A gas separation membrane based on metal organic cage and its preparation method and application

Abstract

The present invention relates to the field of gas separation membrane technology, particularly to a metal-organic cage-based gas separation membrane and its preparation method and application. The method comprises preparing a solution containing a metal salt, an organic ligand, and an organic solvent, reacting the solution at a temperature range of 50-200°C for 2-160 hours to obtain a metal-organic cage material; preparing an aqueous dispersion containing the metal-organic cage and an organic reaction solution containing a polyacyl chloride or polyaldehyde; placing the organic reaction solution on the surface of a support membrane to obtain a support membrane that adsorbs organic monomers; placing the aqueous dispersion on the surface of the support membrane that adsorbs organic monomers to obtain a nascent separation membrane; and repeating the above steps, pouring the organic reaction solution and the aqueous dispersion onto the surface of the nascent separation membrane multiple times, to obtain a metal-organic cage-based gas separation membrane. The metal-organic cage gas separation membrane prepared by the present invention has a high CO2 permeation rate, high CO2 / N2 and CO2 / H2 separation factors, and good long-term operational stability.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation membranes, and in particular to a gas separation membrane based on metal organic cages, and a preparation method and application thereof. Background Art

[0002] Human industrial activities release large amounts of greenhouse gases, a primary cause of global warming. CO2 accounts for 77% of this gas and contributes 49% to the greenhouse effect. The efficient use of CO2 separation technology is crucial for achieving carbon emission reductions.

[0003] Common CO2 separation technologies include solvent absorption, pressure swing adsorption, cryogenic distillation, and membrane separation. Gas membrane separation technology, with its advantages of low energy consumption, simple process, and environmental friendliness, holds broad application prospects in industrial flue gas CO2 capture. Currently, membrane separation technology has achieved industrial application in air separation, organic vapor recovery, hydrogen recovery, and natural gas (containing H2S, CO2, etc.) dehumidification and purification. However, in the natural gas purification sector, it holds only 10-20% of the global market share. CO2 capture from flue gas and synthesis gas decarbonization are still in the laboratory development and industrial demonstration stages. However, the limited separation performance of CO2 separation membranes severely restricts their large-scale industrial application.

[0004] Metal-organic cages (MOCs) are discrete supramolecular coordination compounds with confined cavities, formed by coordination-driven self-assembly of metal ions or metal clusters with organic ligands. MOCs possess well-defined internal and intercage cavities, large surface areas, and ordered microporous structures that facilitate the adsorption of guest molecules. Due to their weak intercage interactions, MOCs exhibit good solubility in a variety of solvents, demonstrating their enormous potential for application in gas adsorption and separation. However, current MOC gas separation membranes are primarily constructed by densely packing MOC crystals or by blending them with polymer matrices to form mixed-matrix membranes. However, due to the weak intermolecular interactions within MOCs, MOCs typically require grafting to form pure MOC membranes. The grafted molecules occupy both the intracage and intercage cavities, restricting the transport of gas molecules. Preparing a mixed matrix membrane by mixing with a polymer matrix is another method for preparing an organic metal cage membrane, but the agglomeration of the organic metal cage will affect the uniformity of the membrane, the agglomeration will hinder the effective transmission of gas molecules within the membrane, and the interface layer between the polymer and the metal organic cage is prone to defects, thereby reducing the selectivity of the membrane. In addition, the polymer matrix easily penetrates into the pores of the metal organic cage, reducing the inherent pore size of the metal organic cage or even completely blocking it. Therefore, these methods cannot fully utilize the pore advantages of the metal organic cage, greatly affecting the gas permeation rate and selectivity. In response to this, the present application proposes a metal organic cage gas separation membrane with high CO2 / N2 permeation selectivity prepared by a simple interfacial polymerization method. Summary of the Invention

[0005] The purpose of the present invention is to provide a gas separation membrane based on metal organic cages, a preparation method and application thereof, wherein the prepared metal organic cage gas separation membrane has a high CO2 permeation rate, a relatively high CO2 / N2 and CO2 / H2 separation factors, and has good long-term operation stability.

