A metal organic framework material ZIF composite film and a preparation method and application thereof

Abstract

The application discloses a kind of metal organic framework material ZIF composite film and its preparation method and application, the ZIF composite film includes porous support film layer, polypyrrole layer and ZIF layer in turn.The porous support film is modified using polypyrrole polymer in the application, more conducive to improving the interface binding between ZIF crystal and porous support film, and more dense and continuous ZIF composite film is obtained.In addition, pyrrole monomer is low in price, which significantly reduces the preparation cost.The metal organic framework ZIF composite film provided by the application has good separation performance when used in hydrogen / carbon dioxide separation system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane separation materials, and particularly relates to a metal-organic framework material, and specifically relates to a metal-organic framework material ZIF composite membrane and a preparation method and application thereof. BACKGROUND

[0002] Generally, hydrogen is produced by reforming or gasification of traditional fossil fuels, and carbon dioxide is captured and utilized or stored as a byproduct. Separating hydrogen from carbon dioxide and achieving efficient purification of hydrogen are key steps to improve the economic competitiveness of the technology and promote the use of hydrogen energy. Compared with traditional separation technologies such as adsorption and crystallization, membrane separation technology has the advantages of low energy consumption, high efficiency, and convenient operation, and is considered as one of the most promising technologies in the 21st century. The key to developing membrane separation technology for purifying hydrogen lies in developing high-performance membrane materials, improving hydrogen flux, reducing membrane area and system cost, and improving selectivity to improve product purity.

[0003] According to the solution-diffusion model, the gas permeation rate P A is expressed as P A = S A × D A , where S A is the gas solubility coefficient, and D A is the gas diffusion coefficient. The gas selectivity (P A / P B ) is the ratio of the permeation rates of two gases, that is, the product of the solubility selectivity (S A / S B ) and the diffusion selectivity (D A / D B ). In terms of solubility coefficient, the critical temperature of carbon dioxide is 304K, and the critical temperature of hydrogen is 33K, carbon dioxide is more easily compressed than hydrogen, and the solubility coefficient of carbon dioxide in the membrane material is higher than that of hydrogen. In terms of diffusion coefficient, the molecular kinetic diameter of hydrogen is 0.289nm, and the molecular kinetic diameter of carbon dioxide is 0.33nm, and the diffusion coefficient of hydrogen in the membrane material is higher than that of carbon dioxide. Therefore, the free volume or pore size of the membrane material should be as close to the range of 0.289-0.33nm as possible to improve the molecular sieving ability, so as to maximize the diffusion selectivity of hydrogen and carbon dioxide.

[0004] Metal-organic frameworks (MOFs) are a class of organic-inorganic hybrid porous materials with periodic framework structure, which are formed by self-assembly of inorganic metal centers and organic ligands. MOFs have regular pore structure, controllable pore size, high porosity and high specific surface area, as well as excellent chemical and thermodynamic stability, showing great development potential and wide application prospect in the fields of separation, catalysis, sensing, etc. Traditional polymer separation membranes have disordered chain network structure, and the gas separation process is limited by the solution-diffusion model, resulting in a mutual restraint between permeability and selectivity, i.e. the separation membrane with high permeability often has low selectivity, and vice versa. MOF separation membranes have regular porous channels, which are expected to break through the upper limit of the separation performance of traditional polymer membranes, so the preparation and application of MOF separation membranes have become a research hotspot in the field of membrane separation. Among them, the crystal structure of MOF ZIF-8 has window structure with a size of 0.34 nm and cavity structure with a size of 1.16 nm, and the window size is close to the molecular kinetic diameter of hydrogen and carbon dioxide, so the molecular sieving effect of ZIF-8 membrane is expected to realize the separation of hydrogen / carbon dioxide.

[0005] In recent years, researchers have done a lot of work on the preparation method of ZIF-8 membrane, taking ZIF-8 as an example. At present, the more mainstream methods include: 1. Secondary solvothermal synthesis method (CN 107349805A), that is, ZIF-8 seed particles are generated on the filter paper support layer by solvothermal synthesis reaction, and then a second solvothermal synthesis reaction is carried out to promote the growth of the seed particles to form a dense and continuous ZIF-8 membrane. However, this method separates the nucleation and growth steps of the seed particles, resulting in a complex operation process, inability to accurately control the membrane layer thickness, and difficulty in large-scale production. 2. Spray preparation method (CN 114733368A), that is, ZIF-8 precursor solution is sprayed onto a porous support layer treated at high temperature to obtain a crystallized support, which is then placed in a high-temperature sealed condition to prepare a ZIF-8 membrane by sol-gel method. Although this method is suitable for preparing ZIF-8 membranes on inorganic porous supports under high-temperature conditions, it is not suitable for preparing ZIF-8 membranes on organic polymer supports with poor thermal stability, and high-temperature reaction leads to high energy consumption and high cost, which is not conducive to industrial large-scale production.

[0006] However, the ZIF membranes disclosed in the prior art still have problems such as poor strength, poor dense continuity, and the need to further improve permeability. SUMMARY

[0007] In order to overcome the problems in the prior art, the application provides a metal organic framework material ZIF composite film, a preparation method and application thereof, the ZIF-8 composite film prepared by the method has excellent strength, compactness and permeability, and the preparation method is simple and easy to control. The metal organic framework ZIF composite film provided by the application has good separation performance in a hydrogen / carbon dioxide separation system.

[0008] The first aspect of the application provides a metal organic framework material ZIF composite film, which comprises a porous support film layer, a polypyrrole layer and a ZIF layer in sequence.

[0009] In the application, the thickness of the porous support film layer is 1-3000 mu m, preferably 10-2000 mu m; and / or, the thickness of the polypyrrole layer is 50-500 nm, preferably 100-200 nm; and / or, the thickness of the ZIF layer is 0.3-5 mu m, preferably 0.5-3 mu m.

