Metal organic structure film and method for producing same

Abstract

Provided is a metal organic structure (MOF) film having a higher gas adsorption rate. The present invention relates to a metal-organic structure film, the surface of which is covered with protrusions, and the protrusions have an average adjacent distance p of 1 nm or more and 100 nm or less.

Description

Technical Field

[0001] The present invention relates to a metal organic structure film and a method for manufacturing the same. Background Art

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

[0003] For example, Patent Document 1 discloses a method of forming a MOF film by using a metal oxide as a precursor and converting the metal oxide into MOF.

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

[0005] For example, Patent Document 3 describes a carbon dioxide adsorbent in which polyamine is supported on a composite membrane of a metal oxide membrane and MOF.

[0006] In addition, for example, Patent Document 4 describes that a silica-based gas adsorbent having pores of about 100 nm can provide an effect of improving the specific surface area (ie, an effect of increasing the CO 2 adsorption sites (adsorption amount)).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application No. 2017-519896

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2018-187574

[0011] Patent document 3: WO2021 / 261271

[0012] Patent Document 4: Japanese Patent Application Laid-Open No. 2021-095306 Summary of the invention

[0013] Problems to be solved by the invention

[0014] However, the inventors of the present invention have discovered that the conventional technology has the following new problems.

[0015] (1) In the techniques of Patent Documents 1 and 3, MOF such as Fig.13As shown in Figure 1, the pore shape is uniform and the crystallinity is high. Therefore, not only is the probability of contact between MOF and gas relatively low, but the diffusion rate of gas G into the crystal is also slow. As a result, there is a problem of low gas adsorption rate. Fig.13 This is a schematic diagram of MOF schematically showing the crystal structure of an example of MOF in the prior art. Fig.13 In the above, MA represents a metal atom (especially a metal atom ion), and OM represents an organic molecule.

[0016] (2) In the technology of Patent Document 2, since a binder is used to form the gas adsorbent, Fig.14 As shown, the binder component B enters into the MOF pores, deteriorating the gas adsorption performance. Therefore, there is a problem of low gas adsorption rate. Fig.14 FIG. 1 is a schematic diagram of MOF schematically showing the crystal structure of another example of MOF in the prior art. Fig.14 In the above, MA represents a metal atom (especially a metal atom ion), and OM represents an organic molecule.

[0017] (3) In the technology of Patent Document 4, since no gas penetrates into the interior of the silica-based gas adsorbent, only the surface of the gas adsorbent contributes to gas adsorption. Therefore, the gas adsorption rate is low.

[0018] An object of the present invention is to provide a metal organic structure (MOF) film having a higher gas adsorption rate.

[0019] Means for solving problems

[0020] The present invention relates to a metal organic structure film, the surface of which is covered with protrusions, wherein the protrusions have an average adjacent distance p of 1 nm to 100 nm.

[0021] The present invention also relates to a method for producing a metal organic structure film, comprising immersing a metal oxide in a solution containing organic molecules while applying heating and ultrasonic waves.

[0022] Effects of the Invention

[0023] The metal organic structure film of the present invention shows a higher gas adsorption rate. The surface area of ​​the metal organic structure film of the present invention is large enough, so the probability of contact with the gas is relatively high. In addition, the metal organic structure film of the present invention has sufficient and moderate lattice defects, so the gas easily enters the lattice and the gas easily diffuses. As a result, it can be considered that the gas adsorption rate of the metal organic structure film of the present invention is sufficiently improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1AThis is a schematic cross-sectional view for explaining an example of the structure of a metal oxide having the metal-organic structure film of the present invention.

[0025] Figure 1B is a schematic enlarged perspective view of a metal organic structure film for explaining the structure of the metal organic structure film of the present invention. Figure 1A Schematic enlargement of the X portion.

[0026] Figure 1C This is a schematic diagram of the metal-organic structure schematically showing the crystal structure of the metal-organic structure film of the present invention.

[0027] Figure 1D This is a schematic diagram of a metal-organic structure schematically showing the crystal structure of the metal-organic structure film of the present invention using 2-methylimidazole as an organic molecule.

[0028] Figure 2A It is a schematic plan view of an example of a gas sensor according to a second embodiment of the present invention.

[0029] Figure 2B This is a schematic cross-sectional view of an example of a gas sensor according to a second embodiment of the present invention.

[0030] Figure 2C It is a schematic process diagram showing a method for manufacturing the gas sensor according to the second embodiment of the present invention.

[0031] Figure 2D This is a schematic plan view of an example of a multi-gas sensor according to a second embodiment of the present invention.

[0032] Figure 2E This is a schematic cross-sectional view of an example of a multi-gas sensor according to a second embodiment of the present invention.

[0033] Figure 2F It is a schematic diagram of an example of the gas adsorption filter according to the third embodiment of the present invention.

[0034] Figure 2G This is a schematic diagram of an example of a gas removal device according to a fourth embodiment of the present invention.

[0035] Figure 3A is a schematic perspective view of a gas adsorption filter produced in Examples.

[0036] Figure 3B (1) represents the XRD spectrum of the metal organic structure (ZIF-8) monomer. Figure 3B (2) shows the XRD spectrum of a sample having a metal organic structure (ZIF-8) film formed on zinc oxide (ZnO). Figure 3B(3) shows the XRD spectrum of zinc oxide (ZnO) monomer.

[0037] Figure 4A This is a SEM photograph (magnification 5000 times) of a sample collected from the outer side surface of the gas adsorption filter manufactured in Example 1.

[0038] Figure 4B This is a further enlarged SEM photograph (200,000 times) of a portion of a sample collected from the outer side surface of the gas adsorption filter produced in Example 1.

[0039] Figure 5A This is a SEM photograph of a sample collected from the outer side surface of the gas adsorption filter manufactured in Example 2 (magnification 5000).

[0040] Figure 5B This is a further enlarged SEM photograph (200,000 times) of a portion of a sample collected from the outer side surface of the gas adsorption filter produced in Example 2.

[0041] Fig. 6A This is a SEM photograph (magnification 5000 times) of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 1.

[0042] Figure 6B This is a further enlarged SEM photograph (200,000 times) of a part of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 1.

[0043] Fig. 7A This is a SEM photograph (magnification 1000 times) of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 2.

[0044] Figure 7B This is a further enlarged SEM photograph (200,000 times) of a portion of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 2.

[0045] Fig. 8A This is a SEM photograph (5000 times) of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 4.

[0046] Figure 8B This is a further enlarged SEM photograph (200,000 times) of a portion of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 4.

[0047] Fig. 9A This is a SEM photograph (magnification 5000 times) of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 5.

[0048] Fig. 9BThis is a further enlarged SEM photograph (200,000 times) of a portion of a sample collected from the outer side surface of the gas adsorption filter produced in Comparative Example 5.

[0049] Fig.10 This is a graph showing the evaluation results of the gas adsorption test performed in Examples and Comparative Examples.

[0050] Fig.11 This is a schematic diagram of a metal-organic structure schematically showing the actual crystal structure of the metal-organic structure.

[0051] Fig.12 This is a graph showing the relationship between gap size and diffusion resistance.

[0052] Fig.13 This is a schematic diagram of a metal-organic structure schematically showing the crystal structure of a metal-organic structure as an example of the prior art.

[0053] Fig.14 FIG. 1 is a schematic diagram of a metal-organic structure schematically showing the crystal structure of a metal-organic structure of another example of the prior art. DETAILED DESCRIPTION

[0054] [First embodiment]

[0055] 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 surface of the MOF film of the present invention is covered with protrusions and has a nano-protrusion structure on the surface. Figure 1A As shown, the MOF film 1 is usually configured (or formed) on the surface of the metal oxide 2, such as Figure 1B As shown, the surface of the MOF film 1 is covered with protrusions 11 of nanometer size. Figure 1A This is a schematic cross-sectional view for explaining an example of the structure of a metal oxide having the metal-organic structure film of the present invention. Figure 1B is a schematic enlarged perspective view of a metal organic structure film for explaining the structure of the metal organic structure film of the present invention. Figure 1A Schematic enlarged view of the X part in the figure. In this specification, the various elements in the drawings are only shown schematically and illustratively for the purpose of understanding the present invention, and the appearance and size ratio may be different from the actual objects. Unless otherwise specified, the "up and down direction", "left and right direction" and "front and back direction" used directly or indirectly in this specification are equivalent to the directions corresponding to the up and down direction, left and right direction and front and back direction in the figure, respectively. Unless otherwise specified, the same symbols or signs represent the same components or the same meanings, and the shapes may be different.

