Benzimidazole-containing polyimide carbon molecular sieve membrane as well as preparation method and application thereof

Abstract

The invention discloses a benzimidazole-containing polyimide carbon molecular sieve membrane as well as a preparation method and application thereof. A polymer of the polyimide carbon molecular sieve membrane has a repeating unit shown in the following formula: # imgabs0 #, A is derived from a dianhydride monomer, and B is derived from a diamine monomer. A novel diamine monomer containing a benzimidazole structure is introduced and polymerized to obtain a polyimide polymer precursor containing the benzimidazole structure, so that polymer structure collapse and dense accumulation of molecular chains caused by carbonization treatment are avoided; meanwhile, the benzimidazole-containing polyimide carbon molecular sieve membrane provided by the invention has good permeability and carbon dioxide / methane selectivity.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane preparation and application, and specifically relates to a polyimide carbon molecular sieve membrane containing benzimidazole and a preparation method and application thereof. Background Art

[0002] Biogas, which consists of a mixture of carbon dioxide and methane (CO2 / CH4) gases, has become a renewable fuel alternative to natural gas. Compared with traditional chemical fuels such as coal and oil, methane releases a relatively small amount of carbon dioxide per unit of energy, which also reduces the greenhouse effect caused by the combustion of fossil fuels to a certain extent. With the increase in people's energy consumption, the demand for natural gas and biogas is increasing. However, natural gas and biogas often contain a large amount of carbon dioxide (CO2), which not only affects the combustion effect of biogas and causes corrosion to transportation pipelines, but also brings a series of environmental problems. At the same time, the greenhouse effect caused by CO2 gas is causing more and more serious consequences. Therefore, it is imperative to separate CO2 from these mixed gases.

[0003] The main industrial methods for CO2 removal include absorption (including physical absorption, chemical absorption and mixed solvent absorption), membrane separation, cryogenic distillation and adsorption, etc. Among them, membrane separation technology has the advantages of simple operation, low energy consumption, high cost-effectiveness, high selectivity, easy scale-up and can be used in combination with other separation technologies.

[0004] Polyimide has become a widely used gas separation membrane material because of its good film-forming properties, mechanical properties and high radiation resistance, and its wide variety and diverse forms. Aromatic heterocyclic polymers containing benzimidazole groups are well-known for their excellent molecular sieving properties, which are attributed to highly stacked polymer chains and strong intermolecular hydrogen bonds (Hu L, BuiV T, Huang L, et al. Facilely crosslinking polybenzimidazole with polycarboxylicacids to improve H2 / CO2 separation performance [J]. ACS Appl. Mater. Inter., 2021, 13, 12521-12530), but polyimide membranes containing benzimidazoles greatly reduce the permeability of the membrane while improving the selectivity. Summary of the invention

[0005] The main purpose of the present invention is to provide a polyimide carbon molecular sieve membrane containing benzimidazole and a preparation method and application thereof, so as to overcome the deficiencies of the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] The embodiment of the present invention provides a polyimide carbon molecular sieve membrane containing benzimidazole, wherein the polymer of the polyimide carbon molecular sieve membrane has a repeating unit as shown in formula (I):

[0008]

[0009] Wherein, A is derived from a dianhydride monomer, and the dianhydride monomer is selected from any one or more combinations of the following structures:

[0010]

[0011] B is derived from a diamine monomer, and the diamine monomer is selected from any one or a combination of two of the following structures:

[0012]

[0013] The embodiment of the present invention also provides a method for preparing the aforementioned polyimide carbon molecular sieve membrane containing benzimidazole, which comprises:

[0014] A mixed reaction system comprising at least a dianhydride monomer, a benzimidazole diamine, a diamine monomer, and a catalyst is reacted to obtain a benzimidazole-containing polyimide;

[0015] The benzimidazole-containing polyimide is mixed with a solvent and applied to the surface of a substrate to form a precursor film;

[0016] And, in a protective atmosphere, the precursor film is carbonized to obtain a polyimide carbon molecular sieve film containing benzimidazole.

