Metal organic structure film and method for producing the same

Abstract

The present invention provides a metal-organic framework (MOF) film having a higher gas adsorption rate. The present invention pertains to a metal-organic framework film in which the surface is covered with protrusions and the average adjacent distance p of the protrusions is 1-100 nm.

Description

[Technical Field]

[0001] The present invention relates to a metal-organic framework film and a method for producing the same. [Background technology]

[0002] Conventionally, attempts have been made to recover gases such as carbon dioxide using adsorbents, such as metal-organic frameworks (MOFs) and amine compounds (Patent Documents 1 to 4).

[0003] For example, Patent Document 1 discloses that a metal oxide is used as a precursor, and this is converted into an MOF to form an MOF membrane.

[0004] Furthermore, for example, Patent Document 2 proposes a carbon dioxide absorbent in which an amine compound is supported on porous particles in which hydrophilic fibers and porous powder are combined with a hydrophilic binder. MOF is used as the porous powder. It is described that the voids (pore diameter) are set to 1 μm to 20 μm in order to improve the carbon dioxide adsorption rate.

[0005] Furthermore, for example, Patent Document 3 describes a carbon dioxide adsorption material in which polyamine is supported on a composite film of a metal oxide film and an MOF.

[0006] Furthermore, for example, Patent Document 4 describes that a silica-based gas adsorption material having pores of about 100 nm can provide an effect of improving the specific surface area (that is, an effect of increasing the CO2 adsorption sites (adsorption amount)). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Table 2017-519896 [Patent Document 2] Patent Publication No. 2018-187574 [Patent Document 3] WO2021 / 261271 [Patent Document 4] Patent Publication No. 2021-095306 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the inventors of the present invention have found that the conventional techniques have the following new problems. (1) In the techniques of Patent Documents 1 and 3, the MOFs had uniform pore shapes and high crystallinity, as shown in FIG. 13. Therefore, not only was the probability of contact between the MOF and gas relatively low, but the diffusion rate of gas G into the crystal interior was slow. As a result, there was a problem of a low gas adsorption rate. FIG. 13 is a schematic diagram of an MOF that shows the crystal structure of an MOF according to an example of conventional technology. In FIG. 13, MA represents a metal atom (particularly a metal atom ion), and OM represents an organic molecule.

[0009] (2) In the technology of Patent Document 2, a binder is used to form the gas adsorption material, and as shown in Figure 14, the binder component B enters the MOF pores, degrading the gas adsorption performance. This causes a problem of a low gas adsorption rate. Figure 14 is a schematic diagram of an MOF showing the crystal structure of another example of a conventional MOF. In Figure 14, MA represents a metal atom (particularly a metal atom ion), and OM represents an organic molecule.

[0010] (3) In the technology of Patent Document 4, gas does not penetrate into the interior of the silica-based gas adsorption material, so only the surface of the gas adsorption material contributes to gas adsorption, resulting in a slow gas adsorption rate.

[0011] The present invention aims to provide a metal-organic framework (MOF) membrane with a higher gas adsorption rate. [Means for solving the problem]

[0012] The present invention relates to a metal-organic structure film whose surface is covered with protrusions, and the protrusions have an average adjacent distance p of 1 nm or more and 100 nm or less.

[0013] The present invention also relates to a method for producing a metal-organic framework film, in which heating and ultrasonic waves are applied while a metal oxide is immersed in a solution containing organic molecules. [Effects of the Invention]

[0014] The metal-organic structure film of the present invention exhibits a higher gas adsorption rate. The metal-organic structure film of the present invention has a sufficiently large surface area, so the probability of contact with gas is relatively high. The metal-organic structure film of the present invention also has a sufficient and moderate number of lattice defects, so gas can easily enter the crystal lattice and diffuse easily. As a result, it is believed that the metal-organic structure film of the present invention has a sufficiently high gas adsorption rate. [Brief explanation of the drawings]

[0015] [Figure 1A] FIG. 1 is a schematic cross-sectional view illustrating an example of the structure of a metal oxide having a metal organic structure film of the present invention. [Figure 1B] FIG. 1B is a schematic enlarged perspective view of the metal-organic structure film for explaining the structure of the metal-organic structure film of the present invention, and is a schematic enlarged view of the X portion in FIG. 1A. [Figure 1C] 1 is a schematic diagram of a metal-organic framework showing the crystal structure of a metal-organic framework film according to the present invention. FIG. [Figure 1D] FIG. 1 is a schematic diagram of a metal-organic framework showing the crystal structure of a metal-organic framework film according to the present invention, which uses 2-methylimidazole as an organic molecule. [Figure 2A] FIG. 4 is a schematic plan view of an example of a gas sensor according to a second embodiment of the present invention. [Figure 2B] FIG. 4 is a schematic cross-sectional view of an example of a gas sensor according to a second embodiment of the present invention. [Figure 2C] 5A to 5C are schematic process diagrams illustrating a method for manufacturing a gas sensor according to a second embodiment of the present invention. [Figure 2D]FIG. 4 is a schematic plan view of an example of a multi-gas sensor according to a second embodiment of the present invention. [Figure 2E] FIG. 4 is a schematic cross-sectional view of an example of a multi-gas sensor according to a second embodiment of the present invention. [Figure 2F] FIG. 10 is a schematic view of an example of a gas adsorption filter according to a third embodiment of the present invention. [Figure 2G] FIG. 10 is a schematic diagram of an example of a gas removal device according to a fourth embodiment of the present invention. [Figure 3A] FIG. 1 is a schematic perspective view of a gas adsorption filter produced in an example. [Figure 3B] (1) shows the XRD spectrum of the metal-organic framework (ZIF-8) alone, (2) shows the XRD spectrum of a sample in which a metal-organic framework (ZIF-8) film is formed on zinc oxide (ZnO), and (3) shows the XRD spectrum of zinc oxide (ZnO) alone. [Figure 4A] 1 is an SEM photograph (5000x magnification) of a sample taken from the outer surface of the gas adsorption filter produced in Example 1. [Figure 4B] 1 is a further enlarged SEM photograph (200,000 times) of a portion of a sample taken from the outer surface of the gas adsorption filter produced in Example 1. [Figure 5A] 1 is an SEM photograph (5000x magnification) of a sample taken from the outer surface of the gas adsorption filter produced in Example 2. [Figure 5B] 1 is a further enlarged SEM photograph (200,000 times) of a portion of a sample taken from the outer surface of the gas adsorption filter produced in Example 2. [Figure 6A] 1 is an SEM photograph (5000x magnification) of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 1. [Figure 6B] 1 is a further enlarged SEM photograph (200,000 times) of a portion of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 1. [Figure 7A] 1 is an SEM photograph (1000x magnification) of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 2. [Figure 7B] 1 is a further enlarged SEM photograph (200,000 times) of a portion of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 2. [Figure 8A] 1 is an SEM photograph (5000x magnification) of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 4. [Figure 8B] 1 is a further enlarged SEM photograph (200,000 times) of a portion of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 4. [Figure 9A] 10 is an SEM photograph (5000x magnification) of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 5. [Figure 9B] 1 is a further enlarged SEM photograph (200,000 times) of a portion of a sample taken from the outer surface of the gas adsorption filter produced in Comparative Example 5. [Figure 10] 1 is a graph showing the evaluation results of a gas adsorption test carried out in Examples and Comparative Examples. [Figure 11] FIG. 1 is a schematic diagram of a metal-organic framework, showing the crystal structure of an actual metal-organic framework. [Figure 12] 10 is a graph showing the relationship between gap size and diffusion resistance. [Figure 13] FIG. 1 is a schematic diagram of a metal-organic framework showing a crystal structure of a metal-organic framework according to an example of the prior art. [Figure 14] FIG. 1 is a schematic diagram of a metal-organic framework showing a crystal structure of a metal-organic framework according to another example of the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0016] [First embodiment] A first embodiment of the present invention provides a metal-organic framework film (hereinafter, sometimes referred to as a MOF (metal-organic framework) film). The MOF film of the present invention has a surface covered with protrusions, and has a nanoprotrusion structure on the surface. Specifically, as shown in FIG. 1A, a MOF film 1 is typically disposed (or formed) on the surface of a metal oxide 2, and the surface of the MOF film 1 is covered with nano-sized protrusions 11 as shown in FIG. 1B. FIG. 1A is a schematic cross-sectional view illustrating an example of the structure of a metal oxide having a metal-organic framework film of the present invention. FIG. 1B is a schematic enlarged perspective view of a metal-organic framework film of the present invention, illustrating the structure of the metal-organic framework film, and is a schematic enlarged view of the X portion in FIG. 1A. In this specification, various elements in the drawings are merely shown schematically and exemplarily to facilitate understanding of the present invention, and the appearances, dimensional ratios, etc. may differ from the actual ones. Unless otherwise specified, the terms "up-down direction," "left-right direction," and "front-back direction" used directly or indirectly in this specification correspond to the directions corresponding to the up-down direction, left-right direction, and front-back direction in the drawing, respectively. Unless otherwise specified, the same symbols or symbols indicate the same components or the same meanings, and may have different shapes.

