Lithium ion coordination polybenzimidazole gas separation membrane as well as preparation method and application thereof
By adding small molecule organic matter and lithium salt to polybenzimidazole solution, a lithium-ion coordinated polybenzimidazole network was constructed, which solved the problem of low selectivity of polybenzimidazole membrane and achieved efficient hydrogen separation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-31
AI Technical Summary
Existing polybenzimidazole membranes have low selectivity in hydrogen separation, and traditional modification methods result in insufficient compatibility between polymer chains and severe phase separation, which affects separation selectivity.
By adding small molecule organic matter and lithium salt to polybenzimidazole solution, lithium ion-coordinated polybenzimidazole network is constructed by utilizing the ion-dipole interaction between lithium ions and small molecule organic matter, thereby reducing the polymer chain spacing and improving the sieving ability.
It enhances hydrogen separation performance, improves membrane selectivity and flux, and features a simple process, convenient operation, and good production repeatability.
Smart Images
Figure CN121755070A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane separation technology, and in particular to a lithium-ion coordinated polybenzimidazole gas separation membrane, its preparation method, and its application. Background Technology
[0002] Hydrogen energy is of strategic significance for environmental protection, climate change, and future energy security and economic development, and is a key component in building a modern clean energy system. Currently, 96% of the world's H2 comes from fossil fuel conversion. The main products of coal gasification are H2 and CO, which are then converted into H2 and CO2 through water-gas shift reaction. Furthermore, the production of H2 through alcohol chemicals and alkane reforming also requires the conversion of CO to CO2, resulting in a significant amount of CO2 in the generated H2 gas stream, which needs to be removed from the gas mixture. Therefore, it is necessary to obtain high-purity H2 from hydrogen-rich gases using gas separation technology. Common hydrogen purification methods include cryogenic separation and pressure swing adsorption membrane separation. Among these, membrane separation technology shows great potential in the field of hydrogen separation and purification due to its environmental friendliness, ease of operation, and high separation efficiency.
[0003] Currently, polymer membranes such as polyimide, polybenzimidazole, ethyl cellulose, polyethersulfone, and polymethyl methacrylate have significant advantages in terms of cost-effectiveness and ease of preparation, making them more suitable for industrial applications in hydrogen separation. Among them, polybenzimidazole membranes are widely used in high-temperature gas separation due to their excellent thermal stability and chemical inertness. However, the low hydrogen selectivity of polybenzimidazole membranes limits their large-scale application to some extent. Traditional crosslinking, doping, or blending modification methods can improve the mechanical properties and thermal stability of the membrane to some extent, but they often lead to problems such as insufficient compatibility between polymer chains, severe phase separation, and inhomogeneous microstructure, resulting in decreased separation selectivity. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a lithium-ion coordinated polybenzimidazole gas separation membrane, its preparation method, and its applications. This invention prepares the separation membrane using polybenzimidazole, small-molecule organic compounds, and lithium salts. The small-molecule organic compounds promote the formation of a lithium-ion coordinated polybenzimidazole network through ion-dipole interactions, reducing polymer chain spacing, enhancing sieving capacity, and thus improving gas selectivity. Furthermore, the separation membrane is prepared using a one-step method, which is simple, convenient, efficient, and has good production repeatability. It can be used for the efficient separation of hydrogen / carbon dioxide, hydrogen / nitrogen, and hydrogen / methane.
[0005] The technical solution of the present invention is as follows: The first aspect of this invention protects a method for preparing a lithium-ion coordinated polybenzimidazole gas separation membrane, the method comprising the following steps: Small molecule organic compounds and metal salts were added to a polybenzimidazole solution, stirred, and sonicated to obtain a casting solution. The casting solution was cast into a film and dried to obtain a lithium-ion coordinated polybenzimidazole gas separation membrane. The small molecule organic compound includes at least one of benzenesulfonamide, N-methylbenzenesulfonamide, and N-acryloylmorpholine; The metal salt includes lithium salt.
