Membrane material, gas separation membrane, and method for producing membrane material

Abstract

To provide a membrane material capable of suppressing occurrence of defects, exhibiting superior gas separation performance, and being producible by a simple method.SOLUTION: A membrane material according to the present invention is a membrane material comprising a metal-organic framework, the metal-organic framework being constituted by metal ions and organic ligands and including at least 5 mass% of an amorphous component. A method for producing the membrane material of the present invention includes: step 1 of forming a film by coating a substrate with a solution containing a fatty acid metal salt and an organic ligand; and step 2 of producing a membrane material containing a metal-organic framework by contacting the film with gaseous alcohol.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a membrane material and a gas separation membrane containing a metal-organic framework, and a method for producing the membrane material. [Background technology]

[0002] Metal-organic frameworks (MOFs), formed by the interaction of metal ions and organic ligands, are known as materials with porous structures, or so-called three-dimensional microporous materials. Metal-organic frameworks are expected to exhibit a variety of functions, and therefore have the potential for a wide range of applications in various fields, such as gas storage, gas separation, catalysis, and drug delivery. Research and development into metal-organic frameworks has been actively conducted in recent years.

[0003] Many types of metal-organic frameworks are known to exist, and a representative example is ZIF (Zeolitic Imidazolate Framework), which uses zinc (Zn) or cobalt (Co) as the metal and imidazole as the organic bridging ligand. Research into the synthesis and characterization of ZIF has been widely conducted. For example, Non-Patent Document 1 discloses a technique for producing ZIF-8 membranes by a method of directly growing a membrane on a surface-modified support (in-situ method). It is expected that such ZIF-8 membranes will be able to efficiently separate gases such as hydrogen / methane mixtures. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Journal of Membrane Science 472(2014), 29-38 Summary of the Invention [Problem to be solved by the invention]

[0005] Various membrane materials containing metal-organic frameworks are known, but such membrane materials are prone to defects on the surface or inside. For this reason, in recent years, there has been a demand for densifying membrane materials in order to further improve the functions of membrane materials, such as their separation performance. However, conventional technologies have had limitations on the degree to which membrane materials can be densified, and such densification has not been easy. If it were possible to construct a structure in which the voids in the membrane material are reduced as much as possible and the occurrence of defects is suppressed, it would be possible to obtain a metal-organic framework-containing membrane material with unprecedentedly excellent functions, making it a highly useful material.

[0006] The present invention has been made in view of the above, and aims to provide a membrane material that suppresses the occurrence of defects, has excellent gas separation performance, and can be produced by a simple method. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the present inventors have found that the above object can be achieved by using a metal organic framework and containing 5 mass % or more of an amorphous component, and have thus completed the present invention.

[0008] That is, the present invention includes, for example, the subject matter described in the following sections. Item 1 A film material containing a metal organic framework, the metal-organic framework is formed of metal ions and organic ligands, A film material containing 5% or more by mass of amorphous components. Section 2 Item 1. The membrane material according to Item 1, wherein the metal organic framework is a zeolitic imidazolate framework (ZIF). Section 3 Item 1 or 2. A gas separation membrane comprising the membrane material according to item 1 or 2. Section 4 A method for producing a film material containing a metal organic framework, comprising: Step 1: forming a coating by coating a substrate with a solution containing a fatty acid metal salt and an organic ligand; Step 2 of contacting the film with a gaseous alcohol to obtain a film material containing a metal organic framework; A method for producing a membrane material, comprising: Section 5 Item 5. The method for producing a membrane material according to Item 4, wherein the metal organic framework is a zeolitic imidazolate framework (ZIF). [Effects of the Invention]

[0009] The membrane material of the present invention is suppressed from generating defects, has excellent gas separation performance, and can be produced by a simple method.

[0010] According to the method for producing a membrane material of the present invention, the occurrence of defects is suppressed and a membrane material having excellent gas separation performance can be easily produced. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating the manufacturing process of the membrane material of Example 1. FIG. [Figure 2] 1 shows the results of thermogravimetric changes of glass-solated ZIF-8 prepared to produce the membrane material of Example 1. [Figure 3] 1 shows XRD spectra of the membrane materials (including anodized alumina supports) prepared in the examples. [Figure 4] 1 shows the results of scanning electron microscope observation of the membrane material obtained in Example 1 and the membrane material obtained in Comparative Example 2. [Figure 5] (a) is an enlarged photograph of the membrane material, (b) is a further enlarged photograph of (a), and (c) is a cross-sectional photograph of the membrane material taken by a scanning electron microscope. [Figure 6] 1 shows the results of scanning electron microscope observation of the film material obtained in Comparative Example 1. [Figure 7] 1 shows the results of measuring the gas permeability of the membrane material obtained in Example 1 to each gas. [Figure 8] 1 is a schematic explanatory diagram of an apparatus used for measuring gas permeability. FIG. 2 shows the results of measuring the gas permeability of the membrane material obtained in Example 1 to each gas. DETAILED DESCRIPTION OF THE INVENTION

