An organic molecular cage modified polymer film, and a preparation method and application thereof

Abstract

The application provides an organic molecular cage modified polymer membrane, a preparation method and application, which uses a secondary amine super-primitive organic molecular cage as a modifier, uses a modified polybenzimidazole as a polymer membrane matrix, and the modifier is connected with the polymer matrix through a covalent bond. In the polymer membrane, the intramolecular cavity of the secondary amine super-primitive organic molecular cage provides a low-resistance transmission channel for protons, a large number of proton transmission sites on the cage accelerate the transmission of protons, and high proton conductivity can be ensured; the sub-nanometer sieving channel of the secondary amine super-primitive organic molecular cage forms a hierarchical structure of ion channels, the molecular scale sieving of the 'effective' channel size can be realized, and the high selectivity of the membrane can be ensured; and the secondary amine super-primitive organic molecular cage has solution processing and high compatibility with the polymer, the molecular scale sieving ion channels can be constructed in the polymer matrix through a simple solution casting method, and the polymer membrane has the potential of continuous and large-scale production. The modified polymer membrane can be applied as a diaphragm in a redox flow battery.

Description

Technical Field

[0001] This invention belongs to the field of ion-conducting membrane technology, specifically relating to an organic molecular cage-modified polymer membrane, its preparation method, and its application. Background Technology

[0002] The continued use of fossil fuels and the ever-increasing energy consumption in society have led to an energy crisis and severe environmental pollution, making the deployment of unconventional yet efficient energy sources imperative. Renewable energy sources, such as wind and solar power, are widely considered alternatives to fossil fuels. However, renewable energy sources are typically intermittent and volatile, posing a severe challenge to the stable operation of the power system when connected to the grid on a large scale. Large-scale energy storage can not only overcome this challenge and improve grid stability but also improve power efficiency by peak shaving and valley filling. Redox flow batteries (RFBs) have advantages such as energy and power decoupling, modular design, and high safety, making them one of the preferred technologies for large-scale, long-term energy storage.

[0003] The ion-conducting membrane is a crucial component of the reactive energy storage (RFB) cell, responsible for transferring current-carrying ions and forming a current loop. Simultaneously, it blocks dissolved positive and negative electrode active materials in aqueous solutions, preventing cross-contamination and self-discharge. Therefore, an ideal ion-conducting membrane should possess high ion conductivity and high selectivity, along with high stability (long lifespan) to ensure long-term, efficient, and stable battery operation. However, the ion conductivity and selectivity of the membrane are often mutually restrictive and difficult to achieve simultaneously. Therefore, developing an ion-conducting membrane that combines high ion conductivity and high selectivity has become one of the key research areas and technical challenges in large-scale, long-term RFB energy storage technology.

[0004] Current research on RFB membranes can be divided into two main categories: dense membranes and porous membranes.

[0005] Dense membranes typically consist of a hydrophobic polymer backbone and side chains containing ion-exchange groups. Due to the polarity difference between the backbone and side chains, hydrophilic and hydrophobic microphase separation structures spontaneously form during membrane formation, which is an effective method for constructing high-speed ion transport channels in dense membranes. However, the ion channels formed by microphase separation are usually in the nanometer scale, making it difficult to achieve molecular-scale sieving and effective control, and the selectivity of the membrane needs further improvement.

[0006] Research on porous membranes mainly focuses on optimizing solvent-inducible phase inversion (RII) methods and developing new membrane fabrication processes to achieve effective control over the microstructure of porous membranes. However, because the active substances in reactive ions (RFBs) (mostly metal ions or small molecules) are only slightly different in size from the carrier ions, the requirements for the pore size and distribution of porous membranes are stringent. Ion channels constructed using RIB methods are difficult to sieve at the molecular scale, and the membrane fabrication process must be strictly controlled to ensure the channel's controllability at the nanoscale. To address these issues, materials with intrinsic pores have begun to be used to prepare RIB membranes, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), zeolite molecular sieves, and self-porous polymers. These materials with intrinsic pores of sub-nanometer size are ideal choices for constructing RIB membranes with molecular-scale sieving and high-efficiency ion conduction. However, the membrane materials currently used for RFB are all blocky crystals or polymers formed by covalent or coordination bonds. They have problems such as poor processability, low compatibility with polymers (such as MOF, COF, molecular sieves) or difficulty in accurately and effectively controlling pore structure and pore chemistry (such as self-microporous polymers), which bring great difficulties and challenges to membrane preparation process and membrane performance control. Summary of the Invention

[0007] In view of the problems existing in the prior art, one of the objectives of the present invention is to provide a polymer membrane modified with an organic molecular cage, which has good molecular-scale sieving performance, as well as high proton conductivity and high selectivity.

