JP6202295B2 - Composite porous body and method for producing the same - Google Patents

Description

  The present invention relates to a porous body having gas or liquid permselectivity, and a composite such as a composite porous membrane in which a metal organic structure (MOF) is formed inside the pores of a porous substrate such as a porous membrane. The present invention relates to a porous body and a method for producing the same.

  Porous membranes with many fine pores are used for liquid separation such as seawater desalination, wastewater treatment, concentration of alcohol and various chemical products, and gas separation such as hydrogen production, oxygen enrichment, and carbon dioxide separation. The separation performance is being improved and put to practical use. Specifically, developments have been made on zeolite membranes, silica membranes, porous α-alumina membranes, porous glass membranes, porous carbon membranes, porous polymer membranes and the like. It is necessary to develop a new porous membrane and improve its performance with the aim of further improving the separation performance of the porous membrane and applying the porous membrane to various difficult hydrocarbon separations.

In recent years, a new porous material called metal organic structure (MOF) has attracted attention as a new porous material. This is a crystalline, regular porous material formed by forming a coordination bond between a metal ion generated by dissolving a metal salt in a solution and an organic ligand capable of forming a coordination bond with the metal ion. It is a substance. Many types have been reported from combinations of metal ions and organic ligands. Metal organic structures (MOF), the pore size is 3nm order of about 0.3 nm, a specific surface area of the maximum from about 1000-2000m ² / g have been reported to over 5000 m ² / g. Development of a new porous film has been advanced by utilizing the feature of the metal organic structure (MOF) having a regular pore size and a high specific surface area.

  For example, Non-Patent Document 1 reports a composite porous body that is a film in which a metal organic structure (MOF) crystal is formed on the surface of a porous α-alumina substrate. Here, a porous α-alumina substrate is immersed in a solution containing both a metal salt and an organic ligand, and hydrothermal synthesis is performed to form a metal organic structure (MOF) on the surface of the porous α-alumina substrate. The crystal of MOF-5 which is a kind of the above is formed.

  In Non-Patent Document 2, a process of adjusting each aqueous solution of a metal salt and an organic ligand, which are raw materials of a metal organic structure (MOF), and alternately immersing the porous α-alumina base material is performed a plurality of times. A thin crystal layer is formed, and further immersed in a solution containing both a metal salt and an organic ligand, hydrothermal synthesis is performed, and a metal organic structure (MOF) is formed on the surface of the porous α-alumina substrate. A kind of Cu-BTC crystal is formed.

  In Non-Patent Document 3, a solution containing fine crystals of metal organic structure (MOF) is dropped onto a porous α-alumina substrate heated to high temperature to attach the fine crystals to the surface, and further, a metal salt and A crystal of Cu-BTC which is a kind of metal organic structure (MOF) is formed on the surface of the porous α-alumina base material by dipping in a solution containing both organic ligands and hydrothermal synthesis. .

  In Non-Patent Document 4, synthesis is performed by supplying respective aqueous solutions of a metal salt and an organic ligand from both sides of a porous nylon membrane. Two kinds of aqueous solutions permeate through the membrane surface and mix to form ZIF-8 crystals, which are a kind of metal organic structure (MOF), on the surface of the porous nylon membrane.

  In these non-patent literature methods, the metal organic structure (MOF) crystals are densely formed on the surface of the porous substrate, and the crystals formed by observation with a scanning electron microscope (SEM) Has been observed. Moreover, although the pore diameter of the porous base material used in these is about 100-200 nm, the crystal diameter of the metal organic structure (MOF) formed on the surface of the porous base material is a scanning electron. It is at least 1 μm or more from observation with a microscope (SEM). In the cross-sectional direction, a dense layer of metal organic structure (MOF) of at least 5 μm or more is observed on the surface of the porous substrate by scanning electron microscope (SEM) observation. Measurement of gas permeability of hydrogen, carbon dioxide, nitrogen, methane, etc. has also been reported, and it has been confirmed that it exhibits performance as a separation membrane.

  In Patent Document 1, a material obtained by combining a metal organic structure (MOF) and a porous substrate such as mesoporous silica, zeolite, metal oxide, porous clay, activated carbon and the like is reported as a hybrid porous material. . In this conventional method, a porous base material is impregnated into one of two kinds of raw materials, a metal salt which is a raw material of a metal organic structure (MOF) and an organic ligand, dried, and then impregnated into the other one. A substance obtained by a process of forming a metal organic structure (MOF) by hydrothermal synthesis has been filed as a hybrid porous substance. As an example, a composite porous material composed of mesoporous silica and MOF-5 which is a kind of metal organic structure (MOF) is shown.

JP2011-126775 (Samsung Electronics Co., Ltd.)

Liu, Y. Y .; Ng, Z. F .; Khan, E. A .; Jeong, H. K .; Ching, C. B .; Lai, Z. P. Microporous and Mesoporous Materials 2009, 118, 296-301. Nan, J. P .; Dong, X. L .; Wang, W. J .; Jin, W. Q .; Xu, N. P. Langmuir 2011, 27, 4309-4312. Guerrero, V. V .; Yoo, Y .; McCarthy, M. C .; Jeong, H. K. Journal of Materials Chemistry 2010, 20, 3938. Yao, J. F .; Dong, D. H .; Li, D .; He, L .; Xu, G. S .; Wang, H. T. Chemical Communications 2011, 47, 2559-2561.