[0010] In the application, the material of the porous support film layer is selected from at least one of polypropylene, polysulfone, polyethersulfone, aluminum oxide and silicon oxide; and / or, the material of the polypyrrole layer is selected from polypyrrole and / or polypyrrole derivatives.

[0011] The second aspect of the application provides a preparation method of a metal organic framework material ZIF composite film, preferably for preparing the metal organic framework material ZIF composite film in the first aspect of the application, comprising: (1) modifying a layer of polypyrrole polymer on the surface of a porous support film to obtain a modified porous support film; (2) enriching metal ions on the surface of the modified porous support film to obtain a porous support film rich in metal ions; (3) immersing the porous support film rich in metal ions in a ZIF precursor solution to obtain the metal organic framework material ZIF composite film after treatment.

[0012] In the application, the shape of the porous support film is selected from at least one of a flat plate, a tube and a hollow fiber membrane, and / or the material of the porous support film is selected from at least one of polypropylene, polysulfone, polyethersulfone, aluminum oxide and silicon oxide.

[0013] In the application, step (1) comprises: (1.1) placing the porous support film in a solution containing a pyrrole monomer, (1.2) adding an initiator solution to the solution, and (1.3) obtaining the modified porous support film after reaction and post-treatment.

[0014] In the application, the pyrrole monomer is selected from at least one of pyrrole and / or its derivatives; and / or, the initiator is selected from at least one of ammonium persulfate and ferric chloride; preferably, the molar ratio of the pyrrole monomer to the initiator is 1:(0.5-3), preferably 1:(1-2).

[0015] In the present application, the reaction of step (1.3) is carried out at 20-40℃ for 1-4h; and / or, the post-treatment of step (1.3) comprises: rinsing once or more times with water, acid solution, and base solution in sequence, and then drying.

[0016] In the present application, step (2) comprises: (2.1) placing the modified porous support membrane into an aqueous solution containing metal ions, (2.2) heating treatment, (2.3) post-treatment, to obtain the metal ion-rich porous support membrane.

[0017] In the present application, the metal ions are selected from at least one of transition metal ions, preferably at least one of zinc ions, cobalt ions, and optionally nickel ions.

[0018] In the present application, the heating treatment of step (2.2) is carried out at a temperature of 40-100℃, preferably 50-80℃, more preferably 60-70℃; and / or, the heating treatment of step (2.2) is carried out for a time of 0.5-5h, preferably 1-3h, more preferably 1.5-2h; and / or, the post-treatment of step (2.3) comprises: cooling to room temperature, taking out from the solution, rinsing once or more times with water, placing at room temperature for 5-40h, and drying.

[0019] In the present application, the ZIF precursor solution of step (3) contains metal ions, ligands, and water; preferably, the metal ions are selected from at least one of transition metal ions, preferably at least one of zinc ions, cobalt ions, and optionally nickel ions; preferably, the ligands are selected from at least one of imidazole ligands, preferably the imidazole ligands are selected from imidazole and / or its derivatives; preferably, in the ZIF precursor solution, the molar ratio of the metal ions to the ligands is 1:(1-80), preferably 1:(30-75); the molar ratio of the metal ions to water is 1:(1000-8000), preferably 1:(1000-3000).

[0020] In the present application, the treatment of step (3) comprises reaction and post-treatment; preferably, the temperature of the reaction is 20-40℃; and / or, the post-treatment comprises rinsing with water, placing, and drying.

[0021] The third aspect of the present application provides the application of the metal organic framework material ZIF composite membrane of the first aspect of the present application or the metal organic framework material ZIF composite membrane obtained by the preparation method of the second aspect of the present application in gas separation, especially in the separation of hydrogen and carbon dioxide.

[0022] The endpoints of the ranges and any values disclosed in the present disclosure are not limited to the precise values recited as the exact range between each endpoint should be considered to be from the lower value to the upper value of the stated range, and each intermediate value. For ranges comprising numerical values, the lower and upper values of each range are inclusive of the recited values, and the intermediate values are not precluded. The endpoints of the ranges and any values disclosed in the present disclosure are not to be understood as limited to the exact values recited as the exact range between each endpoint should be considered to be from the lower value to the upper value of the stated range, and each intermediate value. In the following, the technical solutions of various embodiments can be combined with each other to obtain new technical solutions, which should also be considered to be specifically disclosed herein.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The present application uses polypyrrole polymer to modify the porous support film, which is more conducive to improving the interface bonding between the ZIF crystal and the porous support film, and a more dense and continuous ZIF composite film is obtained. In addition, the price of the pyrrole monomer is low, which significantly reduces the preparation cost.

[0025] (2) The ZIF composite film provided by the present application has excellent dense continuity and good separation performance in the separation of hydrogen and carbon dioxide.

[0026] (3) The preparation method provided by the present application is simple and easy to control, and the ZIF composite film prepared has high quality and good strength. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of the surface of the ZIF-8 composite film prepared in Example 1 of the present application;

[0028] Figure 2 XRD diffraction spectrum of the ZIF-8 composite film prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0029] The characteristics and advantages of the present application will become more apparent with the following detailed description of the present application.

[0030] One of the objects of the present application is to provide a metal organic framework material ZIF composite film, which comprises a porous support film layer, a polypyrrole layer and a ZIF layer in sequence.

[0031] In a preferred embodiment, the thickness of the porous support film layer is 1-3000 μm, preferably 10-2000 μm, for example 1 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 60 μm, 80 μm, 100 μm, 500 μm, 1000 μm, 1500 μm, 2000 μm, 2500 μm or 3000 μm.