[0012]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0013] 1. Membrane material The membrane material of the present invention contains a metal-organic framework, which is formed from metal ions and organic ligands. In particular, the membrane material of the present invention contains 5% by mass or more of an amorphous component. The membrane material of the present invention suppresses the occurrence of defects, has excellent gas separation performance, and can be produced by a simple method. Therefore, the membrane material of the present invention has excellent gas separation performance and can be suitably used, for example, as a gas separation membrane for separating a specific gas from a mixed gas.

[0014] The membrane material of the present invention contains, as a main component, a metal-organic framework, which, as described above, is formed by the interaction between metal ions and organic ligands and is known as a "MOF."

[0015] The metal (metal ion) contained in the metal organic framework will be referred to as "metal M" below. Examples of such metal M include a wide variety of metals such as alkaline earth metals and transition metals, and among these, preferred examples include Group 8 elements (e.g., iron, ruthenium), Group 9 elements (e.g., cobalt, rhodium), Group 10 elements (e.g., nickel, palladium), Group 11 elements (e.g., copper), and Group 12 elements (e.g., zinc, cadmium). More preferred metals M include cobalt, nickel, copper, zinc, etc., even more preferably cobalt or zinc, and particularly preferably zinc.

[0016] The organic ligand contained in the metal organic framework will be referred to below as "organic ligand L." Examples of the organic ligand L include at least one ligand selected from the group consisting of imidazole, azole, benzimidazole, azabenzimidazole, dicarboxylic acid, tricarboxylic acid, and derivatives thereof.

[0017] The organic ligand L may have a substituent to the extent that coordination with the metal ion is not inhibited. The substituent is not particularly limited, but examples thereof include an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a halogen atom, an amino group, a nitro group, a cyano group, and a hydroxyl group.

[0018] For example, when the organic ligand L is imidazole or a derivative thereof, the organic ligand L refers to unsubstituted imidazole or imidazole having one to three substituents selected from the group consisting of alkyl groups having 1 to 6 carbon atoms (e.g., 1 to 4 carbon atoms (C1 to 4) or 1 to 3 carbon atoms (C1 to 3)), halogen groups, and nitro groups on at least one of the carbon atoms at the 2-, 4-, or 5-positions (mono-substitution at the 2-position is preferred) on the imidazole, or the adjacent substituents at the 4- and 5-positions on the imidazole may join together to form a fused 5- or 6-membered aromatic carbocyclic or aromatic heterocyclic ring that may have a substituent. Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, neobutyl, t-butyl, n-pentyl, n-hexyl, etc., with methyl, ethyl, n-propyl, and isopropyl being more preferred, methyl and ethyl being even more preferred, and methyl being particularly preferred. Halogen groups include fluoro, chloro, bromo, and iodo, with chloro being preferred.

[0019] In addition, adjacent substituents at the 4- and 5-positions on the imidazole may join together to form a fused 5- or 6-membered aromatic carbocyclic or aromatic heterocyclic ring, which may have a substituent. An example of a fused 5- or 6-membered aromatic carbocyclic ring is a benzo group. The fused 5- or 6-membered aromatic heterocyclic ring refers to a fused 5- or 6-membered aromatic heterocyclic ring containing at least one atom selected from oxygen, nitrogen, or sulfur as a heteroatom. Examples of 5-membered aromatic heterocyclic rings include a furo group, a thiopheno group, a pyrrolo group, an imidazolo group, a pyrazolo group, an isoxazolo group, and a tetrazolo group. Examples of 6-membered aromatic heterocyclic rings include a pyrido group, a pyrazino group, a pyrimidino group, and a pyridazino group.

[0020] Further specific examples of the organic ligand L include imidazole, 2-methylimidazole, 2-formylimidazole, 4,4'-bipyridyl, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, biphenylenedicarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, trimesic acid, 2-imidazolecarbaldehyde, 1,4-benzenedicarboxylate, 1,4-diazabicyclo[2.2.2.]octane, pyrazine-2,3-dicarboxylate, isophthalate, 1,3,5-benzenetricarboxylate, and 2-aminoterephthalate.

[0021] The metal organic framework can be a wide range of known metal organic frameworks (MOFs), including, for example, metal organic frameworks formed by various combinations of the above-mentioned metal M and organic ligand L.

[0022] Among these, the metal-organic framework is preferably a zeolitic imidazolate framework known as ZIF (Zeolitic Imidazolate Framework). In this case, the membrane material of the present invention is more likely to be densified due to the reduced occurrence of defects, which can further improve, for example, the gas separation performance.

