.8 eV NA The ratio (S NA / S NI ) is 0.6 or more. (2) Peak area ratio (S NA / S NI ) is 0.7 or more. (3) The metal complex nanosheet according to (1) or (2), wherein the X-ray diffraction pattern of the metal complex nanosheet recorded at an X-ray wavelength of 0.8 Å includes peaks at diffraction angles (2θ) of 4.0±0.2, 8.0±0.2, and 14.3±0.2. (4) The metal organic framework layer is a compound represented by the following formula (II): [ka] (In formula (II), M is at least one selected from the group consisting of Cu, Ni, and Co, and X1 to X 12 are each independently -NH- or -NH2-, and the dashed lines indicate bonds to coordinating groups in other structural units. The metal complex nanosheet according to any one of (1) to (3), comprising a region in which structural units represented by the following formula are developed in the plane direction. (5) The metal organic framework layer is a compound represented by the following formula (III): [ka] (In formula (III), M is at least one selected from the group consisting of Cu, Ni, and Co, and X1 to X 36 are each independently -NH- or -NH2-, and the dashed lines indicate bonds to coordinating groups in other structural units. The metal complex nanosheet according to any one of (1) to (4), comprising a region in which structural units represented by the following formula are developed in the plane direction. (6) The metal organic framework layer is represented by the following formula (IV): [ka] (In formula (IV), M is at least one selected from the group consisting of Cu, Ni, and Co, and the dashed line indicates a bond to -NH- or -NH2- as a coordinating group in another structural unit.) The metal complex nanosheet according to any one of (1) to (5), comprising a region in which structural units represented by the following formula are developed in the plane direction. (7) The metal complex nanosheet according to any one of (1) to (6), which has proton conductivity. (8) A metal complex nanosheet including a metal-organic framework layer in which metal nuclei and organic ligands are coordinated so as to extend in the plane direction, the metal core is at least one selected from the group consisting of Cu, Ni, and Co; The organic ligand has the formula (A): [ka] or a salt thereof, The coordinating group bonded to the metal core is a group derived from the NH group of the organic ligand, and is a -NH- group or a -NH- group; Two adjacent coordinating groups in an organic ligand bind to one metal nucleus, One organic ligand coordinates to three metal nuclei at three positions, In the N1s XPS spectrum of the metal complex nanosheet, the area S of the peak due to the imine structure that appears around 397.4 eV NI The area S of the peak due to the amine structure that appears around 398.8 eV NA The ratio (S NA / S NI ) is 0.6 or more. (9) Peak area ratio (S NA / S NI ) is 0.7 or more. (10) The metal complex nanosheet according to (8) or (9), wherein the X-ray diffraction pattern of the metal complex nanosheet recorded at an X-ray wavelength of 0.8 Å includes peaks at diffraction angles (2θ) of 4.0±0.2, 8.0±0.2, and 14.3±0.2. (11) The metal complex nanosheet according to any one of (8) to (10), which has proton conductivity. (12) A method for producing a metal complex nanosheet according to any one of (1) to (11), preparing a first solution containing at least a metal compound as a source of metal nuclei and a first solvent; providing a second solution containing at least an organic ligand or a salt thereof and a second solvent; and A step of forming two phases, a phase containing a first solution and a phase containing a second solution, and forming a metal complex nanosheet at the interface between the two phases. Including, At least one of the first solution and the second solution further comprises a base agent; The method, wherein at least one of the first solution and the second solution further comprises an oxidizing agent. (13) The manufacturing method according to (12), wherein the first solution further contains an oxidizing agent and the second solution further contains a base agent. (14) The manufacturing method according to (12) or (13), wherein the content of the base agent in the first solution or the second solution is 5 mM or less. (15) The method according to any one of (12) to (14), wherein the content of the base agent in the first solution or the second solution is 1 mM or less. (16) The method according to any one of (12) to (15), wherein the basic agent is Na2CO3. (17) The method according to any one of (12) to (16), wherein the standard redox potential of the oxidizing agent is lower than the standard redox potential of chloranil. (18) The oxidizing agent was 2,5-dichloro-1,4-benzoquinone (DCBQ), 2,5-dimethyl-1,4-benzoquinone (DMBQ), 2,5-dimethoxy-1,4-benzoquinone (MeOBQ), 2,5-di-tert-butyl-1,4-benzoquinone ( t The method according to any one of (12) to (17), wherein the compound is at least one selected from the group consisting of tetramethylbenzoquinone (TMBQ), tetramethylbenzoquinone (TMBQ), and tetramethylbenzoquinone (TMBQ). (19) The method according to any one of (12) to (18), wherein the content of the oxidizing agent in the first solution or the second solution is 20 mM or less. [Effects of the Invention]

[0013] The present disclosure can provide a metal complex nanosheet having new properties, specifically, a metal complex nanosheet having proton conductivity that has not been observed in conventional bis(diimino)metal complex nanosheets. [Brief explanation of the drawings]

[0014] [Figure 1] AFM images of CuHAB film-1, CuHAB film-10, and CuHAB film-100. [Figure 2] TEM images of CuHAB film-1, CuHAB film-10, and CuHAB film-100. [Figure 3] IR spectra (a) of CuHAB film-1, CuHAB film-10, and CuHAB film-100, and expanded spectra (b) of the NH stretching vibration region. [Figure 4] XPS spectra of N1s in CuHAB film-1 (a), CuHAB film-10 (b), and CuHAB film-100 (c). [Figure 5] XPS spectra of Cu2p3 / 2 in CuHAB film-1 (a), CuHAB film-10 (b), and CuHAB film-100 (c). [Figure 6] 1 shows X-ray diffraction patterns measured for CuHAB film-1, CuHAB film-10, and CuHAB film-100, as well as simulation patterns based on a model structure. [Figure 7] The unit cell structure (left) and model structure of CuHAB film-1 (right) were created based on the X-ray diffraction pattern of CuHAB film-1. [Figure 8] The unit cell structure (right) and model structure (left) of CuHAB films-10 and 100 were created based on the X-ray diffraction patterns of CuHAB films-10 and 100. [Figure 9A] 1 is a graph showing the results of measuring the electrical conductivity of CuHAB film-1 by changing the humidity of the ambient atmosphere. [Figure 9B] 1 is a graph showing the results of measuring the electrical conductivity of CuHAB film-10 while changing the humidity of the ambient atmosphere. [Figure 9C] 1 is a graph showing the results of measuring the electrical conductivity of CuHAB Film-100 by changing the humidity of the ambient atmosphere. [Figure 10]Diffraction patterns obtained by GIXS measurement for the prepared CuDI-DCBQ, CuDI-DMBQ, CuDI-MeOBQ, and CuDI-TMBQ are shown. [Figure 11] 1 shows a diffraction pattern obtained by GIXS measurement of the metal complex nanosheet prepared in Reference Example D. [Figure 12] 1 shows a diffraction pattern obtained by GIXS measurement of the metal complex nanosheet prepared in Reference Example E. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present embodiment is a metal complex nanosheet including a metal-organic framework layer in which metal nuclei and organic ligands are coordinated so as to extend in the plane direction, and the metal-organic framework layer is represented by the following formula (I): [ka] (In formula (I), each M is independently at least one selected from the group consisting of Cu, Ni, and Co; each of X1 to X6 is independently -NH- or -NH2-; and the dashed line represents a bond to a coordinating group in another structural unit.) The area of ​​the peak derived from the imine structure that appears around 397.4 eV in the N1s XPS spectrum of the metal complex nanosheet is S NI The area S of the peak due to the amine structure that appears around 398.8 eV NA The ratio (S NA / S NI ) is 0.6 or more.