  The conventional metal organic structure (MOF) composite membrane raises various problems when put to practical use as a separation membrane. In Non-Patent Documents 1-4, the metal organic structure (MOF) crystal formed on the surface of the porous substrate is detached from the surface, and further, the volume at the time of mechanical impact, heat, and solvent drying. There are problems with durability such as crystal breakage due to changes and strains. In fact, Non-Patent Document 3 reports that the crystal of the metal organic structure (MOF) formed on the surface of the porous substrate is cracked by the surface tension of water when dried from the water-containing state, and this is prevented. For this purpose, a process of drying after replacing with ethanol having a low surface tension is required, and this complicates and lengthens the handling process.

In Patent Document 1, the crystal diameter of the metal organic structure (MOF) formed on the porous substrate in the examples is estimated to be about 100-500 μm from the scanning electron micrograph, and further on the porous substrate. In this state, the surface of the porous substrate is exposed. Therefore, this conventional method is a method in which a metal organic structure (MOF) is dispersed and formed on the surface of the porous substrate, and the metal organic structure formed in the pores of the porous substrate ( Since there are gaps between the MOF) particles, and gas and liquid easily pass through the gaps, a crystal layer of metal organic structure (MOF) sufficient for practical use as a separation membrane cannot be obtained.
Non-Patent Document 4 uses a counter diffusion method in which the raw material solution is supplied from both sides of the membrane, which is the same format as the manufacturing method used in the present invention. However, Non-Patent Document 4 aims to form a metal organic structure (MOF) on the surface of the porous substrate, and has succeeded in forming MOF in the pores of the porous substrate. Absent. This is because the reaction conditions at the time of production do not use conditions necessary for forming the metal organic structure (MOF) in the pores, but the metal organic structure (MOF) is formed in the pores. The fundamental reason is that they do not recognize the benefits of doing so.

  The present invention solves the above-mentioned problems of the prior art, and a composite porous body comprising a metal organic structure (MOF) crystal layer that can be sufficiently expected to be put to practical use as a separation element such as a separation membrane An object is to provide a manufacturing method thereof.

  As a result of intensive studies, the inventors have concluded that the problem in the prior art is due to the formation of a metal organic structure (MOF) on the surface of the porous substrate. It has been found that the problem of the conventional method can be solved by forming a metal organic structure (MOF) inside the pores of the present invention, leading to the development of a novel composite porous body and its production method.

  That is, the composite porous body of the present invention is a composite porous body in which a metal organic structure (MOF) is formed inside the pores of the porous substrate, and the pore diameter of the porous substrate is 10 μm or less. In addition, the crystal diameter of the composite porous metal-organic structure (MOF) is smaller than the pore diameter of the porous substrate obtained by measuring the pore diameter of the porous substrate.

  Furthermore, the composite porous body of the present invention has a metal salt and an organic ligand formed on a porous substrate based on a film base or the like when forming a metal organic structure (MOF) inside the pores of the porous substrate. It is characterized by being supplied in a solution state from both sides of the material.

The present invention has the features as described above, and can be summarized as follows.
(1) A composite porous body in which a metal organic structure (MOF) is formed inside the pores of a porous substrate,
The average pore diameter of the porous substrate obtained by measuring the pore diameter of the porous substrate is 10 μm or less,
The crystal diameter of the composite porous metal-organic structure (MOF) is smaller than the average pore diameter of the porous substrate;
A composite porous body characterized by
(2) The material of the porous substrate was selected from the group consisting of α-alumina, zirconia, titania, silicon carbide, magnesia, glass, carbon, zeolite, clay mineral, PTFE, polyimide, polyethylene and derivatives thereof. The composite porous body according to (1) above, which is at least one kind.
(3) The metal salt that is the raw material of the metal organic structure (MOF) is metal nitrate, metal sulfate, metal chloride, metal bromide, metal iodide, metal fluoride, metal carbonate, metal formate, metal It is at least one selected from the group consisting of phosphates, metal sulfides and metal hydroxides, and the metal elements of the metal salts are Cu, Zn, Co, In, Al, Fe, V, Mg, Mn, The composite porous body according to (1) or (2) above, which is at least one selected from the group consisting of Ni, Ru, Mo, Cr, W, Rh and Pd.
(4) The organic ligand that is a raw material of the metal organic structure (MOF) is at least one selected from the group consisting of dicarboxylic acid, tricarboxylic acid, imidazole, benzimidazole, azabenzimidazole, and derivatives thereof. The composite porous body according to any one of (1) to (3) above, wherein
(5) A method for producing a composite porous body in which a metal organic structure (MOF) is formed inside a porous substrate having a large number of pores communicating between one surface and another surface. A metal salt solution is supplied from the one side and an organic ligand solution is supplied from the other side under the condition that a metal organic structure (MOF) is formed inside the pores. A method for producing a composite porous body.
(6) The composite porous body as described in (5) above, wherein a coating layer having fine pores of 2 to 5 nm is formed in advance on one surface of the porous substrate and the other surface. Manufacturing method.

