Method for producing a MOF membrane complex and MOF membrane complex

Abstract

In the fabrication of a MOF membrane complex, seed crystals of a CAU-10-MOF are deposited on a support (step S12), an aluminum source solution, which is an aqueous solution containing an aluminum ion source, is prepared (step S13a), and a ligand solution is prepared in which an organic ligand used for the synthesis of the CAU-10-MOS is dissolved in a solvent (step S13b). Subsequently, a starting material solution is prepared by mixing the aluminum source solution and the ligand solution at a rate that does not cause turbidity in the starting material solution (step S14). The support is immersed in the starting material solution to form a MOF membrane, which is the CAU-10-MOF on the support, via solvothermic synthesis (step S15).

Description

TECHNICAL AREA

[0001] The present invention relates to a method for producing a MOF membrane complex and a MOF membrane complex. NOTICE REGARDING RELATED REGISTRATIONS

[0002] This application enjoys priority over Japanese patent application No. JP2023-144625, which was filed with the Japanese Patent Office on September 6, 2023, the entire disclosure of which is incorporated herein. TECHNICAL BACKGROUND

[0003] In recent years, active research has been conducted on metal-organic frameworks (hereinafter also referred to as "MOFs"), which are crystalline porous materials composed of coordination bonds between metal ions and organic ligands. MOFs are porous materials with large surface areas and are expected to be used, similar to zeolite membranes, for the separation of gases or liquids by deposition on porous supports.

[0004] A well-known type of MOF is referred to as "CAU-10". CAU-10 MOFs are represented by Al(OH)(C8H3O4X) and contain aluminum ions as the metal ions and organic ligands in which functional groups X (including the case where X is a hydrogen atom) are bonded to carbon atoms at position 5 in aromatic rings of isophthalic acid. Here, Al(OH)(C8H3O4X) is expressed as "CAU-10-X", and the article "Highly CO2 Selective Metal-Organic Framework Membranes with Favorable Coulombic Effect" by Da-Shiuan Chiou and seven co-workers, Advanced Functional Materials, 2021, 31, 2006924, Wiley-VCH GmbH (Document 1) reports on a CAU-10-H membrane formed on a flat plate.“Structures, Sorption Characteristics, and Non Linear Optical Properties of a New Series of Highly Stable Aluminum MOFs” by Helge Reinsch and six other colleagues, Chemistry of Materials, 2013, 25, 17-26, American Chemical Society (Document 2) concerns powders made from CAU-10-NH2, but only mentions cases where XH, CH3, OCH3, NO2, NH2 or OH are present.

[0005] Incidentally, only CAU-10-H is known as the membrane of the MOF expressed by CAU-10-X (hereinafter referred to as "CAU-10 MOF") according to Document 1. The other CAU-10 MOFs are only known as powders.

[0006] When different types of starting materials are mixed in the ratios described in known documents such as Documents 1 and 2, the resulting solutions become cloudy. In this state, the concentrations of the different starting materials within a solution vary, rendering the starting materials unsuitable for forming a CAU-10 MOF membrane. Even if a CAU-10 MOF membrane can be formed, areas will remain where no membrane is formed, or the membrane may have uneven thickness. In particular, if a substrate of a certain size is immersed in a deep container to form a MOF membrane, it is not possible to form a membrane of uniform thickness. BRIEF SUMMARY OF THE INVENTION

[0007] One object of the present invention is to provide a method for producing a MOF membrane complex comprising a membrane made of a CAU-10 MOF with low thickness variations. A further object of the present invention is to provide a MOF membrane complex comprising a membrane made of a plurality of CAU-10 MOFs.

[0008] Aspect 1 of the present invention is the method for producing a MOF membrane complex, comprising: a) depositing a seed crystal of CAU-10-MOF onto a support, b) preparing an Al source solution, which is an aqueous solution containing an Al ion source, c) preparing a ligand solution in which an organic ligand used for the synthesis of the CAU-10-MOF is dissolved in a solvent, d) preparing a starting material solution by mixing the Al source solution and the ligand solution at a rate that does not cause turbidity of the starting material solution, and e) immersing the support in the starting material solution to form a MOF membrane, which is the CAU-10-MOF on the support, by solvothermic synthesis.

[0009] According to aspect 1 of the present invention, it is possible to obtain the MOF membrane complex comprising a membrane made of CAU-10-MOF with small variations in thickness. It is also possible to obtain the MOF membrane complex comprising a membrane made of a plurality of CAU-10-MOFs.

[0010] Aspect 2 of the present invention is the process for producing a MOF membrane complex according to aspect 1, wherein in process d) the ligand solution is added dropwise to the Al source solution while stirring.

[0011] Aspect 3 of the present invention is the process for producing a MOF membrane complex according to aspect 1 (or according to aspect 1 or 2), wherein in process d) the prepared starting material solution has a pH value that is maintained at a value higher than or equal to 2.5 and lower than or equal to 3.5.

[0012] Aspect 4 of the present invention is the process for producing a MOF membrane complex according to aspect 1 (or according to one of aspects 1 to 3), wherein the molar ratio of the solvent to the organic ligand in the ligand solution is higher than or equal to 40 and lower than or equal to 500.

[0013] Aspect 5 of the present invention is the process for producing a MOF membrane complex according to aspect 1 (or according to any one of aspects 1 to 4), wherein the organic ligand is any selected from isophthalic acid, 5-aminoisophthalic acid, 5-methylisophthalic acid, 5-methoxyisophthalic acid, 5-nitroisophthalic acid and 5-hydroxyisophthalic acid.

[0014] Aspect 6 of the present invention is the method for producing a MOF membrane complex according to one of aspects 1 to 5, wherein the support has a through hole and in process e) the support is immersed in the starting material solution in a state in which the expansion direction of the through hole is parallel to a vertical direction.

[0015] Aspect 7 of the present invention is a MOF membrane complex comprising a support with a through-hole and an MOF membrane, which is a CAU-10 MOF formed on an inner surface of the through-hole or an outer surface of the support. If the support is divided into three equal parts in the longitudinal direction along which the through-hole extends, and a membrane thickness of the MOF membrane is determined at the center of each of the three equal parts in the longitudinal direction to obtain three membrane thicknesses, the maximum value of the differences between an average membrane thickness value in the hole, which is an average of the three membrane thicknesses, and the three membrane thicknesses is less than or equal to 30% of the average membrane thickness value in the hole.

[0016] Aspect 8 of the present invention is the MOF membrane complex according to aspect 7, wherein the support has two through-holes which contain the through-hole and are parallel to each other, and a maximum value of the differences between an average membrane thickness value between the holes, which is an average value of the average membrane thickness values ​​in the holes of the two through-holes, and the average membrane thickness values ​​in the holes of the two through-holes is less than or equal to 30% of the average membrane thickness value between the holes.

[0017] Aspect 9 of the present invention is the MOF membrane complex according to aspect 7 (or according to aspect 7 or 8), wherein the through-hole has a length greater than or equal to 10 cm and less than or equal to 200 cm.

[0018] Aspect 10 of the present invention is the MOF membrane complex according to aspect 7 (or according to any one of aspects 7 to 9), wherein the through-hole has a maximum width greater than or equal to 1 mm and less than or equal to 20 mm in a cross-section perpendicular to the longitudinal direction and the through-hole has a length that is 10 times or more and 100 times or less than the maximum width of the through-hole.

[0019] Aspect 11 of the present invention is a MOF membrane complex comprising a support and an MOF membrane, which is a CAU-10-MOF formed on the support. An organic ligand used to form the MOF membrane is selected from 5-methylisophthalic acid, 5-aminoisophthalic acid, and 5-nitroisophthalic acid.