[0016] Furthermore, the present embodiment provides a metal complex nanosheet including a metal-organic framework layer in which a metal core and an organic ligand are coordinated so as to extend in a plane direction, wherein the metal core is at least one selected from the group consisting of Cu, Ni, and Co, and the organic ligand is represented by the formula (A): [ka] The coordination group bonded to the metal nucleus is a group derived from the NH2 group of the organic ligand, and is an -NH- group or an -NH2- group, two adjacent coordination groups in the organic ligand are bonded to one metal nucleus, one organic ligand is coordinated to three metal nuclei at three positions, and the area S of the peak derived from the imine structure that appears around 397.4 eV in the N1s XPS spectrum of the metal complex nanosheet NI The area S of the peak due to the amine structure that appears around 398.8 eV NA The ratio (S NA / S NI ) is 0.6 or more.

[0017] This embodiment can provide a metal complex nanosheet with new properties. Specifically, this embodiment can provide a metal complex nanosheet with proton conductivity not observed in conventional bis(diimino) metal complex nanosheets. The reason why the metal complex nanosheet according to this embodiment has proton conductivity is presumed to be as follows. First, as shown by the analysis by XPS measurement in this example, the metal complex nanosheet according to this embodiment contains more amine structures (-NH2-) than conventional bis(diimino) metal complex nanosheets. The conventional bis(diimino) metal complex nanosheets are not disclosed to contain amine structures, even when considering the use of "diimino" in their names and the structural formulas disclosed in Patent Document 1 and Non-Patent Documents 1 to 5. In this embodiment, the area S of the peak derived from the imine structure appearing near 397.4 eV in the N1s XPS spectrum of the metal complex nanosheet is NI The area S of the peak due to the amine structure that appears around 398.8 eV NA The ratio (S NA / S NI The characteristic that the "value of .gtoreq..times ...

[0018] Hereinafter, the metal complex nanosheet according to this embodiment will be described in detail with reference to the drawings as appropriate.

[0019] <Metal complex nanosheet> The metal complex nanosheet according to this embodiment includes a metal-organic framework layer in which metal nuclei and organic ligands are coordinated so as to extend in the plane direction. The metal-organic framework layer is usually present in a plurality of layers.

[0020] The metal core is at least one selected from the group consisting of Cu, Ni, and Co.

[0021] The metal organic framework layer is a compound represented by the following formula (I): [ka] (In formula (I), each M is independently at least one selected from the group consisting of Cu, Ni, and Co; each of X1 to X6 is independently -NH- or -NH2-; and the dashed line represents a bond to a coordinating group in another structural unit.) The structural unit represented by the formula (I) is expanded in the plane direction.

[0022] In the structural unit represented by formula (I), the coordinating group that coordinates to the metal nucleus is -NH- or -NH2-. In -NH-, one of the two bonds "-" is bonded to a benzene ring, and the structure has an imine structure. In addition, in the structural unit represented by formula (I), the two dashed lines extending from M indicate bonds to the coordinating group (-NH- or -NH2-) in another structural unit. X1 to X6 are each independently -NH- or -NH2-, and X1 to X6 are each independent of X1 to X6 in other structural units. That is, X1 to X6 are each independent for each structural unit.

[0023] In this embodiment, in the N1s XPS spectrum of the metal complex nanosheet, the area S of the peak derived from the imine structure appearing around 397.4 eV NIThe area S of the peak due to the amine structure that appears around 398.8 eV NA The ratio (S NA / S NI ) is 0.6 or more. As described above, as shown by the analysis by XPS measurement in this example, the metal complex nanosheet according to this embodiment contains more amine structures (-NH2-) than the conventional bis(diimino)metal complex nanosheet. The peak area ratio (S NA / S NI ) indirectly indicates the ratio of amine structures to imine structures, and indicates that the metal complex nanosheet according to this embodiment has a greater number of amine structures than conventional bis(diimino)metal complex nanosheets. It is believed that the presence of a greater number of amine structures allows the amino groups in the structure to contribute to the formation of hydrogen bonds with water molecules, resulting in the development of proton conductivity. The peak area ratio (S NA / S NI ) is preferably 0.7 or more, more preferably 0.8 or more, and even more preferably 0.9 or more. NA / S NI ) is not particularly limited, but is, for example, 5.0 or less, 4.0 or less, 3.0 or less, 2.0 or less, or 1.5 or less.

[0024] In this embodiment, Cu2p of the metal complex nanosheet 3 / 2 In the XPS spectrum of CuI The area S of the peak due to Cu(II) appearing around 933.9 eV CuII The ratio (S CuII / S CuI ) is preferably 3.0 or more. CuII The ratio (S CuII / S CuI ) is preferably 3.2 or more. CuII / S CuI ) is not particularly limited, but is, for example, 10.0 or less, 5.0 or less, or 4.0 or less.

[0025] In this embodiment, the X-ray diffraction pattern of the metal complex nanosheet preferably includes peaks at diffraction angles (2θ) of 4.0±0.2, 8.0±0.2, and 14.3±0.2 when measured using X-rays with a wavelength of 0.8 Å.

[0026] The metal organic framework layer in this embodiment is a compound represented by the following formula (II): [ka] (In formula (II), M is at least one selected from the group consisting of Cu, Ni, and Co, and X1 to X 12 are each independently -NH- or -NH2-, and the dashed lines indicate bonds to coordinating groups in other structural units. It is preferable that the structural unit represented by formula (II) contains a region that extends in the plane direction. In the structural unit represented by formula (II), the coordinating group that coordinates to the metal nucleus is -NH- or -NH2-. In -NH-, one of the two bonding bonds "-" is bonded to a benzene ring, and it has an imine structure. Furthermore, in the structural unit represented by formula (II), the two dashed lines extending from M indicate bonds to the coordinating group (-NH- or -NH2-) in another structural unit. X1 to X 12 are each independently -NH- or -NH2-, and X1 to X 12 is the X1 to X in other structural units 12 are independent of each other. That is, X1~X 12 are independent for each structural unit.

[0027] The metal organic framework layer in this embodiment is represented by the following formula (III): [ka] (In formula (III), M is at least one selected from the group consisting of Cu, Ni, and Co, and X1 to X 36 are each independently -NH- or -NH2-, and the dashed lines indicate bonds to coordinating groups in other structural units. It is preferable that the structural unit represented by formula (III) contains a region that extends in the plane direction. In the structural unit represented by formula (III), the coordinating group that coordinates to the metal nucleus is -NH- or -NH2-. In -NH-, one of the two bonding bonds "-" is bonded to a benzene ring, and it has an imine structure. Furthermore, in the structural unit represented by formula (III), the two dashed lines extending from M indicate bonds to the coordinating group (-NH- or -NH2-) in another structural unit. X1 to X 36 are each independently -NH- or -NH2-, and X1 to X 36 is the X1 to X in other structural units 36 are independent of each other. That is, X1~X 36 are independent for each structural unit.