[0023] Specific examples of ZIF include ZIF-8 (in this case, the metal M is zinc and the organic ligand L is 2-methylimidazole), ZIF-7, ZIF-8, ZIF-22, ZIF-67, ZIF-69, ZIF-90, etc. Specific examples of metal-organic frameworks include MIL-47, MIL-53, MIL-88, MIL-96, MIL-101, MIL-100, Cu-BTC, MOF-5, IRMOF-3, MMOF, and SIM-1.

[0024] The film material of the present invention may contain other components as long as the effects of the present invention are not impaired, as long as it contains the metal-organic framework. Other components may include residues of raw materials and by-products used in producing the metal-organic framework, as well as intentionally added additive components. The content of the metal-organic framework in the film material of the present invention is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The film material of the present invention may consist solely of the metal-organic framework.

[0025] The membrane material of the present invention contains 5% by mass or more of an amorphous component relative to the entire membrane material. This suppresses the occurrence of defects in the membrane material of the present invention, resulting in a densified state. If the content of the amorphous component in the membrane material of the present invention is less than 5% by mass, the occurrence of defects increases, preventing the membrane material from becoming densified, resulting in, for example, a decrease in gas separation performance. In the present invention, the amorphous component can refer to a component derived from the metal-organic framework, which is an amorphous metal-organic framework that is not crystallized.

[0026] Here, in the present invention, the amorphous component content of the film material refers to a numerical value calculated from the X-ray diffraction spectrum obtained by X-ray diffraction (XRD) measurement of the film material. Specifically, a laminate is prepared by laminating the film material of the present invention on a substrate, and X-ray diffraction measurement of this laminate is performed. The amorphous component content in the film material is calculated based on the X-ray diffraction spectrum obtained by this measurement. The amorphous component content is calculated using the following formula (1). A(mass%)=100×{(a)-(b)-(c)} / {(a)-(c)}···(1)

[0027] In formula (1), A is the content (mass%) of the amorphous component in the film material, (a) is the total integrated intensity of the X-ray diffraction spectrum of the laminate, (b) is the integrated intensity of the X-ray diffraction peak attributable to the metal-organic framework in the X-ray diffraction spectrum of the laminate, and (c) is the integrated intensity of the X-ray diffraction spectrum attributable to the base material alone contained in the laminate. The integrated intensity refers to the area of ​​the region formed between the baseline of the X-ray diffraction spectrum and the spectrum. The baseline of the X-ray diffraction spectrum is the straight line connecting the point on the spectrum where 2θ is 3° and the point on the spectrum where 2θ is 60°.

[0028] The laminate used to calculate the amorphous component content of the film material is, as described above, formed by laminating the film material on a substrate. The type of substrate is not particularly limited, and for example, a substrate such as an anodized aluminum oxide (AAO) wafer is used. The laminate is configured such that no layer is formed between the substrate and the film material. The method for forming the film material on the substrate is not particularly limited, and it is preferable to form the laminate using, for example, the method for producing the film material described below.

[0029] When the membrane material is formed of ZIF-8, diffraction peaks derived from ZIF-8 appear, for example, at 7.4 °, 10.4 °, 12.8 °, 14.7 °, 16.5 °, 18.1 °, 19.5 °, 22.2 °, 23.4 °, 24.6 °, 25.7 °, 26.7 °, 28.8 °, 29.7 °, 30.7 °, 31.6 °, 32.5 °, 34.2 °, 35.0 °, and 37.4 °.

[0030] The film material of the present invention preferably contains 10% by mass or more of amorphous components, more preferably 15% by mass or more, and even more preferably 20% by mass or more. The upper limit of the amorphous component content in the film material of the present invention is, for example, 80% by mass, preferably 70% by mass, more preferably 60% by mass, and even more preferably 50% by mass.

[0031] The membrane material of the present invention contains an amorphous component, and more specifically, the membrane material of the present invention is a MOF membrane in which amorphous regions and crystalline regions are mixed.

[0032] The membrane material of the present invention may be formed on, for example, various supports. Examples of the support include a wide range of substrates used in the manufacturing method of the membrane material described below.

[0033] The thickness of the membrane material of the present invention can be adjusted to an appropriate range depending on the application, purpose, etc. For example, the thickness of the membrane material of the present invention is 0.1 μm or more and 50 μm or less, preferably 0.2 μm or more, more preferably 0.3 μm or more, and preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. The method for adjusting the thickness of the membrane material is not particularly limited, and for example, a wide variety of known methods can be used.