[0006] Preferably, the polybenzimidazole solution is obtained by dissolving polybenzimidazole in a solvent; Preferably, the molecular weight of the polybenzimidazole is 40,000 to 100,000 Daltons.
[0007] Preferably, the mass concentration of the polybenzimidazole solution is 5-15%.
[0008] Preferably, the molar ratio of the polybenzimidazole, the small molecule organic compound, and the metal salt is (0.4~1.2):(0.4~1.2):(0.4~1.2), and more preferably 1:1:1.
[0009] Preferably, the lithium salt includes at least one of lithium chloride, lithium nitrate, lithium phosphate, and lithium acetate.
[0010] Preferably, the drying is gradient drying.
[0011] Preferably, the gradient drying involves first drying the casting solution at 50-90°C for 12-24 hours, and then raising the temperature to 120-150°C and drying for another 12-24 hours.
[0012] The second aspect of this invention protects a lithium-ion coordinated polybenzimidazole gas separation membrane prepared by the preparation method described in the first aspect above, wherein the thickness of the lithium-ion coordinated polybenzimidazole gas separation membrane is 20~40μm.
[0013] The third aspect of this invention protects a lithium-ion coordinated polybenzimidazole gas separation membrane prepared by the preparation method described in the second aspect above, or the application of the lithium-ion coordinated polybenzimidazole gas separation membrane described in the second aspect above, wherein the separation membrane is used for the separation of hydrogen from other gases. The other gases include at least one of carbon dioxide, nitrogen, and methane.
[0014] The beneficial technical effects of this invention are as follows: The lithium-ion coordinated polybenzimidazole separation membrane provided by this invention utilizes small molecule organic matter to promote the formation of lithium-ion coordinated polybenzimidazole network through ion-dipole interaction, which can reduce the polymer chain spacing, improve sieving capacity and hydrogen selectivity, and thus improve the hydrogen separation performance of the polybenzimidazole hydrogen separation membrane.
[0015] Furthermore, the lithium ions used in the lithium-ion coordinated benzimidazole separation membrane provided by the present invention do not cause premature gelation of the casting solution. This in-situ coordination process, in which metal ions spontaneously undergo coordination reactions within the polymer, eliminates post-processing steps, ensures uniform membrane cross-linking, and avoids the generation of internal stress.
[0016] Meanwhile, the lithium-ion coordinated polybenzimidazole separation membrane of the present invention is prepared by a one-step method, which is simple, easy to operate, highly efficient, and has good production repeatability. Attached Figure Description
[0017] Figure 1 The infrared spectra of the polybenzimidazole films prepared in Example 1 and Comparative Example 1 of this invention are shown.
[0018] Figure 2 The images show the X-ray diffraction patterns of the polybenzimidazole films prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation
[0019] The present invention will now be described in detail with reference to the embodiments.
[0020] To address the low selectivity of existing gas separation membranes for hydrogen, and the problems that existing modification methods can lead to insufficient polymer chain compatibility, severe phase separation, and consequently decreased separation selectivity, this invention provides a lithium-ion coordinated polybenzimidazole gas separation membrane, its preparation method, and its applications.
[0021] The first aspect of this invention provides a method for preparing a lithium-ion coordinated polybenzimidazole gas separation membrane, the method comprising the following steps: Small molecule organic compounds and metal salts were added to a polybenzimidazole solution, stirred, and sonicated to obtain a casting solution. The casting solution was cast into a film and dried to obtain a lithium-ion coordinated polybenzimidazole gas separation membrane. The small molecule organic compound includes at least one of benzenesulfonamide, N-methylbenzenesulfonamide, and N-acryloylmorpholine; the metal salt is a lithium salt.