[0028] The metal organic framework layer in this embodiment is represented by the following formula (IV): [ka] (In formula (IV), M is at least one selected from the group consisting of Cu, Ni, and Co, and the dashed line indicates a bond to -NH- or -NH2- as a coordinating group in another structural unit.) It is preferable that the structural unit represented by formula (IV) includes a region in which a structural unit represented by formula (IV) is expanded in the plane direction. In the structural unit represented by formula (IV), the coordinating group coordinated to the metal nucleus is -NH- or -NH2-. In -NH-, one of the two bonds "-" is bonded to a benzene ring, and it has an imine structure. Furthermore, in the structural unit represented by formula (IV), the two dashed lines extending from M indicate bonds to the coordinating group (-NH- or -NH2-) in another structural unit. In the region having the structural unit represented by formula (IV), the number (or number of moles) of -NH- groups and the number (or number of moles) of -NH2- groups can be equal.

[0029] In this embodiment, the organic ligand has the formula (A): [ka] The organic ligand referred to here corresponds to the one before bonding with the metal nucleus.

[0030] The coordinating group bonded to the metal nucleus is a group derived from the NH group of the organic ligand, and is an -NH- group or an -NH- group. That is, the NH group of the organic ligand represented by formula (A) functions as a coordinating group and is bonded to the metal nucleus as an -NH- group or an -NH- group.

[0031] In the organic ligand represented by formula (A), two adjacent NH2 groups act as coordinating groups and bond to one metal nucleus, and one organic ligand coordinates to three metal nuclei at three positions (two adjacent NH2 groups correspond to one position).

[0032] The metal complex nanosheet according to this embodiment has proton conductivity. Specifically, the electrical conductivity of the metal complex nanosheet according to this embodiment increases as the environmental humidity increases, and decreases as the environmental humidity decreases. This indicates that the metal complex nanosheet has proton conductivity. The reason why the metal complex nanosheet according to this embodiment has proton conductivity is thought to be that the amino groups in the structure contribute to the formation of hydrogen bonds with water molecules, resulting in the development / increase of proton conductivity. Conventional metal complex nanosheets do not exhibit significant changes in electrical conductivity depending on humidity. The conductivity of the metal complex nanosheet according to this embodiment is, for example, 1.0 to 3.5 × 10 when measured in an environmental atmosphere at a temperature of 25°C and a humidity of 10%. -5 The conductivity of the metal complex nanosheet according to this embodiment, when measured in an ambient atmosphere at a temperature of 25°C and a humidity of 75%, is greater than the value measured in an ambient atmosphere at a temperature of 25°C and a humidity of 10%.

[0033] <Method of manufacturing metal complex nanosheets> The metal complex nanosheet according to this embodiment can be obtained by reacting a metal nucleus with an organic ligand under oxidizing conditions. Preferably, the metal complex nanosheet according to this embodiment can be obtained by reacting a metal nucleus with an organic ligand at a liquid-liquid interface in the presence of an oxidizing agent and a base. A preferred embodiment of the method for producing a metal complex nanosheet according to this embodiment will be described below.

[0034] The method for producing a metal complex nanosheet according to this embodiment includes the steps of preparing a first solution containing at least a metal compound as a source of metal nuclei and a first solvent, preparing a second solution containing at least an organic ligand or a salt thereof and a second solvent, and forming two phases, one containing the first solution and the other containing the second solution, and forming a metal complex nanosheet at the interface between the two phases, wherein at least one of the first solution and the second solution further contains a base agent, and at least one of the first solution and the second solution further contains an oxidizing agent.

[0035] (First solution preparation step) The manufacturing method according to this embodiment includes a step of preparing a first solution containing at least a metal compound as a supply source of metal nuclei and a first solvent.

[0036] The metal compound is a compound containing Cu, Ni, or Co, which serves as a metal nucleus. The metal compound is not particularly limited, and examples thereof include acetates, chlorides, sulfates, tetrafluoroborates, hexafluorophosphates, perchlorates, acetylacetonate complexes, and ammine complexes, but are not limited thereto. The metal compound may preferably be a metal complex. One type of metal compound may be used alone, or two or more types may be used in combination.

[0037] The first solvent is one capable of dissolving a metal compound, and when the first solvent contains a base agent and / or an oxidizing agent, one capable of dissolving them is used. The first solvent and the second solvent are solvents that separate into two phases. One type of first solvent may be used alone, or two or more types may be used in combination.

[0038] The content of the metal compound in the first solution is not particularly limited and can be adjusted appropriately taking into consideration the type and concentration of the metal compound used, the film thickness of the target metal complex nanosheet, etc. The content of the metal compound in the first solution is not particularly limited, but is, for example, 0.01 to 5 mM.

[0039] The first solution preparation step is preferably carried out under oxygen-free conditions, for example, in an inert atmosphere such as an argon gas atmosphere or a nitrogen gas atmosphere.

[0040] (Second solution preparation step) The production method according to this embodiment includes a step of preparing a second solution containing at least an organic ligand or a salt thereof and a second solvent.

[0041] The organic ligand is hexaaminobenzene, and examples of the salt include inorganic acid salts such as hydrochloride, acetate, nitrate, sulfate, etc. The organic ligand or the salt thereof may be used alone or in combination of two or more.

[0042] The second solvent is one capable of dissolving the organic ligand or its salt. When the second solvent contains a base agent and / or an oxidizing agent, the second solvent is one capable of dissolving them. The second solvent and the first solvent are solvents that separate into two phases. The second solvent may be used alone or in combination of two or more.

[0043] The content of the organic ligand in the second solution is not particularly limited and can be adjusted appropriately taking into consideration the type and concentration of the metal compound used, the film thickness of the target metal complex nanosheet, etc. The content of the organic ligand in the second solution is not particularly limited, but is, for example, 0.01 to 5 mM.

[0044] The second solution preparation step is preferably carried out under oxygen-free conditions, for example, in an inert atmosphere such as an argon gas atmosphere or a nitrogen gas atmosphere.

[0045] (base agent) In this embodiment, at least one of the first solution and the second solution further contains a basic agent. In this embodiment, it is preferable that the second solution further contains a basic agent.

[0046] The basic agent contains a base and has the function of abstracting a proton from an organic ligand or a salt thereof during the reaction. In this embodiment, the basic agent promotes the reaction of forming an imine structure. The basic agent is not particularly limited as long as it contains a base and can serve as a source of base in a solution, and examples thereof include inorganic salts, inorganic bases, and organic bases. The inorganic salt used as the basic agent is not particularly limited, and examples thereof include alkali metal salts of bicarbonate ions such as potassium bicarbonate and sodium bicarbonate; alkali metal salts of carbonate ions such as potassium carbonate and sodium carbonate (Na2CO3); hydroxide salts such as sodium hydroxide and potassium hydroxide; and acetate salts such as sodium acetate. An example of an inorganic base is ammonia. An example of an organic base is amines such as triethylamine and ethylenediamine, or pyridine. One type of basic agent may be used alone, or two or more types may be used in combination.

