Polyimide gas separation membrane as well as preparation method and application thereof

Abstract

The invention provides a polyimide gas separation membrane as well as a preparation method and application thereof, and relates to the technical field of gas separation membranes. The preparation method provided by the invention comprises the following steps: carrying out electrostatic spinning on a polyamide acid glue solution, and then carrying out imidization to obtain a fiber membrane; carrying out in-situ MOF growth on the basis of the fiber membrane, and then potting a polyimide glue solution containing MOF particles; and drying to obtain the polyimide gas separation membrane with the MOF loading capacity of 5wt%-35wt%. The gas separation membrane can effectively improve gas permeability and selectivity, meanwhile, the mechanical strength of the gas separation membrane is improved, and the gas separation membrane is effectively suitable for separation work of special gas.

Description

Technical Field

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

[0002] With the adjustment of global energy structure and the advancement of carbon emission reduction strategy, gas separation technology has become a key technical support. In industrial scenarios such as petrochemicals, natural gas purification, and biogas utilization, the commonly used low-temperature distillation and pressure swing adsorption processes are relatively mature, but the defects of high energy consumption, large equipment footprint, and easy secondary pollution are becoming increasingly prominent. With the continuous development of material chemistry, membrane separation technology, with its unique "molecular sieving" mechanism, achieves selective permeation of gas molecules through the microporous structure on the surface of the membrane material, and does not require phase change conversion during the separation process. The energy consumption is greatly reduced compared to traditional processes. Therefore, it is widely used in the separation and recovery of hydrogen, separation and recovery of carbon dioxide, air separation (oxygen-rich, nitrogen-rich), and separation of acidic corrosive gases.

[0003] Polyimide is a class of polymer compounds containing imide groups in its molecular structure. The imide ring contained in its main chain is formed by the condensation of diamine and dianhydride compounds in a non-protonic polar solvent. It has excellent thermal stability and good electrical insulation properties. Therefore, it has a good theoretical basis in gas separation. At the same time, in order to meet the application requirements in the field of gas separation, inorganic materials are usually added to the polyimide matrix to prepare mixed matrix membranes to improve its gas separation performance. However, the content of fillers has a significant effect on the performance of polymers. Too much or too little filler content may have a negative impact on the performance of polyimide films. For example, too little filler cannot form a gas transmission path, thereby failing to significantly improve the gas permeation and separation performance of the gas separation membrane, while too much filler may cause the polymer to become too hard and brittle, affecting its mechanical properties. Therefore, it is urgent to provide a solution to improve the above problems. Summary of the invention

[0004] The object of the present invention is to provide a polyimide gas separation membrane and a preparation method and application thereof.

[0005] In a first aspect, the present invention provides a method for preparing a polyimide gas separation membrane, comprising: electrostatically spinning a polyamic acid glue solution and then imidizing it to obtain a fiber membrane; in situ MOF growth based on the fiber membrane and then encapsulating a polyimide glue solution containing MOF particles; and drying to obtain a polyimide gas separation membrane with a MOF loading of 5wt%-35wt%.

[0006] The preparation method provided by the present invention uses electrostatic spinning technology to form a fiber membrane, and uses an in-situ growth method to load MOF on the fiber membrane, so that a three-dimensional MOF structure oriented along the fiber direction is formed on the fiber membrane, and then a polyimide glue containing MOF particles is encapsulated in the fiber membrane, thereby obtaining a polyimide gas separation membrane with a high loading amount and a specific loading morphology, which can effectively improve the gas permeability and selectivity, while improving the mechanical strength of the gas separation membrane, and is effectively suitable for the separation of special gases.

[0007] Optionally, electrospinning is performed at 25°C-50°C.

[0008] Optionally, the electrospinning is performed at a humidity of 25 RH%-50 RH%.

[0009] Optionally, the solid content of the polyamic acid glue is 5%-25%.

[0010] Optionally, the electrospinning is followed by pre-imidization at 60°C-120°C.

[0011] Optionally, after electrospinning, the temperature is gradually increased to 380° C.-420° C. for imidization.

[0012] Optionally, the electrospinning is followed by imidization treatment for 10 min to 60 min.