[0034] Because the film material of the present invention contains a predetermined amount of amorphous components as described above, the surface structure of the film material differs from that of film materials prepared by, for example, conventional secondary growth methods or in-situ methods. For example, as shown in Figures 4 and 5 described below, the surface of the film material of the present invention may have a surface structure that spreads radially on the surface. Such a surface structure is not found in conventional polycrystalline films (see also Figure 6).

[0035] The membrane material of the present invention contains a metal-organic framework, and by adjusting the amorphous component as described above, the occurrence of defects is suppressed, the membrane material has excellent gas separation performance, and can be produced by a simple method. Because the membrane material of the present invention has excellent gas separation performance, it can be suitably used, for example, as a gas separation membrane for separating a specific gas from a mixed gas.

[0036] Therefore, the present invention can include a gas separation membrane comprising the above-mentioned membrane material. Such a gas separation membrane is capable of separating a specific gas from a mixed gas, and has so-called molecular sieving ability.

[0037] Examples of gases contained in the mixed gas include methane, ethane, ethylene, acetylene, propane, propene, methylacetylene, propadiene, butane, 1-butene, 2-butene, isobutene, 1,3-butadiene, 1,2-butadiene, carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, rare gases (helium, neon, argon, krypton, xenon, etc.), hydrogen sulfide, ammonia, sulfur oxides, nitrogen oxides, and siloxanes (hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, etc.). The mixed gas may contain two or more types of gases.

[0038] In gas separation using the gas separation membrane of the present invention, for example, a mixed gas containing hydrogen and methane, a mixed gas containing carbon dioxide and nitrogen, a mixed gas containing carbon dioxide and methane, a mixed gas containing propane and propene, and a mixed gas containing hydrogen and propane can be used, and one gas can be separated from these mixed gases.

[0039] The gas separation membrane of the present invention has excellent gas separation performance and can therefore be applied to, for example, various reactions involving the use or generation of gas. For example, in the propane dehydrogenation reaction, propane is dehydrogenated to generate propene and hydrogen. By using the gas separation membrane of the present invention in this reaction, for example, hydrogen and propane can be efficiently separated. In this way, the gas separation membrane of the present invention can be used as a membrane reactor that integrates separation and reaction.

[0040] The gas separation membrane of the present invention can be formed by combining the membrane material of the present invention with other materials, or the gas separation membrane can be formed using only the membrane material of the present invention without using other materials.

[0041] The membrane material of the present invention can be used for various purposes other than gas separation membranes, and can be expanded into sensors, adsorbents, insulating films, etc.

[0042] 2.Membrane material manufacturing method The membrane material of the present invention can be produced, for example, by a production method including the following steps 1 and 2. Step 1: A solution containing a fatty acid metal salt and an organic ligand is coated onto a substrate to form a film. Step 2: A step of obtaining a film material containing a metal organic framework by contacting the film with a gaseous alcohol.

[0043] In step 1, a solution containing a fatty acid metal salt and an organic ligand is used. Such a solution is a raw material for preparing a metal-organic framework. The solution used in step 1 is a solution in which a fatty acid metal salt and an organic ligand are dissolved in a solvent, and more specifically, is a glass sol of an organometallic substance formed by the fatty acid metal salt and the organic ligand.

[0044] The fatty acid metal salt can be, for example, a wide variety of known metal salts of fatty acids. In the fatty acid metal salt, examples of the metal include the metal M described above. Therefore, examples of the metal in the fatty acid metal salt include a wide variety of metals, such as alkaline earth metals and transition metals. Among these, preferred examples include Group 8 elements (e.g., iron, ruthenium), Group 9 elements (e.g., cobalt, rhodium), Group 10 elements (e.g., nickel, palladium), Group 11 elements (e.g., copper), and Group 12 elements (e.g., zinc, cadmium). More preferred metals include cobalt, nickel, copper, zinc, etc., even more preferred are cobalt or zinc, and particularly preferred is zinc.

[0045] The fatty acid metal salts can be, for example, metal salts of saturated fatty acids having about 2 to 10 carbon atoms or unsaturated fatty acids having about 2 to 10 carbon atoms. Specific examples of the fatty acids in the fatty acid metal salts include acetic acid, propanoic acid, butyric acid, pentanoic acid, and hexanoic acid, with acetic acid being preferred.

[0046] Preferable fatty acid metal salts are zinc acetate, cobalt acetate, etc., and more preferably zinc acetate. For example, when the metal organic framework is ZIF-8, zinc acetate can be used as the fatty acid metal salt.

[0047] The fatty acid metal salt may be a hydrate. The fatty acid metal salt may be produced by a known method or may be available as a commercially available product such as a reagent.