[0008] To achieve the above objectives, the following technical solution is proposed: Through extensive research, the inventors have discovered that by using secondary amine hypervast organic molecular cages as modifiers and modified polybenzimidazole as the membrane matrix, an organic molecular cage-modified polymer membrane can achieve molecular-scale sieving and exhibits high proton conductivity and high selectivity. More specifically, the intrinsic cavities of the secondary amine hypervast organic molecular cages provide low-resistance transport channels for protons, and the numerous proton transport sites on the cages accelerate proton transport, both of which ensure the membrane's high proton conductivity. The sub-nanometer sieving channels of the secondary amine hypervast organic molecular cages enable the formation of a hierarchical structure of ion channels, achieving molecular-scale sieving at the "effective" channel size and ensuring the membrane's high selectivity. Furthermore, the secondary amine hypervast organic molecular cages possess solution processability and high compatibility with polymers, allowing for the construction of molecular-scale sieving ion channels within the polymer matrix using a simple solution casting method, demonstrating potential for continuous and large-scale production.

[0009] Specifically, this invention provides an organic molecular cage-modified polymer film, which uses a secondary amine hypervironmental organic molecular cage as a modifier and a modified polybenzimidazole as a polymer film matrix, wherein the modifier and the polymer matrix are connected by covalent bonds. The chemical formula of the secondary amine hypervironmental organic molecular cage is shown in general formula 1, and the chemical formula of the modified polybenzimidazole is shown in general formula 2, wherein... Selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups; R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I. .

[0010] Preferably, the modified polybenzimidazole is selected from one or more compounds of chemical formulas 1-4, and the secondary amine hypermeric organic molecular cage is selected from one or more compounds of chemical formulas 5-7. .

[0011] Preferably, the halogen on the modified polybenzimidazole side chain reacts with the NH on the secondary amine hypermeric organic molecular cage to form a connection.

[0012] As a general inventive concept, this invention also provides a method for preparing an organic molecular cage modified polymer film, comprising: dissolving modified polybenzimidazole in solvent 1 to obtain solution 1; dissolving a secondary amine hyperpigmented organic molecular cage in solvent 2 to obtain solution 2; mixing solution 1 and solution 2 uniformly to obtain a casting solution; subjecting the casting solution to degassing treatment, casting, and drying to form a film; and post-treating the obtained film to remove uncrosslinked secondary amine hyperpigmented organic molecular cages and residual solvent, thereby obtaining the final product. The chemical formula of the secondary amine hyperpigmented organic molecular cage is shown in general formula 1, and the chemical formula of the modified polybenzimidazole is shown in general formula 2, wherein... Selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups; R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I. .

[0013] Further preferably, the modified polybenzimidazole is selected from one or more compounds of chemical formulas 1-4, and the secondary amine hypermeric organic molecular cage is selected from one or more compounds of chemical formulas 5-7. .

[0014] Preferably, solvent 1 is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; solvent 2 is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0015] Preferably, the mass ratio of the modified polybenzimidazole to the secondary amine hypermeric organic molecular cage is 5:1 to 5:12.

[0016] Preferably, the drying temperature is 40-100℃; the drying time is 6-24 h; and the drying atmosphere is a vacuum or an inert gas.

[0017] Preferably, the mixing is carried out by stirring; the stirring time is 3-16 hours.

[0018] Preferably, the preparation method of the modified polybenzimidazole includes: first dissolving polybenzimidazole and compound A in dimethylacetamide, adding a certain amount of Bronsted base, reacting at 0-100℃, and after the reaction is completed, pouring the reaction solution into deionized water to precipitate, and then repeatedly washing and drying to obtain the product; the chemical formula of compound A is XRX, where R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I; its chemical reaction equation is: .

[0019] Preferably, the molar ratio of the polybenzimidazole repeating unit to compound A is 1:20-1:150; the polybenzimidazole is dissolved in dimethylacetamide at a concentration of 5-30 g / L; compound A is dissolved in dimethylacetamide at a concentration of 250-800 g / L; and the molar ratio of the bronzted base to the polybenzimidazole repeating unit is 80:1-1:1.

[0020] Preferably, in the preparation method of the modified polybenzimidazole, the reaction time is 5-10 days.

[0021] Optionally, the repeated washing can be performed using water and acetone.