[0032] In a further preferred embodiment, the material of the porous support membrane layer is selected from at least one of polypropylene, polysulfone, polyethersulfone, aluminum oxide, silicon oxide.

[0033] In a preferred embodiment, the poly-pyrrole layer has a thickness of 50 to 500 nm, preferably 100 to 200 nm, for example 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm.

[0034] In a further preferred embodiment, the material of the poly-pyrrole layer is selected from poly-pyrrole and / or poly-pyrrole derivatives.

[0035] In a preferred embodiment, the ZIF layer has a thickness of 0.3 to 5 pm, preferably 0.5 to 3 pm, more preferably 1 to 2 pm, for example 0.3 pm, 0.5 pm, 1 pm, 1.5 pm, 2 pm, 2.5 pm, 3 pm, 4 pm, 5 pm.

[0036] In a further preferred embodiment, the ZIF is ZIF-8.

[0037] A second object of the present application is to provide a method for preparing a metal-organic framework material ZIF composite membrane, comprising: (1) modifying a layer of poly-pyrrole polymer on the surface of a porous support membrane to obtain a modified porous support membrane; (2) enriching metal ions on the surface of the modified porous support membrane to obtain a porous support membrane rich in metal ions; (3) immersing the porous support membrane rich in metal ions in a ZIF precursor solution to obtain the metal-organic framework material ZIF composite membrane after treatment.

[0038] In a preferred embodiment, the shape of the porous support membrane is selected from at least one of a flat plate, a tube, a hollow fiber membrane, and / or the material of the porous support membrane is selected from at least one of polypropylene, polysulfone, polyethersulfone, aluminum oxide, silicon oxide.

[0039] In a preferred embodiment, step (1) comprises: (1.1) placing the porous support membrane in a solution containing a pyrrole monomer, (1.2) adding an initiator solution to the solution, (1.3) reacting and optionally post-treating to obtain the modified porous support membrane.

[0040] In a further preferred embodiment, the pyrrole monomer is selected from at least one of pyrrole and / or derivatives thereof; and / or the initiator is selected from at least one of ammonium persulfate, ferric trichloride.

[0041] Preferably, the initiator solution is slowly added to the solution containing the pyrrole-based monomer. More preferably, the solution containing the pyrrole-based monomer is an aqueous solution, and the initiator solution is an aqueous solution.

[0042] In a further preferred embodiment, the molar ratio of the pyrrole-based monomer to the initiator is 1:(0.5-3), preferably 1:(1-2), for example 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3.

[0043] In a further preferred embodiment, the molar ratio of the pyrrole-based monomer to the initiator is 1:(0.5-3), preferably 1:(1-2), for example 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3.

[0044] In a preferred embodiment, the reaction of step (1.3) is carried out at 20-40°C (e.g. room temperature) for 1-4h (preferably 2-3h).

[0045] In a preferred embodiment, the concentration of the pyrrole-based monomer in the solution containing the pyrrole-based monomer is 0.01-1 mol / L, preferably 0.05-0.5 mol / L, more preferably 0.1-0.3 mol / L (e.g. 0.15-0.25 mol / L), for example 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L.

[0046] In a preferred embodiment, the post-treatment of step (1.3) comprises washing with water (to remove precipitates attached to the surface of the membrane), acid solution (to remove unreacted residues on the surface of the membrane), and base solution (to deprotonate the polypyrrole layer) one or more times in sequence, followed by drying.

[0047] In a preferred embodiment, the post-treatment of step (1.3) comprises washing with water (to remove precipitates attached to the surface of the membrane), acid solution (to remove unreacted residues on the surface of the membrane), and base solution (to deprotonate the polypyrrole layer) one or more times in sequence, followed by drying.

[0048] In a further preferred embodiment, the acid solution is selected from at least one of an aqueous hydrochloric acid solution, an aqueous acetic acid solution; and / or, the base solution is selected from at least one of an aqueous ammonia solution, an aqueous sodium hydroxide solution.

[0049] In a further preferred embodiment, the concentration of the acid in the acid solution is 0.01-0.2 mol / L, preferably 0.05-0.15 mol / L; and / or, the concentration of the base in the base solution is 0.05-0.2 mol / L, preferably 0.1-0.15 mol / L.

[0050] In a preferred embodiment, the thickness of the polypyrrole-based polymer in step (1) is 50-500 nm, preferably 100-200 nm.

[0051] In which, if the thickness is too small, the mechanical strength is not enough, and if the thickness is too large, the gas permeation is blocked, and the gas permeation rate is reduced.

[0052] In a preferred embodiment, step (2) comprises: (2.1) placing the modified porous support film into the aqueous solution containing metal ions, (2.2) heating treatment, (2.3) post-treatment, to obtain the porous support film rich in metal ions.

[0053] In which, through this process, the metal ions can be enriched on the modified porous support film.

[0054] In a further preferred embodiment, the metal ions are selected from at least one of transition metal ions, preferably at least one of zinc ions, cobalt ions, and optionally nickel ions.

[0055] In a further preferred embodiment, the concentration of the metal ions in the aqueous solution containing metal ions is 0.005-0.335 mol / L, preferably 0.03-0.1 mol / L, for example 0.005 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, or 0.335 mol / L.

[0056] In a preferred embodiment, the temperature of the heating treatment in step (2.2) is 40-100°C, preferably 50-80°C, more preferably 60-70°C; and / or, the time of the heating treatment in step (2.2) is 0.5-5 h, preferably 1-3 h, more preferably 1.5-2 h.

[0057] In a preferred embodiment, the post-treatment in step (2.3) comprises: cooling to room temperature, taking out from the solution, washing with water once or more times, placing at room temperature for 5-40 h, and drying.