[0020] These and other tasks, features, aspects and advantages of the present invention will become clearer from the following detailed description of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a cross-sectional view of a separation membrane complex (MOF membrane complex). Fig. Figure 2 is a sectional view showing part of the separation membrane complex in enlarged dimensions. Fig. 3A is a diagram showing an X-ray diffraction pattern of CAU-10-H. Fig. Figure 3B is a diagram showing an X-ray diffraction pattern of CAU-10-NH2. Fig. 3C is a diagram showing an X-ray diffraction pattern of CAU-10-CH3. Fig. 3D is a diagram showing an X-ray diffraction pattern of CAU-10-NO2. Fig. 3E is a diagram showing an X-ray diffraction pattern of CAU-10-OCH3. Fig. 3F is a diagram showing an X-ray diffraction pattern of CAU-10-OH. Fig. Figure 4 is a flowchart showing the production of the separation membrane complex. Fig. Figure 5 is a diagram showing the solvothermic synthesis. Fig. Figure 6 is a diagram showing a separation device. Fig. Figure 7 is a flowchart showing the separation of a mixture of substances by the separation device. DESCRIPTION OF THE EXECUTION FORMS

[0021] Fig.Figure 1 is a sectional view of a MOF membrane complex 1, which includes a membrane made of a metal-organic framework (MOF) (hereinafter also referred to as the “MOF membrane”). In the present embodiment, the MOF membrane complex 1 is used for the separation of a specific fluid and is therefore referred to below as the “separation membrane complex 1”, but the use of the MOF membrane complex 1 is not limited to the separation of a specific fluid. Fig. Figure 2 is a sectional view showing a portion of the separation membrane complex 1 in enlarged dimensions. The separation membrane complex 1 comprises a porous support 11 and a separation membrane 12, which is a MOF membrane provided on the support 11. The MOF membrane refers to at least one MOF formed in membrane form on a surface of the support 11 and does not include MOFs in which MOF particles are simply dispersed in organic membranes. Fig.Figure 1 shows the separating membrane 12 with thick lines for emphasis. Fig. 2 shows the separating membrane 12 hatched. The separating membrane 12 in Fig. Number 2 is shown as thicker than its actual thickness.

[0022] The support 11 is a porous component that is permeable to gases and liquids. In the Fig. In the example shown, the support 11 is a so-called monolithic support, in which a multitude of through holes 111, each extending longitudinally (i.e., in the right-left direction) Fig. 1) extend, are incorporated into a single-piece, column-like body. In which in Fig. In the example shown, the support 11 has an approximately column-like shape. Each through-hole 111 (i.e., cell), for example, has an approximately circular shape in a cross-section perpendicular to the longitudinal direction. Fig.The diameter of the through holes 111 is larger than the actual diameter shown, and the number of through holes 111 is smaller than the actual number shown. The separating membrane 12 is formed on the inner surfaces of the through holes 111 and covers approximately the entire inner surface of the through holes 111.

[0023] The length of the support 11 (i.e. the length in the right-left direction in Fig.1) The length, for example, is in the range of 10 cm to 200 cm (where "to" here means values ​​greater than or equal to the first value and less than or equal to the last value). The outer diameter of the support 11 is, for example, in the range of 0.5 cm to 30 cm. The distance between the center axes of adjacent through holes 111 is, for example, in the range of 0.3 mm to 10 mm. The surface roughness (Ra) of the support 11 is, for example, in the range of 0.1 µm to 5.0 µm and preferably in the range of 0.2 µm to 2.0 µm. It should be noted that the support 11 can have any other shape, such as a honeycomb shape, a flat plate-like shape, a tube-like shape, a cylindrical shape, a column-like shape, or a prism shape. In the case that the support 11 has a tubular or cylindrical shape, the thickness of the support 11 is, for example, in the range of 0.1 mm to 10 mm.

[0024] The support 11 is made of ceramic. Examples of a ceramic sintered body selected as the material for the support 11 include aluminum oxide, silicon dioxide, mullite, zirconium oxide, titanium oxide, yttrium oxide, silicon nitride, and silicon carbide. In the present embodiment, the support 11 comprises at least one type selected from aluminum oxide, silicon dioxide, and mullite. The support 11 may contain an inorganic binder. The usable inorganic binder may be at least one selected from titanium dioxide, mullite, readily sinterable aluminum oxide, silicon dioxide, glass frit, clay minerals, and readily sinterable cordierite.

[0025] The support 11 has a mean pore diameter of, for example, 0.01 µm to 70 µm and preferably 0.05 µm to 25 µm. The mean pore diameter of the support 11 near the surface on which the separation membrane 12 is formed is in the range of 0.01 µm to 1 µm and preferably in the range of 0.05 µm to 0.5 µm. The mean pore diameter can be measured, for example, with a mercury porosimeter, a permporosimeter, or a nanopermporosimeter. Regarding the pore size distribution of the entire support 11, including the surface and the interior, D5, for example, ranges from 0.01 µm to 50 µm, D50 ranges from 0.05 µm to 70 µm, and D95 ​​ranges from 0.1 µm to 2000 µm. The porosity of the support 11 near the surface on which the separation membrane 12 is formed ranges from 20% to 60%.The porosity can be obtained as the ratio of the areas in which space is present in a SEM (scanning electron microscope) image of a cross-section of the substrate 11.

[0026] For example, the support 11 can have a multilayer structure in which a plurality of layers with different mean pore diameters are stacked one above the other in the thickness direction. The mean particle diameter and the sintered particle diameter in the surface layer, including the surface on which the separation membrane 12 is formed, are smaller than those in layers other than the surface layer. The mean pore diameter in the surface layer of the support 11 is in the range of, for example, 0.01 µm to 1 µm, and preferably in the range of 0.05 µm to 0.5 µm. If the support 11 has a multilayer structure, any of the substances described above can be used as the material for each layer. The plurality of layers that form the multilayer structure can consist of the same material or of different materials.If the support 11 has a multilayer structure, the mean pore diameter of the support 11 refers to the mean pore diameter in the surface layer, including the surface on which the separating membrane 12 is formed.

[0027] The separation membrane 12 is a membrane made of CAU-10-MOF and is a porous membrane with fine pores (micropores). The separation membrane 12 is capable of separating a specific substance from a mixture of various types of substances using a molecular sieve function or similar mechanism. The separation membrane 12 is less permeable to the other substances than to the specific substance. In other words, the permeability of the separation membrane 12 to the other substances is lower than its permeability to the aforementioned specific substance.

[0028] The separation membrane 12 has an average membrane thickness of less than or equal to 10 µm. This results in high permeability. There are no particular restrictions regarding the lower limit for the average membrane thickness of the separation membrane 12, but from the perspective of improving separation performance, the lower limit is preferably 0.5 µm and more preferably 0.7 µm. To measure the average membrane thickness of the separation membrane 12, a cross-section of the membrane 12 perpendicular to its surface is exposed, for example, by cross-sectional polishing. In this cross-section, a plurality of randomly selected viewing fields (e.g., seven viewing fields) are observed with a scanning electron microscope (SEM). The SEM has, for example, a 5000x magnification.An average membrane thickness (average field membrane thickness) of the separating membrane 12 in the viewing fields is determined as the average of the membrane thicknesses at five suitably selected locations, and an arithmetic mean of the average field membrane thicknesses in the remaining viewing fields, with the exception of the viewing fields that yield the maximum and minimum average field membrane thicknesses, is determined as the average membrane thickness of the separating membrane 12. The surface roughness (Ra) of the separating membrane 12 is, for example, less than or equal to 2 µm, preferably less than or equal to 1 µm, and more preferably less than or equal to 0.5 µm.

[0029] The mean pore diameter of the MOF membrane comprising separation membrane 12 is greater than or equal to 0.3 nm and less than or equal to 0.7 nm. The "mean pore diameter of the MOF" refers to the arithmetic mean of the major and minor axes of the pore openings, theoretically derived from the MOF's framework structure. Alternatively, the mean pore diameter can be determined by capturing the major and minor axes of the pore openings through observation with a TEM (transmission electron microscope). More precisely, the major and minor axes of the pore openings refer to the lattice spacing of a lattice structure formed from metal ions and organic ligands, exhibiting a high degree of regularity. The MOF possesses a specific pore structure that, depending on the structure type, includes a channel (pores) and a cage (interior).The pore diameter used here refers to the pore size of the channel, and the mean pore diameter is the arithmetic mean of the major and minor axes, where the major axis is the maximum diameter of the channel in cross-section and the minor axis is the diameter of a cross-section in a direction approximately perpendicular to the major axis. This mean pore diameter is smaller than the mean pore diameter of the support 11 near the surface on which the separating membrane 12 is formed.