[0006] To achieve the above objectives, the present invention provides a method for preparing a gas separation membrane based on a metal organic cage, comprising the following steps:

[0007] (1) preparing a solution containing a metal salt, an organic ligand, and an organic solvent, reacting the solution at a temperature range of 50-200 °C for 2-160 h, then washing the solution with an organic solvent, and drying the solution to obtain a metal organic cage material; the organic ligand is a small molecule having a structural formula containing a polycarboxylic acid and an imidazole group ligand;

[0008] (2) uniformly dispersing the metal organic cage material in water to obtain an aqueous dispersion containing the metal organic cage, and dissolving the polyacyl chloride or polyaldehyde monomer in an organic solvent II to obtain an organic phase reaction liquid containing the polyacyl chloride or polyaldehyde;

[0009] (3) placing an organic phase reaction solution containing polyacyl chloride or polyaldehyde on the surface of a support membrane, allowing it to stand for 1 to 120 minutes, removing excess solution, and obtaining a support membrane that adsorbs organic phase monomers; then taking an aqueous phase dispersion containing metal organic cages and placing it on the surface of a support membrane that adsorbs organic phase monomers, allowing it to stand for 1 to 120 minutes, removing excess solution, and rinsing the membrane surface with deionized water to obtain a primary separation membrane;

[0010] (4) Repeat the above operation and pour the organic phase reaction liquid and the aqueous phase dispersion liquid onto the surface of the primary separation membrane multiple times to obtain a gas separation membrane based on metal organic cages.

[0011] Preferably, in step (1), the concentration of the metal salt is in the range of 0.01 to 3 mol·L -1 , the organic ligand concentration range is 0.01~3 mol·L -1 .

[0012] Preferably, in step (1), the metal salt includes one or more of copper acetate, copper nitrate, copper chloride, rhodium acetate, rhodium nitrate, cobalt acetate, cobalt nitrate, zirconium nitrate, zirconium acetate, dichloro zirconocene, indium nitrate, silver nitrate, ferrous nitrate, nickel nitrate, nickel acetate, rhenium nitrate, zinc nitrate, zinc acetate, chromium nitrate, chromium acetate, gallium nitrate, manganese nitrate, lead nitrate, titanium tetrachloride, and cadmium nitrate.

[0013] Preferably, in step (1), the organic ligands include 1,4-benzenedicarboxylic acid, 2-amino-1,4-benzenedicarboxylic acid, 2-bromo-1,4-benzenedicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,5-dihydroxyterephthalic acid, 2,3-dihydroxyterephthalic acid, 2,5-bis(trifluoromethyl)terephthalic acid, 2,5-dihydroxyphenyl dicarboxylic acid, 1,1'-biphenyl-4,4'-dicarboxylic acid, 2,3,5,6-tetrafluoroterephthalic acid, 4,5,9,10-tetrahydropyrene-2,7-dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid, 2-chloroterephthalic acid, 2,5 -dichlorobenzoic acid, 2,5-dimethyl-1,4-benzenedicarboxylic acid, 4,4'-(1,2-ethynediyl)dibenzoic acid, 5,8-dicarboxy naphthalene-2-sulfonate sodium, 2,5-diaminoterephthalic acid, 4,6-dihydroxyisophthalic acid, tris-(4-imidazolylphenyl)amine, 1,2,3,4,5,6-hexa(1H-imidazol-1-yl)benzene, 4-(1H-imidazol-1-yl)benzoic acid methyl ester, tetrakis(4-imidazophenyl)methane, 2,2'-biimidazole, tetrakis(1-imidazophenyl)ethylene, bisimidazole butane, 2,6-di-(1-imidazole)pyridine, 4,5-dicyanoimidazole, 2-amino-4,5-dicyanoimidazole.

[0014] Preferably, in step (1), the organic solvent 1 includes one or more of benzene, toluene, ethanol, acetone, acetonitrile, n-hexane, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, dichloromethane and chloroform.