[0056] The surface is covered with protrusions means that a plurality of protrusions (or protrusions) are formed relatively densely on one surface of the MOF film 1 (usually the surface on the side opposite to the metal oxide 2 side (hereinafter sometimes referred to as the "outer surface")). The surface is covered with protrusions, so that the proportion of the MOF crystal surface (the part where the metal atoms or organic molecules are exposed) is relatively increased, and thus the intrusion of gas into the MOF film is promoted. Therefore, the gas adsorption rate is improved.

[0057] The density of the protrusions is not particularly limited as long as the effect of the present invention can be obtained. For example, as shown in the examples described below, Figure 4B and Figure 5B As shown in the SEM image of , the protrusions can be densely formed on the outer surface to the extent that villi (i.e., soft protrusions) exist on the inner surface of the small intestine. In detail, the average adjacent distance p of the protrusions is usually 1 nm or more and 100 nm or less. 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, further 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 decreases.

[0058] The average neighbor distance p is, for example, Figure 1B As shown, it is the average value of the distance between any two adjacent protrusions. In detail, the distance between two protrusions can be the distance between the vertices of the two protrusions. In this specification, the average adjacent distance uses the average value obtained by measuring the distance between any 100 groups of two protrusions in the SEM image representing the cross section of the MOF film. The SEM image representing the cross section of the MOF film can be obtained by cutting the surface using FIB (Focused Ion Beam) to expose the cross section and observe it by SEM. The cross-sectional shape and the spacing between the protrusions can also be measured by TEM (Transmission Electron Microscope) instead of SEM.

[0059] The MOF film generally has a protrusion 11 and a base 12 supporting the protrusion 11 , and both the protrusion 11 and the base 12 are formed of MOF.

[0060] The protrusions 11 usually have an average depth d of 1 nm to 100 nm. From the viewpoint of further improving the gas adsorption rate, the average depth d is preferably 1 nm to 50 nm, more preferably 5 nm to 50 nm, further preferably 10 nm to 40 nm, and particularly preferably 20 nm to 30 nm.

[0061] The average depth d is, for example, Figure 1B, which is a characteristic value related to the depth (height) from the vertex to the base 12 of the protrusion 11. In this specification, the average depth d is the average value obtained by measuring the depth (height) of any 100 protrusions in the SEM image showing the cross section of the MOF film. The SEM image showing the cross section of the MOF film can be the same as the SEM image showing the cross section of the MOF film when the average adjacent distance p is measured.

[0062] The base 12 usually has an average film thickness t of 1 nm to 1000 nm. From the viewpoint of further improving the gas adsorption rate, the average film thickness t is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, further preferably 10 nm to 90 nm, sufficiently preferably 20 nm to 80 nm, and even more preferably 30 nm to 80 nm.

[0063] The average film thickness t is, for example, Figure 1B , which is a characteristic value related to the thickness of the base 12. In this specification, the average film thickness t is the average value obtained by measuring the thickness directly below any 100 protrusions in the SEM image showing the cross section of the MOF film. The SEM image showing the cross section of the MOF film can be the same as the SEM image showing the cross section of the MOF film when the average adjacent distance p is measured.

[0064] The protrusions 11 only need to be formed relatively densely in at least a part of the outer surface of the MOF membrane. From the viewpoint of further increasing the gas adsorption rate, they are preferably formed relatively densely over the entire outer surface (or the entire surface).

[0065] like Figure 1AAs shown, the MOF film 1 is usually arranged (or formed) directly in contact with the surface of the metal oxide 2. In detail, the MOF of the MOF film 1 can be formed by the metal atoms constituting the metal oxide 2. Therefore, the MOF film 1 can also be called a "degenerate film" (or "degenerate layer"). That is, the degeneration of the "degenerate film" refers to the chemical degeneration of the metal oxide 2, and the "degenerate film" can be a film (or layer) in which the MOF is formed by the metal atoms of the metal oxide 2. In more detail, at the interface (or between) the metal oxide 2 and the MOF of the MOF film 1, there are metal atoms shared by the metal oxide and the MOF. For example, at the interface, there are metal atoms constituting any of the metal oxide and the MOF. In addition, for example, in the degenerate film, the MOF is constituted while containing the metal atoms constituting the metal oxide. As a result, the metal atoms between the metal oxide and the MOF (for example, at the interface) are shared by both the metal oxide and the MOF. In the present invention, the MOF is formed on the surface of the metal oxide and the metal atoms of the metal oxide are shared, so the adhesion of the MOF film is fully improved. At the interface between the metal oxide 2 and the MOF constituting the MOF film 1 , metal atoms are shared by the metal oxide and the MOF.

[0066] The metal oxide 2 is not particularly limited as long as it is a metal oxide that can supply metal atoms that can constitute MOF, and examples thereof include one or more metal oxides selected from 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.

[0067] Metal oxide 2 Figure 1A The metal oxide 2 has a form in which two particles are connected, but it can also have the form of one particle, or it can also have the form of a molded body or a molded sintered body of multiple particles. The molded body of multiple particles is manufactured by a known method such as an extrusion molding method, and can also contain a binder for connecting between particles. The molded sintered body of multiple particles is manufactured by sintering the molded body of multiple particles, and therefore does not contain a binder. From the viewpoint of further improving the gas adsorption rate, the metal oxide 2 preferably has the form of a molded body or a molded sintered body of multiple particles, and more preferably has the form of a molded sintered body. In the case where the metal oxide 2 has the form of a molded body or a molded sintered body of multiple particles, it has a porous structure.

[0068] The average primary particle size of the particles constituting the metal oxide 2 is usually greater than 1 μm and less than 25 μm. From the viewpoint of further improving the gas adsorption rate, it is preferably greater than 2 μm and less than 25 μm, more preferably greater than 2 μm and less than 20 μm, further preferably greater than 5 μm and less than 20 μm, and particularly preferably greater than 6 μm and less than 15 μm.

[0069] The average primary particle size of the metal oxide 2 can be obtained by averaging the particle sizes of any 50 particles constituting the metal oxide 2 in the SEM image representing the cross section of the MOF film. The SEM image representing the cross section of the MOF film can be the same as the SEM image representing the cross section of the MOF film when the average adjacent distance p is measured.

[0070] In the present invention, the gas adsorption rate of the MOF membrane 1 is sufficiently excellent, so the MOF membrane 1 alone can be referred to as a "gas adsorbent", or a material including at least the MOF membrane 1 and a metal oxide supporting the MOF membrane 1 as constituent elements can be referred to as a "gas adsorbent".

[0071] The MOF membrane 1 is composed of MOF, and is usually composed of only MOF. The MOF membrane 1 is composed of only MOF, which means that it intentionally contains no substances other than MOF, and may contain, for example, unintentional substances and impurities such as metal atoms and organic molecules constituting MOF.

[0072] Specifically, the MOF membrane 1 is a porous membrane based on the coordination bonds between organic molecules and metal atoms, wherein the metal atoms include metal atoms derived from the metal oxide 2. More specifically, the MOF constituting the MOF membrane 1 is a MOF based on the coordination bonds between organic molecules and metal atoms, wherein the metal atoms include metal atoms derived from the metal oxide 2, and the MOF membrane 1 is constituted as a porous membrane. Figure 1C As shown, MOF is a crystalline complex formed by cross-linking metal atoms (especially metal atom ions) MA with organic molecules OM as ligands, and is a porous body based on the coordination bonds between organic molecules and metal atoms (especially metal atom ions). In the case of MOF, not all metal atoms constituting the MOF must be shared by the metal oxide 2, as long as 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 fact that the metal atoms of the MOF adjacent to the metal oxide are shared by the metal oxide can be confirmed by high-magnification observation (e.g., more than 1 million times) of a transmission electron microscope (TEM). Figure 1C This is a schematic diagram of MOF schematically showing the crystal structure of the MOF film of the present invention.