[0017] The embodiment of the present invention also provides the use of the aforementioned benzimidazole-containing polyimide carbon molecular sieve membrane in carbon dioxide / methane separation.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention introduces a novel diamine monomer containing a benzimidazole structure to polymerize a polyimide polymer precursor containing a benzimidazole structure, thereby avoiding the collapse of the polymer structure caused by carbonization treatment and causing dense accumulation of molecular chains;

[0020] (2) The polyimide carbon molecular sieve membrane containing benzimidazole in the present invention has good permeability and carbon dioxide / methane selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 is the infrared spectra of the polyimide carbon molecular sieve membrane containing benzimidazole prepared in Examples 1-3 of the present invention and Comparative Example 1;

[0023] Figure 2 1 is the XRD diagram of the polyimide carbon molecular sieve membrane containing benzimidazole prepared in Examples 1-3 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0024] In view of the defects of the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. 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.

[0025] Specifically, as one aspect of the technical solution of the present invention, it relates to a polyimide carbon molecular sieve membrane containing benzimidazole, wherein the polymer of the polyimide carbon molecular sieve membrane has a repeating unit as shown in formula (I):

[0026]

[0027] Wherein, A is derived from a dianhydride monomer, and the dianhydride monomer is selected from any one or more combinations of the following structures:

[0028]

[0029] B is derived from a diamine monomer, and the diamine monomer is selected from any one or a combination of two of the following structures:

[0030]

[0031] In some preferred embodiments, the thickness of the polyimide carbon molecular sieve membrane is 60-80 μm.

[0032] In some preferred embodiments, the polyimide carbon molecular sieve membrane has a bimodal structure of micropores and ultramicropores, and the pore size of the micropores contained in the polyimide carbon molecular sieve membrane is less than The pore size of the ultra-micropores contained is

[0033] Another aspect of the embodiments of the present invention further provides a method for preparing the aforementioned polyimide carbon molecular sieve membrane containing benzimidazole, which comprises:

[0034] A mixed reaction system comprising at least a dianhydride monomer, a benzimidazole diamine, a diamine monomer, and a catalyst is reacted to obtain a benzimidazole-containing polyimide;

[0035] The benzimidazole-containing polyimide is mixed with a solvent and applied to the surface of a substrate to form a precursor film;

[0036] And, in a protective atmosphere, the precursor film is carbonized to obtain a polyimide carbon molecular sieve film containing benzimidazole.

[0037] In some preferred embodiments, the preparation method specifically includes: in a protective atmosphere, mixing the dianhydride monomer, the catalyst and ethanol and heating to dissolve, then distilling off the ethanol and adding benzimidazole diamine, diamine monomer, solvent, and dehydrating agent to form the mixed reaction system and reacting at 180-190°C for 12-24h to obtain a polyimide containing benzimidazole.

[0038] Furthermore, the molar ratio of the dianhydride monomer, benzimidazole diamine, diamine monomer and catalyst is 1:0.5:0.5:3-5.

[0039] Further, the catalyst includes triethylamine, but is not limited thereto.

[0040] Further, the benzimidazole diamine includes 2-(4-aminophenyl)-5-aminobenzimidazole, but is not limited thereto.

[0041] Further, the solvent includes N-methylpyrrolidone and / or N,N-dimethylacetamide, but is not limited thereto.

[0042] Further, the dehydrating agent includes toluene and / or xylene, but is not limited thereto.

[0043] Furthermore, the protective atmosphere includes any one or more combinations of nitrogen atmosphere, helium atmosphere, and argon atmosphere, but is not limited thereto.

[0044] In some preferred embodiments, the preparation method further comprises: after the reaction of the mixed reaction system is completed, adding a solvent to adjust the solid content of the obtained mixture to 10-15wt%, then cooling to 80-100°C and adding the obtained product to an ethanol-water mixture for sedimentation, and then dissolving-sedimenting and vacuum drying to obtain a polyimide containing benzimidazole.

[0045] Furthermore, the dissolution-sedimentation is repeated 2 to 3 times.

[0046] Furthermore, in the dissolution-sedimentation, chloroform is used for dissolution and an ethanol-water mixture is used for sedimentation.

[0047] Furthermore, the vacuum drying treatment is carried out at a temperature of 50 to 100° C. and for a time of 12 to 24 hours.