[0058] In a preferred embodiment, the ZIF precursor solution in step (3) contains metal ions, ligands, and water.

[0059] In a further preferred embodiment, the metal ion is selected from at least one of transition metal ions, preferably at least one of zinc ion, cobalt ion (preferably zinc ion), and optionally nickel ion, more preferably in accordance with the metal ion of step (2).

[0060] In a further preferred embodiment, the ligand is selected from at least one of imidazole-based ligands, preferably the imidazole-based ligand is selected from at least one of imidazole and / or its derivatives, for example from 2-methylimidazole, benzimidazole, 2-formylimidazole (preferably 2-methylimidazole).

[0061] In a still further preferred embodiment, in the ZIF precursor solution, the molar ratio of the metal ion to the ligand is 1 : (1-80), preferably 1 : (30-75); and the molar ratio of the metal ion to water is 1 : (1000-8000), preferably 1 : (1000-3000).

[0062] For example, in the ZIF precursor solution, the molar ratio of the metal ion to the ligand is 1 : 1, 1 : 5, 1 : 10, 1 : 20, 1 : 30, 1 : 40, 1 : 50, 1 : 55, 1 : 60, 1 : 70 or 1 : 80, and the molar ratio of the metal ion to water is 1 : 1000, 1 : 1500, 1 : 2000, 1 : 3000, 1 : 4000, 1 : 5000, 1 : 6000, 1 : 6200, 1 : 6400, 1 : 6600, 1 : 6800, 1 : 7000 or 1 : 8000.

[0063] In the preparation of the ZIF precursor solution, it is preferred to be prepared in a clear state, for example by strong stirring or ultrasonic treatment to be clear.

[0064] In a preferred embodiment, the treatment of step (3) comprises a reaction and an optional post-treatment.

[0065] In a further preferred embodiment, the temperature of the reaction is 20-40 °C (e.g. at room temperature), the time of the reaction is 10-48 h, preferably 18-24 h; and / or, the post-treatment comprises water washing, standing (preferably 5-40 h), and drying. The inventors have unexpectedly found in the experiment that ZIF can be synthesized at room temperature, which does not require heating, the reaction condition is more mild, the energy consumption is lower, and thus the cost is lower.

[0066] In the process of the reaction, crystallization growth is carried out to form ZIF particles.

[0067] In a preferred embodiment, the thickness of the ZIF layer on the metal organic framework ZIF composite membrane is 0.3-5 μm, preferably 0.5-3 μm, and more preferably 1-2 μm. In addition, in the present application, the thickness of the polypyrrole layer is about 50-500 nm, preferably 100-200 nm; and the thickness of the porous support membrane layer is 1-3000 μm, preferably 10-40 μm.

[0068] In the present application, a layer of polypyrrole polymer is first coated on the porous support membrane, then a layer of metal ions is enriched, and finally a ZIF composite membrane is formed in situ. The membrane material prepared by the method of the present application not only has excellent strength (e.g. not easy to peel off), but also has good gas separation effect (e.g. hydrogen and carbon dioxide separation).

[0069] A third object of the present application is to provide the use of the metal organic framework ZIF composite membrane according to the first object of the present application or the metal organic framework ZIF composite membrane prepared by the method according to the second object of the present application in gas separation, in particular in hydrogen and carbon dioxide separation.

[0070] In a preferred embodiment, when the metal organic framework ZIF composite membrane is applied to hydrogen / carbon dioxide separation, the hydrogen permeation rate is about 11600-22300 Barrer, preferably 15000-20000 Barrer, at a temperature of 35°C, and the hydrogen / carbon dioxide permeation selectivity is 5.0-8.0, preferably 6.0-7.0.

[0071] In the present application, the gas separation evaluation is as follows: the prepared metal organic framework ZIF composite membrane is sealed in a gas separation membrane cell, and the hydrogen / carbon dioxide separation performance of the metal organic framework ZIF composite membrane is investigated by constant volume pressure change method. The gas is introduced from the upstream of the membrane cell by a gas cylinder; the temperature of the upstream and downstream of the membrane cell is controlled by a thermostat; the downstream of the membrane cell is vacuumed by a vacuum pump; and the gas pressure of the downstream of the membrane cell is recorded in real time by a pressure sensor. The evaluation indexes of the gas separation performance of the metal organic framework ZIF composite membrane are hydrogen permeation rate, carbon dioxide permeation rate, and hydrogen / carbon dioxide permeation selectivity.

[0072] The gas permeability is determined by the following formula:

[0073]

[0074] The gas permeation selectivity is determined by the following formula:

[0075]

[0076] wherein P is the gas permeability (Barrer, 1 Barrer = 1 x 10-10 cm 3 (STP) cm / cm 2 s cmHg), V is the volume of the downstream cavity of the membrane (cm 3 ), L is the thickness of the membrane (cm), A is the effective membrane area (cm 2 ), T is the test temperature (K), and p2is the inlet pressure upstream of the membrane (psia). It is theoretically desirable to have high hydrogen permeance and low carbon dioxide permeance, i.e., high gas permeation selectivity.

[0077] Examples

[0078] It is necessary to point out here that the following examples are only used to further illustrate the present application and should not be construed as limiting the scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present application are still within the scope of the present application.

[0079] It should be further noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0080] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the present application, and the technical solutions thus formed are part of the original disclosure of the present specification and also fall within the protection scope of the present application.

[0081] The raw materials used in the examples and comparative examples, if not specifically limited, are publicly known in the art, for example, can be directly purchased or prepared according to the publicly known preparation methods. Among them, the porous polypropylene support membrane is purchased from the American celgard company, the porous polyether sulfone support membrane is purchased from the American sterlitech company, and the porous aluminum oxide support membrane is purchased from the Guizhou Membrane Ray New Material Technology Co., Ltd.