[0073] Specifically, for example, a MOF including 2-methylimidazole as an organic molecule and a zinc atom as a metal atom may have the following structure: Figure 1D The crystal structure shown. At this time, Figure 1D Any one or more zinc atoms among the 18 zinc atoms MA shown in can be shared by the metal oxide. Figure 1DThis is a schematic diagram of MOF schematically showing the crystal structure of the MOF membrane of the present invention using 2-methylimidazole as an organic molecule. This structure is only a schematic diagram, and the crystal structure is accurately described in, for example, the following literature.

[0074] ANH PHAN et al., “Synthesis, Structure, and Carbon Dioxide CaptureProperties of Zeolitic Imidazolate Frameworks” (ACCOUNTS OF CHEMICAL RESEARCH58 67 January 2010 Vol. 43, No. 1)

[0075] The organic molecules may be all organic molecules known in the field of MOF as organic molecules capable of constituting MOF. From the viewpoint of further improving the gas adsorption rate, the organic molecules preferably contain one or more organic molecules selected from azole organic molecules, cyanide organic molecules and carboxylic acid organic molecules. From the same viewpoint, the organic molecules more preferably contain one or more organic molecules selected from azole organic molecules and cyanide organic molecules, and further preferably contain one or more organic molecules selected from azole organic molecules. Azole organic molecules (particularly imidazole organic molecules) such as Figure 1D As shown, the organic molecule is bonded to the metal atom via the nitrogen atom, so the adsorption rate of gas (especially carbon dioxide gas) is faster.

[0076] The azole organic molecules constituting MOF include organic molecules selected from 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 further preferred.

[0077] The azole-based organic molecule may or may not have a substituent.

[0078] The substituents that the azole organic molecule may have are, for example, one or more substituents selected from 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.

[0079] The alkyl group is, for example, an alkyl group having 1 to 5 carbon atoms (particularly 1 to 3 carbon atoms). Specific examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, and n-pentyl.

[0080] Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

[0081] From the viewpoint of further improving the gas adsorption rate, the azole organic molecules constituting MOF are preferably selected from azole organic molecules without substituents and azole organic molecules having only hydrophobic groups (especially alkyl groups or nitro groups) even if they have substituents, and are more preferably selected from azole organic molecules having only hydrophobic groups (especially alkyl groups).

[0082] Examples of azole organic molecules constituting MOF include imidazole molecules represented by the following general formula (1), benzimidazole molecules represented by the following general formula (2), triazole molecules represented by the following general formulas (3) and (4), and purine molecules represented by the following general formula (5).

[0083]

Chemical formula 1

[0084]

[0085] In formula (1), R 1 ~R 3 Each independently represents 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, it is preferably a hydrogen atom or the above-mentioned hydrophobic group, and more preferably a hydrogen atom, an alkyl group, a halogen atom, a nitro group or a cyano group. From the same viewpoint, in a more preferred embodiment, R 1 is a hydrogen atom, an alkyl group or a nitro group, R 2 and R 3 is a hydrogen atom, an alkyl group, a halogen atom, or a nitro group. From the same viewpoint, in a further preferred embodiment, R 1 is an alkyl group, R 2 and R 3 A hydrogen atom.

[0086] Specific examples of the imidazole-based molecule represented by the general formula (1) include the following compounds.

[0087] Imidazole, methylimidazole (especially 2-methylimidazole), ethylimidazole, nitroimidazole, aminoimidazole, chloroimidazole, bromoimidazole, imidazolecarbonitrile.

[0088]

Chemical formula 2

[0089]

[0090] In formula (2), R 11 ~R 15Each is 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, it is preferably a hydrogen atom or the above-mentioned hydrophobic group, and more preferably a hydrogen atom, an alkyl group, a halogen atom, a nitro group or a cyano group. From the same viewpoint, in a more preferred embodiment, R 11 , R 14 and R 15 is a hydrogen atom, R 12 and R 13 Each is independently a hydrogen atom, an alkyl group, a halogen atom or a nitro group.

[0091] Specific examples of the benzimidazole-based molecules represented by the general formula (2) include the following compounds.

[0092] Benzimidazole, chlorobenzimidazole, dichlorobenzimidazole, methylbenzimidazole, bromobenzimidazole, nitrobenzimidazole, aminobenzimidazole, benzimidazolecarbonitrile.

[0093]

Chemical formula 3

[0094]

[0095] In formula (3), R 21 ~R 22 Each is independently a hydrogen atom; a hydrophobic group of 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.

[0096] Specific examples of the triazole-based molecule represented by the general formula (3) include the following compounds.

[0097] 1,2,3-Triazole.

[0098]

Chemical formula 4

[0099]

[0100] In formula (4), R 31 ~R 32 Each is independently a hydrogen atom; a hydrophobic group of 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.

[0101] Specific examples of the triazole-based molecules represented by the general formula (4) include the following compounds.

[0102] 1,2,4-Triazole.

[0103]

Chemical formula 5

[0104]

[0105] In formula (5), R 41 ~R 43 Each is independently a hydrogen atom; a hydrophobic group of 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.

[0106] Specific examples of the purine-based molecule represented by the general formula (5) include the following compounds.

[0107] Purine.

[0108] As the cyanide organic molecule, for example, potassium ferrocyanide, potassium ferrocyanide, hydrocyanic acid, or the like is used.

[0109] As the carboxylic acid-based organic molecule, terephthalic acid, trimellitic acid, phthalic acid, etc. can be used.

[0110] The metal atoms constituting MOF are metal atoms including metal atoms that can constitute metal oxide 2, for example, selected from zinc atoms, copper atoms, nickel atoms, iron atoms, indium atoms, aluminum atoms, cobalt atoms, praseodymium atoms, cadmium atoms, mercury atoms, and manganese atoms. From the viewpoint of further improving the gas adsorption rate, it is preferably selected from zinc atoms, cobalt atoms, and iron atoms, more preferably selected from zinc atoms and cobalt atoms, and further preferably zinc atoms. There is no particular limitation on the compound supplying such metal atoms, and examples thereof include zinc nitrate, copper nitrate, aluminum nitrate, and nickel nitrate.

[0111] The combination of the organic molecules and the metal atoms in MOF is not particularly limited, but 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:

[0112] Combination (C1) = a combination of an imidazole molecule represented by the general formula (1) (particularly 2-methylimidazole and / or nitroimidazole) and one or more metal atoms selected from zinc atoms and iron atoms (particularly zinc atoms);

[0113] Combination (C2) = a combination of an imidazole molecule represented by the general formula (1) (particularly 2-methylimidazole and / or nitroimidazole) and one or more metal atoms selected from zinc atoms and cobalt atoms (particularly zinc atoms);

[0114] Combination (C3) = a combination of a benzimidazole-based molecule represented by the general formula (2) and one or more metal atoms selected from the group consisting of a zinc atom and a cobalt atom.

[0115] The ratio of organic molecules to metal atoms in MOF is not particularly limited, and is generally determined according to the types of organic molecules and metal atoms constituting the MOF.

[0116] For example, a molecular structure only includes an imidazole molecule (Im) (for example, an imidazole molecule represented by the general formula (1)) and one or more divalent metal atoms (M) selected from zinc atoms, cobalt atoms, and iron atoms. 1 ) can be composed of the formula: M 1 (Im)2 indicates;

[0117] For example, a molecule containing only a benzimidazole-based molecule (bIm) (for example, a benzimidazole-based molecule represented by the general formula (2)) and one or more divalent metal atoms (M) selected from zinc atoms, cobalt atoms, and iron atoms 1 ) can be composed of the formula: M 1 (bIm)2 indicates;

[0118] For example, a triazole-based molecule (Tra) (for example, a triazole-based molecule represented by the general formula (3) and / or (4)) and one or more divalent metal atoms (M) selected from zinc atoms, cobalt atoms, and iron atoms 1 ) can be composed of the formula: M 1 (Tra)2 means;

[0119] For example, a purine-based molecule (Pur) (for example, a triazole-based molecule represented by the general formula (5)) and one or more divalent metal atoms (M) selected from zinc atoms, cobalt atoms, and iron atoms 1 ) can be composed of the formula: M 1 (Pur)2 indicates.