[0022] Preferably, the preparation method of the secondary amine hyperphenone organic molecular cage includes: dissolving hexaaminomethylbenzene and compound B in methanol, stirring the reaction under a non-oxidizing atmosphere at 40-80°C, and after the reaction is complete, cooling to room temperature, slowly adding sodium borohydride to carry out a reduction reaction, removing the solvent under vacuum, adding water to remove the salt, extracting with chloroform, collecting the chloroform phase, and removing the solvent under vacuum to obtain (the secondary amine hyperphenone organic molecular cage); the chemical formula of compound B is... ,in The chemical reaction equation is as follows: (The chemical compound is selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups.) Preferably, the molar ratio of hexaaminomethylbenzene to compound B is 1:3-1:4; the hexaaminomethylbenzene is dissolved in methanol at a concentration of 0.1-1 g / L; and the compound B is dissolved in methanol at a concentration of 0.1-3 g / L.

[0023] Preferably, the molar ratio of sodium borohydride to hexaaminomethylbenzene is 30:1-80:1.

[0024] Preferably, the stirring reaction takes 4-24 hours, and the reduction reaction takes 4-16 hours, with the reduction reaction carried out under stirring.

[0025] Preferably, the method further includes immersing the resulting membrane in a dilute sulfuric acid solution until it becomes saturated with acid.

[0026] Optionally, the concentration of the dilute sulfuric acid solution can be 1-5 mol / L.

[0027] As a general inventive concept, the present invention also provides the application of the aforementioned organic molecular cage modified polymer membrane or the organic molecular cage modified polymer membrane prepared by the aforementioned preparation method as a separator in a redox flow battery.

[0028] Compared with the prior art, the present invention has the following beneficial effects: In the modified membrane of this invention, the solution processability of the secondary amine hypervast organic molecular cage (i.e., soluble in common organic solvents) and the crosslinking reaction with modified polybenzimidazole are utilized to allow the secondary amine hypervast organic molecular cage to be molecularly mixed within the polymer membrane, resulting in a uniform distribution. By introducing the intrinsically pore-bearing secondary amine hypervast organic molecular cage into the polymer membrane, a polymer membrane containing sub-nanometer sieves is successfully designed, achieving molecular-scale pore size control and significantly improving membrane selectivity. Furthermore, the nitrogen-rich chemical structure of the secondary amine hypervast organic molecular cage provides abundant proton transport sites for the polymer membrane, and the cage-like spatial structure (internal cavity) provides low-resistance transport channels for protons, significantly improving the membrane's proton conductivity. Therefore, the polymer membrane modified with organic molecular cages not only achieves molecular-scale sieves but also obtains high proton conductivity and high selectivity. Moreover, it can be obtained using a simple solution casting method, possessing potential for continuous and large-scale production. Attached Figure Description

[0029] Figure 1 Infrared spectra of the polymer films prepared in Examples 1-3 and Comparative Examples 1-2.

[0030] Figure 2The images shown are scanning electron microscope (SEM) images of the cross sections of the polymer films prepared in Examples 2 and 3, where (2a) and (2b) are SEM images of the cross sections of the polymer films prepared in Example 2 at magnifications of 4000 and 30000, respectively, and (2c) and (2d) are SEM images of the cross sections of the polymer films prepared in Example 3 at magnifications of 4000 and 30000, respectively.

[0031] Figure 3 The modified polybenzimidazole membranes prepared for Example 3 and Comparative Example 1 were tested at 40-300 mA / cm². 2 Efficiency comparison chart at current density.

[0032] Figure 4 The graphs show the efficiency and capacity of the polymer film prepared in Example 2 during battery charge-discharge cycles, where (4a) is the efficiency graph of the polymer film during the cycle and (4b) is the capacity graph of the polymer film during the cycle. Detailed Implementation

[0033] This invention provides an organic molecular cage-modified polymer film, which uses a secondary amine hypervironmental organic molecular cage as a modifier and a modified polybenzimidazole as a polymer film matrix, wherein the modifier and the polymer matrix are connected by covalent bonds; the chemical formula of the secondary amine hypervironmental organic molecular cage is shown in general formula 1, and the chemical formula of the modified polybenzimidazole is shown in general formula 2, wherein... Selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups; R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I. .

[0034] In this invention, the solution treatability of the secondary amine hypervironment organic molecular cage, i.e., its good solubility in organic solvents such as dimethyl sulfoxide, provides a foundation for membrane processing and the uniform dispersion of the secondary amine hypervironment organic molecular cage within the membrane. Simultaneously, the design of the crosslinking reaction between the secondary amine hypervironment organic molecular cage and modified polybenzimidazole also promotes the uniform distribution of the secondary amine hypervironment within the membrane. The modified polybenzimidazole membrane of this invention exhibits a dense morphology, and no aggregation of the secondary amine hypervironment organic molecular cage within the membrane is observed.