[0047] In the preparation of the metal complex nanosheet according to this embodiment, the content (concentration) of the basic agent is an important factor, and it has been found that the concentration can affect whether the amino group of hexaaminobenzene becomes a coordinating group of an amine structure or an imine structure. This is presumably because the basic agent is involved in abstracting the hydrogen atoms of the amino group. That is, as the concentration of the basic agent increases, more hydrogen atoms are abstracted from the amino group, resulting in the formation of more coordinating groups of an imine structure. Conversely, as the concentration of the basic agent decreases, more hydrogen atoms are abstracted from the amino group than at higher concentrations, resulting in the formation of more coordinating groups of an amine structure. From these perspectives, the content of the basic agent in the first solution or the second solution is preferably 5.0 mM or less, more preferably 3.0 mM or less, more preferably 1.5 mM or less, and more preferably 1.0 mM or less. The lower limit of the content of the base agent in the first solution or the second solution is not particularly limited, but is, for example, 0.1 mM or more, or 0.3 mM or more.

[0048] (oxidizing agent) In this embodiment, at least one of the first solution and the second solution further contains an oxidizing agent. In this embodiment, it is preferable that the first solution further contains an oxidizing agent.

[0049] The oxidizing agent is not particularly limited as long as it has the effect of oxidizing the organic ligand. In this embodiment, it is presumed that the formation of nanosheets proceeds as a result of oxidation of a metal complex (bis(diamino)metal complex) formed by coordination of the organic ligand to the metal ion and the abstraction of protons by a base. The oxidizing agent is not particularly limited, but examples thereof include benzoquinones, triarylamines, ferrocenium salts, iodine, and potassium ferricyanide. One type of oxidizing agent may be used alone, or two or more types may be used in combination.

[0050] In this embodiment, it is preferable to use an oxidizing agent having a standard redox potential lower than that of chloranil (E1: 0.22 [V]). Specifically, in this embodiment, it is preferable that the oxidizing agent used has a standard redox potential lower than 0.22 V. By using an oxidizing agent having a standard redox potential lower than 0.22 V, rapid progress of the oxidation reaction can be suppressed, and metal complex nanosheets with excellent crystallinity can be effectively obtained. Furthermore, in this embodiment, it is preferable to use an oxidizing agent having a standard redox potential lower than that of chloranil (E1: 0.22 [V]) and higher than that of tetramethylbenzoquinone (E1: −0.69 [V]). Specifically, in this embodiment, it is preferable that the oxidizing agent used has a standard redox potential higher than −0.69 V and lower than 0.22 V. By using an oxidizing agent having a standard redox potential higher than −0.69 V, the generation of by-products (e.g., CuO) can be effectively suppressed.

[0051] The oxidation-reduction potential of an oxidizing agent can be calculated from the value of the standard oxidation-reduction potential of the oxidizing agent measured with reference to a normal hydrogen electrode (NHE) using the Nernst equation.

[0052] In this embodiment, it is preferable to use a benzoquinone-based oxidizing agent (benzoquinones). Examples of standard oxidation-reduction potentials of benzoquinone-based oxidizing agents are shown below.

[0053] [Table 1]

[0054] The benzoquinone-based oxidizing agent is not particularly limited, but examples thereof include chloranil, 2,5-dichloro-1,4-benzoquinone (DCBQ), 2,5-dimethyl-1,4-benzoquinone (DMBQ), 2,5-dimethoxy-1,4-benzoquinone (MeOBQ), 2,5-di-tert-butyl-1,4-benzoquinone ( tExamples of suitable oxidizing agents include benzoquinone, benzoquinone-based oxidizing agents, benzoquinone-based oxidizing agents, and tetramethylbenzoquinone. The oxidizing power of these oxidizing agents decreases in the order listed. The benzoquinone-based oxidizing agents may be used alone or in combination of two or more.

[0055] The content of the oxidizing agent in the first solution or the second solution is not particularly limited, but is, for example, 0.1 to 100 mM. The content of the oxidizing agent in the first solution or the second solution is preferably 0.1 to 20 mM, more preferably 0.3 to 15 mM, and even more preferably 0.5 to 10 mM. When the concentration of the oxidizing agent is 0.1 mM or more, the oxidation reaction can be efficiently promoted. Furthermore, when the concentration of the oxidizing agent is 20 mM or less, the generation of by-products in the oxidation reaction can be efficiently suppressed.

[0056] (Reaction step) The production method according to this embodiment includes the steps of forming two phases, a phase containing a first solution and a phase containing a second solution, and forming a metal complex nanosheet at the interface between the two phases.

[0057] The reaction step can be carried out by introducing the first and second solutions into a vessel so that two separate phases, a phase containing the first solution and a phase containing the second solution, are formed. For example, two separate phases can be formed by introducing one solution into a vessel to form a lower layer, and then gently placing the other solution on top of it without disturbing the lower layer to form an upper layer. Alternatively, two separate phases can be formed by placing a solvent on top of the lower layer that is incompatible / poorly miscible with the lower layer but compatible / readily miscible with the solution to be placed in the upper layer, and then introducing the solution that will become the upper layer into that solvent. The specific gravities of the resulting first and second solutions will vary depending on the first and second solvents used. The solution with the higher specific gravity is introduced into the vessel first, followed by the solution with the lower specific gravity, resulting in separation into two phases.

[0058] The reaction time is not particularly limited and can be selected appropriately, but the reaction time is, for example, 1 hour to 20 days, preferably 2 hours to 15 days, preferably 3 hours to 10 days, and preferably 5 hours to 5 days.

[0059] The reaction temperature is not particularly limited and can be selected appropriately. For example, the reaction temperature can be set to any temperature within the range from the melting point to the boiling point of the solvent.

[0060] The reaction step is preferably carried out under oxygen-free conditions, for example, in an inert atmosphere such as an argon gas atmosphere or a nitrogen gas atmosphere.

[0061] After the reaction step, a step of washing the obtained metal complex nanosheet may be performed. For example, an ammonia-containing solution can be used as the washing liquid. The ammonia concentration is, for example, 0.1 to 15 M, preferably 0.2 to 10 M, and more preferably 0.3 to 8 M. For example, an aqueous solvent can be used as the solvent. Examples of the aqueous solvent include water and alcohol (e.g., ethanol).

[0062] By the above steps, a metal complex nanosheet can be obtained. [Example]

[0063] The present embodiment will be described below with reference to examples, but the present embodiment is not limited to these examples.

[0064] (material) Metal source: Copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate) (Cu(TMHD)2)

[0065] [ka]

[0066] Organic ligand source: hexaaminobenzene trihydrochloride (HAB·3HCl) (synthesized according to Non-Patent Documents S1 or S2 below or purchased from Toronto Research Chemicals)

[0067] [ka]

[0068] Oxidizing agent: 2,5-di-tert-butyl-1,4-benzoquinone (commercially available, manufactured by Aldrich) · Base agent: Sodium carbonate (Na2CO3) Water: Purified with Autopure WD500 (Yamato Scientific) was used. Organic solvent: HPLC grade for synthesis (Kanto Chemical Co., Ltd.)