[0017] The surface being covered with protrusions means that a plurality of protrusions (or protruding portions) are formed relatively densely on one side of the MOF membrane 1 (usually the surface opposite the metal oxide 2 side (hereinafter sometimes referred to as the "outer surface")). Covering the surface with protrusions relatively increases the proportion of the MOF crystal surface (the portion where metal atoms or organic molecules are exposed), facilitating the penetration of gas into the MOF membrane. This improves the gas adsorption rate.

[0018] The degree of "density" of the protrusions is not particularly limited as long as the effects of the present invention are obtained. For example, as shown in the SEM images of Figures 4B and 5B taken in the Examples described below, the protrusions may be formed on the outer surface so densely that villi (i.e., villi) are present on the inner surface of the small intestine. Specifically, the average adjacent distance p of the protrusions is usually 1 nm or more and 100 nm or less, and from the viewpoint of further improving the gas adsorption rate, it is preferably 1 nm or more and 50 nm or less, more preferably 5 nm or more and 50 nm or less, even more preferably 10 nm or more and 30 nm or less, and particularly preferably 17 nm or more and 25 nm or less. If the average adjacent distance is too long, the gas adsorption rate will decrease.

[0019] The average adjacent distance p is the average value of the distance between any two adjacent protrusions, as shown in FIG. 1B, for example. Specifically, the distance between two protrusions may be the distance between the vertices of the two protrusions. In this specification, the average adjacent distance is the average value obtained by measuring the distance between two protrusions in each of 100 arbitrary pairs in an SEM image showing the cross section of the MOF membrane. An SEM image showing the cross section of the MOF membrane can be obtained by scraping the surface with a FIB (Focused Ion Beam) to expose the cross section and then performing SEM observation. The cross-sectional shape and the spacing between the protrusions can also be measured using a TEM (Transmission Electron Microscope) instead of an SEM.

[0020] A MOF membrane typically has protrusions 11 and bases 12 that support the protrusions 11, and both the protrusions 11 and the bases 12 are formed from MOFs.

[0021] The protrusions 11 usually have an average depth d of 1 nm or more and 100 nm or less. From the viewpoint of further improving the gas adsorption rate, the average depth d is preferably 1 nm or more and 50 nm or less, more preferably 5 nm or more and 50 nm or less, even more preferably 10 nm or more and 40 nm or less, and particularly preferably 20 nm or more and 30 nm or less.

[0022] The average depth d is a characteristic value relating to the depth (height) from the apex to the base 12 of the protrusion 11, as shown in FIG. 1B, for example. In this specification, the average depth d is the average value obtained by measuring the depth (height) of 100 random protrusions in an SEM image showing the cross section of the MOF membrane. The SEM image showing the cross section of the MOF membrane may be the same as the SEM image showing the cross section of the MOF membrane used to measure the average adjacent distance p.

[0023] The base 12 typically has an average film thickness t of 1 nm to 1000 nm, which, from the viewpoint of further improving the gas adsorption rate, is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, even more preferably 10 nm to 90 nm, sufficiently preferably 20 nm to 80 nm, and even more preferably 30 nm to 80 nm.

[0024] The average film thickness t is a characteristic value relating to the thickness at the base 12, as shown in FIG. 1B, for example. In this specification, the average film thickness t is the average value obtained by measuring the thickness directly below 100 random protrusions in an SEM image showing the cross section of the MOF membrane. The SEM image showing the cross section of the MOF membrane may be the same as the SEM image showing the cross section of the MOF membrane used to measure the average adjacent distance p.

[0025] The protrusions 11 may be formed relatively densely in at least a portion of the outer surface of the MOF membrane, and from the viewpoint of further improving the gas adsorption rate, it is preferable that the protrusions 11 are formed relatively densely over the entire outer surface (or the entire surface).

[0026] As shown in FIG. 1A, the MOF membrane 1 is typically disposed (or formed) directly on the surface of the metal oxide 2. Specifically, the MOFs in the MOF membrane 1 may be formed using metal atoms constituting the metal oxide 2. For this reason, the MOF membrane 1 may be referred to as an "altered membrane" (or "altered layer"). That is, the alteration of the "altered membrane" refers to chemical alteration of the metal oxide 2, and the "altered membrane" may be a membrane (or layer) in which MOFs are formed using metal atoms of the metal oxide 2. More specifically, at the interface (or between) between the metal oxide 2 and the MOFs in the MOF membrane 1, metal atoms shared by both the metal oxide and the MOFs are present. For example, at the interface, metal atoms constituting both the metal oxide and the MOFs are present. Furthermore, for example, in the altered membrane, the MOFs are formed while including metal atoms constituting the metal oxide. As a result, metal atoms are shared by both the metal oxide and the MOFs between the metal oxide and the MOFs (e.g., at the interface). In the present invention, the MOFs are formed on the surface of the metal oxide while sharing the metal atoms of the metal oxide, which sufficiently improves the adhesion of the MOF film. At the interface between the metal oxide 2 and the MOFs that make up the MOF film 1, the metal atoms are shared by the metal oxide and the MOFs.

[0027] The metal oxide 2 is not particularly limited as long as it is a metal oxide that can supply metal atoms that can constitute an MOF, and examples thereof include one or more metal oxides selected from the group consisting of zinc oxide, copper oxide, nickel oxide, iron oxide, indium oxide, and aluminum oxide. From the viewpoint of further improving the gas adsorption rate, the metal oxide 2 is preferably composed of zinc oxide.

[0028] In FIG. 1A, metal oxide 2 has a form in which two particles are connected, but it may have the form of a single particle, or a molded or sintered compact of multiple particles. The molded or sintered compact of multiple particles is produced by a known method such as extrusion molding and may contain a binder to bind the particles together. The molded or sintered compact of multiple particles is produced by sintering a molded or sintered compact of multiple particles and therefore does not contain a binder. From the viewpoint of further improving the gas adsorption rate, metal oxide 2 preferably has the form of a molded or sintered compact of multiple particles, and more preferably has the form of a molded or sintered compact. When metal oxide 2 has the form of a molded or sintered compact of multiple particles, it has a porous structure.

[0029] The average primary particle size of the particles constituting the metal oxide 2 is usually 1 μm or more and 25 μm or less, and from the viewpoint of further improving the gas adsorption rate, it is preferably 2 μm or more and 25 μm or less, more preferably 2 μm or more and 20 μm or less, even more preferably 5 μm or more and 20 μm or less, and particularly preferably 6 μm or more and 15 μm or less.

[0030] The average primary particle size of the metal oxide 2 can be determined by averaging the particle sizes of any 50 particles constituting the metal oxide 2 in an SEM image showing the cross section of the MOF membrane. The SEM image showing the cross section of the MOF membrane may be the same as the SEM image showing the cross section of the MOF membrane used to measure the average adjacent distance p.

[0031] In the present invention, since the MOF membrane 1 has a sufficiently high gas adsorption rate, the MOF membrane 1 alone may be referred to as the "gas adsorption material," or a material containing at least the MOF membrane 1 and a metal oxide supporting the MOF membrane 1 as components may be referred to as the "gas adsorption material."

[0032] The MOF membrane 1 is composed of MOFs, and typically consists solely of MOFs. The fact that the MOF membrane 1 is composed solely of MOFs means that it does not intentionally contain any substances other than MOFs, and may contain, for example, unintended substances and impurities such as metal atoms and organic molecules that constitute the MOFs.

[0033] Specifically, MOF membrane 1 is a porous membrane based on coordinate bonds between organic molecules and metal atoms, including metal atoms derived from metal oxide 2. More specifically, the MOFs constituting MOF membrane 1 are MOFs based on coordinate bonds between organic molecules and metal atoms, including metal atoms derived from metal oxide 2, and MOF membrane 1 is configured as a porous membrane. MOFs are crystalline complexes formed by organic molecules OM acting as ligands to bridge metal atoms (particularly metal atom ions) MA, as shown in Figure 1C, for example. MOFs are porous bodies based on coordinate bonds between organic molecules and metal atoms (particularly metal atom ions). It is not necessary for all metal atoms constituting a MOF to be shared by metal oxide 2; it is sufficient that at least the metal atoms of the MOF adjacent to the metal oxide (or at least the MOF near the metal oxide) are shared by the metal oxide. The shared state of the metal atoms of the MOF adjacent to the metal oxide can be confirmed by high-magnification observation (e.g., 1,000,000x or more) using a transmission electron microscope (TEM). FIG. 1C is a schematic diagram of an MOF that shows the crystal structure of the MOF film according to the present invention.