[0082]

Example 1

[0083] Dissolve 0.67 g of pyrrole in 50 mL of deionized water and mix well. Put the washed and dried porous polypropylene support film into the above pyrrole aqueous solution. Dissolve 2.85 g of ammonium persulfate in 50 mL of deionized water and mix well. Slowly pour the ammonium persulfate aqueous solution into the pyrrole aqueous solution and react at room temperature for 2 h. After the reaction is completed, take out the polypyrrole-modified polypropylene support film and rinse with deionized water, 0.1 mol / L hydrochloric acid aqueous solution, and 0.1 mol / L aqueous ammonia solution several times, and dry at room temperature for 24 h to obtain a polypyrrole-modified porous polypropylene support layer.

[0084] Dissolve 1.0 g of zinc nitrate hexahydrate in 50 mL of deionized water and mix well. Put the above prepared polypyrrole-modified porous polypropylene support layer into the reaction kettle and heat at 60°C for 2 h. After the heating is completed, cool to room temperature, take out, rinse with deionized water several times, and then dry at room temperature for 24 h to obtain a zinc ion-rich polypyrrole / porous polypropylene film.

[0085] Dissolve 0.11 g of zinc nitrate hexahydrate and 2.20 g of 2-methylimidazole in 20 mL of deionized water, respectively, and stir or ultrasonic until clear to prepare a ZIF-8 precursor solution. Put the above prepared zinc ion-rich polypyrrole / porous polypropylene film vertically into the reaction kettle and pour the ZIF-8 precursor solution. React at room temperature for 24 h. After the reaction is completed, take out the zinc ion-rich polypyrrole / porous polypropylene film, rinse with deionized water several times, and then dry at room temperature for 24 h to obtain the metal-organic framework material ZIF-8 composite film. The thickness of the porous polypropylene support layer is 25 μm, the thickness of the polypyrrole layer is 200 nm, and the thickness of the ZIF-8 layer is 1.1 μm.

[0086]

Example 2

[0087] Dissolve 0.67 g of pyrrole in 50 mL of deionized water and mix well. Put the washed and dried porous polypropylene support film into the above pyrrole aqueous solution. Dissolve 2.85 g of ammonium persulfate in 50 mL of deionized water and mix well. Slowly pour the ammonium persulfate aqueous solution into the pyrrole aqueous solution and react at room temperature for 2 h. After the reaction is completed, take out the polypyrrole-modified polypropylene support film and rinse with deionized water, 0.1 mol / L hydrochloric acid aqueous solution, and 0.1 mol / L aqueous ammonia solution several times, and dry at room temperature for 24 h to obtain a polypyrrole-modified porous polypropylene support layer.

[0088] 0.5 g of zinc nitrate hexahydrate was dissolved in 50 mL of deionized water, stirred and mixed uniformly, poured into a reaction kettle, and the above-prepared poly-pyrrole modified porous polypropylene support layer was placed in the reaction kettle and heated at 80°C for 1 h; after heating was completed and cooled to room temperature, it was taken out and rinsed several times with deionized water, then placed at room temperature for 24 h, dried, to obtain a zinc ion-rich poly-pyrrole / porous polypropylene film;

[0089] 0.22 g of zinc nitrate hexahydrate and 1.50 g of 2-methylimidazole were respectively dissolved in 30 mL of deionized water, stirred or ultrasonicated until clear, to prepare a ZIF-8 precursor solution; the above-prepared zinc ion-rich poly-pyrrole / porous polypropylene film was placed vertically in a reaction kettle, the ZIF-8 precursor solution was poured into the reaction kettle, and the reaction was carried out at room temperature for 15 h; after the reaction was completed, the zinc ion-rich poly-pyrrole / porous polypropylene film was taken out, rinsed several times with deionized water, then placed at room temperature for 24 h, dried, to obtain the metal-organic framework material ZIF-8 composite film. The thickness of the porous polypropylene support layer was 30 μm, the thickness of the poly-pyrrole layer was 150 nm, and the thickness of the ZIF-8 layer was 1.4 μm.

[0090]

Example 3

[0091] 0.55 g of pyrrole was dissolved in 50 mL of deionized water, stirred and mixed uniformly. The washed and dried porous polypropylene support film was placed in the above pyrrole aqueous solution. 1.62 g of ferric chloride was dissolved in 50 mL of deionized water, stirred and mixed uniformly. An aqueous ammonium persulfate solution was slowly poured into the pyrrole aqueous solution, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the poly-pyrrole modified polypropylene support film was taken out, rinsed several times with deionized water, 0.15 mol / L hydrochloric acid aqueous solution, and 0.15 mol / L aqueous ammonia solution in sequence, and dried at room temperature for 24 h, to obtain a poly-pyrrole modified porous polypropylene support layer.

[0092] 0.8 g of zinc nitrate hexahydrate was dissolved in 50 mL of deionized water, stirred and mixed uniformly, poured into a reaction kettle, and the above-prepared poly-pyrrole modified porous polypropylene support layer was placed in the reaction kettle and heated at 60°C for 2 h; after heating was completed and cooled to room temperature, it was taken out and rinsed several times with deionized water, then placed at room temperature for 24 h, dried, to obtain a zinc ion-rich poly-pyrrole / porous polypropylene film;

[0093] The ZIF-8 precursor solution was prepared by dissolving 0.20 g of zinc nitrate hexahydrate and 1.80 g of 2-methylimidazole in 20 mL of deionized water, respectively, and stirring or ultrasonicating until clear. The zinc ion-rich polyacrylonitrile / porous polypropylene membrane prepared above was placed vertically in a reaction kettle, and the ZIF-8 precursor solution was poured into the reaction kettle. The reaction was carried out at room temperature for 24 h. After the reaction was completed, the zinc ion-rich polyacrylonitrile / porous polypropylene membrane was taken out, washed with deionized water several times, and then placed at room temperature for 24 h. Drying was performed to obtain the metal organic framework material ZIF-8 composite membrane. The thickness of the porous polypropylene support layer was 20 μm, the thickness of the polyacrylonitrile layer was 110 nm, and the thickness of the ZIF-8 layer was 2.1 μm.