[0069] Non-patent document S1: Z.-G. Tao, X. Zhao, X.-K. Jiang and Z.-T. Li. Tetra. Lett. 2012, 53, 1840 Non-patent document S2: J. Mahmood, D. Kim, I.-Y. Jeon, MS Lah and J.-B. Baek. Synlett. 2013, 24, 246

[0070] Conventionally, when synthesizing bis(diimino)metal complex nanosheets, an oxidation process is required during the complex formation reaction, and in conventional synthesis reactions to obtain bis(diimino)metal complex nanosheets, a small amount of oxygen is introduced into the reaction system as an oxidizing agent. In the liquid-liquid two-phase interfacial synthesis method in this example, a benzoquinone-based oxidizing agent is used instead of oxygen as an oxidizing agent that can be easily introduced quantitatively.

[0071] Example 1 Under an argon atmosphere, an aqueous solution of HAB·3HCl (1 mM, 2.8 mg / 10 mL) and Na2CO3 (1 mM, 1.1 mg / 10 mL) was added to a solution of copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate) (Cu(TMHD)2) (2 mM, 8.6 mg / 10 mL) and 2,5-di-tert-butyl-1,4-benzoquinone ( t A dichloromethane solution of (BuBQ) (3 mM, 6.6 mg / 10 mL) was prepared. 5 mL of the dichloromethane solution was placed in a 20 mL vial, and then pure water (5 mL) was added on top of the dichloromethane solution to form an aqueous phase, forming a liquid-liquid interface. The aqueous solution (5 mL) was then gently added to the aqueous phase. The reaction vessel (vial) was left under an argon atmosphere without stirring. After one day, CuHAB formed as a black film at the interface. After the reaction, the upper aqueous phase was washed with water and replaced with ethanol. The lower organic phase was then removed to obtain CuHAB film-1 in ethanol solution. Note that the number after "-" in the sample name CuHAB film-1 indicates the NaCO concentration in the aqueous solution.

[0072] (Comparative Example 1) A CuHAB film-10 was prepared in the same manner as in Example 1, except that the Na2CO3 concentration in the aqueous solution was 10 mM.

[0073] (Comparative Example 2) A CuHAB film-100 was prepared in the same manner as in Example 1, except that the Na2CO3 concentration in the aqueous solution was 100 mM.

[0074] (analysis) The obtained samples (CuHAB film-1, CuHAB film-10, and CuHAB film-100) were analyzed and characterized by AFM and TEM observation, IR measurement, XPS measurement, and powder X-ray diffraction measurement.

[0075] [AFM and TEM observation] The topography of each sample was observed by AFM and TEM. AFM topography images were obtained using a scanning probe microscope (Agilent Technologies 5500) equipped with an NCH silicon cantilever (NanoWorld) in tapping mode. TEM images were obtained using a JEOL JEM-2100F microscope at an accelerating voltage of 200 kV. The obtained AFM and TEM images are shown in Figures 1 and 2, respectively.

[0076] AFM observation revealed that the film thickness of each sample was approximately 0.3 μm for CuHAB Film-1, and approximately 1.5 to 4 μm for CuHAB Film-10 and CuHAB Film-100. The CuHAB films synthesized under high base concentration conditions had larger thicknesses. It is believed that the reaction rate was faster under high base conditions, resulting in the formation of thicker films. Furthermore, CuHAB Film-100 had a rougher surface compared to CuHAB Film-1 and CuHAB Film-10. TEM observation also showed that CuHAB Film-1 contained crystalline regions approximately 50 nm in diameter, while CuHAB Film-10 had crystalline domains of 100 nm or larger. These values ​​are larger than the crystalline domain size (approximately 15 to 30 nm) of metal complex nanosheets synthesized using conventional one-phase solution reactions using hexaaminobenzene. Furthermore, Fourier transform analysis of the crystalline domains revealed six-fold symmetry. TEM observation revealed a periodicity of approximately 1.3 nm. For CuHAB Film-100, an aggregate of approximately 15 nm crystalline domains was observed. It is believed that the complexation reaction rate increased under high base concentration conditions, inhibiting the formation of large crystalline domains, resulting in the formation of CuHAB Film-100 as an aggregate of small domains. The rough surface observed with AFM for CuHAB Film-100 is likely due to the fact that it was formed as an aggregate of microcrystals.

[0077] [IR measurement] Each sample was analyzed by IR. CuHAB films pelletized with KBr were used as the measurement sample, and FT-IR spectra were obtained using an FT / IR-6100 (JASCO). The measurement samples were dried under vacuum for 30 minutes in the sample chamber of the spectrometer before IR measurement. The obtained IR spectra are shown in Figure 3. Figure 3 shows the IR spectra (a) and the expanded spectrum (b) of the NH stretching vibration region of CuHAB film-1 (labeled CuDI-1), CuHAB film-10 (labeled CuDI-10), and CuHAB film-100 (labeled CuDI-100).

[0078] In the obtained IR spectra, CuHAB film-1, CuHAB film-10, and CuHAB film-100 all had a peak in the range of 3750 to 3000 cm -1 A broad absorption at 1410cm originates from the NH stretching vibration. -1 The peak at 1200 cm is due to the C=C stretching vibration. -1 A peak due to the CN stretching vibration was measured in the NH stretching vibration region (Fig. 3). Only CuHAB film-1 exhibited a peak at 3160 cm -1 This peak suggests that some of the nitrogen atoms coordinated to the Cu center are in an amine structure.

[0079] [XPS measurement] Each sample was drop-cast onto a silicon substrate and analyzed by X-ray photoelectron spectroscopy (XPS). X-ray photoelectron spectra were measured using a PHI 5000 VersaProbe (ULVAC-PHI) equipped with an Al Kα source. Charge neutralization was performed using an argon ion gun during measurement. The binding energy of the obtained spectra was normalized using the carbon C1s peak at 284.6 eV. Spectra were analyzed using Multi Pack software, and peak separation was performed using the software's built-in peak fitting function.

[0080] Figure 4 shows the XPS spectra of N1s in CuHAB film-1(a), CuHAB film-10(b), and CuHAB film-100(c). Figure 5 shows the XPS spectra of Cu2p in CuHAB film-1(a), CuHAB film-10(b), and CuHAB film-100(c). 3 / 2 1 is an XPS spectrum of the above.

[0081] As shown in Figures 4 and 5, the presence of nitrogen and copper was confirmed in all of CuHAB Film-1, CuHAB Film-10, and CuHAB Film-100.

[0082] As shown in Figure 4, peak fitting for the N1s region reveals three different bonding states for the nitrogen atom, each of which is a nitrogen atom coordinated to the Cu center in an imine structure (C-NH - It is thought that there are nitrogen atoms in the amine structure (C-NH2: 397.4 eV) that are coordinated to the Cu center, and nitrogen atoms in the defect sites that are not coordinated to the Cu center (approximately 401 eV).

[0083] As shown in Figure 5, Cu2p 3 / 2 In the region, peaks due to Cu(I) were observed at 931.8 eV and Cu(II) at 933.9 eV, and peak fitting confirmed the presence of Cu(I) and Cu(II). The broad peak seen around 943 eV is a satellite peak of Cu(II).

[0084] Table 2 shows the area S of the peak (398.8 eV) derived from the amine structure (C-NH2) in the XPS spectrum of N1s shown in Figure 4. NA and imine structures (C-NH - ) derived peak (397.4 eV) area S NI , as well as Cu2p shown in FIG. 3 / 2 The area S of the peak (933.9 eV) derived from Cu(II) in the XPS spectrum of CuII and the area S of the peak (931.8 eV) derived from Cu(I). CuI Shows.