In addition, the present invention can include the following aspects.
(7) The composite porous body according to any one of (1) to (4) above, wherein the porous substrate is in the form of a film having a thickness of 0.2 to 5 mm.
(8) The composite porous body according to (7), wherein the thickness of the membranous porous substrate is 1 to 3 mm.
(9) The porous substrate has a porous substrate layer composed of one or more porous layers having pores with a diameter of more than 10 μm, and pores of 10 μm or less on the surface of the porous substrate layer. The composite porous body according to any one of (1) to (4) above, wherein the composite porous body has a laminated structure with a thin porous layer.
(10) The composite porous body according to (9), wherein the porous base material layer has a thickness of more than 5 mm and the thin porous layer has a thickness of 0.1 to 3 mm.
(11) The above (1) to (4), (7) to (10), wherein the porous substrate is any one of a flat plate shape, a curved plate shape, a corrugated plate shape, a tubular shape, a cylindrical shape, a rectangular tube shape, and a monolith shape. The composite porous body according to any one of 1).
(12) The method for producing a composite porous body according to (5), described above in (5) or (6), wherein the another surface is a surface opposite to the one surface.
(13) The composite porous material according to any one of the above (5), (6), and (12), wherein the porous substrate obtained by measuring the pore size of the porous substrate has an average pore size of 10 μm or less. Body manufacturing method.
(14) The material of the porous substrate is selected from the group consisting of α-alumina, zirconia, titania, silicon carbide, magnesia, glass, carbon, zeolite, clay mineral, PTFE, polyimide, polyethylene and derivatives thereof. The method for producing a composite porous body according to any one of (5), (6), (12), and (13) above, wherein the composite porous body is at least one kind.
(15) The metal salt that is the raw material of the metal organic structure (MOF) is metal nitrate, metal sulfate, metal chloride, metal bromide, metal iodide, metal fluoride, metal carbonate, metal formate, metal It is at least one selected from the group consisting of phosphates, metal sulfides and metal hydroxides, and the metal elements of the metal salts are Cu, Zn, Co, In, Al, Fe, V, Mg, Mn, Any one of (5), (6), (12) to (14) above, which is at least one selected from the group consisting of Ni, Ru, Mo, Cr, W, Rh and Pd The manufacturing method of the composite porous body as described in a term.
(16) The organic ligand that is a raw material of the metal organic structure (MOF) is at least one selected from the group consisting of dicarboxylic acid, tricarboxylic acid, imidazole, benzimidazole, azabenzimidazole, and derivatives thereof. The method for producing a composite porous body according to any one of the above (5), (6), and (12) to (15).
(17) The method for producing a composite porous body according to the above (6), wherein the material for forming the coating layer having fine pores of 2 to 5 nm is γ-alumina.
(18) Adjusting at least one of the supply rate of the solution and the formation reaction rate of the metal organic structure (MOF) to form the metal organic structure (MOF) in the pores, (5) (6) The method for producing a composite porous body according to any one of (12) to (17).
(19) Increasing the concentration of the solution and / or increasing the temperature of the solution increases the formation reaction rate of the metal organic structure (MOF), and the metal organic structure (MOF) in the pores. The method for producing a composite porous body according to (18), wherein
(20) By using a porous base material having a small pore diameter and / or using a porous base material having a layer that prevents supply on the surface, the supply speed of the solution is reduced, and the metal is formed in the pores. The method for producing a composite porous body according to (18), wherein the organic structure (MOF) is formed.

  According to the present invention, the composite porous metal organic structure (MOF) is obtained from the fact that the pore diameter of the porous substrate is 10 μm or less and the pore diameter of the porous substrate obtained by measuring the pore diameter of the porous substrate. It is possible to produce a porous composite film in which a microcrystalline layer of a metal organic structure (MOF) is formed in the pores of a porous substrate, characterized by having a small crystal diameter. For this reason, it is possible to overcome the problems of the detachment and durability of the metal organic structure (MOF) crystals on the surface of the porous substrate, which were problems in the conventional method. Further, with respect to gas separation performance, the composite porous body of the present invention is characterized by exhibiting significantly higher gas separation performance compared to the conventional method using the same metal organic structure (MOF), and has higher performance. A composite porous body and a method for producing the same can be provided.

It is a schematic cross section which shows one Embodiment of the composite porous body of this invention, and one Embodiment of the conventional method. It is a schematic diagram which shows one Embodiment of the X-ray-diffraction measurement result of the composite porous body of this invention. It is a schematic cross section which shows one Embodiment of the production method of the composite porous body of this invention. It is a scanning electron microscope observation result in one Example of this invention. (a) shows the outer surface of the tube, and (b) shows the inner surface of the tube. Scanning electron microscope observation results (a) and energy dispersive X-ray spectroscopy (EDX) analysis results [(b) Al, (c) O, (d) C, (e ) Cu]. It is a transmission electron microscope observation result in one Example of this invention. It is a result of the X-ray diffraction measurement in one Example of this invention. It is a result of the gas permeability measurement in one Example of this invention.