[0048] In some preferred embodiments, the preparation method specifically includes: mixing the benzimidazole-containing polyimide with a solvent to form a polymer solution, then stirring and filtering at room temperature, and then coating the obtained solution on the surface of the substrate and drying it to obtain a precursor film; wherein the content of the polymer solution is 5 to 10 wt%.

[0049] In some preferred embodiments, the preparation method specifically comprises: in a protective atmosphere, carbonizing the precursor film at 450N800° C. for 5N10 h to obtain a polyimide carbon molecular sieve membrane containing benzimidazole.

[0050] Furthermore, the carbonization treatment may convert the precursor film into polybenzoxazole.

[0051] In some more specific embodiments, the method for preparing the polyimide carbon molecular sieve membrane containing benzimidazole comprises the following steps:

[0052] (1) Preparation of polyimide precursor film containing benzimidazole:

[0053] Under nitrogen protection, dianhydride monomer A, catalyst triethylamine and ethanol are added to the reactor and dissolved at 80°C. After complete dissolution, add the Dean-Stark device and continue stirring the reaction for 1h. Raise the temperature to 120°C, increase the flow rate of nitrogen, and evaporate ethanol out of the reaction system. Add benzimidazole diamine and diamine monomer B to the reactor, and flush the wall with solvent A and dehydrating agent toluene. Raise the temperature to 180°C and react for 12h. Dilute with solvent A to a solid content of 15%, and reduce the temperature to 80°C. Pour the reaction solution into an ethanol-water mixture to obtain a flocculent precipitate. Dissolve in chloroform, precipitate the ethanol-water mixture, and after three cycles, vacuum dry at 120°C to obtain a white solid. Dissolve the polymer in solvent A to form a 1-5wt.% polymer solution and stir at room temperature for 24-36h. Use a 1μm PFTE filter to filter the solution to remove insoluble impurities. Slowly apply the polymer solution to a flat and dry glass plate. After drying in a constant temperature drying oven, the glass plate is moved to a vacuum oven and dried until the solvent is completely removed.

[0054] Furthermore, the solvent A is N-methylpyrrolidone and / or N,N-dimethylacetamide.

[0055] Furthermore, the mass fraction of the polymer solution is 5-10%.

[0056] Furthermore, the drying temperature of the constant temperature drying oven is 50-100° C., and the drying time is 12-24 hours.

[0057] Furthermore, the drying temperature of the vacuum drying oven is 150-300° C., and the drying time is 12-24 hours.

[0058] (2) Preparation of polyimide carbon molecular sieve membrane containing benzimidazole:

[0059] The polyimide precursor film containing benzimidazole is placed in a tube furnace, and a protective gas A is introduced for carbonization to obtain a polyimide carbon molecular sieve membrane containing benzimidazole;

[0060] Furthermore, the protective gas A is one of nitrogen, helium and argon.

[0061] Furthermore, the heating temperature of the tubular furnace is 450-800° C., and the heating time is 5-10 hours.

[0062] The polyimide carbon molecular sieve containing benzimidazole in the present invention reduces the free molecular volume of the membrane, breaks the trade-off effect of the polymer membrane, enhances the molecular sieving effect, forms a bimodal structure of micropores and ultramicropores, and achieves simultaneous improvement of permeability and selectivity.

[0063] The good permeability of the benzimidazole-containing polyimide carbon molecular sieve membrane of the present invention is attributed to the orderly arrangement of imidazole rings in the polymer main chain and the highly twisted rigid structure. In addition, the highly stacked polymer chains and strong intermolecular hydrogen bonds are beneficial to the selectivity of carbon dioxide / methane.

[0064] Another aspect of the embodiments of the present invention further provides the use of the aforementioned benzimidazole-containing polyimide carbon molecular sieve membrane in carbon dioxide / methane separation.