[0022] This invention, starting from the construction of polymer networks through lithium-ion coordination, provides a lithium-ion coordinated polybenzimidazole gas separation membrane and its preparation method. By regulating the interaction forces between lithium ions, polybenzimidazole, and small organic molecules, a high-performance hydrogen separation membrane is constructed. In the gas separation membrane prepared by this invention, lithium ions, due to their small ionic radius and empty outer electron orbitals, have moderate coordination ability and can generate ion-dipole interactions with small organic molecules such as benzenesulfonamide, N-methylbenzenesulfonamide, or N-acryloylmorpholine, promoting the formation of the coordinated polybenzimidazole network, reducing the polymer chain spacing, and improving its sieving capacity. Specifically, the carbonyl oxygen in the amide group of the N-acryloylmorpholine side chain can form Li₂ with lithium ions to form Li₂.+ ...O=C ion-dipole pair; benzenesulfonamide and N-methylbenzenesulfonamide react with lithium ions through the two carbonyl oxygen atoms in the sulfonyl group RS(=O)2- and the lone pair electrons on the nitrogen atom of the sulfonamide to produce Li... + O = S or Li + ...N-ion-dipole interaction. This ion-dipole interaction can modulate the coordination environment of lithium ions, promoting the coordination and cross-linking of lithium ions with polybenzimidazole, thereby resulting in a more compact chain arrangement, reduced interchain spacing, enhanced sieving capacity and gas selectivity, thus solving the problem of low selectivity in polybenzimidazole hydrogen separation membranes. Furthermore, unlike high-valence metal ions, lithium ions do not cause premature gelation of the casting solution. This in-situ process eliminates post-treatment steps, ensures uniform membrane cross-linking, avoids internal stress generation, and provides a new approach for traditional modification methods.
[0023] In some embodiments, the polybenzimidazole solution is obtained by dissolving polybenzimidazole in a solvent.
[0024] The solvent includes at least one of N,N-dimethylacetamide and N,N-dimethylformamide. The solvent of this invention can fully dissolve polybenzimidazole.
[0025] In some embodiments, the molecular weight of the polybenzimidazole is 40,000 to 100,000 Daltons.
[0026] The polybenzimidazole used in this invention has a high molecular weight, which allows it to construct a dense and stable network structure through the strong entanglement effect of its long molecular chains and abundant intermolecular hydrogen bonding. This structure endows the membrane with excellent mechanical strength and anti-swelling properties, while inducing the formation of mass transfer channels with uniform pore size, significantly reducing the proportion of non-selective defects, thereby achieving a synergistic improvement in separation selectivity and permeation flux.
[0027] In some embodiments, the polybenzimidazole includes at least one of aryl ether polybenzimidazole and aromatic polybenzimidazole. The aryl ether polybenzimidazole backbone has flexible aryl ether bonds, which can reduce the molecular chain entanglement density and improve the solubility and film-forming processability of the polymer. At the same time, it retains the high temperature resistance and chemical corrosion resistance of PBI, and the prepared gas separation membrane has both high gas permeation flux and good mechanical stability.
[0028] In some embodiments, the mass concentration of the polybenzimidazole solution is 5-15%, including but not limited to 5%, 10%, and 15%.
[0029] In some embodiments, the molar ratio of the polybenzimidazole, the small molecule organic compound, and the metal salt is (0.4~1.2):(0.4~1.2):(0.4~1.2), preferably 1:1:1.
[0030] In this invention, the appropriate ratio of polybenzimidazole, small-molecule organic compounds, and metal salts ensures the formation of a polymer network while avoiding agglomeration caused by excessive polymer. Too low a dosage of small-molecule organic compounds affects the density and uniformity of the network, while too high a dosage disrupts the integrity of the polymer network, exacerbates the swelling tendency of the film structure, and generates non-selective defects. Conversely, excessive lithium salts lead to the agglomeration of excess metal ions, hindering their uniform participation in the coordination reaction and interfering with polymer chain crosslinking. Too low a dosage fails to provide sufficient coordination sites, resulting in decreased crosslinking density and hindering polymer network construction.