[0035] The sub-nanometer-scale inherent cavities of the secondary amine hypervanadium organic molecular cage provide molecular-scale sieving, giving the membrane excellent vanadium-blocking ability. When applied to an all-vanadium redox flow battery, it exhibits extremely high coulombic efficiency (close to 100%) and excellent long-cycle stability.

[0036] The secondary amine hypervast organic molecular cage is rich in nitrogen atoms, which can provide abundant proton transport sites. At the same time, the internal cavity of the cage-like molecule provides a low-resistance transport channel for protons. All of these factors significantly improve the proton conductivity of the membrane.

[0037] This invention obtains an organic molecular cage-modified polymer membrane by uniformly crosslinking discrete, solution-processable porous organic cages with inherent porosity and abundant proton transport sites into a polymer membrane. The resulting membrane offers the following advantages: ① The internal cavities of the cage-like molecules provide low-resistance transport channels for protons, while the numerous proton transport sites on the cages accelerate proton transport, ensuring high proton conductivity. ② The sub-nanometer sieving pores of the cage-like molecules create a hierarchical structure of ion channels, enabling molecular-scale sieving of "effective" channel sizes and ensuring high selectivity of the membrane. ③ The organic cage-like molecules possess solution processability and high compatibility with polymers, allowing for the construction of molecular-scale sieving ion channels within the polymer matrix using a simple solution casting method, demonstrating potential for continuous and large-scale production.

[0038] In a preferred embodiment, the modified polybenzimidazole is selected from one or more compounds of chemical formulas 1-4, and the secondary amine hypermeric organic molecular cage is selected from one or more compounds of chemical formulas 5-7. .

[0039] The halogen on the modified polybenzimidazole side chain reacts with the NH on the secondary amine hypermeric organic molecular cage to form a bond.

[0040] At least one specific embodiment of the present invention also provides a method for preparing an organic molecular cage modified polymer film, comprising: dissolving modified polybenzimidazole in solvent 1 to obtain solution 1; dissolving a secondary amine hyperpigmented organic molecular cage in solvent 2 to obtain solution 2; mixing solution 1 and solution 2 uniformly to obtain a casting solution; subjecting the casting solution to degassing treatment, casting, and drying to form a film (a crosslinking reaction also occurs during the drying process); and post-treating the obtained film to remove uncrosslinked secondary amine hyperpigmented organic molecular cages and residual solvent, thereby obtaining the final product; the chemical formula of the secondary amine hyperpigmented organic molecular cage is shown in general formula 1, and the chemical formula of the modified polybenzimidazole is shown in general formula 2, wherein... Selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups; R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I. .

[0041] In some preferred embodiments, the post-treatment involves immersing the membrane in double-distilled water at room temperature for several hours to remove a small amount of uncrosslinked pyridine amine cages and residual solvent.

[0042] In some preferred embodiments, the modified polybenzimidazole includes, but is not limited to, one or more compounds of formulas 1-4 (PBIOCl, PBICl, CPBI, PBI2OCl), and the secondary amine hypermeric organic molecular cage includes, but is not limited to, one or more compounds of formulas 5-7 (pyridineamine cage, aniline cage, furanamine cage). .

[0043] In some preferred embodiments, solvent 1 is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; solvent 2 is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0044] In some preferred embodiments, the mass ratio of the modified polybenzimidazole to the secondary amine hyperbranch is 5:1 to 5:12. By optimizing the mass ratio of the modified polybenzimidazole to the secondary amine hyperbranch, the number of proton transfer sites in the polymer film modified with the organic molecular cage can be increased, thereby further optimizing the proton conductivity of the film.

[0045] In some preferred embodiments, the drying temperature is 40-100℃; the drying time is 6-24 h; and the drying atmosphere is a vacuum or an inert gas.

[0046] In a preferred embodiment, the preparation method of the modified polybenzimidazole includes: first, dissolving polybenzimidazole and compound A in dimethylacetamide, adding a certain amount of bransted base, and reacting at 0-100℃ (e.g., 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, etc.). After the reaction is complete, the reaction solution is poured into deionized water to precipitate, and then repeatedly washed and dried to obtain the product. The chemical formula of compound A is XRX, where R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I. The chemical reaction equation is as follows: Synthetic route of PBIOCl In some preferred embodiments, the molar ratio of the polybenzimidazole repeating unit to compound A is 1:20-1:150, more preferably 1:80-1:90; the polybenzimidazole is dissolved in dimethylacetamide at a concentration of 5-30 g / L; compound A is dissolved in dimethylacetamide at a concentration of 250-800 g / L; and the molar ratio of the bronzted base to the polybenzimidazole repeating unit is 80:1-1:1.