[0065] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments. This embodiment is implemented on the premise of the technical solution of the invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0066] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0067] Example 1

[0068] The benzimidazole-containing polyimide precursor used in the present invention is prepared by a two-step method (esterification method). Under nitrogen protection, 1mmol 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 5mmol triethylamine and 2mL ethanol are added to a reactor and dissolved at 80°C. After complete dissolution, a Dean-Stark device is added and the reaction is continued to be stirred for 1h. The temperature is raised to 120°C, the flow rate of nitrogen is increased, and the ethanol is evaporated out of the reaction system. 0.5mmol 2-(4-aminophenyl)-5-aminobenzimidazole and 0.5mmol 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane are added to the reactor, and the wall is flushed with solvent 2mL N-methylpyrrolidone and 2mL toluene. The temperature is raised to 180°C and the reaction is carried out for 12h. The solvent N-methylpyrrolidone is used to dilute the solid content to 15%, and the temperature is reduced to 80°C. The reaction solution is poured into an ethanol-water mixture to obtain a flocculent precipitate. The product was dissolved in chloroform and precipitated in an ethanol-water mixed solution. After three cycles, the product was dried in vacuum at 120° C. to obtain a white solid.

[0069] Dissolve 0.25g of benzimidazole-containing polyimide precursor in 5mL NMP and stir at room temperature for 24h to form a 5% polymer solution. Filter the solution with a 1μm PFTE filter to remove insoluble impurities. Slowly apply the polymer solution to a flat and dry glass plate, dry it in a constant temperature drying oven at 80℃ for 12h, then move the glass plate to a vacuum oven at 300℃ and dry it for 8h until the solvent is completely removed.

[0070] About 0.1 g of the obtained membrane was taken and put into a tubular furnace, and nitrogen as a protective gas was introduced. The temperature was raised to 450° C. and then naturally cooled to obtain the carbon molecular sieve membrane of Example 1.

[0071] Example 2

[0072] The benzimidazole-containing polyimide precursor used in the present invention is prepared by a two-step method (esterification method). Under nitrogen protection, 1mmol 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 5mmol triethylamine and 2mL ethanol are added to a reactor and dissolved at 80°C. After complete dissolution, a Dean-Stark device is added and the reaction is continued to be stirred for 1h. The temperature is raised to 120°C, the flow rate of nitrogen is increased, and the ethanol is evaporated out of the reaction system. 0.5mmol 2-(4-aminophenyl)-5-aminobenzimidazole and 0.5mmol 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane are added to the reactor, and the wall is flushed with solvent 2mL N-methylpyrrolidone and 2mL toluene. The temperature is raised to 180°C and the reaction is carried out for 12h. The solvent N-methylpyrrolidone is used to dilute the solid content to 15%, and the temperature is reduced to 80°C. The reaction solution is poured into an ethanol-water mixture to obtain a flocculent precipitate. The product was dissolved in chloroform and precipitated in an ethanol-water mixed solution. After three cycles, the product was dried in vacuum at 120° C. to obtain a white solid.

[0073] Dissolve 0.25g of benzimidazole-containing polyimide precursor in 5mL NMP and stir at room temperature for 24h to form a 5% polymer solution. Filter the solution with a 1μm PFTE filter to remove insoluble impurities. Slowly apply the polymer solution to a flat and dry glass plate, dry it in a constant temperature drying oven at 80℃ for 12h, then move the glass plate to a vacuum oven at 300℃ and dry it for 8h until the solvent is completely removed.

[0074] About 0.1 g of the obtained membrane was taken and put into a tubular furnace, and nitrogen as a protective gas was introduced. The temperature was raised to 600° C. and then naturally cooled to obtain the carbon molecular sieve membrane of Example 1.

[0075] Example 3

[0076] The benzimidazole-containing polyimide precursor used in the present invention is prepared by a two-step method (esterification method). Under nitrogen protection, 1mmol 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 5mmol triethylamine and 2mL ethanol are added to a reactor and dissolved at 80°C. After complete dissolution, a Dean-Stark device is added and the reaction is continued to be stirred for 1h. The temperature is raised to 120°C, the flow rate of nitrogen is increased, and the ethanol is evaporated out of the reaction system. 0.5mmol 2-(4-aminophenyl)-5-aminobenzimidazole and 0.5mmol 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane are added to the reactor, and the wall is flushed with solvent 2mL N-methylpyrrolidone and 2mL toluene. The temperature is raised to 180°C and the reaction is carried out for 12h. The solvent N-methylpyrrolidone is used to dilute the solid content to 15%, and the temperature is reduced to 80°C. The reaction solution is poured into an ethanol-water mixture to obtain a flocculent precipitate. The product was dissolved in chloroform and precipitated in an ethanol-water mixed solution. After three cycles, the product was dried in vacuum at 120° C. to obtain a white solid.