[0034] More specifically, for example, a MOF containing 2-methylimidazole (described below) as an organic molecule and a zinc atom as a metal atom may have a crystal structure as shown in FIG. 1D. In this case, one or more of the 18 zinc atoms MA shown in FIG. 1D may be shared by the metal oxide. FIG. 1D is a schematic diagram of a MOF that shows the crystal structure of a MOF film according to the present invention using 2-methylimidazole as an organic molecule. This structure is merely a schematic diagram, and the actual crystal structure is, for example, that described in the following document. ANH PHAN et al., “Synthesis, Structure, and Carbon Dioxide Capture Properties of Zeolitic Imidazolate Frameworks” (ACCOUNTS OF CHEMICAL RESEARCH 58 67 January 2010 Vol. 43, No. 1)

[0035] The organic molecules may be any organic molecules known in the field of MOFs as organic molecules capable of constituting MOFs. From the viewpoint of further improving the gas adsorption rate, the organic molecules preferably include one or more organic molecules selected from the group consisting of azole-based organic molecules, cyanide-based organic molecules, and carboxylic acid-based organic molecules. From the same viewpoint, the organic molecules more preferably include one or more organic molecules selected from the group consisting of azole-based organic molecules and cyanide-based organic molecules, and even more preferably include one or more organic molecules selected from the group consisting of azole-based organic molecules. Azole-based organic molecules (particularly imidazole-based organic molecules) have a faster gas (particularly carbon dioxide) adsorption rate because the organic molecule and metal atom are bonded via a nitrogen atom, as shown in FIG. 1D.

[0036] The azole-based organic molecules constituting the MOF include organic molecules selected from the group consisting of imidazole, benzimidazole, triazole, and purine. From the viewpoint of further improving the gas adsorption rate, imidazole, benzimidazole, and purine are preferred, imidazole and benzimidazole are more preferred, and imidazole is even more preferred.

[0037] The azole-based organic molecule may or may not have a substituent. The substituent that the azole-based organic molecule may have is, for example, one or more substituents selected from the group consisting of hydrophobic groups such as alkyl groups, halogen atoms, nitro groups, phenyl groups, pyridyl groups, and cyano groups; and hydrophilic groups such as amino groups and carboxyl groups. The alkyl group is, for example, an alkyl group having 1 to 5 carbon atoms (particularly 1 to 3). Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and an n-pentyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

[0038] From the viewpoint of further improving the gas adsorption rate, the azole-based organic molecules constituting the MOF are preferably selected from the group consisting of azole-based organic molecules that have no substituents and, even if they have a substituent, only have a hydrophobic group (particularly an alkyl group or a nitro group), and more preferably selected from the group consisting of azole-based organic molecules that have only a hydrophobic group (particularly an alkyl group).

[0039] Examples of azole-based organic molecules that constitute MOFs include imidazole-based molecules represented by the following general formula (1), benzimidazole-based molecules represented by the following general formula (2), triazole-based molecules represented by the following general formulas (3) and (4), and purine-based molecules represented by the following general formula (5).

[0040] [ka]

[0041] In formula (1), R 1 ~R 3 are each independently a hydrogen atom; a hydrophobic group such as an alkyl group, a halogen atom, a nitro group, a phenyl group, a pyridyl group, or a cyano group; or a hydrophilic group such as an amino group or a carboxyl group. From the viewpoint of further improving the gas adsorption rate, a hydrogen atom or the above-mentioned hydrophobic group is preferred, and a hydrogen atom, an alkyl group, a halogen atom, a nitro group, or a cyano group is more preferred. From the same viewpoint, in a more preferred embodiment, R 1 is a hydrogen atom, an alkyl group, or a nitro group, and R 2 and R 3is a hydrogen atom, an alkyl group, a halogen atom, or a nitro group. 1 is an alkyl group, and R 2 and R 3 is a hydrogen atom.

[0042] Specific examples of the imidazole-based molecule represented by general formula (1) include the following compounds. Imidazole, methylimidazole (especially 2-methylimidazole), ethylimidazole, nitroimidazole, aminoimidazole, chloroimidazole, bromoimidazole, imidazolecarbonitrile.

[0043] [ka]

[0044] In formula (2), R 11 ~R 15 are each independently a hydrogen atom; a hydrophobic group such as an alkyl group, a halogen atom, a nitro group, a phenyl group, a pyridyl group, or a cyano group; or a hydrophilic group such as an amino group or a carboxyl group. From the viewpoint of further improving the gas adsorption rate, a hydrogen atom or the above-mentioned hydrophobic group is preferred, and a hydrogen atom, an alkyl group, a halogen atom, a nitro group, or a cyano group is more preferred. From the same viewpoint, in a more preferred embodiment, R 11 , R 14 and R 15 is a hydrogen atom, and R 12 and R 13 are each independently a hydrogen atom, an alkyl group, a halogen atom, or a nitro group.

[0045] Specific examples of the benzimidazole-based molecule represented by general formula (2) include the following compounds: Benzimidazole, chlorobenzimidazole, dichlorobenzimidazole, methylbenzimidazole, bromobenzimidazole, nitrobenzimidazole, aminobenzimidazole, benzimidazole carbonitrile.

[0046] [ka]

[0047] In formula (3), R 21 ~R 22 are each independently a hydrogen atom; a hydrophobic group such as an alkyl group, a halogen atom, a nitro group, a phenyl group, a pyridyl group, or a cyano group; or a hydrophilic group such as an amino group or a carboxyl group. From the viewpoint of further improving the gas adsorption rate, a hydrogen atom or the above-mentioned hydrophobic group is preferred, and a hydrogen atom is more preferred.

[0048] Specific examples of the triazole-based molecule represented by general formula (3) include the following compounds. 1,2,3-triazole.

[0049] [ka]

[0050] In formula (4), R 31 ~R 32 are each independently a hydrogen atom; a hydrophobic group such as an alkyl group, a halogen atom, a nitro group, a phenyl group, a pyridyl group, or a cyano group; or a hydrophilic group such as an amino group or a carboxyl group. From the viewpoint of further improving the gas adsorption rate, a hydrogen atom or the above-mentioned hydrophobic group is preferred, and a hydrogen atom is more preferred.

[0051] Specific examples of the triazole-based molecule represented by general formula (4) include the following compounds. 1,2,4-triazole.

[0052] [ka]

[0053] In formula (5), R 41 ~R43 are each independently a hydrogen atom; a hydrophobic group such as an alkyl group, a halogen atom, a nitro group, a phenyl group, a pyridyl group, or a cyano group; or a hydrophilic group such as an amino group or a carboxyl group. From the viewpoint of further improving the gas adsorption rate, a hydrogen atom or the above-mentioned hydrophobic group is preferred, and a hydrogen atom is more preferred.

[0054] Specific examples of the purine molecule represented by general formula (5) include the following compounds: Pudding.

[0055] Examples of cyanide-based organic molecules that can be used include potassium ferricyanide, potassium ferrocyanide, and hydrocyanic acid. As the carboxylic acid-based organic molecule, terephthalic acid, benzenetricarboxylic acid, benzenedicarboxylic acid, etc. can be used.

[0056] The metal atoms constituting the MOF are metal atoms including those capable of constituting metal oxide 2, and are selected from the group consisting of, for example, zinc, copper, nickel, iron, indium, aluminum, cobalt, praseodymium, cadmium, mercury, and manganese atoms. From the viewpoint of further improving the gas adsorption rate, the metal atoms are preferably selected from the group consisting of zinc, cobalt, and iron atoms, more preferably zinc and cobalt atoms, and even more preferably zinc atoms. The compound that supplies such metal atoms is not particularly limited, and examples thereof include zinc nitrate, copper nitrate, aluminum nitrate, and nickel nitrate.