[0048] The organic ligand contained in the solution used in step 1 can be the aforementioned organic ligand L, i.e., at least one ligand selected from the group consisting of imidazole, azole, benzimidazole, azabenzimidazole, dicarboxylic acid, tricarboxylic acid, and derivatives thereof, which may have the aforementioned substituent.

[0049] Specific examples of the organic ligand used in step 1 include imidazole, 2-methylimidazole, 2-formylimidazole, 4,4'-bipyridyl, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, biphenylenedicarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, trimesic acid, 2-imidazolecarbaldehyde, 1,4-benzenedicarboxylate, 1,4-diazabicyclo[2.2.2.]octane, pyrazine-2,3-dicarboxylate, isophthalate, 1,3,5-benzenetricarboxylate, and 2-aminoterephthalate. For example, when the metal-organic framework is ZIF-8, 2-methylimidazole can be used as the organic ligand.

[0050] In addition to water, various organic solvents can be widely used as the solvent for preparing the solution. Examples of the organic solvent include alcohol compounds, formamides such as N,N-dimethylformamide and N,N-dimethylacetamide, pyrrolidones such as 2-pyrrolidone and N-methylpyrrolidone, ketone compounds such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate, propyl acetate, ethyl carbitol acetate, and butyl carbitol acetate, chlorinated hydrocarbons such as chloroform and 1,2-dichloroethane, ether compounds such as diethyl ether and tetrahydrofuran, aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, and carbonate solvents such as dimethyl carbonate, diethyl carbonate, and propylene carbonate.

[0051] The alcohol compound may be an alcohol having about 1 to 8 carbon atoms, and specific examples thereof include methanol, ethanol, n-propanol, isopropanol, and n-butanol.

[0052] The solvent for preparing the solution is preferably water, an alcohol compound, or a formamide-based solvent. In this case, a glass sol solution of a transparent metal-organic framework can be easily prepared, and a highly dense film material can be easily obtained. The solvent is more preferably at least one selected from the group consisting of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, and N,N-dimethylformamide. Various types of water can be used, such as distilled water, ion-exchanged water, deionized water, pure water, electrolyzed water, tap water, and industrial water. The solvent may also be a mixed solvent.

[0053] The ratio of the fatty acid metal salt and organic ligand contained in the solution to the solvent is not particularly limited. For example, the molar ratio of the fatty acid metal salt and organic ligand contained in the solution (i.e., the number of moles of fatty acid metal salt: the number of moles of organic ligand) can be 1:0.1 to 1:10, preferably 1:0.2 to 1:8, more preferably 1:0.5 to 1:5, and even more preferably 1:1 to 1:3. When the metal-organic framework is ZIF-8, the molar ratio of the fatty acid metal salt and organic ligand is 1:2, which is a stoichiometric ratio.

[0054] The content of the solvent in the solution can be appropriately set taking into consideration solubility, etc. For example, the solvent can be used in an amount sufficient to make the solution of the fatty acid metal salt and organic ligand transparent, i.e., an amount sufficient to form a transparent glass sol. For example, the amount of solvent used can be 1 mol or more per mol of the fatty acid metal salt, preferably 2 mol or more, more preferably 3 mol or more, even more preferably 5 mol or more, and particularly preferably 8 mol or more. There is no particular upper limit to the amount of solvent used, and it is 1,000 mol or less, preferably 500 mol or less, per mol of the fatty acid metal salt.

[0055] For example, if the solvent is water or methanol, a transparent glass sol can be obtained when the amount of solvent per mole of the fatty acid metal salt is in the range of 1 to 500 moles; if the solvent is n-butanol, a transparent glass sol can be obtained when the amount of solvent per mole of the fatty acid metal salt is in the range of 1 to 100 moles; and if the solvent is N,N-dimethylformamide, a transparent glass sol can be obtained when the amount of solvent per mole of the fatty acid metal salt is in the range of 1 to 10 moles.

[0056] The method for preparing the solution used in step 1 is not particularly limited. For example, the solution can be prepared by mixing the fatty acid metal salt, organic ligand, and solvent in predetermined amounts. When preparing the solution, the temperature may be about room temperature, or it may be heated as needed. The solution may contain components other than the fatty acid metal salt, organic ligand, and solvent as needed, or it may consist only of the fatty acid metal salt, organic ligand, and solvent.

[0057] The solution used in step 1 is preferably in a so-called sol state. In the sol state solution (glass sol solution), for example, a complex between the fatty acid metal salt and an organic ligand is formed.

[0058] In step 1, the solution is coated onto a substrate. This coating forms a film. The substrate is a support for supporting the film material of the present invention, and its type is not particularly limited. Examples of substrates used in step 1 include anodized aluminum oxide (AAO) wafers, silicon wafers, glass plates, inorganic plates, metal plates, and resin plates, and may also be various plastic films.