[0013] Optionally, when the in-situ MOF growth is performed based on the fiber membrane, the method includes: cyclically immersing the fiber membrane in an organic ligand solution and a metal salt solution and then drying the solution.

[0014] Optionally, the dipping is cycled 1-10 times.

[0015] Optionally, the organic ligand in the organic ligand solution includes 2-methylimidazole, trimesic acid or terephthalic acid.

[0016] Optionally, the metal salt in the metal salt solution includes cobalt salt, zinc salt, copper salt or iron salt.

[0017] Optionally, the fiber membrane is immersed in the organic ligand solution for 5 min to 20 min at a time.

[0018] Optionally, the fiber membrane is immersed in the metal salt solution for 1 h to 4 h at a time.

[0019] Optionally, the impregnation cycle is followed by drying under vacuum.

[0020] Optionally, the cyclic impregnation is followed by drying at 50°C-80°C.

[0021] Optionally, after the in-situ MOF growth is performed, the MOF is encapsulated in a polyimide filling adhesive solution, wherein the polyimide filling adhesive solution includes a polyimide base adhesive solution and MOF particles dispersed in the polyimide base adhesive solution.

[0022] Optionally, the solid content of the polyimide base adhesive is 10%-30%.

[0023] Optionally, the MOF particles have a particle size of 0.1 μm-5 μm.

[0024] Optionally, the type of the MOF particles is independent of the MOF grown in situ on the fiber membrane.

[0025] Optionally, the polyamic acid glue is formed by condensation polymerization of dibasic acid anhydride and diamine monomers in a polar aprotic solvent.

[0026] Optionally, the dibasic acid anhydride includes pyromellitic dianhydride, 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride or 2,3,3',4'-biphenyltetracarboxylic dianhydride.

[0027] Optionally, the diamine monomer includes 4,4'-diaminodiphenyl ether, p-phenylenediamine, 4,4-diaminobiphenyl, 3,4'-diaminodiphenyl ether, m-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene or 1,3-bis(3-aminophenoxy)benzene.

[0028] Optionally, the polar aprotic solvent includes one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0029] In a second aspect, the present invention also provides a polyimide gas separation membrane prepared by any of the above optional preparation methods.

[0030] In a third aspect, the present invention further provides an application of a polyimide gas separation membrane prepared by any of the above optional preparation methods in gas separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flowchart of a method for preparing a polyimide gas separation membrane provided by the present invention;

[0032] Figure 2 This is a SEM characterization image of the fiber membrane after in-situ growth of MOF prepared in Example 1 of the present invention;

[0033] Figure 3 This is a SEM characterization image of the gas separation membrane prepared in Example 1 of the present invention;

[0034] Figure 4 is a stress-strain curve diagram of the gas separation membrane prepared in Example 1 of the present invention;

[0035] Figure 5 It is a stress-strain curve diagram of the gas separation membrane prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with general skills in the field to which the present invention belongs.

[0037] See also Figure 1 The present invention provides a method for preparing a polyimide gas separation membrane, comprising the following steps:

[0038] S1, electrostatically spinning the polyamic acid glue solution and then imidizing it to obtain a fiber membrane;

[0039] S2, in situ MOF growth based on fiber membrane followed by encapsulation of polyimide glue containing MOF particles;

[0040] S3. After drying, a polyimide gas separation membrane with a MOF loading of 5 wt% to 35 wt% is obtained.

[0041] In fact, the preparation method provided by the present invention can make the grown MOF be oriented along the fiber filaments by in-situ growth of MOF on the surface of the fiber membrane obtained by electrospinning, and use the polyimide glue containing MOF particles to fill the pores between the fiber filaments in the fiber membrane, not only can a dense and defect-free polyimide gas separation membrane be produced, but the MOF particles can also make the MOF oriented on the surface of the fiber filaments have more bridging points, which can significantly increase the gas passage, thereby improving the gas separation performance and mechanical properties of the gas separation membrane at the same time.