Hereinafter, the composite porous body of the present invention and the production method thereof will be described in more detail and specifically.
FIG. 1 is a schematic cross-sectional view showing one embodiment of a composite porous body of the present invention and one embodiment of a conventional method. In the composite porous body of the present invention shown in FIG. 1, a microcrystalline layer of metal organic structure (MOF) is formed inside the pores of the porous substrate. In the conventional method, a metal organic structure (MOF) crystal is formed on the surface of a porous substrate.

  The composite porous body of the present invention is a composite porous body in which a metal organic structure (MOF) is formed inside the pores of the porous substrate, and the pore diameter of the porous substrate is 10 μm or less, The crystal diameter of the composite porous metal organic structure (MOF) is smaller than the pore diameter of the porous substrate obtained by measuring the pore diameter of the porous substrate.

[Description of pore interior]
In the present invention, the inside of the pores of the porous substrate refers to the inside of a space having a diameter of 10 μm or less that leads from one surface of the porous substrate to the other surface. The composite porous body of the present invention is a composite porous body in which a metal organic structure (MOF) is formed inside the pores of a porous substrate. This means a structure in which a metal organic structure (MOF) is formed at least inside the pores of the porous substrate. The metal organic structure (MOF) is simultaneously formed inside the pores and on the surface of the porous substrate. Does not prevent the formation of.

  In the present invention, the structure of the composite porous body in which the metal organic structure (MOF) is formed inside the pores of the porous substrate can be confirmed by observation with an electron microscope. That is, confirmation can be made by detecting an element constituting the metal organic structure (MOF) by electron microscope observation and elemental analysis inside the composite porous body. For the electron microscope observation, a method of observing the cross section of the composite porous body with a scanning electron microscope is the simplest, and a structure in which the inside of the pores of the porous substrate is blocked can be confirmed. In a method combining scanning electron microscope and elemental analysis, a composite in which a metal organic structure (MOF) is formed inside the pores of a porous substrate by detecting elements constituting the metal organic structure (MOF). The structure of the porous body can be confirmed. Even in a transmission electron microscope and a method combining elemental analysis with this, the structure of the composite porous body can be confirmed in more detail.

In the present invention, the pore diameter can be measured by a palm porometry method or a mercury intrusion method. The palm porometry method measures the widest portion in the pore, and the mercury intrusion method measures the narrowest neck portion in the pore. In this method, since the metal organic structure (MOF) fine particles are generated inside the widest part of the pores of the porous substrate, the most optimal measurement method is the palm porometry method. However, in practice, the mercury intrusion method and the palm porometry method can be evaluated to the same degree of pore diameter, and both are used by those skilled in the art. In the pore diameter measurement of the present invention, the pore diameter can be measured by using at least one of the palm porometry method and the mercury intrusion method, and more preferably, the palm porometry method can be used.
[Description of palm porometry measurement method]
The palm porometry measurement method in the present invention is an extended method of the through pore evaluation method by the bubble point method (JIS K3832). In the bubble point method, an appropriate liquid is filled in the pores of the porous substrate, pressure is applied by gas from one side of the membrane portion, and the liquid in the pores is extruded in order from the pores with the largest pore diameter. In this method, the pore diameter is evaluated using the pressure value when the gas is blown out in the form of bubbles. In the palm porometry measurement method, in the state where the pores of the porous substrate are filled with a liquid, the measurement by the bubble point method and the pressure are further increased to measure the change in the gas flow rate to obtain a wet flow curve. Next, a change in the gas flow rate is measured in a state where the porous substrate is dried to obtain a dry flow curve. In Palm Polo cytometry assay, the pore diameter d _i of the porous substrate in the measured pressure P _i that is obtained by the following equation.
d _i = 4σ cos θ / P _i
Here, σ is the surface tension of the liquid, and θ is the contact angle between the liquid and the material of the porous substrate. The cumulative distribution D _i of pore diameters, which is the cumulative ratio (%) of pore diameters greater than d _i , is obtained by the following equation.
D _i = 100 × (F _Di −F _Wi ) / F _Di
Here, F _Di is a flow rate value in the dry flow curve, and F _Wi is a flow rate value in the wet flow curve. Here the cumulative distribution of pore diameter determined, can be determined (d _i in 50% of該累product distribution D _i) an average pore diameter of the porous substrate.
[Description of mercury intrusion measurement method]
The mercury intrusion method in the present invention is generally used for measuring the diameter and porosity of many porous materials, and can measure a wide pore diameter of about 3 nm to 500 nm. Mercury has a high capillary force and a contact angle of 90 ° or more for most substances. Since mercury enters the pores by applying a pressure higher than the capillary force to the mercury, the pore diameter can be estimated using this property. The equation for the capillary model is:
r = -2σCOSθ / P
Here, r is the pore radius, σ is the surface tension of mercury, 484 erg / cm ² , and θ is the contact angle of around 140 °. Furthermore, it is also possible to measure the pore size distribution by using a porosimeter that measures the volume reduction of mercury during press-fitting.