[0059] The method for coating the solution onto the substrate is not particularly limited, and a wide variety of known coating methods can be used, such as spin coating and dip coating. Alternatively, the solution can be coated onto the substrate by known coating methods. The thickness of the coating is also not particularly limited, and can be adjusted within an appropriate range depending on the thickness of the desired film material.

[0060] In step 2, the coating on the substrate formed in step 1 is brought into contact with gaseous alcohol (alcohol vapor). As a result, a film material containing a metal organic framework as a main component and having an amorphous component content of 5% by mass or more is formed on the substrate. By performing the contact treatment with gaseous alcohol, the crystallization of the resulting film material is controlled within an appropriate range. If the contact treatment with alcohol is not performed, it would be impossible to adjust the amorphous component content of the resulting film material to 5% by mass or more.

[0061] Examples of gaseous alcohols include alcohols having about 1 to 8 carbon atoms, and specific examples include methanol, ethanol, n-propanol, isopropanol, and n-butanol.

[0062] The method for contacting the film with the gaseous alcohol is not particularly limited, and for example, the film can be contacted with the gaseous alcohol by placing the film formed on the substrate in an atmosphere containing the gaseous alcohol. Alternatively, the film can be contacted with the gaseous alcohol by placing the film in a sealed space and introducing alcohol vapor into the space. Furthermore, the film can be contacted with the gaseous alcohol by placing the film and the alcohol independently in the same atmosphere in a sealed space and vaporizing the alcohol in the atmosphere.

[0063] When the film comes into contact with the gaseous alcohol, the ambient temperature can be adjusted to a predetermined temperature range as needed to vaporize the alcohol. For example, the temperature at which the film comes into contact with the gaseous alcohol can be 60 to 180°C, preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher, and preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 140°C or lower. The means for adjusting the temperature are not particularly limited, and a wide variety of known temperature adjustment means can be applied.

[0064] The contact time between the film and the gaseous alcohol is not particularly limited and can be set within an appropriate range depending on the above-mentioned contact temperature, the type of alcohol, etc. For example, the contact time between the film and the gaseous alcohol can be 30 minutes to 24 hours.

[0065] After the contact treatment of the coating with the gaseous alcohol, a heat treatment can be carried out, if necessary. This allows volatile components such as the solvent remaining in the coating to be quickly removed. The temperature of this heat treatment can be, for example, 60 to 180°C, preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher, and preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 140°C or lower. The means for the heat treatment are not particularly limited, and known temperature control means can be widely applied. The heat treatment time can be set within an appropriate range depending on the temperature, and can be, for example, 30 minutes to 24 hours.

[0066] By passing through the above-mentioned step 2, the target membrane material of the present invention is formed on the substrate. Such membrane material contains a metal organic framework, and as described above, the content ratio of the amorphous component is adjusted to a predetermined range. The metal organic framework produced by steps 1 and 2 is, for example, a zeolite-type imidazolate framework such as ZIF-8.

[0067] The method for producing the membrane material of the present invention may include steps other than steps 1 and 2, or may consist of only steps 1 and 2, as long as the desired membrane material is obtained.

[0068] In the manufacturing method of the present invention, a predetermined solution is first coated in step 1, and the film obtained in step 1 is then contact-treated with alcohol vapor in step 2, thereby obtaining a membrane material with an amorphous component content adjusted to a predetermined range. In this way, the membrane material can be manufactured by a simple method. Moreover, the obtained membrane material has reduced defect generation and excellent gas separation performance. Therefore, the membrane material obtained by the manufacturing method of the present invention can be suitably used for the aforementioned gas separation membranes, etc.

[0069] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in the embodiments of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as described in this specification. [Example]

[0070] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0071] Example 1 The membrane material was prepared according to the procedure shown in Figure 1. First, 2.50 mmol of zinc acetate dihydrate and 5.00 mmol of 2-methylimidazole were dissolved in 20.0 mmol of 1-butanol as a solvent to obtain a solution of glass-solized ZIF-8. As can be seen from the blending amounts, the molar ratio of zinc acetate dihydrate to 2-methylimidazole in the solution was 1:2, which is the stoichiometric ratio of ZIF-8. 0.2 mL of the resulting solution was dropped onto an anodized alumina (AAO; diameter 47 mm, pore size 20 nm, thickness 65 μm). The dropped solution was spread by spin coating (3000 rpm x 60 s) to form a film of the ZIF-8 solution on the support (anodized alumina support) (Step 1). In this way, an anodized alumina support with a film of the ZIF-8 solution formed was obtained.