[0077] Dissolve 0.25g of benzimidazole-containing polyimide precursor in 5mL NMP and stir at room temperature for 24h to form a 5% polymer solution. Filter the solution with a 1μm PFTE filter to remove insoluble impurities. Slowly apply the polymer solution to a flat and dry glass plate, dry it in a constant temperature drying oven at 80℃ for 12h, then move the glass plate to a vacuum oven at 300℃ and dry it for 8h until the solvent is completely removed.

[0078] About 0.1 g of the obtained membrane was taken and put into a tubular furnace, and nitrogen as a protective gas was introduced. The temperature was raised to 800° C. and then naturally cooled to obtain the carbon molecular sieve membrane of Example 1.

[0079] Comparative Example 1

[0080] The benzimidazole-containing polyimide precursor used in the present invention is prepared by a two-step method (esterification method). Under nitrogen protection, 1mmol 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 5mmol triethylamine and 2mL ethanol are added to a reactor and dissolved at 80°C. After complete dissolution, a Dean-Stark device is added and the reaction is continued to be stirred for 1h. The temperature is raised to 120°C, the flow rate of nitrogen is increased, and the ethanol is evaporated out of the reaction system. 0.5mmol 2-(4-aminophenyl)-5-aminobenzimidazole and 0.5mmol 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane are added to the reactor, and the wall is flushed with solvent 2mL N-methylpyrrolidone and 2mL toluene. The temperature is raised to 180°C and the reaction is carried out for 12h. The solvent N-methylpyrrolidone is used to dilute the solid content to 15%, and the temperature is reduced to 80°C. The reaction solution is poured into an ethanol-water mixture to obtain a flocculent precipitate. The product was dissolved in chloroform and precipitated in an ethanol-water mixed solution. After three cycles, the product was dried in vacuum at 120° C. to obtain a white solid.

[0081] Dissolve 0.25g of benzimidazole-containing polyimide precursor in 5mL NMP and stir at room temperature for 24h to form a 5% polymer solution. Filter the solution with a 1μm PFTE filter to remove insoluble impurities. Slowly apply the polymer solution to a flat and dry glass plate, dry it in a constant temperature drying oven at 80℃ for 12h, then move the glass plate to a vacuum oven at 300℃ and dry it for 8h until the solvent is completely removed.

[0082] Figure 1 The infrared spectra of the polyimide carbon molecular sieve membrane containing benzimidazole prepared in Examples 1-3 and Comparative Example 1 of the present invention are as follows: Figure 1 It can be seen that the comparative example 1 shows ~1780cm- 1 The asymmetric stretching vibration absorption peak of C=O at 1700cm- 1 The symmetric stretching vibration absorption peak of C=O at 1365cm- 1 The stretching vibration absorption peak of CN at is the characteristic absorption peak of the imide group. As the carbonization temperature gradually increases, most of the functional groups in the examples gradually disappear, which is related to the decomposition of the polymer functional groups at higher carbonization temperatures.

[0083] The methane and carbon dioxide permeabilities and selectivities of the carbon molecular sieve membranes prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0084] Table 1

[0085]

[0086] Compared with Control Example 1, at different carbonization temperatures of the same polyimide precursor, the carbon molecular sieve membrane containing benzimidazole structure, such as the embodiment, has higher permeability. Aromatic heterocyclic polymers containing benzimidazole groups are well-known for their excellent molecular sieving performance, which is attributed to highly stacked polymer chains and strong intermolecular hydrogen bonds. However, while the benzimidazole-containing polyimide membrane improves selectivity, it greatly reduces the permeability of the membrane. It can be seen from the performance of Example 3 that with the increase of carbonization temperature, the membrane permeability decreases, while the selectivity increases, which is related to the shrinkage of discontinuous micropores in the membrane caused by the increase of carbonization temperature.