[0030] The mean particle size of the MOF from which the separation membrane 12 is composed, i.e., the mean diameter of the crystal grains, is, for example, in the range of 0.1 µm to 2 µm. The mean particle size is preferably less than or equal to 1 µm and more preferably less than or equal to 0.5 µm. The separation membrane 12 with a small mean particle size of the MOF can reduce intergranular defects that can be caused by excessively large gaps between the MOF crystals and can exhibit improved separation performance. The mean particle size of the MOF according to the present embodiment is an arithmetic mean of the maximum diameters of a plurality of MOF particles (e.g., 30 particles), measured by observing a membrane surface with a scanning electron microscope (SEM). The particles to be measured can be randomly selected from an SEM image.

[0031] At the interface between the separating membrane 12 and the support 11, a composite layer 13 is formed in which the MOF crystals are embedded in the pores of the support 11. Fig. Figure 2 shows the composite layer 13 with hatching over a portion of the substrate 11. The composite layer 13 is part of the substrate 11. The composite layer 13 has a thickness of, for example, less than or equal to 2 µm. This prevents a reduction in permeability due to the presence of the composite layer 13. The composite layer 13 can be omitted; that is, the lower limit for the thickness of the composite layer 13 is zero.

[0032] When measuring the thickness of the composite layer 13, a boundary position of the composite layer 13 is identified in a direction perpendicular to the interface between the support 11 and the separating membrane 12 (hereinafter referred to as the "depth direction") near a measurement position in a direction along the interface during observation of the cross-section with a scanning electron microscope (SEM). More precisely, the boundary position of the composite layer 13 on the side closer to the separating membrane 12 corresponds to the interface between the separating membrane 12 and the support 11. The boundary position of the composite layer 13 on the side opposite the separating membrane 12 corresponds, in the MOF present in the pores of the support 11, to the edge of the MOF that is furthest from the separating membrane 12 in the depth direction.The distance in the depth direction between the boundary position of the composite layer 13 on the side closer to the separation membrane 12 and its boundary position on the side opposite the separation membrane 12 is recorded as the thickness of the composite layer 13 at the measurement position. Then, an average of the thicknesses of the composite layer 13 at a large number of different measurement positions (e.g., 10 measurement positions) is determined as the thickness of the composite layer 13 in the separation membrane complex 1.

[0033] Not only in the case where the composite layer 13 is absent, but also in the case where the composite layer 13 is present, no additional intermediate layer is formed between the support 11 and the separating membrane 12 in the separation membrane complex 1. Thus, the support 11 and the separating membrane 12 are in direct contact with each other. That is, no intermediate layer is formed between the support 11 and the separating membrane 12 in any step other than the formation of the MOF membrane. This structure is only an example; for instance, the support 11 could contain an intermediate layer formed separately on a base section, and the separating membrane 12 could be positioned on top of this intermediate layer.

[0034] The MOF forming the separating membrane 12 contains metal ions and organic ligands (hereinafter simply referred to as "ligands") coordinated to the metal ions. The metal ions serving as components of the CAU-10 MOF are Al 3+ (Aluminum ions). The ligands used as components of CAU-10-MOF include, for example, any of the following: isophthalic acid (benzene-1,3-dicarboxylic acid), 5-aminoisophthalic acid, 5-methylisophthalic acid, 5-methoxyisophthalic acid, 5-nitroisophthalic acid, and 5-hydroxyisophthalic acid. The ligands do not necessarily have to be of the same type, and several types of ligands can be used.

[0035] The Fig. 3A, Fig. 3B, Fig. 3C, Fig. 3D, Fig. 3E and Fig.Figure 3F are diagrams showing the X-ray diffraction patterns of CAU-10-H, CAU-10-NH2, CAU-10-CH3, CAU-10-NO2, CAU-10-OCH3, and CAU-10-OH MOFs obtained by an X-ray diffraction method. The horizontal axis indicates the diffraction angle (2θ / °), and the vertical axis indicates the intensity (intensity au). The X-ray diffraction patterns of the CAU-10 MOF exhibit peaks near at least 2θ = 8.1°, 14.8°, and 22.4°.

[0036] Next, with reference to Fig.Section 4 describes a method for the preparation of the separation membrane complex 1. In the preparation of the separation membrane complex 1, seed crystals are first produced, which are used to form the separation membrane 12 (step S11). The seed crystals have a CAU-10 MOF of the same type as a MOF membrane to be formed. Specifically, an aluminum ion source (Al ion source) and ligands are first mixed with stirring in a solution containing water and an organic solvent such as dimethylformamide (DMF). After the solution has undergone solvothermic synthesis by heating, the resulting product is separated from the solution by centrifugal separation and purified with water and ethanol to obtain a powder of the MOF. This MOF powder is pulverized (ball milled) with zirconium dioxide (ZrO2) spheres in ethanol to obtain seed crystals. The MOF powder can be produced by any other known preparation method.The MOF powder can be used unchanged as seed crystals.

[0037] The mean particle size (D50) of the seed crystals is preferably less than or equal to 0.5 µm. This suppresses the development of intergranular defects in the MOF membrane due to an excessive increase in the mean particle size of the MOF. There are no specific restrictions regarding the lower limit for the mean particle size of the seed crystals, but if, for example, the mean particle size is greater than or equal to 0.1 µm, it is possible to suppress a deterioration of the crystallinity of the seed crystals. The mean particle size (D50) of the seed crystals can be measured, for example, by a laser scattering method.

[0038] The seed crystals are then dispersed in a solvent (water and / or an organic solvent) to produce a liquid dispersion in an amount of 0.01 wt% to 1 wt%. The porous support 11 is immersed in the liquid dispersion so that the seed crystals are deposited onto the support 11 (immersion coating) (step S12). Alternatively, the liquid dispersion containing the seed crystals dispersed in the solvent can be applied to a section of the support 11 where the separation membrane 12 is to be formed, in order to deposit the seed crystals onto the support 11. The solvent is then removed by drying to produce a seed-coated support. It should be noted that any other technique can be used to deposit the seed crystals onto the support 11.

[0039] A starting material solution (also called synthetic sol or synthetic solution) is then prepared (steps S13a and S13b) for MOF membrane formation. Preparation of the starting material solution can be performed before or in parallel with step S12. This involves mixing a solvent (water and / or an organic solvent), ligands, a metal ion source, and other required starting materials in a specific sequence.

[0040] In particular, a solution is prepared in which an aluminum ion source dissolves in water (i.e., ion-exchanged water) (hereinafter referred to as the "Al source solution") (step S13a). Thus, the Al source solution is prepared. Examples of suitable aluminum nitrate nonahydrate, aluminum chloride hexahydrate, aluminum sulfate-14,18-water, or aluminum hydroxide can be used as the aluminum ion source. Subsequently, a solution is prepared in which ligands are dissolved in an organic solvent (hereinafter referred to as the "ligand solution") (step S13b). Thus, the ligand solution is prepared. The ligands are of the type used in CAU-10-MOF and are, for example, isophthalic acid (benzene-1,3-dicarboxylic acid), 5-aminoisophthalic acid, 5-methylisophthalic acid, 5-methoxyisophthalic acid, 5-nitroisophthalic acid, or 5-hydroxyisophthalic acid. The organic solvent is, for example, DMF, diethylformamide (DEF), or methanol.Steps S13a and S13b can be performed in any order and in parallel.