[0057] The combination of organic molecules and metal atoms in the MOF is not particularly limited. However, from the viewpoint of further improving the gas adsorption rate, the following combinations (C1) to (C3) are preferred, and the following combination (C1) is more preferred: Combination (C1) = a combination of an imidazole molecule represented by general formula (1) (particularly 2-methylimidazole and / or nitroimidazole) and one or more metal atoms selected from the group consisting of zinc atoms and iron atoms (particularly zinc atoms); Combination (C2) = a combination of an imidazole molecule represented by general formula (1) (particularly 2-methylimidazole and / or nitroimidazole) and one or more metal atoms (particularly zinc atoms) selected from the group consisting of zinc atoms and cobalt atoms; Combination (C3) = A combination of a benzimidazole molecule represented by general formula (2) and one or more metal atoms selected from the group consisting of zinc atoms and cobalt atoms.

[0058] The ratio of organic molecules to metal atoms in a MOF is not particularly limited, but is usually determined by the types of organic molecules and metal atoms that constitute the MOF. For example, an imidazole-based molecule (Im) (for example, an imidazole-based molecule represented by general formula (1)) and one or more divalent metal atoms (M) selected from the group consisting of zinc atoms, cobalt atoms, and iron atoms can be used. 1 ) is a MOF with the composition formula: M 1 (Im)2; Further, for example, a compound containing a benzimidazole-based molecule (bIm) (for example, a benzimidazole-based molecule represented by general formula (2)) and one or more divalent metal atoms (M 1 ) is a MOF with the composition formula: M 1 (bIm)2; Further, for example, a compound containing a triazole-based molecule (Tra) (for example, a triazole-based molecule represented by general formula (3) and / or (4)) and one or more divalent metal atoms (M) selected from the group consisting of zinc atoms, cobalt atoms, and iron atoms can be used. 1 ) is a MOF with the composition formula: M 1 It can be represented by (Tra)2; Furthermore, for example, a compound containing a purine-based molecule (Pur) (for example, a triazole-based molecule represented by general formula (5)) and one or more divalent metal atoms (M 1 ) is a MOF with the composition formula: M 1 It can be represented by (Pur)2. Further, for example, imidazole-based molecules (Im) (for example, imidazole-based molecules represented by general formula (1)) and benzimidazole-based molecules (bIm) (for example, benzimidazole-based molecules represented by general formula (2)) and one or more divalent metal atoms (M 1 ) is a MOF with the composition formula: M 1 (Im) x (bIm) y where x+y=2.

[0059] The MOFs constituting the MOF membrane 1 typically have pore diameters of 1 Å to 50 Å. MOFs with appropriate pore diameters can be used in terms of the characteristics appropriate for the application. For example, in the case of a sensor using the MOF membrane of the present invention, MOFs with pore diameters close to the size of the target gas molecules are desirable. In the case of a carbon dioxide sensor, MOFs with pore diameters of 2 to 5 Å, and more preferably 2 to 4 Å, which are close to the molecular diameter of carbon dioxide molecules (3.3 Å), are desirable. Furthermore, when a polyamine, such as polyethyleneimine, is supported to form a carbon dioxide adsorption filter, MOFs with pore diameters of 5 Å to 20 Å, and more preferably 10 Å to 15 Å, are preferred due to the unit structure of the polyamine.

[0060] The pore size depends on the types of organic molecules and metal atoms that make up the MOF, and can therefore be adjusted by selecting the types of organic molecules and metal atoms.

[0061] In this specification, the pore diameter is defined as "the diameter of the largest sphere that can contain each atom in a crystal when it is treated as a hard sphere with a van der Waals radius," and is the pore diameter when no molecules are contained in the pore. Therefore, the pore diameter can be calculated from the crystal structure. Such pore diameters are shown in Table 1 of the following document: p (Å), and the values given in the literature can be used: ANH PHAN et al., “Synthesis, Structure, and Carbon Dioxide Capture Properties of Zeolitic Imidazolate Frameworks” (ACCOUNTS OF CHEMICAL RESEARCH 58 67 January 2010 Vol. 43, No. 1)

[0062] The MOFs constituting the MOF membrane 1 may be, for example, the following MOFs: ZIF-1 (compositional formula: Zn(Im)2); ZIF-4 (compositional formula: Zn(Im)2); ZIF-7 (compositional formula: Zn(bIm)2); ZIF-8 (compositional formula: Zn(mIm)2); ZIF-9 (compositional formula: Co(bIm)2); ZIF-14 (compositional formula: Zn(eIm)2); ZIF-81 (compositional formula: Zn(cbIm)(nIm)); ZIF-75 (compositional formula: Co(mbIm)(nIm)); ZIF-77 (compositional formula: Zn(nIm)2); ZIF-81 (compositional formula: Zn(brbIm)(nIm)). Here, the abbreviations in the composition formula represent the following compounds. Im: imidazole, bIm: benzimidazole, mlm: methylimidazole, eIm: ethylimidazole, nIm: nitroimidazole, cbIm: chlorobenzimidazole, brbIm: bromobenzimidazole.

[0063] The MOF membrane 1 may contain an adsorbent. For example, the MOF membrane 1 may support an adsorbent within the crystal lattice that constitutes the MOF membrane. The adsorbent is not particularly limited as long as it can adsorb gas (particularly carbon dioxide gas), and any adsorbent used in the field of gas adsorption can be used. From the viewpoint of adsorbing carbon dioxide gas, it is preferable to use an amine compound as the adsorbent. The amine compound is not particularly limited as long as it has an amino group, and an amino group-containing organic compound is usually used. The weight-average molecular weight of the amino group-containing organic substance is not particularly limited and may be, for example, 100 or more. The weight-average molecular weight of the amino group-containing organic substance is 300 or more, preferably 500 or more, from the viewpoint of preventing a decrease in the carbon dioxide gas adsorption capacity due to volatilization. The upper limit of the weight-average molecular weight is not particularly limited, and the weight-average molecular weight may usually be 10,000 or less, particularly 1,000 or less. Specific examples of amino group-containing polymers include polyethyleneimine, polyamidoamine, and polyvinylamine. The amino group-containing polymer may be linear or branched, and is preferably branched from the viewpoint of further improving the carbon dioxide gas adsorption capacity.

[0064] From the viewpoint of further improving the adsorption capacity of carbon dioxide gas, the adsorbent is preferably polyethyleneimine, particularly branched polyethyleneimine.

[0065] The amine value of the amine compound (particularly the amino group-containing polymer) is not particularly limited, but is usually 15 to 25 mmol / g solid, and from the viewpoint of further improving gas (particularly carbon dioxide gas) adsorption, it is preferably 17 to 19 mmol / g solid.

[0066] The amine value is a value measured by a neutralization method, which is calculated from the amount of hydrochloric acid required to neutralize the amine compound.

[0067] In the present invention, the MOF film 1 preferably has a crystalline structure (or crystal lattice) but also has lattice defects, as shown in FIG. 1C. Lattice defects refer to the presence of missing metals and / or missing organic molecules in a portion (particularly a portion of the surface) of the crystal lattice of the MOF crystal. The presence of lattice defects in the MOF film 1 facilitates the penetration of gas molecules into the interior of the MOF film 1, resulting in a higher gas adsorption rate.

[0068] MOF membrane 1 can be produced by the following method: A metal oxide is immersed in a solution containing organic molecules, and is heated and exposed to ultrasonic waves. For example, the metal oxide and the organic molecule solution are brought into contact with each other in a container with a lid made of polypropylene or stainless steel, and are exposed to heat and ultrasonic waves.

[0069] The organic molecule is an organic molecule that constitutes the MOF membrane and may be selected from the organic molecules described above. The metal oxide is a metal oxide that can supply metal atoms that constitute the MOF film, and may be selected from the metal oxides described above.

[0070] The organic molecule concentration in the solution is not particularly limited as long as it can form a MOF, and may be, for example, 5 g / L or more, preferably 50 g / L or more, and more preferably 120 g / L or more. The upper limit of the organic molecule concentration is not particularly limited, and the concentration may usually be 200 g / L or less, particularly 150 g / L or less.

[0071] The solvent constituting the solution is not particularly limited as long as it is a solvent capable of dissolving the predetermined organic molecules, and examples thereof include organic solvents such as N,N-diethylformamide, N,N-dimethylformamide, methanol, and ethanol; and water.

[0072] The film is formed (e.g., immersed) under heating. The heating temperature is usually 40°C or higher, and from the viewpoint of further improving the gas adsorption rate, it is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 80°C or higher, and particularly preferably 140°C or higher. If the heating temperature is too low, protrusions will not form on the MOF film surface, and even if protrusions are formed, the average adjacent distance will be too long. This will result in a lower gas adsorption rate. The heating temperature may usually be 150°C or lower.

[0073] The heating time is not particularly limited as long as the MOF can be formed, and may be, for example, 1 hour or more and 100 hours or less, particularly 1.5 hours or more and 24 hours or less.