[0085] [Table 2]

[0086] Peak area S NA and peak area S NI are the amine structure (C-NH2) and the imine structure (C-NH - ) and the peak area ratio (S NA / S NI ) has an imine structure (C-NH - As shown in Table 2, the abundance ratio of the amine structure (C-NH2) to the C-NH - The abundance ratio of C-NH2 (amine structure) to C-NH2 (imine structure) is approximately 1 for CuHAB Film-1. Specifically, it is suggested that in CuHAB Film-1, half of the nitrogen atoms coordinated to the copper ions have an amine structure, and the remaining half have an imine structure. On the other hand, for CuHAB Film-10 and CuHAB Film-100, - The abundance ratio of C-NH2 (amine structure) to C-NH2 (imine structure) was approximately 0.3. These results indicate that CuHAB film-1 contains the most amine structure. This is consistent with the results suggested by IR measurements.

[0087] Peak area S CuII and peak area S CuI indicate the amounts of Cu(II) and Cu(I), respectively, and the peak area ratio (S CuII / S CuI ) indicates the abundance ratio of Cu(II) to Cu(I). As shown in Table 2, the abundance ratio of Cu(II) to Cu(I), i.e., the peak area ratio (S CuII / S CuI ) was approximately 3.4 for CuHAB Film-1. On the other hand, for CuHAB Film-10 and CuHAB Film-100, the abundance ratio of Cu(II) to Cu(I) was approximately 2.1 and 2.5, respectively. These results indicate that CuHAB Film-1 contains the highest proportion of Cu(II).

[0088] [Powder X-ray diffraction measurement] Powder X-ray diffraction (PXRD) measurements were performed on each of the obtained samples. Powder X-ray diffraction measurements were performed at BL44B2 of SPring-8 to obtain information on the periodic structures of CuHAB Film-1, CuHAB Film-10, and CuHAB Film-100. Powder X-ray diffraction (PXRD) measurements were performed using synchrotron radiation from the BL44B2 beamline (X-ray wavelength: 0.8 Å) of the Super Photon ring-8 (SPring-8). The samples for PXRD measurements were collected from CuHAB films in ethanol solution by centrifugation and dried under vacuum. The resulting powder samples were crushed in an agate mortar and then packed into a glass capillary. The capillary containing the sample was attached to the PXRD measurement apparatus and rotated at a constant speed during the measurement. Measurements were performed at room temperature, and diffraction patterns were recorded using a MYTHEN detector.

[0089] FIG. 6 shows the X-ray diffraction patterns measured for CuHAB film-1, CuHAB film-10, and CuHAB film-100, as well as the simulation patterns based on the model structure.

[0090] As shown in FIG. 6, diffraction patterns were confirmed in all of CuHAB film-1, CuHAB film-10, and CuHAB film-100, demonstrating that they all have a periodic structure.

[0091] Furthermore, the diffraction patterns obtained indicated that CuHAB film-1, synthesized under low base concentration conditions, had different periodic structures than CuHAB film-10 and CuHAB film-100, synthesized under high base concentration conditions. The IR and XPS measurements of CuHAB film-1 suggested that approximately half of the nitrogen atoms coordinated to the copper ions had amine structures, with the remaining nitrogen atoms forming imine structures. Based on this, a model unit cell (space group P31c, a = 13.2 Å, c = 6.38 Å) was created as shown in Figure 7. This model allowed us to reproduce the diffraction pattern observed for this structure, as shown in the simulated pattern in Figure 6.

[0092] The model structure of CuHAB film-1, shown in the boxed area on the right side of Figure 7, is composed of two adjacent layers, A and A', stacked together. The atoms in the A and A' layers are arranged in a point-symmetric relationship with respect to the center of the unit cell (metal nucleus). Therefore, the N atoms in the A' layer are arranged on top of the N atoms in the imine structure of the A layer, and these are stacked alternately with an interlayer distance of 3.19 Å. In this structure, hydrogen bonding between the layers is expected, and this interaction is thought to be the factor that forms the stacked structure.

[0093] In contrast, the diffraction patterns of CuHAB Film-10 and CuHAB Film-100 differ from those of CuHAB Film-1 and do not match the previously reported structures (P6 / mmm, Cmcm, C2221) for MDI nanosheets. Therefore, by creating a new periodic structure, a unit cell of space group Cm (a = 23.35 Å, b = 13.48 Å, c = 3.52 Å, β = 116.5°) as shown in Figure 8, we were able to reproduce the diffraction patterns of CuHAB Film-10 and CuHAB Film-100 (simulated pattern shown in Figure 6). This structure results in each CuHAB layer being stacked while shifting along the a-axis. CuHAB Film-10 and CuHAB Film-100, formed under highly basic conditions, contain a significantly higher proportion of N atoms in the imine structure, which weakens the stabilizing effect of interlayer hydrogen bonding, as in CuHAB Film-1. In addition, the XPS results above indicate that the proportion of Cu(I) is increased in CuHAB Film-10 and CuHAB Film-100, suggesting a greater electron density at the Cu center. In this environment, the presence of Cu atoms in adjacent layers directly above and below a Cu atom increases electronic repulsion, requiring each layer to shift to resolve this. Therefore, the decrease in interlayer interaction due to hydrogen bonding and the increase in electronic repulsion between layers at the copper complex sites likely led to the formation of a stacked structure in which each layer shifts in the a-axis direction, as shown in Figure 8.

[0094] In Figure 6, the X-ray diffraction pattern of CuHAB film-1 includes peaks at diffraction angles (2θ) of 4.0±0.2, 8.0±0.2, and 14.3±0.2. Also, in Figure 6, the X-ray diffraction patterns of CuHAB film-10 and CuHAB film-100 include peaks at diffraction angles (2θ) of 4.0±0.2, 4.3±0.2, 8.0±0.2, 8.8±0.2, and 14.6±0.2.

[0095] (evaluation) [Humidity response of electrical conductivity] For each sample, a piece of CuHAB film was drop-cast onto an interdigitated gold electrode, and the electrical conductivity was measured. The electrical conductivity was measured by alternating the humidity of the measurement environment between 10% and 75%. Figure 9 shows the results of measuring the electrical conductivity of CuHAB film-1 (Figure 9A), CuHAB film-10 (Figure 9B), and CuHAB film-100 (Figure 9C) at different humidity levels.

[0096] As shown in Figure 9A, the electrical conductivity of CuHAB Membrane-1 changed in response to the humidity of the measurement environment when the humidity was changed between 75% and 10%. Specifically, the electrical conductivity of CuHAB Membrane-1 increased as the humidity increased, and decreased as the humidity decreased. This result indicates that CuHAB Membrane-1 has proton conductivity. The reason for CuHAB Membrane-1's proton conductivity is thought to be that the amino groups in its structure contribute to the formation of hydrogen bonds with water molecules, resulting in the development / increase of proton conductivity. For CuHAB Membrane-10 and CuHAB Membrane-100, no significant change in electrical conductivity was observed even when the humidity was increased to 75%.

[0097] From the above results, it was confirmed that CuHAB membrane-1 has proton conductivity.