[0041] The ligand solution is then gradually added to the Al source solution while stirring (step S14). If the ligand solution is added all at once to the Al source solution at this stage, the resulting mixture will be cloudy. Therefore, the ligand solution is mixed into the Al source solution at a rate that does not cause cloudiness in order to produce a clear starting material solution. In this way, the clear starting material solution is prepared. In step S14, the ligand solution is preferably added dropwise to the Al source solution while stirring. The drop rate is preferably set to greater than or equal to 0.01 g per second and less than or equal to 0.5 g per second to more reliably obtain the clear starting material solution.The phenomenon of the mixed solution becoming cloudy when the ligand solution is added all at once to the Al source solution is presumably due to the ligands precipitating without dissolving in the water, leaving the mixed solution in an incomplete state. When stirring is stopped, such an incomplete starting material solution settles to the bottom over time. That is to say, in the description of the present invention, the statement that the solution is not cloudy refers to a state in which no sediments are present at the bottom, even when stirring is stopped, and does not depend on the clarity of the solution.

[0042] Once the starting material solution has been prepared, the carrier 11 with the seed crystals deposited on it is immersed in a starting material solution 51 in a container 52, as described in Fig.Figure 5 shows that in the starting material solution 51, the support 11 is held by a support frame (not shown) and does not come into contact with the bottom surface of the container 52. If the support 11 is a so-called monolith type with a plurality of parallel through-holes 111, it is immersed in the starting material solution 51 in a state where the expansion direction of the through-holes 111 is parallel to the vertical direction, in order to reduce differences in the conditions between the through-holes 111. If the starting material solution used is turbid, the turbidity concentration will be higher in the lower part of the container 52, in which the starting material solution 51 is stored. This leads to differences in the MOF production conditions between the upper and lower parts of the through-holes 11 during the subsequent solvothermic synthesis.As a result, a MOF membrane of insufficient thickness may form in the upper parts of the through holes 111, although the MOF membrane formed in the lower parts of the through holes 111 has a suitable thickness.

[0043] In contrast, when using the starting material solution 51, which is produced as non-turbid in steps S13a, S13b, and S14, there are hardly any differences in the MOF production requirements between the upper and lower parts of each through-hole 111. This allows the MOF membrane to be formed with a uniform thickness across the entire surface of each through-hole 111 and across all through-holes 111. That is, it is possible to form the CAU-10 MOF membrane with minimal thickness variations within each through-hole 111 and minimal thickness variations between the multitude of through-holes. It should be noted that similar effects can be achieved even if the support 11 has a shape other than a monolithic one.

[0044] The starting material solution is then heated to initiate the solvothermic synthesis (also called hydrothermal synthesis if the solvent is water). During the solvothermic synthesis, the CAU-10-MOF grows using the seed crystals as nuclei, and a dense MOF membrane forms as a separating membrane 12 on the support 11 (step S15). The MOF membrane is one of the membranes made of CAU-10-H, CAU-10-NH2, CAU-10-CH3, CAU-10-OCH3, CAU-10-NO2, and CAU-10-OH (see "PRIN OF THE ART"). The synthesis temperature (the heating temperature to which the starting material solution is heated) during the solvothermic synthesis is, for example, in the range of 80°C to 180°C and preferably in the range of 110°C to 140°C. The duration of the solvothermic synthesis, for example, ranges from 2 hours to 72 hours and preferably from 3 hours to 35 hours.

[0045] After completion of the solvothermic synthesis, the support 11 and the MOF membrane are purified with ion-exchanged water and subsequently with ethanol, methanol, or the like. Preferably, the purification with water and ethanol, methanol, or the like can be repeated several times. After purification, the support 11 and the MOF membrane are dried at a temperature of, for example, 60°C to 100°C (step S16). The term "dried" used here refers to the removal of molecules of substances used for purification with water and ethanol, methanol, or the like from the interior of the pores of the MOF membrane. This drying completes the separation membrane complex 1.

[0046] The above-described method for producing the separation membrane complex 1 yields a clear solution as the starting material for the MOF membrane. This makes it possible to obtain the MOF membrane complex containing the membrane of the CAU-10-MOF with minimal variations in thickness. It is also possible to obtain the MOF membrane complex containing the membrane of a large number of CAU-10-MOFs.

[0047] Next, the separation of a substance mixture using the separation membrane complex 1 will be described with reference to the Fig. 6 and Fig. 7 described. Fig. Figure 6 is a diagram showing a separation device 2. Fig. Figure 7 is a flowchart showing the separation of a mixture of substances by the separation device 2.

[0048] The separation device 2 feeds a mixture of substances, containing a variety of fluid types (i.e., gases or liquids), to the separation membrane complex 1, causing a high-permeability substance in the mixture to permeate the separation membrane complex 1 in order to separate the high-permeability substance from the mixture. For example, the separation by the separation device 2 can be carried out for the purpose of extracting a high-permeability substance from the mixture or for the purpose of condensing a low-permeability substance.

[0049] The mixture of substances (i.e., a fluid mixture) can be a gas mixture containing a variety of gas types, a mixed solution containing a variety of liquid types, or a gas-liquid biphase fluid containing both a gas and a liquid.

[0050] For example, the mixture of substances may contain one or more types of substances selected from hydrogen (H2), helium (He), nitrogen (N2), oxygen (O2), water (H2O), carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides, ammonia (NH3), sulfur oxides, hydrogen sulfide (H2S), sulfur fluorides, mercury (Hg), arsine (AsH3), hydrogen cyanide (HCN), carbonyl sulfide (COS), C1 to C8 hydrocarbons, organic acids, alcohol, mercaptan, ester, ether, ketone and aldehyde.

[0051] Nitrogen oxides are compounds of nitrogen and oxygen. For example, the nitrogen oxides mentioned above can be gases known as NOₓ. x These can be named, for example, nitric oxide (NO), nitrogen dioxide (NO2), dinitrogen oxide (also called dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4) or dinitrogen pentoxide (N2O5).

[0052] Sulfur oxides are compounds of sulfur and oxygen. For example, the sulfur oxides mentioned above can be gases known as SO₂. x They are referred to as sulfur dioxide (SO2) or sulfur trioxide (SO3).

[0053] Sulfur fluorides are compounds of fluorine and sulfur. Examples of the sulfur fluorides mentioned above include disulfur difluoride (FSSF, S=SF2), sulfur difluoride (SF2), sulfur tetrafluoride (SF4), sulfur hexafluoride (SF6), and disulfur decafluoride (S2F). 10 ) be.

[0054] C1 to C8 hydrocarbons are hydrocarbons containing one or more, but no more than eight, carbon atoms. C3 to C8 hydrocarbons can be linear-chain, side-chain, or cyclic compounds. C2 to C8 hydrocarbons can be either saturated (i.e., those in which no double or triple bonds are present) or unsaturated (i.e., those in which double and / or triple bonds are present). Examples of C1 to C4 hydrocarbons are methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), normal butane (CH3(CH2)2CH3), isobutene (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3) or isobutene (CH2=C(CH3)2).

[0055] The organic acids mentioned above can be, for example, carboxylic acids or sulfonic acids. Examples of carboxylic acids include formic acid (CH₂O₂), acetic acid (C₂H₄O₂), oxalic acid (C₂H₂O₄), acrylic acid (C₃H₄O₂), or benzoic acid (C₆H₅COOH). Examples of sulfonic acids include ethanesulfonic acid (C₂H₆O₃S). The organic acids can be either chain compounds or cyclic compounds.

[0056] The aforementioned alcohol can be, for example, methanol (CH3OH), ethanol (C2H5OH), isopropanol (2-propanol) (CH3CH(OH)CH3), ethylene glycol (CH2(OH)CH2(OH)) or butanol (C4H9OH).

[0057] Mercaptans are organic compounds with terminal sulfur hydrides (SH) and are also known as thiols or thioalcohols. Examples of mercaptans mentioned above include methyl mercaptan (CH3SH), ethyl mercaptan (C2H5SH), and 1-propanethiol (C3H7SH).

[0058] The aforementioned ester can be, for example, formic acid esters or acetic acid esters.

[0059] The aforementioned ether can be, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3) or diethyl ether ((C2H5)2O).

[0060] The aforementioned ketone can be, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3) or diethyl ketone ((C2H5)2CO).

[0061] The aforementioned aldehyde can be, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO) or butanal (butyraldehyde) (C3H7CHO).

[0062] The following description is based on the assumption that the mixture of substances to be separated by the separation device 2 is a mixed gas containing a variety of gases.