[0120] For example, the present invention only contains imidazole molecules (Im) (for example, imidazole molecules represented by general formula (1)), benzimidazole molecules (bIm) (for example, benzimidazole molecules represented by general formula (2)), and one or more divalent metal atoms (M) selected from zinc atoms, cobalt atoms, and iron atoms. 1 ) can be composed of the formula: M 1 (Im) x (bIm) y (where x+y=2) represents.

[0121] The MOF constituting the MOF film 1 generally has a pore size of more than 1Å and less than 50Å. From the viewpoint of the characteristics corresponding to the purpose, a MOF with an appropriate pore size can be used. For example, in the case of a sensor using the MOF film of the present invention, a MOF having a pore size close to the size of the target gas molecule is preferred. In the case of a carbon dioxide sensor, a MOF having a pore size of more than 2Å and less than 5Å, more preferably more than 2Å and less than 4Å, which is close to the molecular diameter 3.3Å of the carbon dioxide molecule, is preferably a MOF having a pore size of more than 2Å and less than 5Å, more preferably more than 2Å and less than 4Å. In addition, in the case of a carbon dioxide adsorption filter made by supporting polyamines such as polyethyleneimine, a MOF having a pore size of more than 5Å and less than 20Å, more preferably more than 10Å and less than 15Å, is preferably used based on the unit structure of the polyamine.

[0122] The pore diameter depends on the types of organic molecules and metal atoms that constitute MOF. Therefore, the pore diameter can be adjusted by selecting the types of organic molecules and metal atoms.

[0123] In this specification, the pore diameter is defined as "the diameter of the largest sphere that can be contained when each atom in the crystal is set as a rigid 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 based on the crystal structure. Such a pore diameter is recorded as d in Table 1 of the following document. p (Å), the value reported in the literature can be used:

[0124] ANH PHAN et al., “Synthesis, Structure, and Carbon Dioxide CaptureProperties of Zeolitic Imidazolate Frameworks” (ACCOUNTS OF CHEMICAL RESEARCH58 67 January 2010 Vol. 43, No. 1)

[0125] The MOF constituting the MOF film 1 may be, for example, the MOF shown below:

[0126] ZIF-1 (composition formula: Zn(Im)2);

[0127] ZIF-4 (composition formula: Zn(Im)2);

[0128] ZIF-7 (composition formula: Zn(bIm)2);

[0129] ZIF-8 (composition formula: Zn(mIm)2);

[0130] ZIF-9 (composition formula: Co(bIm)2);

[0131] ZIF-14 (composition formula: Zn(eIm)2);

[0132] ZIF-81 (composition formula: Zn(cbIm)(nIm));

[0133] ZIF-75 (composition formula: Co(mbIm)(nIm));

[0134] ZIF-77 (composition formula: Zn(nIm)2);

[0135] ZIF-81 (composition formula: Zn(brbIm)(nIm)).

[0136] Here, the abbreviations in the composition formula represent the following compounds.

[0137] Im: imidazole, bIm: benzimidazole, mIm: methylimidazole, eIm: ethylimidazole, nIm: nitroimidazole, cbIm: chlorobenzimidazole, brbIm: bromobenzimidazole.

[0138] The MOF membrane 1 may contain an adsorbent. For example, the MOF membrane 1 may support an adsorbent in the lattice constituting the MOF membrane. The adsorbent is not particularly limited as long as it can adsorb gas (especially carbon dioxide gas), and all adsorbents used in the field of gas adsorption can be used. As an adsorbent, from the viewpoint of adsorbing carbon dioxide gas, an amine compound is preferably used. The amine compound is not particularly limited as long as it is a substance having an amino group, and an organic compound containing an amino group can generally be used. The weight average molecular weight of the amino-containing organic substance is not particularly limited, for example, it can be 100 or more. From the viewpoint of preventing the adsorption capacity of carbon dioxide gas from being reduced due to volatilization, the weight average molecular weight of the amino-containing organic substance is 300 or more, preferably 500 or more. The upper limit of the weight average molecular weight is not particularly limited, and the weight average molecular weight can generally be 10,000 or less, and in particular, it can be 1000 or less. As specific examples of amino-containing polymers, for example, polyethyleneimine, polyamide amine, polyethyleneamine, etc. can be cited. The amino-containing polymer can be linear or branched, and from the viewpoint of further improving the adsorption capacity of carbon dioxide gas, it is preferably branched.

[0139] From the viewpoint of further improving the adsorption capacity of carbon dioxide gas, the adsorbent is preferably polyethyleneimine, and particularly preferably branched polyethyleneimine.

[0140] 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 preferably 17 to 19 mmol / g·solid from the viewpoint of further improving the adsorption of gas (particularly carbon dioxide gas).

[0141] As the amine value, a value measured by a neutralization method and calculated from the amount of hydrochloric acid required to neutralize the amine compound was used.

[0142] In the present invention, if Figure 1C As shown, the MOF film 1 has a crystal structure (or lattice), but preferably also has lattice defects. Lattice defects refer to the absence of metal and / or organic molecules in a part (particularly a part of the surface) of the MOF crystal lattice. The MOF film 1 has lattice defects, so that the intrusion of gas molecules into the inside of the MOF film 1 becomes easier, and the gas adsorption rate becomes greater.

[0143] The MOF membrane 1 can be manufactured by the following method:

[0144] The metal oxide is immersed in a solution containing organic molecules, and heating and ultrasonic waves are applied. For example, in a container with a lid such as polypropylene or stainless steel, the metal oxide is brought into contact with the organic molecule solution while heating and ultrasonic waves are applied.

[0145] The organic molecule is an organic molecule constituting the MOF film, and can be selected from the above-mentioned organic molecules.

[0146] The metal oxide is a metal oxide that can supply metal atoms constituting the MOF film, and can be selected from the above-mentioned metal oxides.

[0147] The organic molecule concentration of the solution is not particularly limited as long as it can form MOF, and is, 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 can generally be 200 g / L or less, and particularly 150 g / L or less.

[0148] The solvent constituting the solution is not particularly limited as long as it can dissolve predetermined organic molecules, and examples thereof include organic solvents such as N,N-diethylformamide, N,N-dimethylformamide, methanol, and ethanol; and water.

[0149] The formation of the film (e.g., impregnation) is performed under heating. The heating temperature is usually 40°C or more, preferably 50°C or more, more preferably 55°C or more, more preferably 80°C or more, and particularly preferably 140°C or more from the viewpoint of further improving the gas adsorption rate. If the heating temperature is too low, no protrusions are formed on the surface of the MOF film, and even if protrusions are formed, the average adjacent distance is too long. Therefore, the gas adsorption rate is reduced. The heating temperature can usually be 150°C or less.

[0150] The heating time is not particularly limited as long as MOF can be formed, and may be, for example, 1 hour to 100 hours, and particularly 1.5 hours to 24 hours.

[0151] The formation of the membrane (e.g., impregnation) is performed under ultrasonic application. The frequency of the ultrasonic wave is usually 30 kHz or more. If the frequency is too low, no protrusions are formed on the surface of the MOF membrane, and even if protrusions are formed, the average adjacent distance is too long. Therefore, the gas adsorption rate is reduced. The upper limit of the frequency is not particularly limited, and the frequency can usually be 100 kHz or less (especially 50 kHz or less).

[0152] The film formation (e.g., impregnation) may be performed under pressure or not. As a pressurization method, for example, a method of pressurizing by heating in a covered container such as polypropylene or stainless steel may be cited. The pressurization pressure is not particularly limited, and for example, it may be 1 atm or more and 2 atm or less, and in particular, it may be 1.2 atm or more and 1.5 atm or less. The heating method is not particularly limited, and may be electric heating, or heating based on ultrasound or microwaves.