[0047] In some preferred embodiments, compound A includes, but is not limited to, 1,5-dichloropentane, di(2-chloroethyl) ether, 1-bromo-4-chlorobutane, and 1,2-di(2-chloroethoxy)ethane.

[0048] In some optional embodiments, the bronsted base is selected from one or more of KOH, K2CO3, and NaH.

[0049] In some preferred embodiments, the reaction time in the preparation of modified polybenzimidazole is 5-10 days.

[0050] In some specific embodiments, the repeated washing can be done using water and acetone.

[0051] In a preferred embodiment, the preparation method of the secondary amine hyperphosphine organic molecular cage includes: dissolving hexaaminomethylbenzene and compound B in methanol, stirring the mixture under a non-oxidizing atmosphere at 40-80 °C, and after the reaction is complete, cooling to room temperature, slowly adding sodium borohydride to carry out a reduction reaction, removing the solvent under vacuum, adding water, extracting with chloroform, collecting the chloroform phase, and removing the solvent under vacuum to obtain the secondary amine hyperphosphine organic molecular cage; the chemical formula of compound B is... ,in It is selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups; its chemical reaction equation is as follows: Synthetic route of pyridine amine cage.

[0052] In some preferred embodiments, the molar ratio of hexaaminomethylbenzene and compound B is 1:3-1:4; the hexaaminomethylbenzene is dissolved in methanol at a concentration of 0.1-1 g / L; and the compound B is dissolved in methanol at a concentration of 0.1-3 g / L.

[0053] In some preferred embodiments, the molar ratio of sodium borohydride to compound B is 30:1-80:1.

[0054] In some preferred embodiments, compound B includes, but is not limited to, one or more of pyridine-2,6-bisaldehyde, benzene-2,6-bisaldehyde, furan-2,5-bisaldehyde, etc.

[0055] In some preferred embodiments, the stirring reaction time is 4-24 h.

[0056] In some preferred embodiments, the reduction reaction takes 4-16 hours; the reduction reaction is carried out under stirring.

[0057] In some preferred embodiments, the method further includes immersing the obtained membrane in a dilute sulfuric acid solution until it becomes saturated with acid.

[0058] In some preferred embodiments, the mixing is carried out by stirring; the stirring time is 3-16 h.

[0059] In some specific embodiments, the non-oxidizing atmosphere may be a nitrogen atmosphere or an inert gas atmosphere.

[0060] In some specific embodiments, the concentration of the dilute sulfuric acid solution can be 1-5 mol / L.

[0061] In a specific embodiment, the aforementioned organic molecular cage modified polymer membrane is also provided as a separator in a redox flow battery.

[0062] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but the present invention is not limited to the following embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention.

[0063] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0064] Example 1 (S1) Synthesis of modified polybenzimidazole-PBIOCl (chemical formula as shown in Formula 1): First, 1 g of polybenzimidazole (0.0025 mol) was dissolved in 100 mL of dimethylacetamide, followed by the addition of 10 g of potassium hydroxide (0.179 mol) and 30 g of di(2-chloroethyl) ether (0.211 mol), and the mixture was stirred to dissolve. The reaction solution was allowed to react at room temperature for 7 days, during which time its color changed from brown to yellow. After the reaction was complete, the reaction solution was poured into deionized water to precipitate the product, which was then washed repeatedly with water and acetone. Finally, the product was dried at room temperature to obtain a yellow solid product (PBIOCl). The chemical reaction formula is as follows: Synthesis of a secondary amine hyperproteromeric organic molecular cage—pyridineamine cage (chemical formula as shown in Formula 5): Hexaaminomethylbenzene (1.27 g, 5 mmol) and pyridine-2,6-bis(2.36 g, 17.5 mmol) were dissolved in methanol (1600 mL). The solution was stirred at 65 °C for 12 h under a nitrogen atmosphere. Then, the solution was cooled to room temperature, and sodium borohydride (7 g, 185 mmol) was slowly added, followed by stirring for another 12 h. Finally, the solvent was removed under vacuum, 500 mL of water was added, and the mixture was extracted with chloroform (3 × 250 mL). The chloroform phase was collected, and the solvent was removed under vacuum to obtain a pale yellow solid (pyridineamine cage). The chemical reaction formula is as follows: Membrane preparation: At room temperature, 0.1 g of PBIOCl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.02 g of pyridineamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S1.

[0065] Example 2 The synthesis of PBIOCl and pyridineamine cages is the same as in Example 1.

[0066] Membrane preparation: At room temperature, 0.1 g of PBIOCl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.06 g of pyridineamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60 ℃ under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S2.

[0067] Example 3 The synthesis of PBIOCl and pyridineamine cages is the same as in Example 1.