[0015] Preferably, in step (2), the polyvalent acid chloride or polyvalent aldehyde monomer includes 2,2',4,4'-biphenyltetracarboxylic acid chloride, 1,3,5-trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride, oxalyl chloride, malonyl chloride, methylmalonyl chloride, succinyl chloride, tetrafluorosuccinyl chloride, glutaryl chloride, hexafluoroglutaryl chloride, adipoyl chloride, octafluoroadipoyl chloride, pimeloyl chloride, suberyl chloride, azelayl chloride, Sebacoyl chloride, 4,4'-oxybis(benzoyl chloride), 1,4-phenylenediacryl chloride, azobenzene-4,4'-dicarbonyl chloride, diethylmalonyl chloride, o-phenylenedisulfonyl chloride, m-phenylenedisulfonyl chloride, p-phenylenedisulfonyl chloride, 1,3,5-benzenetrisulfonyl chloride, 2,4-disulfonylchloro-mesitylene, 4,4'-biphenylenedisulfonyl chloride, methylenedisulfonyl chloride, 2,6-naphthalenedisulfonyl chloride, 2,6-pyridinedicarbonyl chloride Acyl chloride, dimethylmalonyl chloride, fumaryl chloride, 1,3,5-trialdehyde phloroglucinol, trimesic acid, terephthalaldehyde, biphenyldicarboxaldehyde, 1,3,5-trialdehyde benzene, 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, 1,3,5-tris(4-formaldehyde phenyl)benzene, 1,3,5-tris(4-formaldehyde phenyl)amine, 3,3'-bipyridine-dicarboxaldehyde, 2,5-dihydroxyterephthalaldehyde, One or more of 2-hydroxy-1,3,5-benzenetricarboxaldehyde, 2,5-dibromoterephthalaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 2,4,6-trimethoxy-pyromellitic acid trimesic acid, tetraaldehyde biphenyl, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,3,5-tris(4-hydroxy-3'-aldehydephenyl)benzene, and 1,4-dialdehyde-2,5-divinylbenzene.

[0016] Preferably, in step (2), the second organic solvent comprises one or more of ethanol, acetone, mesitylene, acetonitrile, n-hexane, n-heptane, ethyl acetate, dimethyl sulfoxide and dichloromethane.

[0017] Preferably, in step (2), the mass concentration of the metal organic cage material in the aqueous dispersion is 0.1-5 g·L -1 The mass concentration of polyacyl chloride or polyaldehyde monomer in the organic phase reaction solution is 0.1~5 g·L -1 .

[0018] A metal-organic cage-based gas separation membrane is prepared by the above-mentioned method for preparing a metal-organic cage-based gas separation membrane.

[0019] The invention discloses an application of a gas separation membrane based on metal organic cages, which is used for the separation of CO2 / N2 and CO2 / H2 in mixed gases.

[0020] Mechanism of the present invention:

[0021] The metal-organic cage material of the present invention is formed by a solvothermal method to cause a coordination reaction between metal ions and polycarboxylic acid ligands or imidazole ligands to form a metal-organic cage structure. The metal-organic cage material has an adjustable pore structure and abundant reactive functional groups.

[0022] Metal-organic cage materials react with polyacyl chlorides via residual amino groups to form long-range ordered, highly cross-linked, and dense metal-organic cage gas separation membranes. Metal-organic cages possess an ordered pore structure of specific dimensions, resulting in the fabricated separation membranes possessing the same uniform, ordered pore structure as the metal-organic cage materials. The presence of numerous amino and carboxyl reactive groups within the membrane pores facilitates the transport of CO2 molecules within the pores. Furthermore, the pore size of the designed metal-organic cage membranes ranges from 0.35 to 0.65 nm, between the kinetic diameter of a CO2 molecule (0.33 nm) and the sum of the kinetic diameters of a CO2 molecule and a N2 molecule (0.36 nm) (0.69 nm). This pore size allows CO2 molecules to diffuse within the pores, facilitating their rapid passage. Adsorption of CO2 molecules further reduces the pore size, blocking N2 molecules from entering the pores. This reduces the passage of molecules like nitrogen and improves the permeability of the metal-organic cage membranes. In addition, the ordered and regular pore structure of metal-organic cage materials and their characteristics of being connected by coordination bonds give metal-organic cage gas separation membranes a higher CO2 transfer rate and high stability.

[0023] Beneficial effects of the present invention:

[0024] (1) The gas separation membrane based on metal organic cages in the present invention utilizes the ordered pore structure of metal organic cages with specific sizes to effectively separate CO2 / N2 and CO2 / H2 molecules that are difficult to separate in mixed gases, and has high gas molecule selectivity.

[0025] (2) The metal organic cage-based gas separation membrane of the present invention has a long-range ordered regular pore structure, thereby having a high CO2 transmission rate and good long-term operation stability.