[0153] When the adsorbent is supported on the MOF film 1, the adsorbent can be dissolved in a solution containing organic molecules, or the manufactured MOF film can be immersed in a solution containing the adsorbent. Thus, after drying, the adsorbent can be supported in the lattice of the MOF film. From the viewpoint of further improving the gas adsorption rate, it is preferred to dissolve the adsorbent in a solution containing organic molecules to manufacture the MOF film, and it is more preferred to dissolve the adsorbent in a solution containing organic molecules to manufacture the MOF film, and to immerse the manufactured MOF film in a solution containing the adsorbent. In either case, the concentration of the adsorbent in the solution is not particularly limited, for example, it can be more than 1% by volume, from the viewpoint of further improving the gas adsorption rate, preferably more than 5% by volume, more preferably more than 10% by volume. The upper limit of the adsorbent concentration is not particularly limited, and the adsorbent concentration can be, for example, less than 50% by volume (particularly less than 20% by volume).

[0154] When the MOF membrane is immersed 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; organic solvents such as methanol, ethanol, and dimethylformamide can be used. The immersion of the MOF membrane in a solution containing an adsorbent can be repeated multiple times. By such an immersion, a cleaning effect can also be obtained. It can be cleaned with a solvent monomer that does not contain an adsorbent, but at least in order to impregnate the adsorbent in the end, it is preferably immersed in a solution containing an adsorbent and dried.

[0155] After the MOF film is formed, the residual solvent and adsorbed gas are preferably removed by heating. The heating is preferably carried out in a vacuum (or under a reduced pressure atmosphere). The heating temperature is not particularly limited, and for example, it can be above 40°C, preferably above 50°C, and more preferably above 80°C. The upper limit of the heating temperature is not particularly limited, and the heating temperature can usually be below 100°C. The drying time is not particularly limited, and for example, it can be above 1 minute, preferably above 10 minutes, and more preferably above 30 minutes. The upper limit of the drying time is not particularly limited, and the drying can usually be below 200 minutes (especially below 50 minutes).

[0156] By manufacturing the MOF film 1 by the above-described method, protrusions can be formed on the surface of the MOF film at a predetermined average adjacent distance, and lattice defects can be appropriately formed in the crystal structure (or lattice) of the MOF film.

[0157] [Second embodiment]

[0158] The second embodiment of the present invention provides a sensor using the composite membrane structure of 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, as in the first embodiment, the gas adsorption rate of the MOF membrane is sufficiently improved. Therefore, a sensor with high adsorption can be obtained, and as a result, a sensor with high reliability (for example, a gas sensor and an odor sensor) can be realized.

[0159] In the sensor of the present invention, the MOF film can adsorb a large amount of gas through its protrusions (preferably protrusions and lattice defects), and the adsorption amount varies according to the surrounding gas concentration. Therefore, the MOF film can function as a sensitive film of a gas sensor.

[0160] Specifically, since the weight and electrical properties of MOF change due to gas adsorption, the amount of gas adsorption can be converted into an electrical signal, that is, a gas sensor can be made.

[0161] Preferred embodiments of the sensor of the present invention are as follows.

[0162] For example, a device whose frequency changes according to weight, such as a quartz resonator or a resonator using piezoelectric ceramics, is preferably used as the support. A weight change type gas sensor can be fabricated by sequentially forming a layer of the metal oxide 2 and the MOF film 1 on the support.

[0163] In addition, for example, a weight change type gas sensor can be produced by forming a zinc oxide layer (a layer of metal oxide 2) and a MOF film 1 such as ZIF-8 on a quartz oscillator (support) by the method of the first embodiment. The layer of metal oxide 2 can be formed by a method such as plating, CVD, evaporation, sputtering, etc.

[0164] In the present embodiment, the constituent material of the layer of the metal oxide 2 is not limited to zinc oxide, and can be selected from the same metal oxides as those described as the constituent material of the metal oxide 2 in the first embodiment.

[0165] The constituent material of the MOF membrane 1 can be determined according to the target gas and the required sensitivity and selectivity. For example, as the MOF constituting the MOF membrane 1, imidazole-based MOFs such as ZIF-1, ZIF-4, ZIF-7, and ZIF-8 can be used.

[0166] In order to reduce the influence of humidity and improve the accuracy of the sensor, and to obtain a faster response and a faster recovery, a heater (particularly a heating heater) may be built in to heat the MOF film.

[0167] By arranging multiple MOF materials in arrays on different oscillators, a multi-gas sensor capable of detecting multiple gases simultaneously can be produced. Such a multi-gas sensor can be used as an odor sensor.

[0168] After forming a piezoelectric film and electrodes on a silicon substrate, after forming heater wiring and the MOF film on the above-mentioned metal oxide, the silicon substrate is etched, thereby forming a MEMS type gas sensor / odor sensor with suppressed power consumption.

[0169] As an example of the gas sensor of the present invention, there can be cited Figure 2A and Figure 2B The MEMS type gas sensor shown. Figure 2A and Figure 2B 1 and 2 are respectively a schematic plan view and a schematic cross-sectional view of an example of a gas sensor according to a second embodiment of the present invention.

[0170] Figure 2A and Figure 2B The gas sensor 40 shown includes a layer of metal oxide 2 (not shown) formed on a piezoelectric vibrator 41 and a MOF film 43 included in the layer of metal oxide 2. Figure 2B The layer of the metal oxide 2 is omitted. The piezoelectric vibrator 41 corresponds to the support body 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.

[0171] The gas sensor 40 generally also 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, a contact pad 47c for wire bonding 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.

[0172] In the gas sensor 40, CP1 is a connection terminal (positive) to the heater, CP2 is a connection terminal (negative) to the heater, CP3 is a connection terminal to the upper electrode of the vibrator, and CP4 is a connection terminal to the lower electrode of the vibrator. The wire bonding contact pad 47c functions as such a connection terminal.

[0173] The gas sensor 40 can be manufactured, for example, by the following method.

[0174] In detail, first, Figure 2C As shown, a support film 45 is 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 a contact pad 47c for wire bonding is formed on the heater electrode 47a and the vibrator electrode 47b (step (2)). An insulating layer 48 is further formed to insulate the heater wiring 46 from the 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 a MOF film 43 is formed on the layer of metal oxide 2 (not shown), and a portion of the insulating layer 48 is etched to expose the contact pad 47c for wire bonding (step (7)). Then, a portion of the components (MOF film 43, layer of metal oxide 2 (not shown), upper electrode 413, piezoelectric film 412 and lower electrode 411) on the insulating layer 48 is etched (step (8)), and a portion of the silicon substrate 43 is etched (step (9)), so that the sensor 40 can be obtained (step (10)). Figure 2C This is a schematic process diagram showing an example of a method for manufacturing the gas sensor according to the second embodiment of the present invention.

[0175] The power consumption of the gas sensor 40 is suppressed.

[0176] As an example of the multi-gas sensor of the present invention, there can be cited Figure 2D and Figure 2E The MEMS type multi-gas sensor shown. Figure 2D and Figure 2E 1 and 2 are respectively a schematic plan view and a schematic cross-sectional view of an example of a multi-gas sensor according to a second embodiment of the present invention.

[0177] Figure 2D and Figure 2E The multi-gas sensor 50 shown has multiple (eg, four) Figure 2A and Figure 2B The four gas sensors 40 shown have MOF films containing MOFs different from each other.

[0178] The multi-gas sensor 50 can manufacture multiple (e.g., 4) Figure 2A and Figure 2B The gas sensor 40 shown is manufactured in the same manner as the gas sensor 40, except that the four gas sensors 40 have MOF films containing different MOFs. The MOFs of the four gas sensors 40 are different MOFs corresponding to different gases.

[0179] The power consumption of the multi-gas sensor 50 is suppressed. The multi-gas sensor 50 can function as an odor sensor.

[0180] [Third embodiment]

[0181] The third embodiment of the present invention provides a gas adsorption filter using the MOF membrane of 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, as in the first embodiment, the gas adsorption rate of the MOF membrane is sufficiently improved. Therefore, a highly reliable gas adsorption filter can be realized.