For the evaluation of the crystal diameter in the present invention, a method using a transmission electron microscope or a method using X-ray diffraction measurement can be used, and measurement using a transmission electron microscope can be more preferably used.
[Transmission electron microscope measurement in the present invention]
The transmission electron microscope measurement in the present invention can be performed using a general transmission electron microscope. By producing a thin piece with a thickness of about 100 nm and observing it with a transmission electron microscope, direct observation of fine particles of the metal organic structure (MOF) formed in the pores of the porous substrate is performed. It is possible to measure the particle size. In the measurement with a transmission electron microscope, the inside of any three pores of the porous substrate is observed, and the center of gravity of the three crystal particles arbitrarily extracted from the inside of each pore is determined. Measure the major and minor diameters that pass through. The average value of a total of nine crystal diameters obtained from these is used as the average crystal diameter of the crystal particles present in the pores of the composite porous body.
[X-ray diffraction measurement in the present invention]
The X-ray diffraction measurement in the present invention is a technique for analyzing the structure of the composite porous body of the present invention by measuring the diffraction intensity while changing the incident angle of the CuKα ray (wavelength 0.15418 nm). By this measurement, first, the lattice structure of the crystal formed in the composite porous body can be confirmed. This can be easily achieved by comparing the obtained X-ray diffraction measurement results with the data described in the past non-patent literature. Second, the crystal diameter of the crystals formed in the composite porous body can be analyzed. The crystal diameter obtained by this method is the average crystal diameter of the metal organic structure (MOF) present in the measurement part. This is an analysis method based on the generally known Scherrer equation, and the crystal diameter D is obtained by the following equation (see the following reference).
D = Kλ / Bcos θ
B = B _obs −b
Here, K is Scherrer's constant, generally 0.89, λ is the X-ray wavelength, CuKα ray is 0.15418 nm, θ is the X-ray incident angle, and B is the X-ray diffraction peak. The full width at half maximum, B _obs is a measured value of the full width at half maximum of the X-ray diffraction peak, and b is the spread of the X-ray diffraction peak by the apparatus. B _obs is a value obtained as the full width at half maximum of the diffraction peak in the X-ray diffraction measurement, as shown in FIG. b is the full width at half maximum of the X-ray diffraction peak obtained from the X-ray diffraction measurement measured using a sufficiently large crystal prepared separately from the composite porous body.
[References] Guinier. A (1963). X-ray Diffraction. San Francisco: Freeman & Co.

[Summary about claim 1]
The composite porous body according to claim 1 of the present invention can be characterized based on the above analysis method. That is, the presence of the metal organic structure (MOF) in the pores of the porous substrate can be confirmed by analysis combining an electron microscope and elemental analysis. The pore diameter of the porous substrate can be measured by palm porometry measurement or mercury porosimetry. It is possible to confirm the lattice structure of the metal organic structure (MOF) crystal by X-ray diffraction measurement. Furthermore, the crystal diameter of the metal organic structure (MOF) can be analyzed based on Scherrer's equation, and transmitted. It can also be determined by means of a scanning electron microscope. With the above method, the characteristics of the composite porous body of the present invention can be confirmed.

[Porous substrate]
The porous substrate in the present invention has pores that communicate from one surface to another surface (preferably, the surface opposite to the one surface), and have an average pore diameter of 10 μm or less by pore diameter measurement. . When the average pore diameter measured by the pore diameter exceeds 10 μm, it becomes difficult to perform fine filling without defects when filling the pores of the porous substrate with the metal organic structure (MOF). In the present invention, it is defined as 10 μm or less. The average pore diameter is preferably 5 μm or less, more preferably 1 μm or less. The average pore diameter measured by the palm porometry method may be as small as the metal organic structure (MOF) is formed inside the pore. The average pore diameter capable of forming a metal organic structure (MOF) inside is usually about 10 nm or more (preferably 50 nm or more). (Various pore diameters from about 50 nm to about 10 μm can be produced.)

The material of the porous substrate is not limited, but includes α-alumina, zirconia, titania, silicon carbide, magnesia, glass, carbon, zeolite, clay mineral, PTFE, polyimide, polyethylene and derivatives thereof. It can be at least one kind selected. Of these, α-alumina, zirconia, titania, glass, and derivatives thereof are more preferable, and α-alumina and derivatives thereof are more preferable. α-alumina is a ceramic material having a composition of Al ₂ O ₃ .

  The porous substrate in the present invention may be a laminated structure of a plurality of types of materials, or a structure in which two or more types of materials are dispersed in an appropriate pattern such as a sea-island structure. May be. For example, a coating layer having fine pores of about 3 to 6 nm can be formed in advance on one surface of the porous substrate and the other surface. When a coating layer having such fine pores is formed on one surface of the porous substrate, it becomes a resistance when the raw material solution penetrates into the pores of the membrane, and a metal organic structure (MOF) It is desirable in that a thin layer is formed. As a material for the coating layer having such fine pores, for example, γ-alumina, polymer coating, or the like can be used. (As a derivative of α-alumina, a porous substrate whose surface is coated with γ-alumina having a pore diameter of about 4 nm can also be used.) As a polymer coating, polyether, polyphenylene oxide, polyethylene, polyimide, At least one selected from the group consisting of polyamide, PTFE, and nylon can be used.