[0042] Specifically, the polyamic acid glue used in step S1 can be formed by polycondensing dibasic acid anhydride and diamine monomer in a polar aprotic solvent to obtain a polyamic acid glue with a solid content of 5%-25%, and the fiber is spun by an electrostatic spinning device in an environment of 25°C-50°C and 25RH%-50RH%. Specifically, the size of the fiber filaments in the fiber material obtained after fiber spinning is 0.05μm-1μm.

[0043] In some embodiments, the dibasic acid anhydride used in the preparation of the polyamic acid glue may include isophthalic acid anhydride, 3,3',4,4'-dibenzophenone tetracarboxylic acid anhydride, 4,4'-oxydiphthalic anhydride, 3,3,4,4-diphenyl sulfone tetracarboxylic acid anhydride, 3,3',4,4'-biphenyl tetracarboxylic acid anhydride or 2,3,3',4'-biphenyl tetracarboxylic acid anhydride, the diamine monomer used may include 4,4'-diaminodiphenyl ether, p-phenylenediamine, 4,4-diaminobiphenyl, 3,4'-diaminodiphenyl ether, m-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene or 1,3-bis(3-aminophenoxy)benzene, and the polar aprotic solvent used may include one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0044] In fact, when executing step S1, the fiber material obtained after electrospinning is pre-imidized at 60°C-120°C, and then placed at 380°C-420°C for complete imidization treatment, thereby obtaining a polyimide fiber membrane. In some embodiments, the fiber material can be pre-imidized at 60°C-120°C using multiple gradually increasing temperature values. Specifically, the insulation time of each temperature value is independently 1min-30min. In addition, when performing the complete imidization treatment, the pre-imidized fiber material can be fixed in the needle plate frame clamp, which is conducive to the formation of a membrane structure after the complete imidization treatment. At the same time, it can be kept at 380°C-420°C for 10min-60min for complete imidization treatment.

[0045] Specifically, the fiber membrane obtained after executing step S1 is one of the following: a nanofiber membrane made of polyimide in an original fluffy state, a nanofiber membrane in a physically cross-linked state, and a nanofiber membrane in a chemically cross-linked state. In fact, the nanofiber membrane in a physically cross-linked state is a nanofiber membrane in which fiber filaments overlap each other after mechanical calendering, and the nanofiber membrane in a chemically cross-linked state is a nanofiber membrane in which the fiber filaments are mutually melted and infiltrated at the contact points, and the ultra-long polyimide molecular chains jump out of the fiber filaments and pin into another fiber filament.

[0046] In some embodiments, when performing step S2, the fiber membrane may be surface treated in advance to improve the efficiency and quality of in-situ MOF growth on the surface. In fact, the fiber membrane may be surface treated by soaking it in an alkaline solution, such as an inorganic alkaline solution such as sodium hydroxide solution or potassium hydroxide, and the concentration of the alkaline solute in the alkaline solution may be 0.2 mol / L-2 mol / L.

[0047] In some embodiments, when performing in-situ MOF growth based on the fiber membrane in step S2, the fiber membrane can be cyclically immersed in an organic ligand solution and a metal salt solution and then dried. In fact, when the fiber membrane is immersed in an organic ligand solution, the organic ligand can penetrate into the interior and surface of the fiber, so that when immersed in a metal salt solution, the metal ions can coordinate with the organic ligand to generate a metal organic framework (MOF) in situ on the surface of the fiber.

[0048] Specifically, when executing step S2, the fiber membrane is cyclically immersed in the organic ligand and metal salt solution for 1-10 times. This is beneficial to adjust the loading amount and morphology of the MOF grown in situ on the surface of the fiber. In addition, the cyclic immersion can enable the MOF on the surface of the fiber to grow in layers, which is beneficial to improve the density of MOF on the surface of the fiber membrane.

[0049] In some embodiments, the organic ligand in the organic ligand solution used in step S2 includes 2-methylimidazole, trimesic acid or terephthalic acid, and the metal salt in the metal salt solution used includes cobalt salt, zinc salt, copper salt or iron salt. In fact, when the fiber membrane is cyclically immersed in the 2-methylimidazole solution and the cobalt salt solution, ZIF-67 can be generated in situ on the surface of the fiber membrane. Specifically, by selecting different organic ligands and metal salts, the type of MOF generated can be adjusted, such as UiO-66, UiO-66-NH 2 , ZIF-8, MIL-101(Fe), MIL-101(Cr) or HKUST-1.