[0182] The gas adsorption filter of the present embodiment has the same structure as the composite membrane structure of the first embodiment, except that an adsorbent different from the MOF is added to or supported on the surface of the MOF membrane.

[0183] Preferred embodiments of the gas adsorption filter of the present invention are as follows.

[0184] like Figure 2F As shown, the gas adsorption filter 60 includes a metal oxide layer 62 formed on a support 61 having a honeycomb structure, a MOF film 63 included in the metal oxide layer 62, and an adsorbent 65 included in the MOF film 63. In this embodiment, the metal oxide layer 62 corresponds to the layer of the metal oxide 2 in the first embodiment. The MOF film 63 corresponds to the MOF film 1 in the first embodiment. The adsorbent 65 corresponds to the adsorbent in the first embodiment. Figure 2F It is a schematic diagram of an example of the gas adsorption filter according to the third embodiment of the present invention.

[0185] By using a support body 61 having a honeycomb structure, the surface area of ​​the support body itself can be greatly increased. In addition, as in the first embodiment, the gas adsorption rate is improved. In addition, more MOF can be added or loaded. Therefore, more adsorbent 65 can be added or loaded while maintaining the adsorption rate of carbon dioxide gas per unit area. Therefore, the adsorption capacity of carbon dioxide gas is significantly improved. In this embodiment, the metal oxide layer 62 acts as a close-fitting layer, so that the MOF film 63 can be fully prevented from falling off, and the durability is improved.

[0186] Specifically, in this embodiment, the effective surface area in contact with carbon dioxide becomes extremely large due to the combined effect of the increase in surface area caused by the honeycomb structure of the support 61 and the increase in surface area caused by the porosity of the MOF film 63 and the protruding surface irregularities and MOF crystals (internal irregularities (i.e., pores)). As a result, the adsorption capacity of carbon dioxide gas is significantly improved. In addition, by making the metal oxide layer porous, the adsorption capacity of carbon dioxide gas can be further improved.

[0187] By using azole organic molecules (especially imidazole organic molecules) or cyanide organic molecules as organic molecules constituting the MOF membrane, the water resistance of MOF is improved. Therefore, even if an adsorbent (especially an amino group-containing polymer) is supported, the reliability is higher.

[0188] By forming the support body 61 into a honeycomb structure, the carbon dioxide adsorption capacity can be improved while maintaining the pressure loss.

[0189] The gas adsorption filter of the present embodiment can be manufactured by forming a metal oxide layer 62 (a layer of "metal oxide 2" in the first embodiment) and a MOF thin film 63 (a layer of "MOF film 1" in the first embodiment) on a support 61, removing residual solvent and adsorbed gas by heating, and adding or supporting an adsorbent 65. Heating is preferably performed in a vacuum (or under a reduced pressure atmosphere).

[0190] The adsorbent 65 can be added or supported by impregnating the MOF membrane with an aqueous solution of the adsorbent (particularly an amine compound) and then drying the solution. Thus, a film of the adsorbent 65 (particularly an amine compound) can be formed on the MOF membrane.

[0191] [Fourth embodiment]

[0192] The fourth embodiment of the present invention provides a gas removal device (or gas removal system) including the gas adsorption filter 60 of 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, for example, the adsorption capacity of carbon dioxide gas can be significantly improved. The present invention can realize a small, energy-saving, low-cost and highly reliable gas removal device (especially a carbon dioxide gas removal device). The gas removal device of the present invention can also be generally used for air conditioning purposes.

[0193] like Figure 2G As shown, the gas removal device 70 of this embodiment can release the carbon dioxide gas in the room to the outside through the following steps. Figure 2G This is a schematic diagram of an example of a gas removal device according to a fourth embodiment of the present invention.

[0194] Step (i):

[0195] The indoor air is blown toward the gas adsorption filter 60 to adsorb the carbon dioxide gas.

[0196] Step (ii):

[0197] The adsorbed carbon dioxide gas is released by blowing heated air to the gas adsorption filter 60 or by heating the gas adsorption filter 60 .

[0198] Step (iii):

[0199] Discharge the released carbon dioxide gas to the outside.

[0200] In the gas removal device 70, as Figure 2G As shown, it is also possible to simultaneously perform adsorption (step (i)) and release and discharge (steps (ii) and (iii)) of carbon dioxide using different positions of 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 release position in the adsorption filter 60. As a result, the adsorption, release, and discharge of carbon dioxide gas can be continuously performed.

[0201] In the gas removal device 70 , as another method, the same position of the adsorption filter 60 may be used to sequentially perform adsorption of carbon dioxide (step (i)) and release and discharge (steps (ii) and (iii)).

[0202] The present invention as described above includes the following preferred embodiments.

[0203] <1> A metal-organic structure film having a surface covered with protrusions, wherein the protrusions have an average adjacent distance p of 1 nm to 100 nm.

[0204] <2> The metal-organic structure film according to <1>, wherein the protrusions have an average depth d of 1 nm to 100 nm.

[0205] <3> The metal-organic structure film according to <1> or <2>, wherein the metal-organic structure film is disposed on a surface of a metal oxide.

[0206] <4> The metal-organic structure film according to <3>, wherein the metal oxide and the metal-organic structure share metal atoms at the interface between the metal oxide and the metal-organic structure constituting the metal-organic structure film.

[0207] <5> The metal-organic structure film according to <3> or <4>, wherein the metal-organic structure film is a porous film based on coordination bonds between organic molecules and metal atoms, and the metal atoms include metal atoms derived from the metal oxide.

[0208] <6> The metal-organic structure film according to <5>, wherein the organic molecules include one or more organic molecules selected from the group consisting of azole organic molecules, cyanide organic molecules, and carboxylic acid organic molecules.

[0209] <7> The metal-organic structure film according to <5> or <6>, wherein the metal atoms include one or more metal atoms selected from the group consisting of zinc, copper, nickel, iron, indium and aluminum.

[0210] <8> The metal-organic structure film according to any one of <3> to <7>, wherein the metal oxide includes one or more metal oxides selected from the group consisting of zinc oxide, copper oxide, nickel oxide, iron oxide, indium oxide, and aluminum oxide.

[0211] <9> The metal-organic structure film according to any one of <3> to <8>, wherein the metal oxide is in the form of particles, or in the form of a molded body or a molded sintered body of the particles.

[0212] <10> The metal-organic structure film according to <9>, wherein the particles have an average primary particle size of 2 μm or more and 25 μm or less.

[0213] <11> The metal-organic structure film according to any one of <1> to <10>, wherein the metal-organic structure film has a film thickness t of 10 nm to 1000 nm.

[0214] <12> The metal-organic structure film according to any one of <1> to <11>, wherein the metal-organic structure constituting the metal-organic structure film has a composition formula of Zn(mIm) 2 .

[0215] <13> The metal-organic structure film according to any one of <1> to <12>, wherein the metal-organic structure film is a gas adsorbent.

[0216] <14> The metal-organic structure film according to <13>, wherein the metal-organic structure film contains an amine compound,

[0217] The above-mentioned gas is carbon dioxide gas.

[0218] <15> The metal-organic structure film according to <14>, wherein the amine compound is an amino group-containing polymer having a weight average molecular weight of 100 or more.

[0219] <16> The metal-organic structure film according to <14> or <15>, wherein the amine compound is polyethyleneimine.

[0220] <17> A method for producing a metal-organic structure film, comprising heating and applying ultrasonic waves while immersing a metal oxide in a solution containing organic molecules.

[0221] <18> The method for producing a metal-organic structure film according to <17>, which produces the metal-organic structure film according to any one of <1> to <16>.

[0222] <19> The method for producing a metal organic structure film according to <17> or <18>, wherein the heating is performed at 40° C. or higher.

[0223] The ultrasonic wave has a frequency of 30 kHz or more.

[0224] Hereinafter, the present invention will be described in more detail based on specific examples, but the present invention is not limited to the following examples at all.