  Regarding the shape of the porous substrate, it is possible to use porous substrates of various shapes that can be produced, and are not limited, for example, flat plate shape, curved plate shape, corrugated plate shape, tubular shape, A shape such as a cylindrical shape, a rectangular tube shape, or a monolith shape can be used. As an example, the monolithic porous substrate has a structure in which a large number of through holes are opened inside a cylindrical shape. The thickness of the porous substrate is not limited, but can be 50 to 1000 μm, preferably 100 to 800 μm, and more preferably 200 to 500 μm.

[Description of Metal Organic Structure (MOF)]
In the metal organic structure (MOF: Metal-Organic Framework) in the present invention, a metal ion and an organic ligand form a coordinate bond, and this basic structure is continuously grown to a crystal structure. Metal organic structures (MOF) is a porous material, having a pore structure of approximately 3nm from about 0.3nm in the crystal lattice, the specific surface area of 5000 m ² / g is up to the order of 1000-2000m ² / g It has been reported to exceed. Among metal organic structures (MOF), there is a zeolite imidazolate structure (ZIF) with a zeolite skeleton, but the zeolite imidazolate structure (ZIF) is also a coordinate bond between a metal ion and an organic ligand. The structure is formed by the above, and is classified as a part of metal organic structure (MOF).
Examples of the metal organic structure (MOF) that can be used in the present invention include Cu-BTC, MOF-5, IRMOF-3, MIL-47, MIL-53, MIL-96, MMOF, SIM-1, and ZIF. -7, ZIF-8, ZIF-22, ZIF-69, and ZIF-90 are mentioned, but the metal organic structure (MOF) is not limited to this because there are more than 200 kinds of structures.

[Description of raw materials for metal organic structure (MOF)]
The metal organic structure (MOF) of the present invention is formed by a metal ion and an organic ligand. The raw materials for the metal organic structure (MOF) are a metal salt capable of obtaining a metal ion in a solution and an organic ligand. This means that at least one of each of the metal salt and the organic ligand is used as a raw material, and does not preclude the use of a plurality of types as raw materials if necessary. Furthermore, if necessary, raw materials other than metal salts and organic ligands can be used.

[Description of metal salt]
The metal salt used as the metal organic structure (MOF) raw material of the present invention can be selected from those containing various metal elements. The metal element contained in the metal salt is preferably selected from the group consisting of Cu, Zn, Co, In, Al, Fe, V, Mg, Mn, Ni, Ru, Mo, Cr, W, Rh and Pd. An element, more preferably an element selected from the group consisting of Cu, Zn, Co, In, Al, Fe, and V, and still more preferably an element selected from the group consisting of Cu, Zn, and Co.

  Examples of the metal salt containing the metal element include metal nitrate, metal sulfate, metal chloride, metal bromide, metal iodide, metal fluoride, metal carbonate, metal formate, metal phosphate, metal sulfide and It can be selected from the group consisting of metal hydroxides. More preferably, it is a metal salt selected from the group consisting of metal nitrates and metal chlorides,

  Specific metal salts that can be used in the present invention are preferably copper nitrate, zinc nitrate, cobalt nitrate, indium nitrate, aluminum nitrate, iron nitrate, vanadium nitrate, copper chloride, zinc chloride, cobalt chloride, indium chloride, chloride. A metal salt selected from the group consisting of aluminum, iron nitrate chloride and vanadium chloride, more preferably a metal salt selected from the group consisting of copper nitrate, zinc nitrate, cobalt nitrate, indium nitrate and vanadium chloride.

[Description of organic ligands]
The organic ligand in the present invention is selected from organic ligands that form coordinate bonds with the metal ions of the above-described metal elements. The organic ligand can be at least one selected from the group consisting of dicarboxylic acid, tricarboxylic acid, imidazole, benzimidazole, azabenzimidazole, and derivatives thereof.

  The organic ligand that can be used as the dicarboxylic acid is preferably at least one selected from the group consisting of isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid and biphenylenedicarboxylic acid. is there.

  The organic ligand that can be used as the tricarboxylic acid is preferably at least one selected from the group consisting of 1,2,3-benzenetricarboxylic acid and 1,3,5-benzenetricarboxylic acid. The organic ligand that can be used as the tetracarboxylic acid is preferably at least one selected from the group consisting of 1,2,3,4-benzenetetracarboxylic acid and 1,2,4,5-benzenetetracarboxylic acid It is.

  In addition, these selected organic ligands are optionally substituted with another substituent in the skeleton, such as hydroxyl group, amino group, methoxy group, methyl group, nitro group, methylamino group, dimethylamino group, cyano group. Groups, chloro groups, bromo groups and fluoro groups.