[0063] The separating device 2 comprises the separating membrane complex 1, seals 21, a housing 22, two sealing components 23, a feeder 26, a first collector 27, and a second collector 28. The separating membrane complex 1, the seals 21, and the sealing components 23 are arranged in the housing 22. The feeder 26, the first collector 27, and the second collector 28 are arranged outside the housing 22 and connected to the housing 22.

[0064] The seals 21 are components that are located at both ends of the support 11 in the longitudinal direction (i.e., in the right-left direction). Fig.6) are attached and cover and seal both end faces of the support 11 in the longitudinal direction, as well as its outer surface near the two end faces. The seals 21 prevent the inflow and outflow of gases from the two end faces of the support 11. For example, the seal 21 can be a plate-like component made of glass or a resin. The material and shape of the seal 21 can be modified accordingly. It should be noted that the seal 21 has a plurality of openings that overlap the through-holes 111 of the support 11, so that both ends of each through-hole 111 of the support 11 in the longitudinal direction are not covered by the seal 21. This allows the inflow and outflow of gases or the like from both ends into and out of the through-holes 111.

[0065] There are no particular restrictions regarding the shape of the housing 22, and the housing 22 is, for example, an approximately cylindrical tubular component. The housing 22 is made, for example, of stainless steel or carbon steel. The longitudinal direction of the housing 22 runs approximately parallel to the longitudinal direction of the separating membrane complex 1. One end of the housing 22 in the longitudinal direction (i.e., the left end in Fig. 6) is provided with an inlet opening 221 and the other end is provided with a first outlet opening 222. The side surface of the housing 22 is provided with a second outlet opening 223. The inlet opening 221 is connected to the feeder 26. The first outlet opening 222 is connected to the first collector 27. The second outlet opening 223 is connected to the second collector 28. The interior of the housing 22 is a closed space that is isolated from the space surrounding the housing 22.

[0066] The two sealing components 23 are arranged longitudinally around the entire circumference between the outer surface of the separating membrane complex 1 and the inner surface of the housing 22, near both ends of the separating membrane complex 1. Each sealing component 23 is an approximately ring-shaped component made of a gas-impermeable material. For example, the sealing components 23 can be O-rings made of a flexible resin. The sealing components 23 are in close contact with the outer surface of the separating membrane complex 1 and the inner surface of the housing 22 along their entire circumference. Fig.In the example shown in Figure 6, the sealing components 23 are in close contact with the outer surfaces of the seals 21 and, via the seals 21, are in indirect close contact with the outer surface of the separating membrane complex 1. The space between the sealing components 23 and the outer surface of the separating membrane complex 1, as well as the space between the sealing components 23 and the inner surface of the housing 22, are sealed in such a way that the passage of gases is almost or completely prevented.

[0067] The feeder 26 introduces a mixed gas into the interior of the housing 22 via the feed opening 221. The feeder 26 is, for example, a blower or a pump that delivers the mixed gas under pressure to the housing 22. The blower or pump includes a pressure regulator that regulates the pressure of the mixed gas supplied to the housing 22. The first collector 27 and the second collector 28 are, for example, containers that store gases originating from the housing 22, or a blower or pump that circulates the gases.

[0068] In the separation of the mixed gas, the separation device 2 described above is manufactured for the production of the separation membrane complex 1 (step S21). The feeder 26 then supplies a mixed gas to the interior of the housing 22, wherein the mixed gas contains a variety of gas types, each exhibiting a different permeability through the separation membrane 12. For example, the main components of the mixed gas are CO2 and N2. The mixed gas may also contain a gas other than CO2 and N2. The pressure of the mixed gas supplied by the feeder 26 to the interior of the housing 22 (i.e., the initial pressure) is, for example, in the range of 0.1 MPa to 20.0 MPa. The temperature during the separation of the mixed gas is, for example, in the range of 10°C to 150°C.

[0069] The mixed gas supplied by the feeder 26 to the housing 22 is introduced from the left end of the separating membrane complex 1 in the drawing into each through-hole 111 of the support 11, as indicated by arrow 251. A gas with high permeability in the mixed gas (e.g., CO2; hereinafter referred to as the "high-permeability substance") permeates through the separating membrane 12, which is provided on the inner surface of each through-hole 111, and then permeates through the support 11, exiting from the outer surface of the support 11. Accordingly, the high-permeability substance is separated from a gas with low permeability in the mixed gas (e.g., N2; hereinafter referred to as the "low-permeability substance") (step S22). The gas discharged from the outer surface of the support 11 (hereinafter referred to as the "permeated substance") is collected by the second collector 28 via the second outlet opening 223, as indicated by arrow 253.The pressure of the gas collected from the second collector 28 via the second outlet opening 223 (i.e. the permeate pressure) is, for example, about one atmospheric pressure (0.101 MPa).

[0070] In the mixed gas, gases (hereinafter referred to as "non-permeated substances") that have not permeated the separating membrane 12 and the support 11 pass through each through-hole 111 of the support 11 from left to right in the drawing and are collected by the first collector 27 via the first outlet opening 222, as indicated by arrow 252. The pressure of the gas collected by the first collector 27 via the first outlet opening 222 corresponds, for example, approximately to the initial pressure. In addition to the aforementioned low-permeable substance, the non-permeated substances may include a high-permeable substance that has not permeated the separating membrane 12.

[0071] Next, examples and comparative examples of the separation membrane complex are described. Table 1 shows the production conditions and measurement results for the examples and comparative examples. [Table 1] Type of CAU-10 pH molar ratio of solvent to ligand average membrane thickness (µm) Valuation value in the hole Rating value between the holes before mixing after mixing Example 1-1 CAU-10-H 3,4 3,5 394 0,5 14 10 Example 1-2 CAU-10-H 3,6 3,7 788 0,3 29 28 Example 2-1 CAU-10-NH2 2,8 2,6 41 0,9 11 10 Example 2-2 CAU-10-NH2 2,8 2,5 41 1,3 14 15 Example 2-3 CAU-10-NH2 2,8 2,6 41 1,2 17 12 Example 2-4 CAU-10-NH2 3,1 2,8 41 2,3 14 25 Example 3 CAU-10-CH3 3,1 2,9 123 3,9 22 20 Example 4 CAU-10-NO2 3,3 3,0 193 2,5 15 10 Example 5 CAU-10-OCH3 3,1 2,9 193 2,5 10 12 Example 6 CAU-10-OH 3,2 3,0 193 2,3 13 16 Comparative example 1 CAU-10-NH2 2,8 2,6 41 0,9 40 31 Comparative example 2 CAU-10-NH2 2,1 1,8 8 4,6 35 31 Example 1-1: CAU-10-H Production of seed crystals

[0072] A mixed solution was prepared by adding 1.43 g of aluminum sulfate 14-18 water as an ion source and 0.71 g of isophthalic acid as a ligand to a mixed solvent consisting of 14 g of ion-exchanged water and 3.5 g of N,N-dimethylformamide (DMF). The mixed solution was then subjected to a solvothermic synthesis at 120°C for 12 hours. The precipitates were separated by centrifugal separator and purified three times with ion-exchanged water and ethanol to obtain seed crystals of CAU-10-H. Carrier of the seed crystals

[0073] One gram of CAU-10-H seed crystals was dispersed in 10 ml of ethanol and pulverized in a ball mill for 24 hours to obtain a fluid dispersion of the seed crystals with a mean particle diameter (D50) of 250 nm. Ethanol was then added to the fluid dispersion to achieve a concentration of 0.01%. A porous aluminum oxide support was immersed in this fluid dispersion to deposit the dispersion onto the support, and the solvent was evaporated in a dryer to fix the seed crystals to the support surface. The support used had a mean pore diameter of approximately 100 nm. Formation of a MOF membrane

[0074] First, a starting material solution was prepared by adding a solution obtained by adding isophthalic acid as a ligand to DMF (ligand solution) dropwise, while stirring, to a solution obtained by adding sodium formate and aluminum sulfate 14-18 water as an Al ion source to ion-exchanged water (Al source solution). The molar ratio of aluminum sulfate 14-18 water, isophthalic acid, sodium formate, ion-exchanged water, and DMF was adjusted to 1:1:2:6394:394. The Al source solution had a pH of 3.4 before mixing, and the starting material solution had a pH of 3.5 after mixing. The starting material solution was clear.