[0068] Membrane preparation: At room temperature, 0.1 g of PBIOCl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.1 g of pyridineamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S3.

[0069] Example 4 The synthesis of PBIOCl is the same as in Example 1.

[0070] Synthesis of aniline cage (chemical formula as shown in Formula 6): Hexaaminomethylbenzene (1.27 g, 5 mmol) and isophthalaldehyde (3.39 g, 15 mmol) were dissolved in methanol (1600 mL). The solution was stirred at 65 °C for 12 h under a nitrogen atmosphere. Then, the solution was cooled to room temperature, and sodium borohydride (7 g, 185 mmol) was slowly added, followed by stirring for another 12 h. Finally, the solvent was removed under vacuum, 500 mL of water was added, and the mixture was extracted with chloroform (3 × 250 mL). The chloroform phase was collected, and the solvent was removed under vacuum to obtain a white solid (aniline cage). The chemical reaction formula is as follows: Membrane preparation: At room temperature, 0.1 g of PBIOCl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.02 g of aniline cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S4.

[0071] Example 5 The synthesis of PBIOCl is the same as in Example 1.

[0072] Synthesis of furanamine cage (chemical formula as shown in Formula 7): Hexaaminomethylbenzene (31.5 mg, 0.125 mmol) and furan-2,5-bis(2,5-dialdehyde) (54 mg, 0.4375 mmol) were dissolved in methanol / dichloromethane (1:1 v / v, 80 mL). The solution was stirred at 65 °C for 12 h under a nitrogen atmosphere. Then, after cooling the solution to room temperature, sodium borohydride (350 mg, 9.25 mmol) was slowly added, and the reaction was stirred for another 12 h. Finally, the solvent was removed under vacuum, 500 mL of water was added, and the mixture was extracted with chloroform (3 × 250 mL). The chloroform phase was collected, and the solvent was removed under vacuum to obtain a pale yellow solid (furanamine cage). The chemical reaction formula is as follows: Membrane preparation: At room temperature, 0.1 g of PBIOCl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.02 g of furanamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S5.

[0073] Example 6 The synthesis of the pyridine amine cage is the same as in Example 1.

[0074] Synthesis of PBICl (chemical formula as shown in Formula 2): First, 1 g of polybenzimidazole (0.0025 mol) was dissolved in 50 mL of dimethylacetamide. Then, under a nitrogen atmosphere, 10 g of potassium hydroxide (0.179 mol) and 30 g of 1,5-dichloropentane (0.213 mol) were added, and the mixture was stirred until dissolved. The reaction solution was left to react at room temperature for 7 days, during which time its color changed from brown to yellow. After the reaction was complete, the reaction solution was poured into deionized water to precipitate the product, which was then washed repeatedly with water and acetone. Finally, the product was dried at room temperature to obtain a yellow solid product (PBICl). The chemical reaction formula is as follows: Membrane preparation: At room temperature, 0.1 g of PBICl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.02 g of pyridineamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S6.

[0075] Example 7 Synthesis of CPBI (chemical formula as shown in Formula 3): First, dissolve 1 g of polybenzimidazole (0.0025 mol) in 50 mL of dimethylacetamide. Then, under a nitrogen atmosphere, add 0.2 g of sodium hydride (0.008 mol) and 30 g of 1-bromo-4-chlorobutane (0.175 mol) and stir to dissolve. The reaction solution needs to be placed at 0°C for 2 days, during which time its color will change from brown to yellow. After the reaction is complete, pour the reaction solution into deionized water to precipitate the product, and wash repeatedly with water and acetone. Finally, dry at room temperature to obtain the yellow solid product (CPBI). The chemical reaction formula is as follows: The synthesis of the pyridine amine cage is the same as in Example 1.

[0076] Membrane preparation: At room temperature, 0.1 g of CPBI was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.02 g of pyridineamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S7.

[0077] Example 8 Synthesis of PBI2OCl (chemical formula as shown in Formula 4): First, 1 g of polybenzimidazole (0.0025 mol) was dissolved in 100 mL of dimethylacetamide, followed by the addition of 5 g of potassium carbonate (0.036 mol) and 30 g of 1,2-bis(2-chloroethoxy)ethane (0.16 mol), and the mixture was stirred to dissolve. The reaction solution was placed at 80 °C for 48 h, during which time its color changed from brown to yellow. After the reaction was complete, the reaction solution was poured into deionized water to precipitate the product, which was then washed repeatedly with water and acetone. Finally, the product was dried at room temperature to obtain a yellow solid product (PBI2OCl). The chemical reaction formula is as follows: The synthesis of the pyridine amine cage is the same as in Example 1.