[0072] Next, the anodized alumina support on which the above-mentioned coating was formed was placed in a predetermined space, and 1-butanol vapor was supplied into the space at 130°C to bring the coating into contact with the gaseous alcohol. The duration of this contact treatment (the duration of supply of 1-butanol vapor) was 2, 4, 7, or 12 hours. After completion of the contact treatment, the coating was heated at 140°C for 60 minutes to remove the solvent that had become mixed into the coating. This formed a membrane material on the anodized alumina support (Step 2).

[0073] (Comparative Example 1) A membrane material made of ZIF-8 was formed on an anodic alumina oxide (AAO) support by the in-situ method disclosed in the aforementioned Non-Patent Document 1 (Journal of Membrane Science 472 (2014), 29-38).

[0074] (Comparative Example 2) A membrane material was formed on an anodized alumina oxide (AAO) support in the same manner as in Example 1, except that 1-butanol vapor was not supplied in step 2.

[0075] (Evaluation results) Figure 2 shows the results of thermogravimetric changes of the glass-solated ZIF-8 (referred to as "Glass ZIF-8sol" in Figure 2) prepared for producing the membrane material of Example 1. For comparison, Figure 2 also shows the results of thermogravimetric changes of zinc acetate dihydrate (referred to as "Zinc acetate dihydrate" in Figure 2) and 2-methylimidazole (referred to as "Hmim" in Figure 2).

[0076] As can be seen from Figure 2, it was confirmed that the thermal decomposition temperature of the glass-sol ZIF-8 was higher than that of the raw materials used, indicating that a metal-organic framework was formed.

[0077] Figure 3 shows XRD spectra of the membrane material (including the anodized alumina support) prepared in the examples, showing the XRD spectra obtained when the 1-butanol vapor supply time was changed. In Figure 3, "12 h" means that the 1-butanol vapor supply time (synonymous with the contact treatment time in step 2; the same applies below) was 12 hours, "4 h" means that the 1-butanol vapor supply time was 4 hours, and "2 h" means that the 1-butanol vapor supply time was 2 hours.

[0078] 3 also shows the XRD spectrum of Comparative Example 2 (an example in which a membrane material was produced without supplying 1-butanol vapor), the XRD spectrum of the anodized alumina support itself on which no membrane material was formed (denoted as "AAO" in FIG. 3), and the XRD spectrum of known ZIF-8 (denoted as "Simulated ZIF-8" in FIG. 3). It was found that the XRD spectrum of the membrane material obtained in the example was in good agreement with the XRD spectrum of known ZIF-8, and it was confirmed that the membrane material obtained in the example was ZIF-8.

[0079] Table 1 shows the results of calculating the content ratio of amorphous components in the membrane material using the formula (1) based on the XRD spectrum in Figure 3. Note that Comparative Example 2 is a ZIF-8 membrane produced by the in-situ method, and is a membrane material obtained without going through steps 1 and 2 in the production process.

[0080] The results in Table 1 show that the film material obtained through steps 1 and 2 has an amorphous component content of more than 5% by mass. In particular, a comparison between the Examples and Comparative Examples reveals that the alcohol vapor treatment in step 2 is important for adjusting the amorphous component content within a desired range, and also suggests that the amorphous component content can be controlled by the vapor supply time.

[0081] [Table 1]

[0082] Fig. 4 shows the results of scanning electron microscope observation of the membrane material obtained in Example 1 and the membrane material obtained in Comparative Example 2. In Fig. 4, the notation "2h" means that the membrane material had a 1-butanol vapor supply time of 2 hours, "4h" means that the membrane material had a 1-butanol vapor supply time of 4 hours, "7h" means that the membrane material had a 1-butanol vapor supply time of 7 hours, and "12h" means that the membrane material had a 1-butanol vapor supply time of 12 hours. Also, in Fig. 4, the notation "0h" means that the membrane material was obtained in Comparative Example 2.

[0083] Figure 5(a) is an enlarged photograph of the membrane material of "7h" in Figure 4, Figure 5(b) is an enlarged photograph of the membrane material of "2h" in Figure 4, and Figure 5(c) is a cross-sectional photograph of the membrane material of Figure 5(b).

[0084] FIG. 6 shows the results of scanning electron microscope observation of the film material obtained in Comparative Example 1.

[0085] From the results shown in Figures 4 and 5, it can be seen that the surface of the membrane material obtained in Example 1 has a surface structure that spreads radially on the support surface, and from the cross-sectional observation results, the thickness of the membrane material was estimated to be approximately 1 μm. From Figures 4 and 5, it can be seen that the surface of the membrane material obtained in Example 1 has a clearly different structure compared to the conventional ZIF-8 membrane shown in Figure 6, and it can be said that this result supports the fact that a large amount of amorphous components is generated.