[0075] The starting material solution and the support containing the seed crystals were then placed in a Teflon container (registered trademark) and subjected to solvothermic synthesis at 130°C for 12 hours to obtain a MOF membrane complex in which a CAU-10-H membrane had formed on the support. This MOF membrane complex was purified three times with ion-exchanged water and ethanol. The MOF membrane complex was then dried at 80°C for 12 hours. Result of the membrane thickness measurement

[0076] A longitudinal section of the MOF membrane was observed in seven randomly selected fields of view using a scanning electron microscope (SEM). As previously described, an average membrane thickness of the MOF membrane was determined in each field image (mean field thickness), and an arithmetic mean of the mean field thicknesses for five fields of view, excluding those with the maximum and minimum mean field thicknesses, was determined as the mean membrane thickness of the MOF membrane. The same procedure was followed for the examples and comparison examples described below.

[0077] As a result of the measurement using the technique described above, the average membrane thickness of the MOF membrane according to Example 1-1 was 0.5 µm. Result of the measurement of the rating value in the hole

[0078] The substrate was divided into three equal parts longitudinally along the through-holes, and a longitudinal section image of the MOF membrane within each through-hole was acquired using a scanning electron microscope (SEM) positioned longitudinally at the center of each part (the position did not necessarily have to be exactly in the center, as long as it was approximately in the center). In each of the three acquired images, the membrane thickness of the MOF membrane was determined by measuring the distance between any point on the membrane surface and a point at the interface between the MOF membrane and the substrate in a direction perpendicular to that point. An average value was calculated from the three membrane thicknesses as the "average membrane thickness value in the hole," and the differences (more precisely, the absolute values ​​of the differences) between each of the three membrane thicknesses and the average membrane thickness value in the hole were determined.The ratio of the maximum value of the differences to the average membrane thickness value in the hole was determined as the evaluation value in the hole. The same applied to the examples and comparison examples described below. By determining the average membrane thickness value in the hole from the three membrane thicknesses, it is possible to determine the average membrane thickness from as few images as possible, taking into account the membrane thicknesses outside the center in the longitudinal direction.

[0079] The rating in the hole according to example 1-1 was 14%. Result of the measurement of the rating value between the holes

[0080] Another through-hole was selected, and the average membrane thickness value within this hole was also determined using the technique described above. Subsequently, an average of the two average membrane thickness values ​​within the hole was calculated as the average membrane thickness value between the holes. The differences (more precisely, the absolute values ​​of the differences) between the average membrane thickness value between the holes and each of the average membrane thickness values ​​within the hole for the two through-holes were determined, and the ratio of a maximum value derived from the differences to the average membrane thickness value between the holes was calculated as the rating value between the holes. The same procedure was followed for the examples and comparison examples described below.

[0081] The rating value between the holes according to example 1-1 was 10%. Example 1-2: CAU-10-H

[0082] A MOF membrane complex was obtained in the same manner as in Example 1-1, except that the molar ratio of aluminum sulfate-14-18-water, isophthalic acid, sodium formate, ion-exchanged water, and DMF in the starting material solution used to form the MOF membrane was adjusted to 1:1:2:12788:788. The Al source solution had a pH of 3.6 before mixing, and the starting material solution had a pH of 3.7 after mixing. The starting material solution was clear. The average membrane thickness of the MOF membrane according to Example 1-2 was 0.3 µm. The in-hole evaluation score was 29%. The inter-hole evaluation score was 28%. Example 2-1: CAU-10-NH2 Production of seed crystals

[0083] A mixed solution was prepared by adding 0.16 g of aluminum chloride hexahydrate as an all-ion source and 0.24 g of 5-aminoisophthalic acid as a ligand to a mixed solvent consisting of 16 g of ion-exchanged water and 4 g of N,N-dimethylformamide (DMF). The mixed solution was then subjected to a solvothermic synthesis at 120°C for 12 hours. The precipitates were separated using a centrifugal separator and purified three times with ion-exchanged water and ethanol to obtain seed crystals of CAU-10-NH2. Carrier for seed crystals

[0084] A support carrying the seed crystals was obtained in the same way as in Example 1-1, except that CAU-10-NH2 was used as the seed crystals. Formation of a MOF membrane

[0085] First, a starting material solution was prepared by adding a solution obtained by adding 5-aminoisophthalic acid as a ligand to DMF (ligand solution) dropwise, while stirring, to a solution obtained by adding aluminum chloride hexahydrate as an Al ion source to ion-exchanged water (Al source solution). The molar ratio of aluminum chloride hexahydrate, 5-aminoisophthalic acid, ion-exchanged water, and DMF was adjusted to 1:1:670:41. The Al source solution had a pH of 2.8 before mixing, and the starting material solution had a pH of 2.6 after mixing. The starting material solution was clear.

[0086] The starting material solution and the support containing the seed crystals were then placed in a Teflon container (registered trademark) and subjected to solvothermic synthesis at 130°C for 12 hours to obtain a MOF membrane structure in which a CAU-10-NH2 membrane had formed on the support. This MOF membrane complex was purified three times with ion-exchanged water and ethanol. The MOF membrane complex was then dried at 80°C for three hours. Additionally, the MOF membrane complex was purified once with methanol and dried at room temperature. Measurement results

[0087] The average membrane thickness of the MOF membrane according to Example 2-1 was 0.9 µm. The score within the hole was 11%. The score between the holes was 10%. Example 2-2: CAU-10-NH2

[0088] A MOF membrane complex was obtained in the same manner as in Example 2-1, except that aluminum nitrate nonahydrate was used as the Al ion source. The Al source solution had a pH of 2.8 before mixing, and the starting material solution had a pH of 2.5 after mixing. The starting material solution was clear. The average membrane thickness of the MOF membrane according to Example 2-2 was 1.3 µm. The in-hole score was 14%. The inter-hole score was 15%. Example 2-3: CAU-10-NH2

[0089] A MOF membrane complex was obtained in the same manner as in Example 2-1, except that the temperature during the solvothermic synthesis for MOF membrane formation was set to 140°C. The average membrane thickness of the MOF membrane according to Examples 2-3 was 1.2 µm. The evaluation value within the hole was 17%. The evaluation value between the holes was 12%. Example 2-4: CAU-10-NH2

[0090] A MOF membrane complex was obtained in the same manner as in Example 2-1, except that the molar ratio of aluminum chloride hexahydrate, 5-aminoisophthalic acid, ion-exchanged water, and DMF in the starting material solution for MOF membrane formation was adjusted to 0.5:1:670:41. The Al source solution had a pH of 3.1 before mixing, and the starting material solution had a pH of 2.8 after mixing. The starting material solution was clear. The average membrane thickness of the MOF membrane according to Example 2-4 was 2.3 µm. The in-hole evaluation was 14%. The inter-hole evaluation was 25%. Example 3: CAU-10-CH3 Production of seed crystals

[0091] Seed crystals of CAU-10-CH3 were obtained in the same way as in Example 1-1, except that 0.77 g of 5-methylisophthalic acid was used as the ligand. Carrier for seed crystals

[0092] A support carrying the seed crystals was obtained in the same way as in Example 1-1, except that CAU-10-CH3 was used as the seed crystals. Formation of the MOF membrane

[0093] A starting material solution was prepared in the same manner as in Example 1-1, except that 5-methylisophthalic acid was used as the ligand and sodium formate was not added to the Al source solution. The molar ratio of aluminum sulfate-14,18-water, 5-methylisophthalic acid, ion-exchanged water, and DMF was adjusted to 1:1:2000:123. The Al source solution had a pH of 3.1 after mixing began, and the starting material solution had a pH of 2.9 after mixing was complete. The starting material solution was clear.