[0087] Depend on Figure 2 It can be seen that the XRD peaks of Examples 1-3 have a certain right shift corresponding to the XRD peak of Control Example 1. As the carbonization temperature of the polyimide precursor containing benzimidazole increases, the XRD peak has a certain right shift, and the molecular chain spacing continues to decrease. This is related to the decomposition of polymer functional groups at higher carbonization temperatures. The methane / carbon dioxide selectivity of Example 3 is significantly increased, which is confirmed by the gas separation data.

[0088] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0089] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A polyimide carbon molecular sieve membrane containing benzimidazole, characterized in that: The polymer of the polyimide carbon molecular sieve membrane has a repeating unit as shown in formula (I): Wherein, A is derived from a dianhydride monomer, and the dianhydride monomer is selected from any one or more combinations of the following structures: B is derived from a diamine monomer, and the diamine monomer is selected from any one or a combination of two of the following structures:

2. The polyimide carbon molecular sieve membrane containing benzimidazole according to claim 1, characterized in that: The thickness of the polyimide carbon molecular sieve membrane is 60 to 80 μm; And / or, the polyimide carbon molecular sieve membrane has a bimodal structure of micropores and ultramicropores, and the pore size of the micropores contained in the polyimide carbon molecular sieve membrane is Ultra-micropores 3. The method for preparing a polyimide carbon molecular sieve membrane containing benzimidazole according to claim 1 or 2, characterized in that: include: A mixed reaction system comprising at least a dianhydride monomer, a benzimidazole diamine, a diamine monomer, and a catalyst is reacted to obtain a benzimidazole-containing polyimide; The benzimidazole-containing polyimide is mixed with a solvent and applied to the surface of a substrate to form a precursor film; And, in a protective atmosphere, the precursor film is carbonized to obtain a polyimide carbon molecular sieve film containing benzimidazole.

4. The preparation method according to claim 3, characterized in that: Specifically include: In a protective atmosphere, the dianhydride monomer, the catalyst and ethanol are mixed and heated to dissolve, then the ethanol is evaporated and benzimidazole diamine, diamine monomer, solvent and dehydrating agent are added to form the mixed reaction system and reacted at 180-190° C. for 12-24 hours to obtain a polyimide containing benzimidazole.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the dianhydride monomer, benzimidazole diamine, diamine monomer and catalyst is 1:0.5:0.5:3-5; and / or, the catalyst comprises triethylamine; and / or, the benzimidazole diamine comprises 2-(4-aminophenyl)-5-aminobenzimidazole; and / or, the solvent comprises N-methylpyrrolidone and / or N,N-dimethylacetamide; And / or, the dehydrating agent includes toluene and / or xylene; And / or, the protective atmosphere includes any one or more combinations of nitrogen atmosphere, helium atmosphere, and argon atmosphere.

6. The preparation method according to claim 4, characterized in that: Also includes: After the reaction of the mixed reaction system is completed, a solvent is added to adjust the solid content of the obtained mixture to 10-15wt%, then the temperature is lowered to 80-100°C and the obtained product is added to an ethanol-water mixture for sedimentation, and then subjected to dissolution-sedimentation and vacuum drying treatment to obtain a polyimide containing benzimidazole.

7. The preparation method according to claim 6, characterized in that: The dissolution-sedimentation is repeated 2 to 3 times; And / or, in the dissolution-sedimentation, chloroform is used for dissolution and an ethanol-water mixture is used for sedimentation; And / or, the vacuum drying treatment is carried out at a temperature of 50 to 100° C. and for a time of 12 to 24 hours.

8. The preparation method according to claim 3, characterized in that: Specifically include: The benzimidazole-containing polyimide is mixed with a solvent to form a polymer solution, which is then stirred and filtered at room temperature, and then the obtained solution is coated on the surface of a substrate and dried to obtain a precursor film; wherein the content of the polymer solution is 5 to 10 wt%.

9. The preparation method according to claim 3, characterized in that: Specifically include: In a protective atmosphere, the precursor film is carbonized at 450-800° C. for 5-10 hours to obtain a polyimide carbon molecular sieve film containing benzimidazole.

10. Use of the benzimidazole-containing polyimide carbon molecular sieve membrane according to claim 1 or 2 in carbon dioxide / methane separation.

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