[Description of manufacturing method]
In the method for producing a composite porous body of the present invention, when the metal organic structure (MOF) is formed inside the pores of the porous substrate, the conditions under which the metal organic structure (MOF) is formed inside the pores. Then, the metal salt and the organic ligand are supplied in a solution state from one side and the other side of the porous substrate (when the porous substrate is a film, from both sides of the membrane part). This is a method for producing a composite porous body. When supplying the solution from both sides of the membrane part of the porous substrate, in order to sufficiently introduce the solution into the pores, the solution is introduced in a state where the porous substrate is previously placed under vacuum, etc. Take the method. In the schematic cross-sectional view showing one embodiment of the method for producing the composite porous body of the present invention shown in FIG. 3, the metal salt and the organic ligand are respectively in a solution state from both sides of the film-like portion of the porous substrate. The manufacturing method to supply is shown as a schematic diagram.
The condition for forming the metal organic structure (MOF) in the pores is a condition for performing a reaction for forming the metal organic structure (MOF) inside the pores of the porous substrate. For this condition, for example, as in the following (1) to (3), the relationship between the supply rate of the reactant (raw material solution) and the reaction rate for forming the metal organic structure (MOF) should be adjusted appropriately. Can be realized.
(1) The formation reaction rate of the metal organic structure (MOF) in the pores of the porous substrate is increased without changing the feed rate of the raw material solution.
For this purpose, for example, raising the concentration of the reaction solution, raising the temperature of the reaction solution, and the like can be mentioned. At this time, it is necessary to use a porous substrate that does not lose its durability even at the selected reaction temperature.
(2) The rate of forming the metal organic structure (MOF) is not changed, and the feed rate of the raw material solution is decreased.
For this purpose, use of a porous substrate having a small pore diameter, use of a porous substrate having a derivative layer that hinders supply on the surface, and the like can be mentioned.
(3) Both the feed rate of the raw material solution and the formation reaction rate of the metal organic structure (MOF) in the pores of the porous substrate are adjusted.
These appropriate supply rates and reaction rates differ depending on the type of metal organic structure (MOF) to be used, but by adjusting the formation status such as the MOF formation position, the metal organic structure (MOF) Can be formed inside the pores.

  Here, supplying the metal salt and the organic ligand in the form of a solution from both sides of the membrane-like portion of the porous substrate means that the space is separated by a membrane having a tubular, flat plate, or monolith shape. It means that a solution of a metal salt and an organic ligand is supplied respectively, and means that these solutions do not mix in a space other than the membrane. For this purpose, the porous membrane to be used needs to be sealed by an appropriate method. If it is a tubular membrane or a monolithic membrane, the end is sealed and placed in the reaction vessel, and if it is flat, It must be arranged so that the solution is supplied separately on both sides using a suitable reaction vessel.

[About the solution]
In the method for producing a composite porous body of the present invention, the state of a solution means a state in which a metal salt and an organic ligand are dissolved in an appropriate solvent. The solvents used for dissolving the metal salt and the organic ligand do not need to be the same. Moreover, a solvent can also be used in mixture of multiple types. As the solvent, at least one selected from the group consisting of water, alcohols, acid amides, cyclic ethers, ketones, nitriles and aromatics can be used.

  As the alcohol, at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and t-butanol can be used. As the acid amide, at least one selected from the group consisting of formamide, dimethylformamide, diethylformamide, t-butylformamide, acetamide, dimethylacetamide, diethylacetamide and t-butylacetamide can be used. As the cyclic ether, at least one selected from the group consisting of tetrahydrofuran and dioxane can be used. As the ketones, at least one selected from acetone and methyl ethyl ketone can be used. As the aromatics, at least one selected from toluene, xylene, chlorobenzene and chloromethylbenzene can be used.

[Production conditions for composite porous bodies]
In the method for producing a composite porous body of the present invention, it is desirable to select an optimum reaction temperature from the reactivity of the selected metal salt and organic ligand and the boiling point of the selected solvent. In general, a metal organic structure (MOF) is synthesized in a temperature range from room temperature to about 250 ° C. In this synthesis, when the reaction temperature is close to the boiling point of the solvent to be used and the decrease in the solvent is large, or when the reaction temperature is higher than the boiling point of the solvent to be used, the reaction is performed under pressurized conditions. In the reaction under a pressurized condition, it is possible to use a generally available pressurized reaction vessel. For example, when the reaction is performed at 120 ° C. using water and ethanol, respectively, the temperature exceeds the boiling points of both water and alcohol.

  Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to such examples, and material changes, setting adjustments, and design changes are made as appropriate without departing from the gist of the present invention. It is possible.

[Example 1]
As an example based on the present invention, a porous composite membrane in which MOF-199 (Cu-BTC), which is a kind of metal organic structure (MOF), is combined with an α-alumina tubular porous substrate is shown.