[0086] 7(a) shows the results of measuring the permeability of each gas through the membrane material obtained in Example 1, and in particular plots the relationship between the 1-butanol vapor supply time and the gas permeability for each type of gas (H, CO, N, CH, C, H, C). Note that these gas permeabilities were calculated as relative values ​​based on the gas permeability of the membrane material obtained in Comparative Example 2 (not treated with alcohol vapor).

[0087] Figure 7(b) shows the plot of the vapor supply time and the change in gas permeability for the membrane material obtained in Example 1 based on Figure 7(a). In Figure 7(b), the notation "2h" indicates a membrane material with a 1-butanol vapor supply time of 2 hours, the notation "4h" indicates a membrane material with a 1-butanol vapor supply time of 4 hours, and the notation "12h" indicates a membrane material with a 1-butanol vapor supply time of 12 hours. Also, in Figure 7(b), the notation "0h" indicates the membrane material obtained in Comparative Example 2. The first axis in Figure 7(b) represents the theoretical diameter of the gas molecule.

[0088] Table 2 shows the hydrogen / methane permeability ratio (H2 / CH4), propene / propane permeability ratio (C3H6 / C3H8), hydrogen / propane permeability ratio (H2 / C3H8), carbon dioxide / nitrogen permeability ratio (CO2 / N2), and carbon dioxide / methane permeability ratio (CO2 / CH4), calculated based on the results of Figures 7(a) and (b). The membrane material obtained in Example 1 exhibited a clear difference in gas permeability between various gases and propane, which is believed to be due to the molecular sieving ability of ZIF-8. In particular, the membrane material obtained in Example 1 with 2 hours of alcohol vapor treatment exhibited a significantly higher H2 / C3H8 ratio than conventional separation membranes, demonstrating its excellent molecular sieving ability.

[0089] Although we do not necessarily wish to limit the interpretation, it is presumed that the molecular sieving ability of the membrane material obtained in Example 1 was exhibited because the glass structure of the MOF was converted to crystals by contact with alcohol vapor, but a certain amount of amorphous components was still contained, resulting in the formation of a denser and less amorphous ZIF-8 membrane, which resulted in the development of excellent molecular sieving ability.

[0090] The above results demonstrate that the membrane material containing the MOF obtained in Example 1 has dense crystal grain boundaries and is extremely effective as a gas separation membrane. Therefore, the vitrified sol obtained in Example 1 can be said to be a raw material that can be effectively used to form membranes with dense crystal grain boundaries.

[0091] [Table 2]

[0092] (Evaluation method) [Measurement of amorphous component amount] The proportion of amorphous components in the membrane material was calculated using the following formula (1) based on the results of XRD spectrum measurement of a laminate (hereinafter referred to as "laminate") in which the membrane material was formed on the substrate (AAO) prepared in the examples and comparative examples. A(mass%)=100×{(a)-(b)-(c)} / {(a)-(c)}···(1)

[0093] In formula (1), A is the content (mass%) of the amorphous component in the film material, (a) is the total integrated intensity of the X-ray diffraction spectrum of the laminate, (b) is the integrated intensity of the X-ray diffraction peak attributable to the metal-organic framework in the X-ray diffraction spectrum of the laminate, and (c) is the integrated intensity of the X-ray diffraction spectrum attributable to the base material alone contained in the laminate. The X-ray diffraction spectrum was measured using a MiniFlex600 X-ray diffractometer manufactured by Rigaku Corporation, using a Cu-Kα (λ=1.5418 Å) radiation source in the 2θ=3 to 60° range.

[0094] [Gas permeability measurement] The gas permeation test was carried out using a differential pressure gas permeation tester "GTR-1ADF-E" manufactured by GTR-TEC, using the differential pressure method with a high-pressure side pressure of 200 kPa and a permeation temperature of 308 K. The change in the low-pressure side pressure over time (dp / dt) was measured as the permeation amount, and the permeability (%) was calculated using the following formula (2).

[0095]

number

[0096] For reference, FIG. 8 shows a schematic explanatory diagram of a differential pressure gas permeation testing device used for measuring gas permeability.

Claims

1. A film material containing a metal organic framework, the metal-organic framework is formed of metal ions and organic ligands, A film material containing 5% by mass or more of an amorphous component.

2. 2. The membrane material of claim 1, wherein the metal organic framework is a zeolitic imidazolate framework (ZIF).

3. A gas separation membrane comprising the membrane material according to claim 1 or 2.

4. A method for producing a film material containing a metal organic framework, comprising: Step 1: forming a coating by coating a substrate with a solution containing a fatty acid metal salt and an organic ligand; Step 2 of contacting the film with a gaseous alcohol to obtain a film material containing a metal organic framework; A method for producing a membrane material, comprising:

5. The method for producing a membrane material according to claim 4 , wherein the metal organic framework is a zeolitic imidazolate framework (ZIF).

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