[0026] (3) The present invention provides a method for preparing a gas separation membrane based on a metal organic cage, which has a simple preparation process, mild preparation conditions, a wide range of applications, and is easy to scale up and promote.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart for preparing the metal-organic cage gas separation membrane of the present invention;

[0029] Figure 2 is a surface scanning electron microscope image of the support film in Example 1 of the present invention;

[0030] Figure 3 This is a surface scanning electron microscope image of a gas separation membrane based on a metal organic cage according to Example 1 of the present invention;

[0031] Figure 4 This is a cross-sectional scanning electron microscope image of the gas separation membrane based on metal organic cages in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described below with reference to the accompanying drawings and examples. Unless otherwise defined, technical or scientific terms used herein shall have the same meanings as those commonly understood by persons of ordinary skill in the art to which the present invention pertains. The above-mentioned features or features described in the specific examples of the present invention may be combined in any manner. These specific examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention.

[0033] The method for detecting gas permeability in the embodiment of the present invention is as follows:

[0034] The selectivity and gas permeation rate of the metal-organic cage gas separation membrane were tested using a laboratory-made membrane performance test device. The test system consists of a gas cylinder, membrane cell, piping, pressure reducing valve, pressure and flow detectors, soap film flowmeter, gas chromatograph, pressure transmitter, and other components. The effective membrane area tested was 4.90 cm 2 , the test pressure is 1-5bar, and the test temperature is 25±0.5℃.

[0035] The calculation formula for gas permeation rate is as follows:

[0036] R i =Q i / (ΔP i *A)

[0037] in, R i For components i The penetration rate is in GPU [1 GPU=10 -6 cm 3 (STP) cm -2 ·s-1 cmHg -1 = 3.35 × 10 -10 mol·m -2 ·s -1 ·Pa -1 ], 𝑄 𝑖 Indicates the permeate side components i The volume flow rate per unit time under standard conditions, in cm 3 (STP)·s -1 , A Indicates the effective membrane area in cm 2 .

[0038] The selectivity of separation membranes for different gases is usually expressed in terms of separation factors. α express, α It can be divided into ideal separation factor and real separation factor. For two gas phase components, the ideal separation factor α * It can be expressed as:

[0039] 𝛼 * 𝑖 / 𝑗 =R * i / R * j

[0040] in, R * i and R * j Represent components i and j However, in the actual membrane separation process, the sample to be separated is a mixed gas containing multiple gases. Therefore, the actual test is mainly based on its true separation factor, which is defined as:

[0041] 𝛼 𝑖 / 𝑗 =(y i / y j ) / (x i / x j )

[0042] in, 𝑦 𝑖 and 𝑦 𝑗 Represent components i andj The mole fraction in the permeate gas, 𝑥 𝑖 and 𝑥 𝑗 Represent components i and j Mole fraction in the feed gas.

[0043] The separation performance of the test gas mixture was: CO2 / N2 = 15:85, CO2 / H2 = 40:60. The gas volume flow rate was measured using a soap film flowmeter, and the gas mole fraction was determined using a gas chromatograph.

[0044] Example 1

[0045] See also Figures 1 to 4 As shown in the figure, the present invention provides a gas separation membrane based on metal organic cages, and its preparation method includes the following steps:

[0046] (1) Prepare 0.1 mol·L -1 Indium nitrate and 0.15 mol·L -1 A solution of 2-amino-4,5-imidazole dicarbonitrile in N,N-dimethylformamide was reacted at 125 °C for 144 h, washed three times with N,N-dimethylformamide, and then dried in vacuum at 80 °C for 24 h to obtain a metal organic cage material.

[0047] (2) Disperse the metal organic cage material evenly in water and prepare a mixture containing 0.1 g·L -1 The aqueous dispersion of metal organic cages was prepared. -1 A n-hexane solution of 1,3,5-trimethylbenzyl chloride was used as the organic phase reaction solution.

[0048] (3) The organic phase reaction solution was placed on the surface of the polysulfone membrane and allowed to stand at 25°C for 5 min. The excess solution was then removed to obtain a polysulfone membrane that adsorbed organic phase monomers. The aqueous dispersion containing the metal organic cage material was placed on the surface of the polysulfone membrane that adsorbed organic phase monomers and allowed to stand at 25°C for 20 min. The excess solution was then removed and the membrane was rinsed with deionized water to obtain a nascent separation membrane.