[0074] The membrane is formed (e.g., immersion) under ultrasonic application. The ultrasonic frequency is typically 30 kHz or higher. If the frequency is too low, protrusions will not form on the MOF membrane surface, and even if protrusions are formed, the average adjacent distance will be too long. This will result in a lower gas adsorption rate. There is no upper limit to the frequency, and the frequency may typically be 100 kHz or lower (particularly 50 kHz or lower).

[0075] Film formation (e.g., immersion) may or may not be performed under pressure. Examples of pressurization methods include heating in a lidded container made of polypropylene or stainless steel. The pressure applied is not particularly limited, and may be, for example, 1 atm or more and 2 atm or less, particularly 1.2 atm or more and 1.5 atm or less. The heating method is not particularly limited, and may be electrical heating, ultrasonic heating, or microwave heating.

[0076] When an adsorbent is supported on the MOF membrane 1, the adsorbent may be dissolved in a solution containing organic molecules, or the produced MOF membrane may be immersed in a solution containing the adsorbent. This allows the adsorbent to be supported within the crystal lattice of the MOF membrane after drying. From the viewpoint of further improving the gas adsorption rate, it is preferable to produce the MOF membrane by dissolving the adsorbent in a solution containing organic molecules, and more preferably, to immerse the MOF membrane produced by dissolving the adsorbent in a solution containing organic molecules in a solution containing the adsorbent. In either case, the concentration of the adsorbent in the solution is not particularly limited and may be, for example, 1% by volume or more. From the viewpoint of further improving the gas adsorption rate, it is preferably 5% by volume or more, more preferably 10% by volume or more. The upper limit of the adsorbent concentration is not particularly limited, and the adsorbent concentration may be, for example, 50% by volume or less (particularly 20% by volume or less).

[0077] When immersing the MOF membrane in a solution containing an adsorbent, the solvent of the solution is not particularly limited as long as it can dissolve the adsorbent. For example, water or organic solvents such as methanol, ethanol, and dimethylformamide may be used. The MOF membrane may be immersed in the solution containing the adsorbent multiple times. This immersion also provides a cleaning effect. While washing with a solvent that does not contain the adsorbent alone is acceptable, it is desirable to immerse the membrane in a solution containing the adsorbent and dry it at least finally to impregnate the adsorbent.

[0078] After forming the MOF film, it is preferable to remove residual solvent and adsorbed gas by heating. Heating is preferably carried out in a vacuum (or under reduced pressure). The heating temperature is not particularly limited and may be, for example, 40°C or higher, preferably 50°C or higher, and more preferably 80°C or higher. The upper limit of the heating temperature is not particularly limited and may usually be 100°C or lower. The drying time is not particularly limited and may be, for example, 1 minute or longer, preferably 10 minutes or longer, and more preferably 30 minutes or longer. The upper limit of the drying time is not particularly limited and drying may usually be 200 minutes or shorter (particularly 50 minutes or shorter).

[0079] By producing the MOF membrane 1 by the above-described method, protrusions can be formed on the MOF membrane surface at a predetermined average adjacent distance, and further, lattice defects can be appropriately formed in the crystal structure (or crystal lattice) of the MOF membrane.

[0080] [Second embodiment] A second embodiment of the present invention provides a sensor using the composite membrane structure according to the first embodiment. The sensor of the present invention may be a sensor for detecting gas (particularly carbon dioxide gas) or odor. In the sensor of the present invention, the gas adsorption rate of the MOF membrane is sufficiently improved, as in the first embodiment. Therefore, a sensor with high adsorption properties can be obtained, resulting in a highly reliable sensor (e.g., a gas sensor or an odor sensor).

[0081] In the sensor of the present invention, the MOF membrane can adsorb a large amount of gas due to its protrusions (preferably protrusions and lattice defects), and the adsorption amount changes depending on the ambient gas concentration. Therefore, the MOF membrane can function as a sensitive membrane of a gas sensor.

[0082] Specifically, the weight and electrical properties of the MOF change upon gas adsorption, making it possible to convert the amount of gas adsorption into an electrical signal, making it possible to use it as a gas sensor.

[0083] A preferred embodiment of the sensor of the present invention is as follows.

[0084] For example, it is preferable to use a device whose frequency changes depending on weight, such as a quartz crystal oscillator or an oscillator using piezoelectric ceramics, as the support. A weight-change type gas sensor can be fabricated by sequentially forming a layer of metal oxide 2 and an MOF film 1 on the support.

[0085] Furthermore, for example, a weight change type gas sensor can be fabricated by forming a zinc oxide layer (metal oxide 2 layer) and an MOF film 1 such as ZIF-8 on a quartz crystal oscillator (support) by the method of the first embodiment. The metal oxide 2 layer can be formed by, for example, plating, CVD, vapor deposition, sputtering, or other methods.

[0086] In this embodiment, the constituent material of the layer of metal oxide 2 is not limited to zinc oxide, but may be selected from metal oxides similar to the metal oxides described as the constituent material of metal oxide 2 in the first embodiment.

[0087] The constituent material of the MOF membrane 1 can be determined based on the target gas and the required sensitivity and selectivity. For example, imidazole-based MOFs such as ZIF-1, ZIF-4, ZIF-7, and ZIF-8 can be used as the MOFs constituting the MOF membrane 1.

[0088] In order to reduce the influence of humidity and improve the accuracy of the sensor, and to obtain a high response speed and recovery speed, a heater (particularly a heater for heating) may be built in to heat the MOF film.

[0089] By arranging multiple types of MOF materials in an array on different oscillators, it is possible to fabricate a multi-gas sensor that can simultaneously detect multiple types of gases. Such a multi-gas sensor can then be used as an odor sensor.

[0090] By forming a piezoelectric film and electrodes on a silicon substrate, then forming heater wiring and an MOF film on the metal oxide, and then etching the silicon substrate, it is possible to form a MEMS gas sensor or odor sensor with reduced power consumption.

[0091] An example of the gas sensor of the present invention is a MEMS gas sensor shown in Figures 2A and 2B, which are a schematic plan view and a schematic cross-sectional view, respectively, of an example of a gas sensor according to a second embodiment of the present invention.

[0092] 2A and 2B includes a layer of metal oxide 2 (not shown) formed on a piezoelectric vibrator 41 and an MOF film 43 included in the layer of metal oxide 2. Note that the layer of metal oxide 2 is omitted in FIG. 2B. The piezoelectric vibrator 41 corresponds to the support and includes a lower electrode 411, a piezoelectric film 412, and an upper electrode 413. The MOF film 43 corresponds to the MOF film 1 in the first embodiment.

[0093] The gas sensor 40 typically further includes a silicon substrate 44, a support film 45 formed on the silicon substrate 44, a heater wiring 46 formed on the support film 45, a heater electrode 47a and a vibrator electrode 47b, wire bond contact pads 47c formed on the heater electrode 47a and the vibrator electrode 47b, and an insulating layer 48 for insulating the heater wiring 46 from the piezoelectric vibrator 41.

[0094] In the gas sensor 40, CP1 is a connection terminal (positive) with the heater, CP2 is a connection terminal (negative) with the heater, CP3 is a connection terminal with the upper electrode of the vibrator, and CP4 is a connection terminal with the lower electrode of the vibrator. The wire bond contact pads 47c function as such connection terminals.

[0095] The gas sensor 40 can be manufactured, for example, by the following method. Specifically, as shown in FIG. 2C, a support film 45 is first formed on a silicon substrate 44 (step (1)). Next, a heater wiring 46, a heater electrode 47a, and a vibrator electrode 47b are formed on the support film 45, and wire bond contact pads 47c are formed on the heater electrode 47a and the vibrator electrode 47b (step (2)). Furthermore, an insulating layer 48 is formed to insulate the heater wiring 46 from a piezoelectric vibrator 41 (described later) (step (3)). A lower electrode 411 is formed on the insulating layer 48 (step (4)), a piezoelectric film 412 is formed on the lower electrode 411 (step (5)), and an upper electrode 413 is formed on the piezoelectric film 412 (step (6)). Then, a layer of metal oxide 2 (not shown) is formed on the upper electrode 413, and then an MOF film 43 is formed on the layer of metal oxide 2 (not shown). Part of the insulating layer 48 is etched to expose the wire bond contact pads 47c (step (7)). Thereafter, the components on the insulating layer 48 (MOF film 43, metal oxide 2 layer (not shown), upper electrode 413, piezoelectric film 412, and lower electrode 411) are partially etched (step (8)), and the silicon substrate 43 is partially etched (step (9)), thereby obtaining the sensor 40 (step (10)). FIG. 2C is a schematic process diagram showing an example of a method for manufacturing a gas sensor according to the second embodiment of the present invention.