[0031] In some embodiments, the lithium salt includes at least one of lithium chloride, lithium nitrate, lithium phosphate, and lithium acetate.
[0032] The lithium salt used in this invention has a moderate coordination ability. It can not only generate ion-dipole coordination interactions with small organic molecules to promote the formation of coordinated polybenzimidazole networks and reduce polymer chain spacing, but also, unlike other metal salts, lithium ions do not cause premature gelation of the casting solution, thus ensuring the uniformity of membrane crosslinking and avoiding the generation of internal stress that could affect the structural integrity and separation performance stability of the membrane.
[0033] In some embodiments, the drying is gradient drying.
[0034] In some embodiments, the gradient drying involves first drying the casting solution at 50-90°C for 12-24 hours, and then raising the temperature to 120-150°C and drying for another 12-24 hours.
[0035] This invention employs a two-step gradient drying process. First, the solvent in the casting solution is gently removed at a low temperature, and then the temperature is increased. This avoids the problems of uneven stress distribution, pore collapse, and interface cracking caused by direct high-temperature drying.
[0036] The second aspect of this invention protects a lithium-ion coordinated polybenzimidazole gas separation membrane prepared by the preparation method described in the first aspect above, wherein the thickness of the lithium-ion coordinated polybenzimidazole gas separation membrane is 20~40μm.
[0037] The gas separation membrane of the present invention can achieve excellent hydrogen separation by controlling the network structure and membrane thickness. When the thickness is too large, the hydrogen permeation path is extended, the flux decreases exponentially, and the separation efficiency is significantly reduced. When the thickness is too small, the mechanical properties of the membrane will be reduced, and it will rupture under pressure difference.
[0038] The third aspect of this invention protects a lithium-ion coordinated polybenzimidazole gas separation membrane prepared by the preparation method described in the second aspect above, or the application of the lithium-ion coordinated polybenzimidazole gas separation membrane described in the second aspect above, wherein the separation membrane is used for the separation of hydrogen from other gases. The other gases include at least one of carbon dioxide, nitrogen, and methane.
[0039] In some embodiments, the lithium-ion coordinated polybenzimidazole hydrogen separation membrane prepared by the present invention is used for the separation of hydrogen / carbon dioxide, hydrogen / nitrogen, and hydrogen / methane.
[0040] The present invention will be further described below through examples and other means.
[0041] Example 1 A lithium-ion coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide at 90 °C for 24 h to form a homogeneous solution. 0.3179 g of LiCl and 1.1789 g of benzenesulfonamide were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 h, and then vacuum dried at 150 °C for 24 h to obtain a polybenzimidazole hydrogen separation membrane. The aryl ether polybenzimidazole was poly[2,2'-(4,4'-oxybis(1,4-phenylene))-5,5'-bibenzimidazole], with a molecular weight of 40,000 Daltons and a relative molecular mass of 400 for each repeating unit, purchased from Zhongke Energy Materials Technology (Dalian) Co., Ltd.
[0042] Example 2 A lithium-ion coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide and dissolved at 90 °C for 24 h to form a homogeneous solution. 0.3179 g of LiCl and 1.2841 g of N-methylbenzenesulfonamide were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 hours, and then vacuum dried at 150 °C for 24 hours to obtain a polybenzimidazole hydrogen separation membrane. The aryl ether polybenzimidazole used was the same as in Example 1.
[0043] Example 3 A lithium-ion coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide and dissolved at 90 °C for 24 h to form a homogeneous solution. 0.3179 g of LiCl and 1.0588 g of N-acryloylmorpholine were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 hours, and then vacuum dried at 150 °C for 24 hours to obtain a polybenzimidazole hydrogen separation membrane. The aryl ether polybenzimidazole used was the same as in Example 1.
[0044] Example 4 A lithium-ion coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 17.0 g of N,N-dimethylacetamide at 90 °C for 24 h to form a homogeneous solution. 0.3179 g of LiCl and 3.53 g of benzenesulfonamide were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 60 °C for 12 hours, and then vacuum dried at 130 °C for 12 hours to obtain a polybenzimidazole hydrogen separation membrane. The aryl ether polybenzimidazole used was the same as in Example 1.