[0049] (4) Then, the organic phase reaction liquid and the aqueous phase dispersion are placed on the surface of the primary separation membrane twice, and finally rinsed with deionized water to obtain a dense metal organic cage gas separation membrane.

[0050] The prepared metal-organic cage gas separation membrane has pure gas permeation rates of 4300 GPU, 215 GPU and 935 GPU for CO2, N2 and H2 respectively at 1 bar; the separation factors for mixed gases CO2 / N2 and CO2 / H2 reach 29 and 7 respectively. The membrane can maintain stable separation performance during 24 h continuous operation.

[0051] Figure 3 This is a surface scanning electron microscope image of the gas separation membrane based on metal organic cages in Example 1 of the present invention. Figure 4 This is a cross-sectional scanning electron microscope image of the gas separation membrane based on metal organic cage in Example 1 of the present invention. Figure 3 It can be seen from the figure that the surface of the metal organic cage membrane is smooth, dense and defect-free. Figure 4 It can be seen from the figure that the thickness of the selective separation layer of the metal-organic cage membrane is about 90 nm.

[0052] Example 2

[0053] The present invention provides a gas separation membrane based on a metal organic cage, and a preparation method thereof comprises the following steps:

[0054] (1) Prepare 0.15 mol·L -1 Zirconocene dichloride and 0.09 mol·L -1 A solution of 2-amino-1,4-benzenedicarboxylic acid in N,N-dimethylacetamide was reacted at 60°C for 10 h, washed three times with N,N-dimethylacetamide, and then dried at 40°C for 24 h to obtain a metal organic cage material.

[0055] (2) Disperse the metal organic cage material evenly in water and prepare a mixture containing 0.1 g·L -1 The aqueous dispersion of metal organic cages was prepared. -1 A n-heptane solution of terephthaloyl chloride was used as the organic phase reaction liquid.

[0056] (3) The organic phase reaction solution was placed on the surface of the polyethersulfone membrane and allowed to stand at 25°C for 5 min. The excess solution was then removed to obtain a polysulfone membrane that adsorbed organic phase monomers. The aqueous dispersion containing the metal organic cage material was placed on the surface of the polysulfone membrane that adsorbed organic phase monomers and allowed to stand at 25°C for 20 min. The excess solution was then removed and the membrane was rinsed with deionized water to obtain a nascent separation membrane.

[0057] (4) Then, the organic phase reaction liquid and the aqueous phase dispersion are placed on the surface of the primary separation membrane twice, and finally rinsed with deionized water to obtain a dense metal organic cage gas separation membrane.

[0058] The prepared metal-organic cage gas separation membrane has pure gas permeation rates of 3200 GPU, 154 GPU and 617 GPU for CO2, N2 and H2 respectively at 1 bar; the separation factors for mixed gases CO2 / N2 and CO2 / H2 reach 26 and 6 respectively. The membrane can maintain stable separation performance during 24 h continuous operation.

[0059] Example 3

[0060] The present invention provides a gas separation membrane based on a metal organic cage, and a preparation method thereof comprises the following steps:

[0061] (1) Prepare 0.011 mol·L -1 Copper acetate and 0.01 mol·L -1 A methanol solution of 2-amino-1,4-benzenedicarboxylic acid was reacted at 80 °C for 72 h, washed three times with methanol and dried at 40 °C for 24 h to obtain a metal organic cage material.

[0062] (2) Disperse the metal organic cage material evenly in water and prepare a mixture containing 0.1 g·L -1 The aqueous dispersion of metal organic cages was prepared. -1 A n-heptane solution of 2,5-dihydroxyterephthalaldehyde was used as the organic phase reaction liquid.

[0063] (3) The organic phase reaction solution was placed on the surface of the polyacrylonitrile membrane and allowed to stand at 25°C for 5 min. The excess solution was then removed to obtain a polyacrylonitrile membrane that adsorbed organic phase monomers. The aqueous dispersion containing the metal organic cage material was placed on the surface of the polyacrylonitrile membrane that adsorbed organic phase monomers and allowed to stand at 25°C for 20 min. The excess solution was then removed and the membrane was rinsed with deionized water to obtain a primary separation membrane.