[0096] The gas sensor 40 consumes less power.

[0097] An example of the multi-gas sensor of the present invention is the MEMS multi-gas sensor shown in Figures 2D and 2E, which are a schematic plan view and a schematic cross-sectional view, respectively, of an example of a multi-gas sensor according to a second embodiment of the present invention.

[0098] The multi-gas sensor 50 shown in FIGS. 2D and 2E includes a plurality (for example, four) of the gas sensors 40 shown in FIGS. 2A and 2B, and the four gas sensors 40 have MOF films containing different MOFs.

[0099] 2A and 2B, the multi-gas sensor 50 is manufactured in the same manner as the gas sensor 40, except that a plurality of (e.g., four) gas sensors 40 shown in FIGS. 2A and 2B are manufactured simultaneously, and the four gas sensors 40 have MOF films containing different MOFs. The MOFs of the four gas sensors 40 are different from each other and correspond to different gases.

[0100] The multi-gas sensor 50 consumes less power and can function as an odor sensor.

[0101] [Third embodiment] A third embodiment of the present invention provides a gas adsorption filter using the MOF membrane according to the first embodiment. The gas adsorption filter of the present invention may be a filter for adsorbing carbon dioxide gas. In the gas adsorption filter of the present invention, the gas adsorption rate of the MOF membrane is sufficiently improved, as in the first embodiment. Therefore, a highly reliable gas adsorption filter can be realized.

[0102] The gas adsorption filter of this embodiment has the same structure as the composite membrane structure of the first embodiment, except that an adsorbent material other than the MOF is attached to or supported on the surface of the MOF membrane.

[0103] A preferred embodiment of the gas adsorption filter of the present invention is as follows. As shown in FIG. 2F , the gas adsorption filter 60 includes a metal oxide layer 62 formed on a support 61 having a honeycomb structure, a MOF membrane 63 provided on the metal oxide layer 62, and an adsorbent 65 provided on the MOF membrane 63. In this embodiment, the metal oxide layer 62 corresponds to the layer of metal oxide 2 in the first embodiment. The MOF membrane 63 corresponds to the MOF membrane 1 in the first embodiment. The adsorbent 65 corresponds to the adsorbent in the first embodiment. FIG. 2F is a schematic diagram of an example of a gas adsorption filter according to a third embodiment of the present invention.

[0104] By using a support 61 having a honeycomb structure, the surface area of the support itself can be made extremely large. Moreover, as in the first embodiment, the gas adsorption rate is improved. Moreover, a larger number of MOFs can be attached or supported. Therefore, it is possible to attach or support a larger number of adsorbents 65 while maintaining the carbon dioxide gas adsorption rate per unit area. Therefore, the carbon dioxide gas adsorption capacity is significantly improved. In this embodiment, the metal oxide layer 62 acts as an adhesive layer, which sufficiently prevents the MOF film 63 from falling off, improving durability.

[0105] Specifically, in this embodiment, the effective surface area in contact with carbon dioxide is significantly increased due to the combined effect of the increased surface area caused by the honeycomb structure of the support 61, the surface irregularities due to the porosity and protrusions of the MOF membrane 63, and the increased surface area caused by the MOF crystals (internal irregularities (i.e., pores)). As a result, the carbon dioxide gas adsorption capacity is significantly improved. Moreover, by making the metal oxide layer porous, the carbon dioxide gas adsorption capacity can be further improved.

[0106] The use of azole-based organic molecules (especially imidazole-based organic molecules) or cyanide-based organic molecules as the organic molecules that make up the MOF membrane improves the water resistance of the MOF, making it more reliable even when supporting adsorbents (especially amino-group-containing polymers).

[0107] By forming the support 61 in a honeycomb structure, it is possible to improve the carbon dioxide adsorption capacity while maintaining the pressure loss.

[0108] The gas adsorption filter of this embodiment can be produced by forming a metal oxide layer 62 (a layer of "metal oxide 2" in the first embodiment) and an MOF thin film 63 ("MOF film 1" in the first embodiment) on a support 61, then removing the residual solvent and adsorbed gas by heating, and attaching or supporting the adsorbent 65. Heating is preferably carried out in a vacuum (or under reduced pressure).

[0109] The attachment or support of the adsorbent 65 can be achieved by impregnating the MOF membrane with an aqueous solution of the adsorbent (especially an amine compound) and then drying, thereby forming a film of the adsorbent 65 (especially an amine compound) on the MOF membrane.

[0110] [Fourth embodiment] A fourth embodiment of the present invention provides a gas removal device (or gas removal system) including the gas adsorption filter 60 according to the third embodiment. The gas removal device of the present invention may be a device (or system) for removing carbon dioxide gas. In the gas removal device of the present invention, as in the third embodiment, the gas adsorption rate of the MOF membrane is sufficiently improved, and for example, the adsorption capacity of carbon dioxide gas can be significantly improved. The present invention makes it possible to realize a small, energy-saving, low-cost, and highly reliable gas removal device (particularly a carbon dioxide gas removal device). The gas removal device of the present invention can also be used for general air conditioning.

[0111] As shown in Fig. 2G, the gas removal device 70 of this embodiment can release carbon dioxide gas inside the chamber to the outside through the following steps: Fig. 2G is a schematic diagram of an example of a gas removal device according to a fourth embodiment of the present invention.

[0112] Step (i): Indoor air is blown onto the gas adsorption filter 60 to adsorb carbon dioxide gas. Step (ii): The adsorbed carbon dioxide gas is released by blowing heated air onto the gas adsorption filter 60 or by heating the gas adsorption filter 60 . Step (iii): The released carbon dioxide gas is discharged outside.

[0113] In the gas removal device 70, as shown in FIG. 2G, the adsorption of carbon dioxide (step (i)) and the release and discharge (steps (ii) and (iii)) may be performed simultaneously using different positions on the adsorption filter 60. In this case, by rotating the adsorption filter 60, the release position can be changed to the discharge position, and the discharge position can be changed to the discharge position. As a result, the adsorption, release, and discharge of carbon dioxide gas can be performed continuously.

[0114] Alternatively, in the gas removal device 70, the adsorption of carbon dioxide (step (i)) and the release and discharge (steps (ii) and (iii)) may be performed sequentially using the same position on the adsorption filter 60.

[0115] The present invention as described above includes the following preferred embodiments. <1> A metal organic structure film, the surface of which is covered with protrusions, the protrusions having an average adjacent distance p of 1 nm or more and 100 nm or less. <2> The protrusions have an average depth d of 1 nm or more and 100 nm or less. <1> The metal organic structure film according to claim 1. <3> the metal organic framework film is disposed on a surface of a metal oxide; <1> or <2> The metal organic structure film according to claim 1. <4> a metal atom is shared by the metal oxide and the metal organic framework at the interface between the metal oxide and the metal organic framework constituting the metal organic framework film; <3> The metal organic structure film according to claim 1. <5> The metal-organic framework film is a porous film based on coordinate bonds between organic molecules and metal atoms including metal atoms derived from the metal oxide. <3> or <4> The metal organic structure film according to claim 1. <6> the organic molecule includes one or more organic molecules selected from the group consisting of an azole-based organic molecule, a cyanide-based organic molecule, and a carboxylic acid-based organic molecule; <5> The metal organic structure film according to claim 1. <7> The metal atoms include one or more metal atoms selected from the group consisting of zinc, copper, nickel, iron, indium, and aluminum. <5> or <6> The metal organic structure film according to claim 1. <8> The metal oxide comprises one or more metal oxides selected from the group consisting of zinc oxide, copper oxide, nickel oxide, iron oxide, indium oxide, and aluminum oxide; <3> ~ <7> 10. The metal organic structure film according to any one of the preceding claims. <9> The metal oxide has the form of particles, or a molded or sintered body of the particles. <3> ~ <8> Metal organic framework film on either <10> The particles have an average primary particle size of 2 μm or more and 25 μm or less. <9> The metal organic structure film according to claim 1. <11> The metal organic structure film has a thickness t of 10 nm or more and 1000 nm or less. <1> ~ <10> 10. The metal organic structure film according to any one of the preceding claims. <12> The metal organic structure constituting the metal organic structure film has a composition formula of Zn(mIm)2, <1> ~ <11> 10. The metal organic structure film according to any one of the preceding claims. <13> The metal organic framework film is a gas adsorption material. <1> ~ <12> 10. The metal organic structure film according to any one of the preceding claims. <14> an amine compound is contained in the metal organic framework film, The gas is carbon dioxide gas. <13> The metal organic structure film according to claim 1. <15> The amine compound is an amino group-containing polymer having a weight average molecular weight of 100 or more. <14> The metal organic structure film according to claim 1. <16> The amine compound is polyethyleneimine. <14> or <15> The metal organic structure film according to claim 1. <17> A method for producing a metal organic structure film, in which a metal oxide is immersed in a solution containing organic molecules, while being heated and subjected to ultrasonic waves. <18> <1> ~ <16> Manufacture of a metal organic structure film according to any one of the above. <17> 2. A method for producing the metal organic structure film according to claim 1 . <19> The heating is at 40°C or higher, The ultrasonic waves have a frequency of 30 kHz or more. <17> or <18> 2. A method for producing the metal organic structure film according to claim 1 .