[0098] (Reference example A) As an oxidizing agent tThree types of metal complex nanosheets were prepared in the same manner as in Example 1, Comparative Example 1, or Comparative Example 2, except that TMBQ (tetramethylbenzoquinone) was used instead of Bu2BQ. Powder X-ray diffraction measurements were performed on these metal complex nanosheets, and the results were as follows: t As with the case of Bu2BQ, the diffraction pattern was found to change depending on the base concentration. Furthermore, the metal complex nanosheet obtained with 1 mM sodium carbonate showed a diffraction pattern similar to that of CuHAB film-1.

[0099] (Reference example B) As an oxidizing agent t A metal complex nanosheet was prepared in the same manner as in Example 1, except that chloranil was used instead of Bu2BQ. When this metal complex nanosheet was subjected to powder X-ray diffraction measurement, a diffraction pattern similar to that of CuHAB film-1 was obtained, although the peaks tended to be broad due to a decrease in crystallinity.

[0100] The results of Reference Examples A and B show that the metal complex nanosheet synthesized using tetramethylbenzoquinone, which has a weak oxidizing power, has a smaller half-width of the diffraction pattern and higher crystallinity. On the other hand, diffraction peaks derived from the by-product Cu2O were also observed in the metal complex nanosheet obtained using tetramethylbenzoquinone.

[0101] (Reference Example C: Examination of the relationship between oxidizing agents and the crystallinity of metal complex nanosheets) Reference Examples A and B demonstrate that the use of chloranil, which has a strong oxidizing power, tends to reduce the crystallinity of metal complex nanosheets, while the use of tetramethylbenzoquinone, which has a weak oxidizing power, improves the crystallinity of metal complex nanosheets but tends to result in the formation of Cu2O as a by-product. Therefore, by using an oxidizing agent with an oxidizing power between chloranil and tetramethylbenzoquinone, it is expected that metal complex nanosheets with high crystallinity can be synthesized while suppressing the formation of Cu2O. Furthermore, the oxidizing power of benzoquinone-based oxidizing agents can be adjusted by modifying their substituents. Therefore, 2,5-dichloro-1,4-benzoquinone (DCBQ), 2,5-dimethyl-1,4-benzoquinone (DMBQ), and 2,5-dimethoxy-1,4-benzoquinone (MeOBQ) were selected as candidate oxidizing agents. Examples of benzoquinone-based oxidizing agents are shown below. The oxidizing power of the benzoquinone-based oxidizing agents increases from left to right.

[0102] [ka]

[0103] Metal complex nanosheets were fabricated using a liquid-liquid two-phase interfacial synthesis method, including the following steps. First, 5 mL of ethyl acetate was gently layered on top of 5 mL of an aqueous solution containing 1 mM each of hexaaminobenzene trihydrochloride (HAB·3HCl) and Na2CO3. Next, 5 mL of an ethyl acetate solution containing 2 mM bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper (Cu(TMHD)2) and 3 mM of a benzoquinone-based oxidant (DCBQ, DMBQ, MeOBQ, or TMBQ) was added to the upper ethyl acetate layer and allowed to stand overnight for reaction. However, MeOBQ has low solubility, so it was used as a saturated solution. Under all synthesis conditions, a black film-like substance formed at the interface between the ethyl acetate and aqueous phases. After the reaction, the upper layer was washed with ethyl acetate and then replaced with ethanol. The lower aqueous phase was then completely removed, yielding metal complex nanosheets in ethanol. The sample names of the metal complex nanosheets are referred to as CuDI-DCBQ, CuDI-DMBQ, CuDI-MeOBQ, and CuDI-TMBQ, respectively.

[0104] Each of the resulting metal complex nanosheets was drop-cast onto a silicon substrate and subjected to GIXS measurements at 1.0 Å X-ray wavelength at SPring-8 BL05XU. Figure 10 shows the diffraction patterns obtained by GIXS for CuDI-DCBQ, CuDI-DMBQ, CuDI-MeOBQ, and CuDI-TMBQ. The half-widths of the peaks in the diffraction patterns for CuDI-DCBQ, CuDI-DMBQ, CuDI-MeOBQ, and CuDI-TMBQ were smaller than those of the metal complex nanosheets prepared using chloranil. This indicates that highly crystalline metal complex nanosheets can be formed using DCBQ, DMBQ, MeOBQ, and TMBQ, which have weaker oxidizing power than chloranil. In particular, the sample synthesized using MeOBQ, which has a relatively weak oxidizing power, exhibited high crystallinity comparable to that obtained using tetramethylbenzoquinone.

[0105] Because MeOBQ has low solubility in ethyl acetate and it was difficult to obtain a 3 mM solution, the same experiment was carried out using dichloromethane as the solvent. In addition, 2,5-di-tert-butyl-1,4-benzoquinone ( t Metal complex nanosheets were also synthesized as film-like materials using the liquid-liquid two-phase interfacial synthesis method using 2-methyl-2-butanol (BuBQ). GIXS measurements confirmed that highly crystalline films could be obtained regardless of the oxidizing agent used.

[0106] (Reference Example D: Examination of oxidizing agent concentration) Oxidizing agent introduced during synthesis t Metal complex nanosheets were synthesized at Bu2BQ concentrations of 1.5 mM, 3 mM, and 30 mM, with a Na2CO3 concentration of 100 mM, and the effect of oxidant concentration was investigated. Figure 11 shows the diffraction patterns obtained by GIXS measurement of the prepared metal complex nanosheets. Figure 11 shows that all metal complex nanosheets have periodicity and have similar structures under all conditions. A strong scattering pattern originating from Cu2O was observed in the sample synthesized at an oxidant concentration of 30 mM. This suggests that a side reaction producing Cu2O is more likely to occur at high oxidant concentrations.

[0107] (Reference Example E: Removal of CuO from metal complex nanosheets using an ammonia solution) Metal complex nanosheets showing the diffraction peak of CuO (synthesis conditions: tFlakes of a 30 mM Bu2BQ (Na2CO3; 100 mM) solution were immersed for one hour in five different solutions: aqueous ammonia (14 M, 7 M, or 1 M) or aqueous ammonia / ethanol (7 M or 1 M). When immersed in the aqueous solutions, the flakes were broken due to the effects of surface tension. After the reaction, the flakes were drop-cast onto a substrate and subjected to GIXS measurements at SPring-8 BL05XU. Figure 12 shows the diffraction patterns. The diffraction patterns derived from Cu2O disappeared in all GIXS measurements, indicating that Cu2O could be removed by aqueous ammonia or aqueous ammonia / ethanol. Furthermore, diffraction peaks derived from the metal complex nanosheets were observed even after immersion, indicating that the periodic structure was maintained.

[0108] Based on the above investigation, 2,5-dimethoxy-1,4-benzoquinone (MeOBQ), 2,5-di-tert-butyl-1,4-benzoquinone ( t By using relatively weak oxidizing agents such as tetramethylbenzoquinone (TMBQ) and tetramethylbenzoquinone (TMBQ), it was possible to obtain highly crystalline metal complex nanosheets. t When Bu2BQ was used as an oxidizing agent and its concentration was changed, no significant differences were observed in the crystallinity or periodic structure of the metal complex nanosheet film formed, but at high concentrations, diffraction patterns derived from Cu2O were observed, suggesting that side reactions were more likely to occur. Furthermore, X-ray diffraction confirmed that immersing the metal complex nanosheet film in an ammonia solution could remove the formed Cu2O while maintaining the periodic structure of the metal complex nanosheet.