[0094] The starting material solution and the support containing the seed crystals were then placed in a Teflon container (registered trademark) and subjected to solvothermic synthesis at 130°C for 12 hours to obtain a MOF membrane complex in which a CAU-10-CH3 membrane had formed on the support. This MOF membrane complex was purified three times with ion-exchanged water and ethanol. The MOF membrane complex was then dried in a dryer at 80°C for three hours.

[0095] The average membrane thickness of the MOF membrane according to Example 3 was 3.9 µm. The score within the hole was 22%. The score between the holes was 20%. Example 4: CAU-10-NO2 Production of seed crystals

[0096] Seed crystals of CAU-10-NO2 were obtained in the same way as in Example 1-1, except that 0.28 g of 5-nitroisophthalic acid was used as the ligand. Carrier for seed crystals

[0097] A support carrying the seed crystals was obtained in the same way as in Example 1-1, except that CAU-10-NO2 was used as the seed crystals. Formation of a MOF membrane

[0098] A starting material solution was prepared in the same manner as in Example 2-1, except that 5-nitroisophthalic acid was used as the ligand. The molar ratio of aluminum chloride hexahydrate, 5-nitroisophthalic acid, ion-exchanged water, and DMF was adjusted to 1:1:2352:193. The Al source solution had a pH of 3.3 before mixing, and the starting material solution had a pH of 3.0 after mixing. The starting material solution was clear.

[0099] The starting material solution and the support containing the seed crystals were then placed in a Teflon container (registered trademark) and subjected to solvothermic synthesis at 130°C for 12 hours to obtain a MOF membrane complex in which a CAU-10-NO2 membrane had formed on the support. This MOF membrane complex was purified three times with ion-exchanged water and ethanol. The MOF membrane complex was then dried in a dryer at 80°C for three hours.

[0100] The average membrane thickness of the MOF membrane according to Example 4 was 2.5 µm. The weighting value within the hole was 15%. The weighting value between the holes was 10%. Example 5: CAU-10-OCH3 Production of seed crystals

[0101] Seed crystals of CAU-10-OCH3 were obtained in the same way as in Example 1-1, except that 0.84 g of 5-methoxyisophthalic acid was used as the ligand. Carrier for seed crystals

[0102] A support carrying the seed crystals was obtained in the same way as in Example 1-1, except that CAU-10-OCH3 was used as the seed crystals. Formation of a MOF membrane

[0103] A starting material solution was prepared in the same manner as in Example 1-1, except that 5-methoxyisophthalic acid was used as the ligand and sodium formate was not added to the Al source solution. The molar ratio of aluminum sulfate-14-18 water, 5-methoxyisophthalic acid, ion-exchanged water, and DMF was adjusted to 1:1:2352:193. The Al source solution had a pH of 3.1 before mixing, and the starting material solution had a pH of 2.9 after mixing. The starting material solution was clear.

[0104] The starting material solution and the support containing the seed crystals were then placed in a Teflon container (registered trademark) and subjected to solvothermic synthesis at 130°C for 12 hours to obtain a MOF membrane complex, in which a CAU-10-OCH3 membrane was formed on the support. This MOF membrane complex was purified three times with ion-exchanged water and ethanol. The MOF membrane complex was then dried in a dryer at 80°C for three hours.

[0105] The average membrane thickness of the MOF membrane according to Example 5 was 2.5 µm. The weighting value within the hole was 10%. The weighting value between the holes was 12%. Example 6: CAU-10-OH Production of seed crystals

[0106] Seed crystals of CAU-10-OH were prepared in the same way as in Example 1-1, except that 0.24 g of 5-hydroxyisophthalic acid was used as the ligand. Carrier for seed crystals

[0107] A support carrying the seed crystals was obtained in the same way as in Example 1-1, except that CAU-10-OH was used as the seed crystals. Formation of the MOF membrane

[0108] A starting material solution was prepared in the same manner as in Example 2-1, except that 5-hydroxyisophthalic acid was used as the ligand. The molar ratio of aluminum chloride hexahydrate, 5-hydroxyisophthalic acid, ion-exchanged water, and DMF was adjusted to 1:1:2352:193. The Al source solution had a pH of 3.2 before mixing, and the starting material solution had a pH of 3.0 after mixing. The starting material solution was clear.

[0109] The starting material solution and the support containing the seed crystals were then placed in a Teflon container (registered trademark) and subjected to solvothermic synthesis at 130°C for 12 hours to obtain a MOF membrane complex in which a CAU-10-OH membrane had formed on the support. This MOF membrane complex was purified three times with ion-exchanged water and ethanol. The MOF membrane complex was then dried in a dryer at 80°C for three hours.

[0110] The average membrane thickness of the MOF membrane according to Example 6 was 2.3 µm. The score within the hole was 13%. The score between the holes was 16%. Comparison example 1: CAU-10-NH2

[0111] In the preparation of the starting material solution for the formation of a MOF membrane, a MOF membrane complex was obtained in the same manner as in Example 2-1, except that the ligand solution was added to the Al source solution all at once and mixed with it. The Al source solution had a pH of 2.8 before mixing, and the starting material solution had a pH of 2.6 after mixing. The starting material solution was turbid. The average membrane thickness of the MOF membrane, as in Comparative Example 1, was 0.9 µm. The score within the hole was 40%. The score between the holes was 31%. Comparison example 2: CAU-10-NH2

[0112] A MOF membrane complex was obtained in the same manner as in Example 2-1, except that the molar ratio of aluminum chloride hexahydrate, 5-aminoisophthalic acid, ion-exchanged water, and DMF in the starting material solution for MOF membrane formation was adjusted to 1:1:134:8. The Al source solution had a pH of 2.1 before mixing, and the starting material solution had a pH of 1.8 after mixing. The starting material solution was turbid. The average membrane thickness of the MOF membrane, as in Comparative Example 1, was 4.6 µm. The in-hole score was 35%. The inter-hole score was 30%.

[0113] The examples described above suppress variations in membrane thickness within the through-holes 111 and achieve a rating in the hole of less than or equal to 30%. The examples mentioned above also suppress variations in membrane thickness between the through-holes 111 and achieve a rating between the holes of less than or equal to 30%.

[0114] As further examples, as shown in Table 2, the turbidity of the starting material solution was checked by adjusting the molar ratio of the organic solvent to the ligand in the ligand solution for the CAU-10-NH2 synthesis to a value within the range between the values ​​in Example 2-1 and Comparative Example 2 and less than 40. The remaining conditions were the same as in Example 2-1 and Comparative Example 2. According to Additional Example 1, in which the molar ratio of the organic solvent to the ligand was 33, the Al source solution had a pH of 2.7 before mixing and a pH of 2.4 after mixing. In Additional Example 2, in which the molar ratio described above was 24, the Al source solution had a pH of 2.6 before mixing and a pH of 2.2 after mixing.In the additional example 3, where the molar ratio described above was 16, the Al source solution had a pH of 2.4 before mixing and a pH of 2.0 after mixing. In all additional examples 1 to 3, the starting material solution was turbid. Table 2 Type of CAU-10 pH molar ratio of solvent to ligand Turbidity of the source material before mixing after mixing Example 2-1 CAU-10-NH2 2,8 2,6 41 No Additional example 1 CAU-10-NH2 2,7 2,4 33 Yes Additional example 2 CAU-10-NH2 2,6 2,2 24 Yes Additional example 3 CAU-10-NH2 2,4 2,0 16 Yes Comparative example 2 CAU-10-NH2 2,1 1,8 8 Yes

[0115] As further additional examples, as shown in Table 3, the turbidity of the starting material solution was checked by adjusting the molar ratio of the organic solvent to the ligand in the ligand solution for the CAU-10-CH3 synthesis to a value in the range of approximately 40. The remaining conditions were the same as in Example 3. In the additional Example 4, where the molar ratio of the organic solvent to the ligand was 42, the Al source solution had a pH of 2.8 before mixing and a pH of 2.5 after mixing. In an additional Example 5, where the molar ratio described above was 33, the Al source solution had a pH of 2.6 before mixing and a pH of 2.4 after mixing.In an additional example 4, the starting material solution was clear, but in an additional example 5, the starting material solution was cloudy. Table 3 Type of CAU-10 pH Molar ratio of solvent to ligand Turbidity of the starting material solution before mixing after mixing Example 3 CAU-10-CH3 3,1 2,9 123 No Additional example 4 CAU-10-CH3 2,8 2,5 42 No Additional example 5 CAU-10-CH3 2,6 2,4 33 Yes