[0116] The present invention will be described in more detail below based on specific examples, but the present invention is not limited to the following examples in any way. [Example]

[0117] Example 1 MOF membrane formation Zinc oxide powder (average primary particle size = 11 μm) and a binder were mixed, and the mixture was extruded into a honeycomb filter and sintered at 1000 °C (Figure 3A). This zinc oxide sintered body was used as a support, and a MOF membrane with nanoprotrusion structures was formed on its surface. Specifically, the support was immersed in an ethanol solution containing the raw materials for MOF synthesis (metal ions and organic molecules) and heated at 60 °C for 2 hours while applying 40 kHz ultrasound. The ethanol solution used contained 10 mM zinc nitrate hexahydrate, 10 mM 2-methylimidazole, and 10 vol% polyethyleneimine (average molecular weight = 600). The support was then immersed in an ethanol solution containing 10 vol% polyethyleneimine for 30 minutes for cleaning. The support containing the MOF membrane was then removed and dried at 80 °C for 30 minutes to obtain a filter.

[0118] ·Confirmation of MOF membrane by XRD spectrum A sample was taken from the outer surface of the filter, and X-ray diffraction (XRD) spectroscopy confirmed the formation of a ZIF-8 film (composition formula: Zn(mIm)2). Specifically, as shown in Figure 3B, in the filter obtained in Example 1 with a MOF film (ZIF-8) formed on a zinc oxide (ZnO) surface, the peaks in the XRD spectrum were the same as those of the ZIF-8 particles alone and the ZnO film alone, confirming that the filter was a composite structure containing both ZIF-8 and ZnO. In Figure 3B, (1) shows the XRD spectrum of the MOF (ZIF-8) alone, (2) shows the XRD spectrum of the sample with a MOF (ZIF-8) film formed on zinc oxide (ZnO), and (3) shows the XRD spectrum of zinc oxide (ZnO) alone.

[0119] - Confirmation of MOF membrane by SEM observation The surface of the obtained filter was observed using a scanning electron microscope (SEM). The SEM images shown in Figures 4A and 4B were obtained at different magnifications. In particular, the SEM image in Figure 4B revealed that protrusions were densely formed over the entire surface of the filter (MOF membrane surface). The cross section of the protrusions can be observed from the fractured areas in the MOF film. From the SEM images showing such cross sections, the average adjacent distance p and average depth d of the protrusions were measured. Specifically, the distance between two protrusions was measured for each of 100 pairs of adjacent protrusions, and the average adjacent distance p was calculated. Measurements were also made for 100 random protrusions, and the average depth d and average film thickness t were calculated. The average adjacent distance p was 20 nm, the average depth d was 25 nm, and the film thickness t was 20 nm.

[0120] Example 2 MOF membrane formation A filter was obtained in the same manner as in Example 1, except that zinc oxide powder having an average primary particle size of 1 μm was used.

[0121] ·Confirmation of MOF membrane by XRD spectrum X-ray diffraction (XRD) spectrum measurement was performed using the same method as in Example 1. As a result, it was confirmed that the peak of the X-ray diffraction (XRD) spectrum of the filter obtained in Example 2 was at the same position as the peak position of the ZIF-8 particle alone and the peak position of the ZnO film alone, and that it was a composite structure having both ZIF-8 and ZnO.

[0122] - Confirmation of MOF membrane by SEM observation Observation was performed with an SEM in the same manner as in Example 1. The magnification was changed to obtain the SEM images shown in Figures 5A and 5B. In particular, the SEM image in Figure 5B revealed that protrusions were densely formed over the entire surface of the filter surface (MOF membrane surface) of Example 2. The average adjacent distance p, average depth d, and average film thickness t of the protrusions were measured from the SEM image using the same method as in Example 1. Specifically, the distance between two protrusions was measured for each of 100 pairs of adjacent protrusions, and the average adjacent distance p was determined. Measurements were also performed for 100 random protrusions, and the average depth d and average film thickness t were determined. The average adjacent distance p was 15 nm, the average depth d was 10 nm, and the average film thickness t was 70 nm.

[0123] (Comparative Example 1) MOF membrane formation A filter was obtained in the same manner as in Example 1, except that no ultrasonic waves were applied when the support was immersed in the ethanol solution.

[0124] ·Confirmation of MOF membrane by XRD spectrum X-ray diffraction (XRD) spectrum measurement was performed using the same method as in Example 1. As a result, it was confirmed that the peak of the X-ray diffraction (XRD) spectrum of the filter obtained in Comparative Example 1 was at the same position as the peak position of the ZIF-8 particle alone and the peak position of the ZnO film alone, and that it was a composite structure having both ZIF-8 and ZnO.

[0125] - Confirmation of MOF membrane by SEM observation Observation was performed with an SEM in the same manner as in Example 1. The SEM images shown in Figures 6A and 6B were obtained at different magnifications. In particular, the SEM image in Figure 6B revealed that no protrusions were formed on the filter surface (MOF membrane surface) of Comparative Example 1, and that the MOF membrane surface was smooth. The average film thickness t was measured in the same manner as in Example 1. Specifically, the film thickness was measured at 100 random locations, and the average film thickness t was calculated. The average film thickness t was 70 nm.

[0126] (Comparative Example 2) MOF membrane formation A filter was obtained in the same manner as in Example 1, except that the heating temperature and ultrasonic frequency were set to room temperature (25° C.) and 28 kHz, respectively, when the support was immersed in the ethanol solution.

[0127] ·Confirmation of MOF membrane by XRD spectrum X-ray diffraction (XRD) spectrum measurement was performed using the same method as in Example 1. As a result, it was confirmed that the peak of the X-ray diffraction (XRD) spectrum of the filter obtained in Comparative Example 2 was at the same position as the peak position of the ZIF-8 particle alone and the peak position of the ZnO film alone, and that it was a composite structure having both ZIF-8 and ZnO.

[0128] - Confirmation of MOF membrane by SEM observation Observation was performed using an SEM in the same manner as in Example 1. The magnification was changed to obtain the SEM images shown in Figures 7A and 7B. In particular, the SEM image in Figure 7B revealed that protrusions were not densely formed over the entire surface of the filter surface (MOF membrane surface) of Comparative Example 2. The average adjacent distance p, average depth d, and average film thickness t of the protrusions were measured from the SEM image using the same method as in Example 1. Specifically, the distance between two protrusions was measured for each of 100 pairs of adjacent protrusions, and the average adjacent distance p was determined. Measurements were also performed for 100 random protrusions, and the average depth d and average film thickness t were determined. The average adjacent distance p was 200 nm, the average depth d was 20 nm, and the average film thickness t was 100 nm.

[0129] (Comparative Example 3) MOF membrane formation An attempt was made to obtain a filter using the same method as in Example 1, except that zinc oxide powder with an average primary particle size of 30 μm was used, but the support collapsed when immersed in an ethanol solution.

[0130] Comparative Example 4 MOF membrane formation A filter was obtained in the same manner as in Example 1, except that the heating temperature was room temperature, 25°C, when the support was immersed in the ethanol solution.

[0131] ·Confirmation of MOF membrane by XRD spectrum X-ray diffraction (XRD) spectrum measurement was performed by the same method as in Example 1. As a result, it was confirmed that the peak of the X-ray diffraction (XRD) spectrum of the filter obtained in Comparative Example 4 was at the same position as the peak position of the ZIF-8 particle alone and the peak position of the ZnO film alone, and that it was a composite structure having both ZIF-8 and ZnO.

[0132] - Confirmation of MOF membrane by SEM observation Observation was performed with an SEM in the same manner as in Example 1. The magnification was changed to obtain the SEM images shown in Figures 8A and 8B. In particular, the SEM image in Figure 8B revealed that protrusions were not densely formed over the entire surface of the filter surface (MOF membrane surface) of Comparative Example 4. The average adjacent distance p, average depth d, and average film thickness t of the protrusions were measured from the SEM image using the same method as in Example 1. Specifically, the distance between two protrusions was measured for each of 100 pairs of adjacent protrusions, and the average adjacent distance p was determined. Measurements were also performed for 100 random protrusions, and the average depth d and average film thickness t were determined. The average adjacent distance p was 200 nm, the average depth d was 20 nm, and the average film thickness t was 100 nm.