[0094] Example 4: Synthesis of a metal organic framework material ZIF-8 composite membrane

[0095] The polyacrylonitrile modified porous polyether sulfone support layer was prepared by dissolving 0.75 g of pyrrole in 50 mL of deionized water and stirring until uniform. The washed and dried porous polyether sulfone support membrane was placed in the pyrrole aqueous solution. Then, 2.43 g of ferric chloride was dissolved in 50 mL of deionized water and stirred until uniform. An aqueous ammonium persulfate solution was slowly poured into the pyrrole aqueous solution, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the polyacrylonitrile modified porous polyether sulfone support membrane was taken out, washed with deionized water, 0.15 mol / L hydrochloric acid aqueous solution, and 0.20 mol / L ammonia water aqueous solution several times, and then dried at room temperature for 24 h to obtain the polyacrylonitrile modified porous polyether sulfone support layer.

[0096] The zinc ion-rich polyacrylonitrile / porous polyether sulfone membrane was prepared by dissolving 1.0 g of zinc nitrate hexahydrate in 50 mL of deionized water, stirring until uniform, and pouring into a reaction kettle. The polyacrylonitrile modified porous polyether sulfone support layer prepared above was placed in the reaction kettle, and the reaction was carried out at 60°C for 2 h. After the reaction was completed, the reaction kettle was cooled to room temperature, and the zinc ion-rich polyacrylonitrile / porous polyether sulfone membrane was taken out and washed with deionized water several times. Then, the membrane was placed at room temperature for 24 h, and drying was performed to obtain the zinc ion-rich polyacrylonitrile / porous polyether sulfone membrane.

[0097] The ZIF-8 precursor solution was prepared by dissolving 0.20 g of zinc nitrate hexahydrate and 1.80 g of 2-methylimidazole in 20 mL of deionized water, respectively, and stirring or ultrasonicating until clear. The zinc ion-rich polyacrylonitrile / porous polyether sulfone membrane prepared above was placed vertically in a reaction kettle, and the ZIF-8 precursor solution was poured into the reaction kettle. The reaction was carried out at room temperature for 24 h. After the reaction was completed, the zinc ion-rich polyacrylonitrile / porous polyether sulfone membrane was taken out, washed with deionized water several times, and then placed at room temperature for 24 h. Drying was performed to obtain the metal organic framework material ZIF-8 composite membrane. The thickness of the porous polyether sulfone support layer was 25 μm, the thickness of the polyacrylonitrile layer was 300 nm, and the thickness of the ZIF-8 layer was 1.8 μm.

[0098] Example 5 Synthesis of metal organic framework material ZIF-8 composite film

[0099] Dissolve 0.67 g of pyrrole in 50 mL of deionized water and mix well. Put the washed and dried porous alumina support film into the pyrrole aqueous solution. Dissolve 3.55 g of ammonium persulfate in 50 mL of deionized water and mix well. Slowly pour the ammonium persulfate aqueous solution into the pyrrole aqueous solution and react at room temperature for 2 h. After the reaction, take out the polypyrrole-modified alumina support film and wash with deionized water, 0.1 mol / L hydrochloric acid aqueous solution, and 0.1 mol / L aqueous ammonia solution several times, and dry at room temperature for 24 h to obtain a polypyrrole-modified porous alumina support layer.

[0100] Dissolve 0.7 g of zinc nitrate hexahydrate in 50 mL of deionized water and mix well, and pour into a reaction kettle. Put the prepared polypyrrole-modified porous alumina support layer into the reaction kettle, heat at 60°C for 2 h, cool to room temperature after heating, and take out and wash with deionized water several times, and then dry at room temperature for 24 h to obtain a zinc ion-rich polypyrrole / porous alumina film.

[0101] Dissolve 0.15 g of zinc nitrate hexahydrate and 1.60 g of 2-methylimidazole in 20 mL of deionized water respectively, and stir or ultrasonic until clear to prepare a ZIF-8 precursor solution. Put the prepared zinc ion-rich polypyrrole / porous alumina film vertically into a reaction kettle, pour the ZIF-8 precursor solution, and react at room temperature for 24 h. After the reaction, take out the zinc ion-rich polypyrrole / porous alumina film, wash with deionized water several times, and then dry at room temperature for 24 h to obtain the metal organic framework material ZIF-8 composite film. The thickness of the porous alumina support layer is 1500 μm, the thickness of the polypyrrole layer is 130 nm, and the thickness of the ZIF-8 layer is 2.3 μm.

[0102] Comparative Example 1

[0103] Repeat the process of Example 1, except that equimolar amount of aniline is used to replace pyrrole, and other conditions remain unchanged.

[0104] Comparative Example 2

[0105] Repeat the process of Example 1, except that the obtained polypyrrole-modified porous polypropylene support layer is not subjected to zinc enrichment treatment, but is directly used for ZIF film growth. Other conditions remain unchanged.

[0106] Experimental Example 1 SEM characterization of the film

[0107] The microstructure of the metal-organic framework material ZIF-8 film obtained in Example 1 was characterized by FESEM (JEOL JSM-7610F (Hitachi High-Technologies, Tokyo, Japan)), and the results are shown in FIG. 1. As can be seen from FIG. 1, the ZIF-8 film is in a dense and continuous state and has no obvious defects. Figure 1 Figure 1 As can be seen from FIG. 1, the ZIF-8 film is in a dense and continuous state and has no obvious defects.