[0064] (4) Then, the organic phase reaction liquid and the aqueous phase dispersion are placed on the surface of the primary separation membrane twice, and finally rinsed with deionized water to obtain a dense metal organic cage gas separation membrane.

[0065] The prepared metal-organic cage gas separation membrane has pure gas permeation rates of 3560 GPU, 251 GPU and 723 GPU for CO2, N2 and H2 respectively at 1 bar; the separation factors for mixed gases CO2 / N2 and CO2 / H2 reach 24 and 6 respectively. The membrane can maintain stable separation performance during 24h continuous operation.

[0066] Comparative Example 1

[0067] A gas separation membrane free of metal-organic cage materials, the preparation method of which comprises the following steps:

[0068] (1) Prepare a solution containing 0.625 g·L -1 Prepare an aqueous solution of piperazine containing 0.66 g·L -1 A n-hexane solution of 1,3,5-benzenetricarboxylic acid chloride was used as the organic phase reaction liquid.

[0069] The organic phase reaction solution was placed on the surface of a polysulfone support membrane and allowed to stand at 25°C for 10 minutes. The excess solution was then removed to obtain a polysulfone membrane that adsorbed organic phase monomers. An aqueous solution containing piperazine was placed on the surface of the polysulfone membrane that adsorbed organic phase monomers and allowed to stand at 25°C for 10 minutes. The excess solution was then removed and the membrane surface was rinsed with deionized water to remove unreacted monomers, resulting in a gas separation membrane that did not contain metal-organic cage materials.

[0070] The prepared gas separation membrane without metal-organic cage materials has a pure gas permeation rate of 650 GPU, 54 GPU and 217 GPU for CO2, N2 and H2 respectively at 1 bar; the separation factors of mixed gases CO2 / N2 and CO2 / H2 reach 14 and 4 respectively, and the membrane can maintain stable separation performance during 24 hours of continuous operation.

[0071] Therefore, the metal-organic cage-based gas separation membrane provided by the present invention has a higher CO2 permeation rate and better CO2 / N2 and CO2 / H2 selectivity than a gas separation membrane formed without a metal-organic cage material.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a gas separation membrane based on a metal organic cage, characterized in that: The following steps are involved: (1) preparing a solution containing a metal salt, an organic ligand, and an organic solvent, reacting the solution at a temperature range of 50 to 200°C for 2 to 160 hours, then washing the solution with an organic solvent, and drying the solution to obtain a metal organic cage material; The metal salt includes one or more of copper acetate, copper nitrate, copper chloride, rhodium acetate, rhodium nitrate, cobalt acetate, cobalt nitrate, zirconium nitrate, zirconium acetate, zirconocene dichloride, indium nitrate, silver nitrate, ferrous nitrate, nickel nitrate, nickel acetate, rhenium nitrate, zinc nitrate, zinc acetate, chromium nitrate, chromium acetate, gallium nitrate, manganese nitrate, lead nitrate, titanium tetrachloride, and cadmium nitrate; The organic ligand includes one or more of 2-amino-1,4-benzenedicarboxylic acid, 2,5-diaminoterephthalic acid, tris-(4-imidazolylphenyl)amine, 1,2,3,4,5,6-hexa(1H-imidazol-1-yl)benzene, 4-(1H-imidazol-1-yl)benzoic acid methyl ester, tetrakis(4-imidazophenyl)methane, 2,2'-biimidazole, tetrakis(1-imidazophenyl)ethylene, bisimidazole butane, 2,6-di-(1-imidazole)pyridine, 4,5-dicyanoimidazole, and 2-amino-4,5-imidazole dicarbonitrile; (2) uniformly dispersing the metal organic cage material in water to obtain an aqueous dispersion containing the metal organic cage, and dissolving the polyacyl chloride or polyaldehyde monomer in an organic solvent II to obtain an organic phase reaction liquid containing the polyacyl chloride or polyaldehyde; (3) placing an organic phase reaction solution containing polyacyl chloride or polyaldehyde on the surface of a support membrane, allowing it to stand for 1 to 120 minutes, removing excess solution, and obtaining a support membrane that adsorbs organic phase monomers; then placing an aqueous phase dispersion containing metal organic cages on the surface of a support membrane that adsorbs organic phase monomers, allowing it to stand for 1 to 120 minutes, removing excess solution, and rinsing the membrane surface with deionized water to obtain a primary separation membrane; (4) Repeating the above operation, pouring the organic phase reaction liquid and the aqueous phase dispersion liquid onto the surface of the primary separation membrane multiple times, thereby obtaining a gas separation membrane based on metal organic cages; The gas separation membrane based on metal-organic cages has a uniform and ordered pore structure with a pore size range of 0.35-0.65 nm.