[0133] (Comparative Example 5) MOF membrane formation A filter was obtained in the same manner as in Example 1, except that the ultrasonic frequency was set to 28 kHz when the support was immersed in the ethanol solution.

[0134] ·Confirmation of MOF membrane by XRD spectrum X-ray diffraction (XRD) spectrum measurement was performed by the same method as in Example 1. As a result, it was confirmed that the peak of the X-ray diffraction (XRD) spectrum of the filter obtained in Comparative Example 5 was at the same position as the peak position of the ZIF-8 particle alone and the peak position of the ZnO film alone, and that it was a composite structure having both ZIF-8 and ZnO.

[0135] - Confirmation of MOF membrane by SEM observation Observation was performed with an SEM in the same manner as in Example 1. The SEM images shown in Figures 9A and 9B were obtained at different magnifications. In particular, the SEM image in Figure 9B revealed that no protrusions were formed on the filter surface (MOF membrane surface) of Comparative Example 5, and that the MOF membrane surface was smooth.

[0136] (Carbon dioxide gas adsorption test) Experimental method The filter sample was placed in a 12 L acrylic chamber, 24 mL of CO2 gas was introduced, and the CO2 concentration was monitored. ·result The results of measuring the CO2 concentration are shown in Figure 10. Figure 10 is a graph showing the evaluation results of the gas adsorption test carried out in the examples and comparative examples. In detail, the carbon dioxide adsorption amount in 30 minutes was as follows: Example 1: Concentration difference from without filter (2500 ppm) is 2400 ppm = 28.8 mL of CO2 adsorption; Example 2: CO2 adsorption with a concentration difference of 1800 ppm compared to the case without a filter (2500 ppm) = 21.6 mL; Comparative Example 1: Concentration difference from without filter (2500 ppm) is 350 ppm = 4.2 mL of CO2 adsorption; Comparison Example 2: CO2 adsorption with no filter (2500 ppm) is 450 ppm = 4.8 mL.

[0137] Thus, the presence of the nanoprotrusion structure increased the carbon dioxide adsorption rate. Furthermore, the carbon dioxide adsorption rate could be increased by appropriately increasing the zinc oxide particle size.

[0138] Consideration 1: Promotion of gas penetration into nanoprotrusion structures MOF membranes are composed of metal ions and organic molecules and typically have a crystal lattice without lattice defects, as shown in Figure 13. However, in reality, as shown in Figure 11, some lattice defects exist, and in these lattice defects, the lattice terminates in both metal and organic molecules, resulting in wider pores. Gas molecules can easily penetrate wider pores. The MOF membrane of the present invention has protrusions at a predetermined average adjacent distance, as shown in Figure 1C. This increases the surface area of the MOF membrane and moderately increases the number of lattice defects. This facilitates the penetration of gas molecules, and is believed to result in a higher gas adsorption rate as a gas adsorption filter. Figure 11 is a schematic diagram of an MOF, showing the crystal structure of an actual MOF.

[0139] Consideration 2: Improvement of gas adsorption rate due to voids between particles Large gaps between the particles that make up the support improve gas flow and the adsorption rate in gas adsorption filters. Figure 12 shows the diffusion resistance when gas flows through straight holes on a capillary. With a hole diameter of 1 μm or more, the diffusion resistance is small and the gas flows smoothly, improving the gas adsorption rate. In Example 2, the MOF filter made with zinc oxide particles having a particle size of 1 μm had gaps of less than 1 μm where they narrowed. On the other hand, in Example 1, the MOF filter made with zinc oxide particles having a particle size of 11 μm had gaps of 1 μm or more where they narrowed. This suggests that in Example 1, the gas adsorption rate was further improved by the effect of the gaps in addition to the effect of the nanoprotrusion structure. Figure 12 is a graph showing the relationship between gap size and diffusion resistance.

[0140] Consideration 3: Metal oxide particle size of the substrate In Example 1, even when a MOF film is formed on a molded body obtained by extruding and then sintering zinc oxide having a particle size of 11 μm, the shape is maintained to be the same as the shape before film formation (FIG. 3). In Comparative Example 3, when an MOF film was formed on a molded body obtained by extruding and sintering zinc oxide having a particle size of 30 μm, the film collapsed. It can be seen that when the particle size is 11 μm, the filter shape can be maintained even without a binder, but when the particle size is too large, the filter shape cannot be maintained. This is thought to be because if the particle size is too large, the contact area between particles is small, resulting in low strength, and the structure is destroyed by the load applied during MOF film formation, i.e., the application of ultrasound. On the other hand, when a MOF film with a nanoprotrusion structure is formed on a support, more MOF films are formed, especially in areas where the gaps between particles are narrow, as shown in Figure 1A. Therefore, it is clear that metal oxide particles (e.g., zinc oxide particles) with a diameter of 1 μm or larger are required to achieve a void size of 1 μm or larger. [Industrial Applicability]

[0141] The MOF membrane of the present invention and the gas adsorption material having the MOF membrane are useful for sensors (particularly gas or odor sensors), gas adsorption filters, and gas removal devices. [Explanation of symbols]

[0142] 1: Metal-organic framework film (MOF film) 2: Metal oxides 11: Protrusion 12: Base 40: Gas sensor 50: Multi-gas sensor 60: Gas adsorption filter 61:Support 62: Metal oxide layer 63: Metal-organic framework film (MOF film) 65: Adsorbent 70: Gas removal device

Claims

1. A metal organic structure film, the surface of which is covered with protrusions, the protrusions having an average adjacent distance p of 1 nm or more and 100 nm or less.

2. The metal organic structure film according to claim 1 , wherein the protrusions have an average depth d of 1 nm or more and 100 nm or less.

3. The metal-organic framework film according to claim 1 , wherein the metal-organic framework film is disposed on a surface of a metal oxide.

4. 4. The metal-organic structure film according to claim 3, wherein a metal atom is shared by the metal oxide and the metal-organic structure at the interface between the metal oxide and the metal-organic structure constituting the metal-organic structure film.

5. 4. The metal-organic structure film according to claim 3, wherein the metal-organic structure film is a porous film based on coordinate bonds between organic molecules and metal atoms including metal atoms derived from the metal oxide.

6. 6. The metal-organic structure film according to claim 5, wherein the organic molecules include one or more organic molecules selected from the group consisting of azole-based organic molecules, cyanide-based organic molecules, and carboxylic acid-based organic molecules.

7. 6. The metal organic structure film according to claim 5, wherein the metal atoms comprise one or more metal atoms selected from the group consisting of zinc, copper, nickel, iron, indium, and aluminum.

8. 4. The metal organic structure film according to claim 3, wherein the metal oxide comprises one or more metal oxides selected from the group consisting of zinc oxide, copper oxide, nickel oxide, iron oxide, indium oxide, and aluminum oxide.

9. The metal organic framework film according to claim 3 , wherein the metal oxide has the form of particles, or a molded or molded sintered body of the particles.

10. The metal organic structure film according to claim 9 , wherein the particles have an average primary particle size of 2 μm or more and 25 μm or less.

11. 2. The metal organic structure film according to claim 1, wherein the metal organic structure film has a thickness t of 10 nm or more and 1000 nm or less.

12. The metal organic framework constituting the metal organic framework film is Zn(mIm) 2 The metal-organic structure film according to claim 1 , having a composition formula:

13. The metal-organic framework film of claim 1 , wherein the metal-organic framework film is a gas adsorbing material.

14. an amine compound is contained in the metal organic framework film, The metal-organic framework film of claim 13 , wherein the gas is carbon dioxide gas.

15. 15. The metal organic structure film according to claim 14, wherein the amine compound is an amino group-containing polymer having a weight average molecular weight of 100 or more.

16. The metal organic structure film according to claim 14, wherein the amine compound is polyethyleneimine.

17. A method for producing a metal organic framework film, comprising the steps of: immersing a metal oxide in a solution containing organic molecules, heating the metal oxide, and applying ultrasonic waves to the metal oxide; A method for producing a metal organic structure film, comprising producing the metal organic structure film according to any one of claims 1 to 16.

18. The heating is at 40°C or higher, The method for producing a metal organic structure film according to claim 17, wherein the ultrasonic waves have a frequency of 30 kHz or more.

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