  The α-alumina tubular porous substrate used in this example is a hollow tube having an outer diameter of about 3 mm, an inner diameter of about 2.4 mm, and an average pore diameter of about 100 nm by mercury porosimetry. One of the α-alumina tubular porous membranes was sealed with molten glass to separate the membrane portions. The solution is introduced into the entire pores of the porous membrane by supplying 0.3 M aqueous solution of copper nitrate 2.5 hydrate to the inside of the hollow tube after vacuum processing the porous substrate. Immerse it in a reaction vessel filled with 0.2M ethanol solution of trimesic acid heated to 75 ° C. with the end sealed with molten glass facing down, and place the reaction vessel in an autoclave for 6 hours at 120 ° C. The reaction was performed. Here, heating the ethanol solution of trimesic acid to 75 ° C. in advance is a condition for forming MOF-199 (Cu-BTC) inside the porous substrate. After the reaction, washing was performed at 75 ° C. for 24 hours using a 50% aqueous solution of ethanol, followed by vacuum drying. Observation of the obtained composite porous body with a scanning electron microscope, elemental analysis of the cross section, and X-ray diffraction measurement were performed. The permeability of helium, hydrogen, carbon dioxide, oxygen, nitrogen, methane, carbon tetrafluoride, and sulfur hexafluoride was measured using a gas permeation measuring device.

  From the observation with a scanning electron microscope shown in FIG. 4, the porous composite film obtained in this example showed that a Cu-BTC crystal was observed on the outer surface of the tube shown in FIG. Exposure was also observed. Cu-BTC crystals were not observed inside the hollow tube shown in FIG. In addition, from the measurement results of the elemental analysis of the cross section perpendicular to the hollow tube axis shown in FIG. 5, the carbon element shown in FIG. 5 (d) and FIG. The presence of the copper element shown in e) was confirmed.

  From the result of the X-ray diffraction measurement shown in FIG. 7, the porous composite film obtained in this example shown in FIG. 7 (c) was produced under the conditions for synthesizing the simple substance of Cu-BTC shown in FIG. 7 (b). The diffraction peak was shown at the same position as the obtained Cu-BTC, and the presence of Cu-BTC was confirmed. From the results of scanning electron microscope observation, elemental analysis, and X-ray diffraction measurement, Cu-BTC exists in a layered range of about 40 μm in the depth direction from the outer surface of the α-alumina tubular porous substrate. Was revealed.

  From the result of the transmission electron microscope observation of the porous composite membrane shown in FIG. 6, the pores of the porous substrate are shown in FIG. 6 (a) and the enlarged view of FIG. 6 (b). Cu-BTC particles having a crystal diameter of about 5 nm were observed in the pores. From these facts, the composite porous body obtained in this example has a very small CuBTC crystal diameter of about 5 nm in the pores of the porous substrate of α-alumina having a pore diameter of about 100 nm. It was found that the structure formed crystals.

FIG. 8 shows the result of measuring the gas permeability of the composite porous body obtained in this example. The measurement was performed at a differential pressure of 1 atm and 25 ° C. using a time lag method. The measurement gas is helium (He), hydrogen (H ₂ ), carbon dioxide (CO ₂ ), oxygen (O ₂ ), nitrogen (N ₂ ), and methane (CH ₄ ). Diameter) increases. As a result, the selectivity of hydrogen was 3.7, 16.2, 123, and 153 for each gas of CO ₂ , O ₂ , N ₂ , and CH ₄ . This is because the larger the size of the molecule, the greater the difference in permeability with hydrogen and the higher the selectivity of hydrogen, so we succeeded in obtaining extremely high molecular sieve permeation behavior. As a gas permeable membrane using Cu-BTC that is the same MOF, for example, in Non-Patent Document 2, the selectivity of hydrogen with respect to each gas of CO ₂ , N ₂ , and CH ₄ is 5.1, 3 A value of .7, 2.9 has been reported and no molecular sieve permeation behavior has been obtained. Therefore, in the composite porous body of Cu-BTC which is an example of the present invention, the case where the composite porous body is manufactured using the same MOF is extremely high as compared with the conventional report example. We succeeded in obtaining the permeation behavior of molecular sieve gas.

  The composite porous body of the present invention has separation performance such as extremely high molecular sieving properties. In addition, by selecting an appropriate MOF according to the separation object, various separation performances that match the separation object can be obtained. Therefore, application to energy-saving membrane separation processes such as seawater desalination, wastewater treatment, liquid separation applications such as alcohol and various chemical products, and gas separation applications such as hydrogen production, oxygen enrichment, and carbon dioxide separation. A wide range of applications are possible.

01 Composite porous body 02 Porous substrate 03 Microcrystalline layer of metal organic structure (MOF) 04 Crystal layer of metal organic structure (MOF) 21 Full width at half maximum of diffraction peak in X-ray diffraction measurement 31 Metal organic structure ( MOF) raw material solution A
32 Solution B of metal organic structure (MOF) raw material

Claims (2)

  A method for producing a composite porous body in which a metal organic structure (MOF) is formed inside a pore of a porous substrate having a large number of pores communicating between one surface and another surface. A composite characterized in that a metal salt solution is supplied from the one surface side and an organic ligand solution is supplied from the other surface side under the condition that a metal organic structure (MOF) is formed inside the pores. A method for producing a porous body. The method for producing a composite porous body according to claim 2 , wherein a coating layer having fine pores of 2 to 5 nm is formed in advance on one side of the porous substrate and the other side.

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