[0108] [Experimental Example 2] XRD characterization of the film

[0109] The microstructure of the metal-organic framework material ZIF-8 composite film obtained in Example 1 was characterized by XRD (D / max-Ultima III (Rigaku Corporation, Japan)), and the results are shown in FIG. 2. As can be seen from FIG. 2, the ZIF-8 composite film contains characteristic peaks of polypropylene and characteristic peaks of ZIF-8 particles, indicating that a ZIF-8 film with high crystallinity is successfully prepared on the polypropylene support layer. Figure 2 Figure 2 As can be seen from FIG. 2, the ZIF-8 composite film contains characteristic peaks of polypropylene and characteristic peaks of ZIF-8 particles, indicating that a ZIF-8 film with high crystallinity is successfully prepared on the polypropylene support layer.

[0110] [Experimental Example 3] Strength characterization of the film

[0111] The surface of the polyaniline / polypropylene film prepared in Comparative Example 1 (before being enriched with zinc ions) and the surface of the polypyrrole / polypropylene film prepared in Example 1 (before being enriched with zinc ions) were rubbed using a laboratory filter paper. It was found that the polyaniline layer showed obvious peeling, while the polypyrrole layer remained intact and showed no peeling phenomenon, indicating that the interface between the polypyrrole layer and the polypropylene is more tightly bonded, and the mechanical strength of the polypyrrole layer is higher than that of the polyaniline layer.

[0112] The surface of the zinc ion-enriched polyaniline / polypropylene film prepared in Comparative Example 1 and the surface of the zinc ion-enriched polypyrrole / polypropylene film prepared in Example 1 were rubbed using a laboratory filter paper. It was found that the zinc ion-enriched polyaniline layer showed obvious peeling, while the zinc ion-enriched polypyrrole layer remained intact and showed no peeling phenomenon, indicating that the interface between the zinc ion-enriched polypyrrole layer and the polypropylene is more tightly bonded, and the mechanical strength of the zinc ion-enriched polypyrrole layer is higher than that of the polyaniline layer.

[0113] [Experimental Example 4] Separation evaluation of the film

[0114] ​​The method for evaluating the hydrogen / carbon dioxide separation performance of the metal organic framework material ZIF-8 composite membrane is described previously. The prepared metal organic framework material ZIF-8 composite membrane is sealed in a membrane cell for gas separation, and the hydrogen / carbon dioxide separation performance of the metal organic framework material ZIF-8 composite membrane is investigated by the constant volume pressure change method. The gas is introduced from the gas cylinder to the upstream of the membrane cell; the temperature of the upstream and downstream of the membrane cell is controlled by the thermostat; the downstream of the membrane cell is vacuumized by the vacuum pump; and the gas pressure of the downstream of the membrane cell is recorded in real time by the pressure sensor. The evaluation indexes of the gas separation performance of the metal organic framework material ZIF-8 composite membrane are the hydrogen permeation rate, the carbon dioxide permeation rate, and the hydrogen / carbon dioxide permeation selectivity.

[0115] The gas permeability is determined by the following formula:

[0116]

[0117] The gas permeation selectivity is determined by the following formula:

[0118]

[0119] wherein P is the gas permeability (Barrer, 1 Barrer = 1 x 10 -10 cm 3 (STP) cm / cm 2 s cmHg), V is the volume of the downstream cavity of the membrane (cm 3 ), L is the thickness of the membrane (cm), A is the effective membrane area (cm 2 ), T is the test temperature (K), and p2 is the inlet pressure of the upstream of the membrane (psia).

[0120] Table 1: Separation performance of the metal organic framework material ZIF-8 composite membranes synthesized in the above examples and comparative examples at 35°C

[0121] Hydrogen permeation rate (Barrer) Hydrogen / carbon dioxide separation factor (a) Example 1 18200 7.2 Example 2 22300 5.4 Example 3 19050 5.8 Example 4 18500 6.5 Example 5 20100 6.8 Comparative Example 1 13800 5.3 Comparative Example 2 42000 1.5

[0122] As shown in Table 1, the dense and continuous ZIF-8 composite membranes are obtained in Examples 1-5, and the obtained composite membranes can be used for separating H 2 / CO2. The hydrogen permeation rate ranges from 18000 to 22300 Barrer, and the hydrogen / carbon dioxide separation coefficient is about 5.0-7.0. The difference in the permeation rate and the separation coefficient in Examples 1-5 is mainly attributed to the thickness of the ZIF-8 membrane and the influence of the preparation conditions on the crystallinity of the ZIF-8 membrane. The thinner the thickness of the ZIF-8 layer, the higher the hydrogen permeation rate. The higher the crystallinity of the ZIF-8 layer and the fewer the defects of the membrane, the higher the hydrogen / carbon dioxide selectivity.

[0123] In Comparative Example 1, the obtained ZIF-8 composite membrane has a lower hydrogen permeation rate than Example 1-5 due to the low gas permeation rate of polyaniline.

[0124] In Comparative Example 2, the obtained polypyrrole-modified porous polypropylene support layer is not subjected to zinc enrichment treatment, which results in the failure to form a dense continuous ZIF composite membrane and a large number of defects, exhibiting a low hydrogen / carbon dioxide permeation selectivity.

[0125] The above detailed description of the application is made in conjunction with the specific embodiments and exemplary examples, but these descriptions cannot be understood as limiting the application. Those skilled in the art understand that the technical solutions and embodiments of the application can be variously replaced, modified or improved without departing from the spirit and scope of the application, and these all fall within the scope of the application. The protection scope of the application is subject to the appended claims.