[0225] [Example]

[0226] (Example 1)

[0227] Formation of MOF membranes

[0228] Zinc oxide powder (average primary particle size = 11 μm) and a binder were mixed, the mixture was formed into a honeycomb filter shape by extrusion molding, and sintered at 1000°C ( Figure 3A). Using the zinc oxide sintered body as a support, a MOF film having a nanoprotrusion structure is formed on its surface. In detail, the support is immersed in an ethanol solution containing raw materials (metal ions and organic molecules) for synthesizing MOF, and heated at 60°C while applying 40kHz ultrasonic waves for 2 hours. Here, the ethanol solution uses a solution containing 10mM zinc nitrate hexahydrate, 10mM 2-methylimidazole, and 10% polyethyleneimine (average molecular weight = 600). Next, for cleaning, the support is immersed in an ethanol solution containing 10vol% polyethyleneimine for 30 minutes. Then, the support containing the MOF membrane is taken out and dried at 80°C for 30 minutes to obtain a filter.

[0229] Confirmation of MOF membrane based on XRD spectrum

[0230] A sample was collected from the outer surface of the filter, and the X-ray diffraction (XRD) spectrum confirmed the formation of a ZIF-8 film (composition formula: Zn(mIm)2). Figure 3B As shown, for the filter having a MOF film (ZIF-8) formed on the surface of zinc oxide (ZnO) (the filter obtained in Example 1), the peak of the X-ray diffraction (XRD) spectrum is located at the same position as the peak position of the particles of the ZIF-8 monomer and the peak position of the film of the ZnO monomer, confirming that it is a composite structure having both ZIF-8 and ZnO. Figure 3B In the figure, (1) shows the XRD spectrum of MOF (ZIF-8) monomer, (2) shows the XRD spectrum of a sample in which a MOF (ZIF-8) film is formed on zinc oxide (ZnO), and (3) shows the XRD spectrum of zinc oxide (ZnO) monomer.

[0231] ·Confirmation of MOF membrane based on SEM observation

[0232] The surface of the obtained filter was observed using a SEM (Scanning Electron Microscope). Figure 4A and Figure 4B SEM images of Figure 4B The SEM image of clearly shows that protrusions are densely formed on the entire surface of the filter (MOF membrane surface).

[0233] The cross section of the protrusion can be observed from the ruptured part existing on the MOF film. The average adjacent distance p and the average depth d of the protrusion are measured based on the SEM image showing such a cross section. In detail, the distance between two protrusions is measured in each of the 100 adjacent groups, and the average adjacent distance p is obtained. The average depth d and the average film thickness t are obtained by measuring any 100 protrusions.

[0234] The average adjacent distance p is 20 nm, the average depth d is 25 nm, and the film thickness t is 20 nm.

[0235] (Example 2)

[0236] Formation of MOF membranes

[0237] A filter was obtained by the same method as in Example 1 except that zinc oxide powder having an average primary particle size of 1 μm was used.

[0238] Confirmation of MOF membrane based on XRD spectrum

[0239] X-ray diffraction (XRD) spectrum was measured by the same method as in Example 1. As a result, for the filter obtained in Example 2, the peak of the X-ray diffraction (XRD) spectrum was located at the same position as the peak position of the particles of the ZIF-8 monomer and the peak position of the film of the ZnO monomer, confirming that it was a composite structure having both ZIF-8 and ZnO.

[0240] ·Confirmation of MOF membrane based on SEM observation

[0241] The SEM was used for observation in the same manner as in Example 1. Figure 5A and Figure 5B SEM images of Figure 5B The SEM image of shows that protrusions are densely formed on the entire surface of the filter (MOF membrane surface) of Example 2.

[0242] The average adjacent distance p, average depth d, and average film thickness t of the protrusions were measured from the SEM image by the same method as in Example 1. Specifically, the distance between two protrusions in any 100 adjacent groups was measured to obtain the average adjacent distance p. The average depth d and average film thickness t were obtained by measuring any 100 protrusions.

[0243] The average adjacent distance p is 15 nm, the average depth d is 10 nm, and the average film thickness t is 70 nm.

[0244] (Comparative Example 1)

[0245] Formation of MOF membranes

[0246] A filter was obtained by the same method as in Example 1 except that ultrasonic waves were not applied when the support was immersed in the ethanol solution.

[0247] Confirmation of MOF membrane based on XRD spectrum

[0248] X-ray diffraction (XRD) spectrum was measured by the same method as in Example 1. As a result, in the filter obtained in Comparative Example 1, the peak of the X-ray diffraction (XRD) spectrum was located at the same position as the peak position of the particles of the ZIF-8 monomer and the peak position of the film of the ZnO monomer, confirming that it was a composite structure having both ZIF-8 and ZnO.

[0249] ·Confirmation of MOF membrane based on SEM observation

[0250] The SEM was used for observation in the same manner as in Example 1. Fig. 6A and Figure 6B SEM images of Figure 6B The SEM image of clearly shows that no protrusions are formed on the filter surface (MOF membrane surface) of Comparative Example 1, and the MOF membrane surface is smooth.

[0251] The average film thickness t was measured by the same method as in Example 1. Specifically, the film thickness was measured at any 100 locations to determine the average film thickness t.

[0252] The average film thickness t is 70 nm.

[0253] (Comparative Example 2)

[0254] Formation of MOF membranes

[0255] A filter was obtained by the same method as in Example 1 except that the heating temperature and the ultrasonic frequency were set to room temperature (25° C.) and 28 kHz, respectively, when the support was immersed in the ethanol solution.

[0256] Confirmation of MOF membrane based on XRD spectrum

[0257] X-ray diffraction (XRD) spectrum was measured by the same method as in Example 1. As a result, in the filter obtained in Comparative Example 2, the peak of the X-ray diffraction (XRD) spectrum was located at the same position as the peak position of the particles of the ZIF-8 monomer and the peak position of the film of the ZnO monomer, confirming that it was a composite structure having both ZIF-8 and ZnO.

[0258] ·Confirmation of MOF membrane based on SEM observation

[0259] The same method as in Example 1 was used for SEM observation. Fig. 7A and Figure 7B SEM images of Figure 7B It is clear from the SEM image that protrusions are not densely formed on the entire surface of the filter surface (MOF membrane surface) of Comparative Example 2.

[0260] The average adjacent distance p, average depth d, and average film thickness t of the protrusions were measured from the SEM image by the same method as in Example 1. Specifically, the distance between two protrusions in any 100 adjacent groups was measured to obtain the average adjacent distance p. The average depth d and average film thickness t were obtained by measuring any 100 protrusions.

[0261] The average adjacent distance p is 200 nm, the average depth d is 20 nm, and the average film thickness t is 100 nm.

[0262] (Comparative Example 3)

[0263] Formation of MOF membranes

[0264] A filter was obtained by the same method as in Example 1 except that zinc oxide powder having an average primary particle size of 30 μm was used. However, the support collapsed when the support was immersed in an ethanol solution.

[0265] (Comparative Example 4)

[0266] Formation of MOF membranes

[0267] A filter was obtained by the same method as in Example 1 except that the heating temperature was set to room temperature, 25°C, when the support was immersed in the ethanol solution.

[0268] Confirmation of MOF membrane based on XRD spectrum

[0269] X-ray diffraction (XRD) spectrum was measured by the same method as in Example 1. As a result, in the filter obtained in Comparative Example 4, the peak of the X-ray diffraction (XRD) spectrum was located at the same position as the peak position of the particles of the ZIF-8 monomer and the peak position of the film of the ZnO monomer, confirming that it was a composite structure having both ZIF-8 and ZnO.

[0270] ·Confirmation of MOF membrane based on SEM observation

[0271] The SEM was used for observation in the same manner as in Example 1. Fig. 8A and Figure 8B SEM images of Figure 8B It is clear from the SEM image that protrusions are not densely formed on the entire surface of the filter surface (MOF membrane surface) of Comparative Example 4.

[0272] The average adjacent distance p, average depth d, and average film thickness t of the protrusions were measured from the SEM image by the same method as in Example 1. Specifically, the distance between two protrusions in any 100 adjacent groups was measured to obtain the average adjacent distance p. The average depth d and average film thickness t were obtained by measuring any 100 protrusions.