[0050] In some embodiments, the concentration of the organic ligand solution and the concentration of the metal salt solution used in step S2 are independently 0.1 mol / L-4 mol / L, and the types of solvents used in the organic ligand solution and the metal salt solution are independent of each other. Specifically, the fiber membrane can be cyclically immersed in the organic ligand methanol solution and the metal salt methanol solution.

[0051] In some embodiments, when executing step S2, the single immersion time of the fiber membrane in the organic ligand solution is 5 min-20 min, so that the organic ligand solution can fully infiltrate the fiber filaments of the fiber membrane. In addition, the single immersion time of the fiber membrane in the metal salt solution is 1 h-4 h, so that the metal ions can fully react with the organic ligands to form a metal organic framework (MOF).

[0052] Specifically, after the fiber membrane is cyclically impregnated in step S2, it is dried in a vacuum environment at 50°C-80°C, thereby improving the positional stability of the metal organic framework (MOF) attached to the surface of the fiber filament, which is beneficial for subsequent encapsulation. In addition, after the in-situ MOF growth based on the fiber membrane is performed in step S2, the loading amount of MOF on the fiber membrane is 5wt%-40wt%.

[0053] In some embodiments, after performing in-situ MOF growth on the fiber membrane surface in step S2, it can be encapsulated in a polyimide-filled adhesive so that the polyimide-filled adhesive can fully infiltrate and fill the pores between fiber filaments in the fiber membrane, thereby improving the density of the gas separation membrane.

[0054] Specifically, the polyimide filling glue includes a polyimide base glue and MOF particles dispersed in the polyimide base glue. In fact, when the polyimide filling glue is filled into the pores between the fiber filaments and solidified, the MOF particles in the filling glue can make the MOF arranged on the surface of the fiber filaments have more bridge points, thereby significantly increasing the gas transmission path, which is beneficial to improving the gas permeability of the gas separation membrane and improving the mechanical properties of the gas separation membrane.

[0055] In some embodiments, the solid content of the polyimide base glue used in step S2 is 10%-30%. Specifically, the polyimide base glue used can be synthesized by condensation polymerization of dianhydride and diamine in a non-polar protic solvent, or can be prepared by stirring and dissolving molding powder in N,N-dimethylacetamide, and the molding powder used includes VespelSP-1, Ultem 1000, Torlon 4203, Upimol, and Aurum PL450c.

[0056] In some embodiments, the MOF particles used in step S2 are independent of the types of MOF generated in situ on the fiber membrane surface. Specifically, the types of MOF particles can be UiO-66, UiO-66-NH 2 , ZIF-8, ZIF-67, MIL-101(Fe), MIL-101(Cr), HKUST-1, and MOF particles can be conventional products available on the market or can be pre-synthesized. Meanwhile, the particle size of the MOF particles used is 0.1 μm-5 μm.

[0057] Specifically, when executing step S2, the fiber membrane with in-situ MOF growth is encapsulated in a polyimide filling glue at a pressure of 0.1MPa-0.5MPa. When executing step S3, the encapsulated fiber membrane is dried in a vacuum drying oven at 60°C for 12 hours to obtain a gas separation membrane with a total metal organic framework loading of 5wt%-35wt%.

[0058] The present invention also provides a polyimide gas separation membrane synthesized by the preparation method provided in any of the above embodiments. At the same time, the present invention also provides an application of the polyimide gas separation membrane in gas separation, which can be applied to the separation of hydrogen and carbon dioxide.