[0109] (Addendum) In the present disclosure, as described above, it has been found that by using an oxidizing agent whose standard redox potential is lower than that of chloranil (E1: 0.22 [V]), the rapid progress of the oxidation reaction can be suppressed, and metal complex nanosheets with excellent crystallinity can be effectively obtained. Furthermore, in the present disclosure, as described above, it has been found that by using an oxidizing agent whose standard redox potential is higher than that of tetramethylbenzoquinone (E1: -0.69 [V]), the generation of by-products (e.g., CuO) can be effectively suppressed. Therefore, one aspect of this embodiment can also be described as follows.

[0110] [Appendix 1] A method for producing a metal complex nanosheet including a metal-organic framework layer in which metal nuclei and organic ligands are coordinated so as to extend in a plane direction, comprising: preparing a first solution containing at least a metal compound as a source of metal nuclei and a first solvent; providing a second solution containing at least an organic ligand or a salt thereof and a second solvent; and A step of forming two phases, a phase containing a first solution and a phase containing a second solution, and forming a metal complex nanosheet at the interface between the two phases. Including, At least one of the first solution and the second solution further comprises a base agent; At least one of the first solution and the second solution further comprises an oxidizing agent; and The standard redox potential of the oxidizing agent is lower than that of chloranil (E1: 0.22 [V]) and higher than that of tetramethylbenzoquinone (E1: -0.69 [V]), The metal organic framework layer is represented by the following formula (X): [ka] (In formula (X), each M is independently at least one selected from the group consisting of Cu, Ni, and Co; each of X1 to X6 is independently -NH- or -NH2-; and the dashed line represents a bond to a coordinating group in another structural unit.) The method includes a region in which a structural unit represented by the formula (I) is expanded in the planar direction. [Appendix 2] 2. The manufacturing method of claim 1, wherein the first solution further comprises an oxidizing agent and the second solution further comprises a base agent. [Appendix 3] The oxidizing agents were 2,5-dichloro-1,4-benzoquinone (DCBQ), 2,5-dimethyl-1,4-benzoquinone (DMBQ), 2,5-dimethoxy-1,4-benzoquinone (MeOBQ), 2,5-di-tert-butyl-1,4-benzoquinone ( t The production method according to claim 1 or 2, wherein the compound is at least one selected from the group consisting of tetramethylbenzoquinone (TMBQ), tetramethylbenzoquinone (TMBQ), and tetramethylbenzoquinone (TMBQ). [Appendix 4] 4. The production method according to any one of Appendices 1 to 3, wherein the content of the oxidizing agent in the first solution or the second solution is 30 mM or less, preferably 20 mM or less, and preferably 10 mM or less. [Appendix 5] The metal organic framework layer is represented by the following formula (Y): [ka] (In formula (Y), M is at least one selected from the group consisting of Cu, Ni, and Co, and X1 to X 12 are each independently -NH- or -NH2-, and the dashed lines indicate bonds to coordinating groups in other structural units. 5. The method according to any one of claims 1 to 4, wherein the structural unit represented by the formula (I) is developed in the planar direction. [Appendix 6] The metal organic framework layer has the following formula (Z): [ka] (In formula (Z), M is at least one selected from the group consisting of Cu, Ni, and Co, and X1 to X 36 are each independently -NH- or -NH2-, and the dashed lines indicate bonds to coordinating groups in other structural units. 6. The method according to any one of claims 1 to 5, wherein the structural unit represented by the formula (I) is developed in the planar direction.

[0111] The upper and / or lower limit values ​​of the numerical ranges described herein can be arbitrarily combined to define a preferred range. For example, the upper and lower limit values ​​of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limit values ​​of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limit values ​​of the numerical ranges can be arbitrarily combined to define a preferred range.

[0112] The claims that follow this written disclosure are expressly incorporated into this written disclosure herein, with each claim standing on its own as a separate embodiment. The present disclosure includes all instances in which an independent claim is replaced by its dependent claim. Furthermore, any additional embodiments derived from the independent claim and the subsequent dependent claims are also expressly incorporated into this written specification.

[0113] Those skilled in the art can use the above description to make the most of the present disclosure. The claims and embodiments disclosed herein are merely descriptive and exemplary and should not be construed as limiting the scope of the present disclosure in any way. With the aid of this disclosure, changes can be made to the details of the above embodiments without departing from the basic principles of the present disclosure. In other words, various modifications and improvements of the embodiments specifically disclosed in the above specification are within the scope of the present disclosure.

[0114] Although the present embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and even if there are design changes within the scope that do not deviate from the gist of this disclosure, they are included in this disclosure.

Claims

1. A metal complex nanosheet comprising a metal-organic framework layer in which metal nuclei and organic ligands are coordinated so as to extend in a plane direction, The metal organic framework layer is a compound represented by the following formula (IV): 【Chemistry 4】 (In formula (IV), M is at least one selected from the group consisting of Cu, Ni and Co, and the dashed line indicates a bond to —NH— or —NH 2 — as a coordinating group in another structural unit.) The structural unit represented by the formula (1) is expanded in the plane direction. In the N1s XPS spectrum of the metal complex nanosheet, the area S of the peak derived from the imine structure that appears around 397.4 eV ＮＩ The area S of the peak due to the amine structure appearing near 398.8 eV ＮＡ The ratio (S ＮＡ / S ＮＩ ) is 0.6 or more.

2. The metal complex nanosheet according to claim 1 , which has proton conductivity.

3. A method for producing the metal complex nanosheet according to claim 1 or 2, comprising: preparing a first solution containing at least a metal compound as a source of metal nuclei and a first solvent; providing a second solution containing at least an organic ligand or a salt thereof and a second solvent; and A step of forming two phases, a phase containing the first solution and a phase containing the second solution, and forming a metal complex nanosheet at the interface between the two phases. Including, At least one of the first solution and the second solution further comprises a base agent; The method, wherein at least one of the first solution and the second solution further comprises an oxidizing agent.

4. The method of claim 3 , wherein the first solution further comprises an oxidizing agent and the second solution further comprises a base agent.

5. The method according to claim 3, wherein the content of the basic agent in the first solution or the second solution is 5 mM or less.

6. The method according to claim 3, wherein the content of the basic agent in the first solution or the second solution is 1 mM or less.

7. The base agent is Na ２ CO ３ The method according to claim 3, wherein

8. 4. The method according to claim 3, wherein the standard redox potential of the oxidizing agent is lower than the standard redox potential of chloranil.

9. The oxidizing agent is 2,5-dichloro-1,4-benzoquinone (DCBQ), 2,5-dimethyl-1,4-benzoquinone (DMBQ), 2,5-dimethoxy-1,4-benzoquinone (MeOBQ), 2,5-di-tert-butyl-1,4-benzoquinone ( ｔ Bu ２ 4. The method according to claim 3, wherein the benzoquinone is at least one selected from the group consisting of tetramethylbenzoquinone (TMBQ), ... and tetramethylbenzoquinone (TMBQ).

10. 4. The method according to claim 3, wherein the content of the oxidizing agent in the first solution or the second solution is 20 mM or less.

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