[0078] Membrane preparation: At room temperature, 0.1 g of PBI2OCl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.02 g of pyridineamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h. Then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h. During the drying process, a cross-linking reaction occurs, resulting in a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain an organic molecular cage modified polymer membrane S8.

[0079] Comparative Example 1 The synthesis of PBIOCl is the same as in Example 1.

[0080] Membrane preparation: At room temperature, 0.1 g of PBIOCl was dissolved in 10 mL of dimethyl sulfoxide solvent to obtain a homogeneous and transparent solution, which was then stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h; then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h to obtain a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain the modified polybenzimidazole membrane DS1.

[0081] Comparative Example 2 The synthesis of PBIOCl and pyridineamine cages is the same as in Example 1.

[0082] Membrane preparation: At room temperature, 0.1 g of PBIOCl was dissolved in 5 mL of dimethyl sulfoxide solvent, and 0.14 g of pyridineamine cage was also dissolved in 5 mL of dimethyl sulfoxide solvent, both of which yielded homogeneous and transparent solutions. The two solutions were then mixed and stirred at 500 rpm for 12 h to obtain the casting solution. Before casting, the casting solution is degassed for 0.5 h; then, the casting solution is cast in a vacuum oven and dried at 60°C under vacuum for 24 h to obtain a yellow transparent film. The above membrane was immersed in double-distilled water at room temperature for 12 h, and then immersed in a 3 mol / L sulfuric acid solution for 24 h to obtain the organic molecular cage modified polymer membrane DS2.

[0083] The membranes prepared in each embodiment and comparative example were assembled with vanadium redox flow batteries, and their battery performance was tested. The test results are shown in Table 1.

[0084] The assembly method of the vanadium redox flow battery is as follows: stainless steel end plates, polytetrafluoroethylene plate frames, graphite plates and carbon felt are connected to form a flow single cell, providing a site for electrochemical reaction; the single cell is also connected to a storage tank for storing electrolyte and a peristaltic pump to form a vanadium redox flow battery test device. The specific test method is as follows: using double-distilled water as solvent, 3 mol / L sulfuric acid solution as supporting electrolyte, and 1.5 mol / L VO2+ as supporting electrolyte. 2+ / VO2 + and 1.5 mol / L V 2+ / V 3+ The electrolyte consists of positive and negative redox active pairs, respectively. Battery performance was monitored using a blue electrode tester, with the charge / discharge voltage window set at 0.8-1.65 V and the current density at 40 mA / cm². 2 and 200 mA / cm 2 During the test, the electrolyte was protected with nitrogen gas.

[0085] Table 1 shows that the organic molecular cage-modified polymer films S1, S2, and S3 prepared using this method, compared to the modified polybenzimidazole film DS1, all exhibit improved coulombic efficiency, voltage efficiency, and energy efficiency, as well as reduced sheet resistivity. This indicates that the modification with organic molecular cages simultaneously improves the ion selectivity and proton conductivity of the films. In particular, the organic molecular cage-modified polymer films S1, S2, and S3 prepared using the embodiments of this invention, when assembled into flow batteries, exhibit improved performance even at low current densities (40 mA / cm²). 2 Even at high current density (200 mA / cm²) 2 All of these membranes achieved a coulombic efficiency of over 99%, indicating their excellent vanadium blocking ability; simultaneously, at 200 mA / cm²...2 It can perform normal charging and discharging under high current density, and the voltage efficiency can reach up to 80%, indicating that it has excellent proton conductivity.

[0086] Table 1: Performance parameters of membranes prepared in the examples and comparative examples The present invention provides, by way of example, infrared spectra of polymer films prepared in Examples 1-3 and Comparative Examples 1-2, such as... Figure 1 As shown, scanning electron microscope (SEM) images of the cross-sections of the polymer films prepared in Examples 2-3 are as follows. Figure 2 As shown, the polymer films prepared in Example 3 and Comparative Example 1 have a performance of 40-200 mA / cm². 2 The efficiency comparison graph at current density is shown below. Figure 3 As shown, the efficiency and capacity of the polymer film prepared in Example 2 during battery charge-discharge cycles are illustrated in the figure. Figure 4 As shown.

[0087] Specifically, Figure 1 These are the infrared spectra of the polymer films prepared in Examples 1-3 and Comparative Examples 1-2. A comparison of the infrared spectra of Comparative Example 1, Example 1, Example 2, Example 3, and Comparative Example 2 reveals that as the mass of the pyridine amine cage in the film increases, the infrared spectrum at 1597 cm⁻¹... -1 The characteristic peaks belonging to the pyridine amine cage gradually increase in size. Meanwhile, PBIOCl at 655 cm⁻¹... -1 and 584 cm -1 The characteristic absorption peak at the point is caused by the stretching vibration of C-Cl, and it gradually decreases or disappears. This result indicates that the pyridine amine cage and the modified polybenzimidazole (PBIOCl) were successfully crosslinked during the casting process.