[0273] The average adjacent distance p is 200 nm, the average depth d is 20 nm, and the average film thickness t is 100 nm.

[0274] (Comparative Example 5)

[0275] Formation of MOF membranes

[0276] A filter was obtained by the same method as in Example 1 except that the ultrasonic frequency was set to 28 kHz when the support was immersed in the ethanol solution.

[0277] Confirmation of MOF membrane based on XRD spectrum

[0278] X-ray diffraction (XRD) spectrum was measured by the same method as in Example 1. As a result, in the filter obtained in Comparative Example 5, the peak of the X-ray diffraction (XRD) spectrum was located at the same position as the peak position of the particles of the ZIF-8 monomer and the peak position of the film of the ZnO monomer, confirming that it was a composite structure having both ZIF-8 and ZnO.

[0279] ·Confirmation of MOF membrane based on SEM observation

[0280] The same method as in Example 1 was used for SEM observation. Fig. 9A and Fig. 9B SEM images of Fig. 9B The SEM image of clearly shows that no protrusions are formed on the filter surface (MOF membrane surface) of Comparative Example 5, and the MOF membrane surface is smooth.

[0281] (Carbon dioxide gas adsorption test)

[0282] Experimental methods

[0283] The filter sample was placed in a 12L acrylic chamber, 24mL of CO2 gas was introduced, and the CO2 concentration was monitored.

[0284] ·result

[0285] The CO2 concentration measurement results are shown in Fig.10 . Fig.10 This is a graph showing the evaluation results of the gas adsorption test performed in Examples and Comparative Examples.

[0286] In detail, the amount of carbon dioxide adsorption within 30 minutes is as follows:

[0287] Example 1: Concentration difference with the case without filter (2500 ppm) 2400 ppm = 28.8 mL of CO2 adsorption;

[0288] Example 2: The concentration difference compared to the case without a filter (2500 ppm) is 1800 ppm = 21.6 mL of CO2 adsorption;

[0289] Comparative Example 1: Concentration difference with the case without filter (2500 ppm) 350 ppm = 4.2 mL of CO2 adsorption;

[0290] Comparative Example 2: The concentration difference from the case without a filter (2500 ppm) was 450 ppm = 4.8 mL of CO2 adsorption.

[0291] Thus, the presence of the nanoprotrusion structure increases the carbon dioxide adsorption rate. In addition, the carbon dioxide adsorption rate can be increased by appropriately increasing the zinc oxide particle size.

[0292] · Investigation 1: Promoting the penetration of gas into nanoprotrusion structures

[0293] MOF membranes are composed of metal ions and organic molecules, typically, such as Fig.13 As shown, it has a lattice without lattice defects. However, in reality, Fig.11 As shown in FIG. 1 , lattice defects partially exist, and in the lattice defects, there are both sites where the lattice is terminated by metal and sites where the lattice is terminated by organic molecules, so the pores are widened. Gas molecules can easily enter the widened pores. The MOF membrane of the present invention has protrusions at a predetermined average adjacent distance, so that Figure 1C As shown in FIG. 1 , the surface area of ​​the MOF film increases, and the lattice defects increase moderately. Therefore, it is considered that the intrusion of gas molecules becomes easier, and as a gas adsorption filter, the gas adsorption rate becomes faster. Fig.11 This is a schematic diagram of MOF schematically showing the actual crystal structure of MOF.

[0294] Study 2: Improvement of gas adsorption rate due to gaps between particles

[0295] The larger the gaps between the particles constituting the support, the better the gas flow and the faster the adsorption rate in the gas adsorption filter. The diffusion resistance of the gas when it flows in the straight holes on the capillary is as follows: Fig.12 When the pore size is 1 μm or more, the diffusion resistance is small, the gas flow becomes smooth, and thus the gas adsorption rate increases.

[0296] In Example 2, the gaps between the particles of the MOF filter made of zinc oxide particles with a particle size of 1 μm are smaller than 1 μm. On the other hand, in Example 1, the gaps between the particles of the MOF filter made of zinc oxide particles with a particle size of 11 μm are also larger than 1 μm. Therefore, it can be considered that in Example 1, in addition to the effect of the nanoprotrusion structure, the gas adsorption rate is further improved by the effect of the gaps. Fig.12 This is a graph showing the relationship between gap size and diffusion resistance.

[0297] · Investigation 3: Metal oxide particle size of the substrate

[0298] In Example 1, even when a MOF film was formed on a molded body obtained by extrusion molding zinc oxide having a particle size of 11 μm and then calcining it, the shape equivalent to the shape before film formation ( FIG. 3 ) was maintained.

[0299] In Comparative Example 3, when a MOF film was formed on a molded body obtained by extrusion molding zinc oxide having a particle size of 30 μm and then calcining it, disintegration occurred.

[0300] It is found that when the particle size is 11 μm, the filter shape can be maintained even without a binder, whereas when the particle size is too large, the filter shape cannot be maintained.

[0301] This is considered to be because when the particle size is too large, the contact area between particles is small, so the strength is reduced, and in addition, the structure is destroyed by the application of ultrasonic waves, which is a load during MOF film formation.

[0302] On the other hand, if a MOF film having a nanoprotrusion structure is formed on a support, then Figure 1A As shown, more MOF films are formed particularly at locations where the gaps between particles are narrow. Therefore, it is clear that metal oxide particles (eg, zinc oxide particles) with a particle size of 1 μm or more are required to obtain a gap size of 1 μm or more.

[0303] Industrial Applicability

[0304] The MOF membrane of the present invention and the gas adsorbent material having the MOF membrane are useful for sensors (particularly gas or odor sensors), gas adsorbent filters, and gas removal devices.

[0305] Description of Reference Numerals

[0306] 1: Metal organic structure membrane (MOF membrane)

[0307] 2: Metal oxides

[0308] 11: Protrusion

[0309] 12: Base

[0310] 40: Gas sensor

[0311] 50: Multi-gas sensor

[0312] 60: Gas adsorption filter

[0313] 61: Support

[0314] 62: Metal oxide layer

[0315] 63: Metal organic structure membrane (MOF membrane)

[0316] 65: Adsorption material

[0317] 70: Gas removal device

Claims

1. A metal organic structure film, the surface of which is covered with protrusions, wherein the protrusions have an average adjacent distance p of 1 nm to 100 nm.

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 structure film according to claim 1 or 2, wherein: The metal organic structure film is disposed on the surface of the metal oxide.

4. The metal-organic structure film according to claim 3, wherein: At the interface between the metal oxide and the metal-organic structure constituting the metal-organic structure film, the metal oxide and the metal-organic structure share metal atoms.

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

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 organic molecules, cyanide organic molecules, and carboxylic acid organic molecules.

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

8. The metal-organic structure film according to any one of claims 3 to 7, wherein The metal oxide includes 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 structure film according to any one of claims 3 to 8, wherein The metal oxide has a particle form, or has a molded body or a molded sintered body form of the particle.

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. The metal-organic structure film according to any one of claims 1 to 10, wherein The metal organic structure film has a film thickness t of 10 nm to 1000 nm.

12. The metal-organic structure film according to any one of claims 1 to 11, wherein The metal organic structure constituting the metal organic structure film has a composition formula of Zn(mIm)2.

13. The metal-organic structure film according to any one of claims 1 to 12, wherein The metal organic structure film is a gas adsorption material.

14. The metal-organic structure film according to claim 13, wherein: An amine compound is contained in the metal organic structure film, The gas is carbon dioxide gas.

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 or 15, wherein: The amine compound is polyethyleneimine.

17. A method for producing a metal organic structure film, wherein: While immersing the metal oxide in a solution containing organic molecules, heating and ultrasonic waves are applied. 18 . The method for producing a metal-organic structure film according to claim 17 , which produces the metal-organic structure film according to any one of claims 1 to 16 .

19. The method for producing a metal organic structure film according to claim 17 or 18, wherein: The heating is heating at 40°C or above. The ultrasonic wave has a frequency of 30 kHz or more.

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