2. The method for preparing a gas separation membrane based on a metal organic cage according to claim 1, characterized in that: In step (1), the concentration of the metal salt is in the range of 0.01 to 3 mol·L -1 , the organic ligand concentration range is 0.01~3 mol·L -1 .

3. The method for preparing a gas separation membrane based on a metal organic cage according to claim 1, characterized in that: In step (1), the organic solvent 1 includes one or more of benzene, toluene, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, acetonitrile, n-hexane, ethyl acetate, dichloromethane and chloroform.

4. The method for preparing a gas separation membrane based on a metal organic cage according to claim 1, characterized in that: In step (2), the polyvalent acid chloride or polyvalent aldehyde monomer includes 2,2',4,4'-biphenyltetracarboxylic acid chloride, 1,3,5-isophthalic acid chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride, oxalyl chloride, malonyl chloride, methylmalonyl chloride, succinoyl chloride, tetrafluorosuccinoyl chloride, glutaryl chloride, hexafluoroglutaryl chloride, adipoyl chloride, octafluoroadipoyl chloride, pimeloyl chloride, suberyl chloride, azelayl chloride, sebacoyl chloride, Chlorine, 4,4'-oxybis(benzoyl chloride), 1,4-phenylenediacryl chloride, azobenzene-4,4'-dicarbonyl chloride, diethylmalonyl chloride, o-phenylenedisulfonyl chloride, m-phenylenedisulfonyl chloride, p-phenylenedisulfonyl chloride, 1,3,5-benzenetrisulfonyl chloride, 2,4-disulfonylchloro-mesitylene, 4,4'-biphenylenedisulfonyl chloride, methylenedisulfonyl chloride, 2,6-naphthalenedisulfonyl chloride, 2,6-pyridinedicarbonyl chloride , dimethylmalonyl chloride, fumaryl chloride, 1,3,5-trialdehyde phloroglucinol, trimesic acid, terephthalaldehyde, biphenyldicarboxaldehyde, 1,3,5-trialdehyde benzene, 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, 1,3,5-tris(4-formaldehyde phenyl)benzene, 1,3,5-tris(4-formaldehyde phenyl)amine, 3,3'-bipyridine-dicarboxaldehyde, 2,5-dihydroxyterephthalaldehyde, 2 -hydroxy-1,3,5-benzenetricarboxaldehyde, 2,5-dibromoterephthalaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 2,4,6-trimethoxy-pyromellitic acid trimesic acid, tetraaldehyde biphenyl, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,3,5-tris(4-hydroxy-3'-formylphenyl)benzene, 1,4-dialdehyde-2,5-divinylbenzene or one or more thereof.

5. The method for preparing a gas separation membrane based on a metal organic cage according to claim 1, characterized in that: In step (2), the second organic solvent includes one or more of ethanol, acetone, mesitylene, acetonitrile, n-hexane, n-heptane, ethyl acetate, dimethyl sulfoxide and dichloromethane.

6. The method for preparing a gas separation membrane based on a metal organic cage according to claim 1, characterized in that: In step (2), the mass concentration of the metal organic cage material in the aqueous dispersion is 0.1~5g·L -1 The mass concentration of polyacyl chloride or polyaldehyde monomer in the organic phase reaction solution is 0.1~5g·L -1 .

7. A gas separation membrane based on a metal organic cage, characterized in that: The gas separation membrane is prepared by the method for preparing a metal organic cage-based gas separation membrane according to any one of claims 1 to 6.

8. An application of a gas separation membrane based on a metal organic cage, characterized by: The metal organic cage-based gas separation membrane as claimed in claim 7 is used for separation of CO2 / N2 and CO2 / H2 in mixed gases.

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