[0059] Example 1

[0060] This embodiment 1 provides a method for preparing a polyimide gas separation membrane, comprising the following steps:

[0061] S1. Mix pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) at a molar ratio of 1.01:1 and put them into N,N-dimethylacetamide (DMAc), obtain a polyamic acid solution with a solid content of 10% by solution polycondensation and adjusting the solid content, and use an electrospinning device to perform electrospinning at 25°C and 30RH% to obtain a fiber material; gradually heat the fiber material at 60°C, 80°C, and 100°C for 15 minutes to perform pre-imidization, and then fix the fiber material on a needle plate frame clamp, gradually increase the temperature to 380°C in an imidization furnace and keep it for 20 minutes to perform complete imidization treatment to obtain a fiber membrane;

[0062] S2, soak the fiber membrane in a 1 mol / L sodium hydroxide solution for 30 min, wash it and soak it in a 1 mol / L 2-methylimidazole methanol solution for 10 min, then soak it in a 1.5 mol / L cobalt acetate methanol solution for 3 h, cycle the soaking once, dry the fiber membrane in a vacuum environment at 60°C for 12 h, then place it in a polyimide filling glue solution (solid content 20%, made by dissolving molding powder Vespel SP-1 in N,N-dimethylacetamide, containing 5 wt% ZIF-67 with a particle size of 500 nm), and pot it at 0.5 MPa for 0.5 h;

[0063] S3. The encapsulated fiber membrane was dried in a vacuum environment at 60° C. for 12 h to obtain a polyimide gas separation membrane with a total ZIF-67 loading of 24.7%.

[0064] Example 2

[0065] This embodiment 2 provides a method for preparing a polyimide gas separation membrane, which is different from the embodiment 1 in that the cyclic impregnation is performed four times in step S2, and then a polyimide gas separation membrane with a total ZIF-67 loading of 29.6% is prepared in step S3.

[0066] Example 3

[0067] This embodiment 3 provides a method for preparing a polyimide gas separation membrane, which is different from embodiment 1 in that the amount of ZIF-67 in the polyimide filling glue used in step S2 is 8 wt%, and then in step S3, a polyimide gas separation membrane with a total ZIF-67 loading of 27.2% is obtained.

[0068] Example 4

[0069] This embodiment 4 provides a method for preparing a polyimide gas separation membrane, which is different from embodiment 1 in that the metal salt solution used in step S2 is a zinc nitrate methanol solution with a concentration of 1.5 mol / L, and the polyimide filling glue has 5 wt% ZIF-8 with a particle size of 100 nm, and then in step S3, a polyimide gas separation membrane with a total ZIF-8 loading of 24.5% is obtained.

[0070] Comparative Example 1

[0071] This comparative example 1 provides a method for preparing a polyimide gas separation membrane, comprising the following steps:

[0072] D1, the polyimide molding powder Vespel SP-1 was stirred and dissolved in N, N-dimethylacetamide, and a polyimide adhesive solution with a solid content of 20% was obtained after mixing and defoaming, and ZIF-67 with a particle size of 500 nm was added, mixed and defoamed to obtain a polyimide adhesive solution containing 6 wt % of ZIF-67;

[0073] D2. A polyimide glue solution containing 6 wt% of ZIF-67 was coated to form a film, and then dried in a vacuum drying oven at 60° C. for 12 h to obtain a polyimide gas separation membrane with a total ZIF-67 loading of 24.2%.

[0074] Structural characterization

[0075] The fiber membrane with in-situ MOF growth on the surface in Example 1 was characterized by SEM. Figure 2 As shown, the gas separation membrane prepared in Example 1 was characterized by SEM. Figure 3 As shown. Figure 2 and Figure 3It can be seen that MOF particles can be tightly and densely attached to the fiber surface of the fiber membrane. At the same time, after being encapsulated with polyimide filling glue, the pores between the fiber filaments can be effectively filled and the loading capacity of MOF can be further increased.

[0076] Performance Testing

[0077] The tensile strength test method described in ASTM D822 was used to test the gas separation membranes prepared in Examples 1 to 4 and Comparative Example 1. The results are shown in Table 1 below. The stress-strain curves of Example 1 and Comparative Example 1 are shown in Table 1 below. Figure 4 and Figure 5 As shown; the method described in GB / T 1038-2000 standard was used to test the gas separation and permeation performance of the gas separation membranes prepared in Examples 1 to 4 and Comparative Example 1, and their structures are shown in Table 1 below.