[0045] Example 5 A lithium-ion coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 97.0 g of N,N-dimethylacetamide at 90 °C for 24 h to form a homogeneous solution. 0.3179 g of LiCl and 0.393 g of benzenesulfonamide were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 50 °C for 20 hours, and then vacuum dried at 120 °C for 20 hours to obtain a polybenzimidazole hydrogen separation membrane. The aryl ether polybenzimidazole used was the same as in Example 1.
[0046] Comparative Example 1 The preparation method of the polybenzimidazole hydrogen separation membrane includes the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide at 90 °C for 24 h to form a homogeneous solution. The solution was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 h, and then vacuum dried at 150 °C for 24 h to obtain a polybenzimidazole hydrogen separation membrane. The aryl ether polybenzimidazole used was the same as in Example 1.
[0047] Comparative Example 2 A lithium-ion coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide and dissolved at 90 °C for 24 h to form a homogeneous solution. 0.3179 g of LiCl was added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 h, and then vacuum dried at 150 °C for 24 h to obtain a polybenzimidazole hydrogen separation membrane.
[0048] Comparative Example 3 The preparation method of the small molecule polybenzimidazole hydrogen separation membrane with added benzenesulfonamide includes the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide and dissolved at 90 °C for 24 h to form a homogeneous solution. 1.1789 g of benzenesulfonamide was added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 h, and then vacuum dried at 150 °C for 24 h to obtain a polybenzimidazole hydrogen separation membrane.
[0049] Comparative Example 4 The sodium ion-coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide and dissolved at 90 °C for 24 h to form a homogeneous solution. 0.4384 g of NaCl and 1.1789 g of benzenesulfonamide were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 h, and then vacuum dried at 150 °C for 24 h to obtain a polybenzimidazole hydrogen separation membrane.
[0050] Comparative Example 5 A lithium-ion coordinated polybenzimidazole hydrogen separation membrane is prepared by the following steps: 3.0 g of aryl ether polybenzimidazole was dissolved in 24.0 g of N,N-dimethylacetamide and dissolved at 90 °C for 24 h to form a homogeneous solution. 0.6359 g of LiCl and 1.1789 g of benzenesulfonamide were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous casting solution. After degassing under vacuum, the solution was cast into a film, dried at 90 °C for 24 h, and then vacuum dried at 150 °C for 24 h to obtain a polybenzimidazole hydrogen separation membrane.
[0051] Test case (1) Membrane structure characterization Figure 1 The images show the infrared spectra of the lithium-ion coordinated polybenzimidazole membrane of Example 1 and the polybenzimidazole membrane of Comparative Example 1. Compared with the polybenzimidazole membrane of Comparative Example 1, the C=N stretching vibration peak of the imidazole ring in the lithium-ion coordinated polybenzimidazole membrane of Example 1 is enhanced and shifted to higher wavenumbers. The CN stretching vibration on the imidazole ring undergoes a blue shift, and the characteristic peak COC stretching vibration of the aromatic ether bond also undergoes a blue shift, confirming the interaction reaction between lithium ions and the imidazole ring and aromatic ether bond.
[0052] Figure 2 These are X-ray diffraction patterns of the lithium-ion coordinated polybenzimidazole film of Example 1 and the polybenzimidazole film of Comparative Example 1. Figure 2 It can be seen that the combined effect of lithium ions and benzenesulfonamide effectively reduces the distance between polymer chains.
[0053] (2) Gas separation performance determination The gas permeability (evaluated by permeability coefficient) and selectivity of the membranes prepared in the embodiments and comparative examples of this invention were determined. The specific methods are as follows: The gas permeation test method is as follows: the gas separation membrane prepared in the example or comparative example is placed in a gas permeation cell, and the gas permeability of the membrane is measured by the constant volume pressure variation method.