[0116] As shown in Tables 2 and 3, the starting material solution was cloudy when the molar ratio was adjusted to 33 or less, even when the drip rate of the ligand solution was slowed. Examples 1-1, 1-2, 2-1 to 2-4, 3, 4, 5 and 6, as well as Comparative Example 2, show that the molar ratio of the organic solvent to the ligand in the ligand solution is preferably greater than or equal to 40 and less than or equal to 500 to prevent clouding of the starting material solution. Furthermore, it can be deduced from Examples 1-1, 1-2, 2-1 to 2-4, 3, 4, 5 and 6, as well as from Comparative Example 1, that although the starting material solution is produced by mixing the ligand solution with the Al source solution, the pH value of the starting material solution is preferably kept higher than or equal to 2.5 and lower than or equal to 3.5 during production.

[0117] The support 11 used in the examples described above had a length of 16 cm in the direction in which the through-holes 111 extend. It is generally assumed that a depth greater than 10 cm leads to variations in thickness that impair quality if the starting material solution becomes cloudy during solvothermic synthesis. Therefore, the above-described method for producing the separation membrane complex 1 is suitable if the length of the through-holes 111 is greater than or equal to 10 cm. In practice, the length of the through-holes 111 in the separation membrane complex 1, i.e., the length of the separation membrane complex 1, is less than or equal to 200 cm.

[0118] In a cross-section perpendicular to the direction of penetration by the support 11, which was used in the examples described above, the maximum width of the through-holes 111 was 2 mm. Thus, it can be said that a low-deviation MOF membrane can be formed at least when this maximum width is greater than or equal to 1 mm. In practical application as a separation membrane complex 1, the maximum width of each through-hole 111 is less than or equal to 20 mm. Since the support 11 used in the examples described above had a length of 16 cm, it is shown from the examples described above that a low-deviation MOF membrane can be formed when the length of the through-holes 111 is 10 times or more and 100 times or less than the maximum width of the through-holes 111 described above.

[0119] The separation membrane complex 1 and the method for preparing the separation membrane complex 1 described above can be modified in various ways.

[0120] The separation membrane complex 1 can be produced by any method other than the manufacturing process described above.

[0121] The separation device 2 can separate any substance other than those mentioned as examples in the preceding description from the mixture of substances. The MOF membrane complex, which constitutes the separation membrane complex 1, is not limited to a permeation-type separation membrane but can also be an adsorption-type separation membrane. The MOF membrane complex can also be used in any application other than the separation of fluids.

[0122] As previously described, the support 11 is not limited to a so-called monolithic type support. The number of through-holes 111 can be one. If fluid permeability through the MOF membrane is not required, the support 11 is not limited to porous materials.

[0123] In the embodiment described above, the carrier 11 is in step S15, which is in Fig.As shown in Figure 4, the substrate 11 is immersed in the starting material solution 51. However, the term "immersed," as used here, does not always mean that the entire substrate 11 is in the starting material solution 51 and also includes a state in which only a portion of the substrate's surface, on which the MOF membrane is to be formed, is in contact with the starting material solution 51. That is, the MOF membrane formation step corresponds to the step of depositing the starting material solution 51 on the portion of the substrate 11's surface on which the MOF membrane is to be formed and heating the starting material solution 51.

[0124] The configurations of the preferred embodiment and variants described above can be combined in a suitable manner, provided there are no mutual inconsistencies.

[0125] Although the invention has been presented and described in detail, the foregoing description is in every respect explanatory and not limiting. It is therefore understood that numerous modifications and variants can be developed without departing from the scope of the invention. INDUSTRIAL APPLICABILITY

[0126] The MOF membrane complex according to the present invention is applicable in various fields, for example those related to the separation of a large number of substances. Reference symbol list 1 separation membrane complex (MOF membrane complex) 11 carriers 12 Separation membrane (MOF membrane) 51 Starting material solution 111 Through hole Step S11 to S16 QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-144625

[0002] Cited non-patent literature

[0000] “Highly CO2 Selective Metal-Organic Framework Membranes with Favorable Coulombic Effect” by Da-Shiuan Chiou and seven other colleagues, Advanced Functional Materials. 2021, 31, 2006924

[0004] Structures, Sorption Characteristics, and Non Linear Optical Properties of a New Series of Highly Stable Aluminum MOFs” by Helge Reinsch and six other employees, Chemistry of Materials, 2013, 25, 17-26

[0004]

Claims

[1] Method for producing a MOF membrane complex, comprising: a) Deposition of a seed crystal of a CAU-10-MOF onto a support; b) Producing an Al source solution, which is an aqueous solution containing an Al ion source; c) Preparation of a ligand solution in which an organic ligand used for the synthesis of CAU-10-MOF is dissolved in a solvent; d) Producing a starting material solution by mixing the Al source solution and the ligand solution at a rate that does not cause turbidity of the starting material solution; and e) Immersion of the support in the starting material solution to form a MOF membrane by solvothermic synthesis, which is the CAU-10-MOF on the support. [2] Method for producing a MOF membrane complex according to claim 1, wherein in process d) the ligand solution is added dropwise to the Al source solution while stirring. [3] Method for producing a MOF membrane complex according to claim 1, wherein in process d) the prepared starting material solution has a pH value which is maintained at higher than or equal to 2.5 and lower than or equal to 3.

5. [4] Method for producing a MOF membrane complex according to claim 1, wherein the molar ratio of the solvent to the organic ligand in the ligand solution is greater than or equal to 40 and less than or equal to 500. [5] Method for producing a MOF membrane complex according to claim 1, wherein the organic ligand is any selected from isophthalic acid, 5-aminoisophthalic acid, 5-methylisophthalic acid, 5-methoxyisophthalic acid, 5-nitroisophthalic acid and 5-hydroxyisophthalic acid. [6] Method for producing a MOF membrane complex according to any one of claims 1 to 5, wherein the support has a through hole and in process e) the support is immersed in the starting material solution in a state in which the expansion direction of the through hole is parallel to a vertical direction. [7] MOF membrane complex, comprising: a support with a through hole; and a MOF membrane, which is a CAU-10 MOF, formed on an inner surface of the through-hole or an outer surface of the support, where, if the carrier is divided into three equal parts in a longitudinal direction along which the through-hole extends, and a membrane thickness of the MOF membrane is determined in the middle of each of the three equal parts in the longitudinal direction to obtain three membrane thicknesses, a maximum value of the differences between an average membrane thickness value in the hole, which is an average value of the three membrane thicknesses, and the three membrane thicknesses is less than or equal to 30% of the average membrane thickness value in the hole. [8] MOF membrane complex according to claim 7, wherein the support has two through holes that include the through hole and are parallel to each other, and a maximum value of the differences between an average membrane thickness value between the holes, which is an average value of the average membrane thickness values ​​in the hole of the two through holes, and the average membrane thickness values ​​in the hole of the two through holes is less than or equal to 30% of the average membrane thickness value between the holes. [9] MOF membrane complex according to claim 7, wherein the through-hole has a length greater than or equal to 10 cm and less than or equal to 200 cm. [10] MOF membrane complex according to claim 7, wherein the through-hole has a maximum width of greater than or equal to 1 mm and less than or equal to 20 mm in a cross-section perpendicular to the longitudinal direction, and the through-hole has a length that is 10 times or more and 100 times or less than the maximum width of the through-hole. [11] MOF membrane complex comprising: a carrier; and a MOF membrane which is a CAU-10 MOF formed on the support, wherein an organic ligand used to form the MOF membrane is selected from 5-methylisophthalic acid, 5-aminoisophthalic acid and 5-nitroisophthalic acid.

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