[0078] Table 1 Test results of mechanical properties, gas separation performance and permeability of gas separation membrane

[0079]

[0080] Combining Example 1 with Comparative Example 1, it can be seen that, under the premise of using the same MOF material and having a similar loading amount, since the gas separation membrane in Comparative Example 1 does not have a fiber skeleton made by electrospinning and does not have a directional arrangement of MOF, its mechanical properties, gas separation performance, and permeability are greatly reduced. This shows that the use of electrospinning fibers as a supporting skeleton in the gas separation membrane provided by the present invention can significantly enhance the mechanical properties of the gas separation membrane, which is manifested in that the tensile strength of the separation membranes in Examples 1 to 4 is greater than 80MPa.

[0081] At the same time, it can be seen that the gas separation membranes in Examples 1 to 4 have better H 2 , CO 2 The permeability and selectivity of MOF are mainly due to the directional arrangement of MOF along the fiber filaments of the polyimide fiber membrane, which is more conducive to the formation of gas transmission channels in the outward direction of the gas separation membrane. At the same time, the MOF particles in the polyimide-filled glue can further make more bridging points appear between the directional MOF particles, thereby further increasing the gas transmission pathway.

[0082] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A method for preparing a polyimide gas separation membrane, characterized in that: include: The polyamic acid glue solution is subjected to electrostatic spinning and then imidization to obtain a fiber membrane; MOF is grown in situ based on the fiber membrane and then the polyimide glue solution containing MOF particles is encapsulated; and after drying, a polyimide gas separation membrane with a MOF loading of 5wt%-35wt% is obtained.

2. The preparation method according to claim 1, characterized in that: Electrospinning is carried out at 25°C-50°C; and / or, electrospinning is carried out at a humidity of 25RH%-50RH%; and / or, the solid content of the polyamic acid glue is 5%-25%; and / or, pre-imidization is carried out at 60°C-120°C after electrospinning; and / or, the temperature is gradually increased to 380°C-420°C for imidization after electrospinning; and / or, imidization treatment is carried out for 10min-60min after electrospinning.

3. The preparation method according to claim 1, characterized in that: When the in-situ MOF growth is performed based on the fiber membrane, the method includes: cyclically immersing the fiber membrane in an organic ligand solution and a metal salt solution and then drying the solution.

4. The preparation method according to claim 3, characterized in that: The cyclic impregnation is performed for 1-10 times; and / or, the organic ligand in the organic ligand solution includes 2-methylimidazole, trimesic acid or terephthalic acid; and / or, the metal salt in the metal salt solution includes cobalt salt, zinc salt, copper salt or iron salt; and / or, the fiber membrane is immersed in the organic ligand solution for 5min-20min at a time; and / or, the fiber membrane is immersed in the metal salt solution for 1h-4h at a time; and / or, after the cyclic impregnation, it is dried under vacuum; and / or, after the cyclic impregnation, it is dried at 50℃-80℃.

5. The preparation method according to claim 1, characterized in that: After in-situ MOF growth, it is encapsulated in a polyimide filling glue; wherein the polyimide filling glue includes a polyimide base glue and MOF particles dispersed in the polyimide base glue; preferably: the solid content of the polyimide base glue is 10%-30%; and / or, the particle size of the MOF particles is 0.1μm-5μm; and / or, the type of the MOF particles is independent of the MOF grown in-situ on the fiber membrane.

6. The preparation method according to claim 1, characterized in that: The polyamic acid glue is formed by polycondensation of a dibasic acid anhydride and a diamine monomer in a polar aprotic solvent; preferably: the dibasic acid anhydride includes pyromellitic dianhydride, 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride or 2,3,3',4'-biphenyltetracarboxylic dianhydride; and / or The diamine monomer includes 4,4'-diaminodiphenyl ether, p-phenylenediamine, 4,4-diaminobiphenyl, 3,4'-diaminodiphenyl ether, m-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene or 1,3-bis(3-aminophenoxy)benzene; and / or the polar aprotic solvent includes one of N,N-dimethylacetamide, N,N-dimethylformamide and N-methylpyrrolidone.

7. A polyimide gas separation membrane prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the polyimide gas separation membrane prepared by the preparation method according to any one of claims 1 to 6 in gas separation.

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