[0054] Gas permeability was determined using pure H2 and CO2 under conditions of 35℃ and 0.5 MPa. P and ideal selectivity α i / j .
[0055] The formula for calculating the gas permeability coefficient P is as follows: (1) In the formula: P Gas permeability coefficient ( ); Q For the gas to permeate from the beginning to t Cumulative osmosis at time (cm) 3 ); A The area of the membrane (cm²) 2 ); l Film thickness (cm); Δ P t represents the pressure difference between the upstream and downstream sides (MPa); t represents the infiltration time (s).
[0056] Selective α i / j The calculation formula is shown below: (2) In the formula α i / j This indicates the membrane's ideal selectivity for gaseous components H2 and CO2; P i This represents the permeability coefficient (barrer) of H2. P j This represents the permeability coefficient (barrer) of the gaseous component CO2.
[0057] The results are shown in Table 1 below.
[0058] The membrane thicknesses of the separation membranes prepared in each embodiment and comparative example are shown in Table 1.
[0059] Table 1. Gas separation performance tests of the membranes prepared in the examples and comparative examples.
[0060] As demonstrated by the examples and comparative examples, the H2 / CO2 selectivity of the lithium-ion coordinated polybenzimidazole gas separation membrane with added small-molecule organic matter is significantly higher than that without small-molecule organic matter. Meanwhile, when sodium chloride is used instead of lithium salt, the permeability of hydrogen decreases, the permeability of carbon dioxide increases, and the ideal H2 / CO2 selectivity decreases. Similarly, increasing the amount of lithium salt decreases the permeability of hydrogen, increases the permeability of carbon dioxide, and decreases the ideal H2 / CO2 selectivity. When neither small-molecule organic matter nor lithium salt is present, the prepared membrane exhibits poor H2 / CO2 selectivity.
[0061] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.
Claims
1. A method for preparing a lithium ion coordination polybenzimidazole gas separation membrane, characterized by, The preparation method comprises the following steps: adding a small-molecule organic matter and a metal salt into a polybenzimidazole solution, stirring and ultrasonicating to obtain a casting solution; casting the casting solution into a film, drying to obtain a lithium ion coordination polybenzimidazole gas separation film; the small-molecule organic matter comprises at least one of benzene sulfonamide, N-methyl benzene sulfonamide and N-acryloyl morpholine; the metal salt is a lithium salt.
2. The production method according to claim 1, characterized by, The polybenzimidazole solution is obtained by dissolving polybenzimidazole in a solvent.
3. The preparation method according to claim 1, characterized in that, The molecular weight of the polybenzimidazole is 40000-100000 Dalton.
4. The method of claim 1, wherein, The mass concentration of the polybenzimidazole solution is 5-15%.
5. The preparation method according to claim 1, characterized in that, The molar ratio of the polybenzimidazole, the small-molecule organic matter and the metal salt is (0.4-1.2):(0.4-1.2):(0.4-1.2), preferably 1:1:
1.
6. The method of claim 1, wherein, The lithium salt comprises at least one of lithium chloride, lithium nitrate, lithium phosphate and lithium acetate.
7. The preparation method according to claim 1, characterized in that, The drying is gradient drying.
8. The preparation method according to claim 7, characterized in that, The gradient drying is first drying the casting solution at 50-90℃ for 12-24h, then increasing the temperature to 120-150℃ and drying for 12-24h.
9. A lithium ion coordination polybenzimidazole gas separation membrane prepared by the method of any one of claims 1-8, wherein, The thickness of the lithium ion coordination polybenzimidazole gas separation film is 20-40μm.
10. A lithium ion coordination polybenzimidazole gas separation membrane prepared by the method of any one of claims 1-8, or use of the lithium ion coordination polybenzimidazole gas separation membrane of claim 9, characterized in that, separating hydrogen from other gases; the other gases comprise at least one of carbon dioxide, nitrogen and methane.