Claims

1. A metal organic framework material ZIF composite membrane, comprising in sequence a porous support membrane layer, a polypyrrole layer and a ZIF layer; a preparation method of the metal organic framework material ZIF composite membrane comprising: (1) modifying a porous support membrane with a layer of polypyrrole polymer to obtain a modified porous support membrane; (2) enriching metal ions on the surface of the modified porous support membrane to obtain a porous support membrane rich in metal ions; (3) immersing the porous support membrane rich in metal ions in a ZIF precursor solution to obtain the metal organic framework material ZIF composite membrane after treatment; step (2) comprises: (2.1) placing the modified porous support membrane in an aqueous solution containing metal ions, (2.2) heating treatment, (2.3) post-treatment to obtain the porous support membrane rich in metal ions; the metal ions are selected from at least one of zinc ions and cobalt ions, or the metal ions are selected from at least one of zinc ions, cobalt ions and nickel ions.

2. The metal organic framework material ZIF composite membrane according to claim 1, wherein the thickness of the porous support membrane layer is 1-3000 μm; and / or, the thickness of the polypyrrole layer is 50-500 nm; and / or, the thickness of the ZIF layer is 0.3-5 μm.

3. The metal organic framework material ZIF composite membrane according to claim 1, wherein the thickness of the porous support membrane layer is 10-2000 μm; and / or, the thickness of the polypyrrole layer is 100-200 nm; and / or, the thickness of the ZIF layer is 0.5-3 μm.

4. The metal organic framework material ZIF composite membrane according to any one of claims 1-3, wherein the material of the porous support membrane layer is selected from at least one of polypropylene, polysulfone, polyethersulfone, aluminum oxide and silicon oxide; and / or, the material of the polypyrrole layer is selected from polypyrrole and / or polypyrrole derivatives. (1) modifying a porous support membrane with a layer of polypyrrole polymer to obtain a modified porous support membrane; (2) enriching metal ions on the surface of the modified porous support membrane to obtain a porous support membrane rich in metal ions; (3) immersing the porous support membrane rich in metal ions in a ZIF precursor solution to obtain the metal organic framework material ZIF composite membrane after treatment; step (2) comprises: (2.1) placing the modified porous support membrane in an aqueous solution containing metal ions, (2.2) heating treatment, (2.3) post-treatment to obtain the porous support membrane rich in metal ions; the metal ions are selected from at least one of zinc ions and cobalt ions, or, the metal ions are selected from at least one of zinc ions, cobalt ions and nickel ions. The shape of the porous support membrane is selected from at least one of flat plate, tube and hollow fiber membrane, and / or the material of the porous support membrane is selected from at least one of polypropylene, polysulfone, polyethersulfone, aluminum oxide and silicon oxide. Step (1) comprises: (1.1) placing the porous support membrane in a solution containing a pyrrole monomer, (1.2) adding an initiator solution to the solution, (1.3) reacting to obtain the modified porous support membrane. The pyrrole monomer is selected from at least one of pyrrole and / or its derivatives; and / or the initiator is selected from at least one of ammonium persulfate and ferric chloride. ​ ​ ​ ​ 5. A method for preparing a metal organic framework ZIF composite membrane, for preparing the metal organic framework ZIF composite membrane according to any one of claims 1 to 4, comprising: ​ 6. The preparation method according to claim 5, characterized in that, ​ 7. The preparation method according to claim 5, characterized in that, ​ 8. The preparation method according to claim 5, characterized in that, ​ 9. The preparation method according to claim 5, characterized in that, The molar ratio of the pyrrole monomer to the initiator is 1:(0.5-3).

10. The method of claim 5, wherein, The molar ratio of the pyrrole monomer to the initiator is 1:(1-2).

11. The preparation method of claim 5, wherein, The temperature of the heating treatment in step (2.2) is 40-100℃; and / or, The time of the heating treatment in step (2.2) is 0.5-5h; and / or, The post-treatment in step (2.3) comprises cooling to room temperature, taking out from the solution, washing with water one or more times, placing at room temperature for 5-40h, and drying.

12. The preparation method of claim 5, wherein, The temperature of the heating treatment in step (2.2) is 50-80℃; and / or, The time of the heating treatment in step (2.2) is 1-3h.

13. The preparation method of claim 5, wherein, The temperature of the heating treatment in step (2.2) is 60-70℃; and / or, The time of the heating treatment in step (2.2) is 1.5-2h.

14. The method of any one of claims 5 to 13, wherein the method further comprises the step of: The ZIF precursor solution in step (3) contains metal ions, ligands, and water.

15. The preparation method according to claim 14, characterized in that, The metal ions are selected from at least one of zinc ions and cobalt ions, or the metal ions are selected from at least one of zinc ions, cobalt ions, and nickel ions.

16. The method of claim 14, wherein, The ligands are selected from at least one of imidazole ligands selected from imidazole and / or derivatives thereof.

17. The preparation method according to claim 14, characterized in that, In the ZIF precursor solution, the molar ratio of the metal ions to the ligands is 1:(1-80); and the molar ratio of the metal ions to water is 1:(1000-8000).

18. The method of claim 14, wherein, In the ZIF precursor solution, the molar ratio of the metal ions to the ligands is 1:(30-75); and the molar ratio of the metal ions to water is 1:(1000-3000).

19. The method of claim 14, wherein, The treatment in step (3) comprises a reaction, and the temperature of the reaction is 20-40℃.

20. The application of the metal organic framework material ZIF composite film of any one of claims 1-4 or the metal organic framework material ZIF composite film obtained by the preparation method of any one of claims 5-19 in gas separation.

21. The use according to claim 20, characterized in that, In the separation of hydrogen and carbon dioxide.

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