[0088] Figure 2 These are scanning electron microscope (SEM) images of cross-sections of the polymer films prepared in Examples 2 and 3. Specifically, Figure (2a) is an SEM image of the polymer film prepared in Example 2 at 4000x magnification, Figure (2b) is an SEM image of the polymer film prepared in Example 2 at 30000x magnification, Figure (2c) is an SEM image of the polymer film prepared in Example 3 at 4000x magnification, and Figure (2d) is an SEM image of the polymer film prepared in Example 3 at 30000x magnification. As can be seen from the figures, the films prepared by this invention are uniform, dense, and non-porous.

[0089] Figure 3 The modified polybenzimidazole membranes prepared in Example 3 and Comparative Example 1 are at 40-300 mA / cm 2Efficiency comparison graph at current density. As shown in the graph, the battery efficiency obtained by S3 is better than that of DS1 at all current densities.

[0090] Figure 4 Figure 4a shows the efficiency and capacity of the polymer film prepared in Example 2 during battery charge-discharge cycles. Figure 4b shows the capacity of the polymer film prepared in Example 2 during cycles.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polymer film modified with an organic molecular cage, characterized in that, A secondary amine hypervironmental organic molecular cage is used as a modifier, and modified polybenzimidazole is used as the polymer film matrix, with the modifier and the polymer matrix linked by covalent bonds; the chemical formula of the secondary amine hypervironmental organic molecular cage is shown in general formula 1, and the chemical formula of the modified polybenzimidazole is shown in general formula 2, wherein... Selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups; R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I. 。 2. The polymer film modified with organic molecular cages as described in claim 1, characterized in that, The modified polybenzimidazole is selected from one or more compounds of chemical formulas 1-4, and the secondary amine hypermeric organic molecular cage is selected from one or more compounds of chemical formulas 5-7. 。 3. A method for preparing a polymer film modified with an organic molecular cage, characterized in that, include: Modified polybenzimidazole was dissolved in solvent 1 to obtain solution 1. Secondary amine hyperpigmented organic molecular cages were dissolved in solvent 2 to obtain solution 2. Solutions 1 and 2 were mixed thoroughly to obtain a casting solution. The casting solution was degassed, cast, and dried to form a film. The resulting film underwent post-treatment to remove uncrosslinked secondary amine hyperpigmented organic molecular cages and residual solvent, thus obtaining the polymer film modified with organic molecular cages. The chemical formula of the secondary amine hyperpigmented organic molecular cage is shown in general formula 1, and the chemical formula of the modified polybenzimidazole is shown in general formula 2. Selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups, where R is selected from... , At least one of the following, where n is 1-8, and X is selected from one or more of Cl, Br, and I. 。 4. The method for preparing the polymer film modified with organic molecular cages as described in claim 3, characterized in that, Solvent 1 is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; solvent 2 is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

5. The method for preparing the polymer film modified with organic molecular cages as described in claim 3, characterized in that, The mass ratio of the modified polybenzimidazole to the secondary amine hypermicrobial organic molecular cage is 5:1-5:12; The modified polybenzimidazole is selected from one or more compounds of chemical formulas 1-4, and the secondary amine hypermeric organic molecular cage is selected from one or more compounds of chemical formulas 5-7. 。 6. The method for preparing the polymer film modified with organic molecular cages as described in claim 3, characterized in that, The drying temperature is 40-100℃; the drying time is 6-24 h; and the drying atmosphere is a vacuum or an inert gas.

7. The method for preparing the polymer film modified with organic molecular cages as described in claim 3, characterized in that, The preparation method of the modified polybenzimidazole includes: first, dissolving polybenzimidazole and compound A in dimethylacetamide, adding a certain amount of Bronsted base, and reacting at 0-100℃. After the reaction is completed, the reaction solution is poured into deionized water to precipitate, and then repeatedly washed and dried to obtain the product; the chemical formula of compound A is XRX, where R is selected from... , At least one of the following, n is 1-8, and X is selected from one or more of Cl, Br, and I.

8. The method for preparing the polymer film modified with organic molecular cages as described in claim 3, characterized in that, The preparation method of the secondary amine hypermeric organic molecular cage includes: dissolving hexaaminomethylbenzene and compound B in methanol, stirring the reaction under a non-oxidizing atmosphere at 40-80 °C, and after the reaction is complete, cooling to room temperature, slowly adding sodium borohydride to carry out a reduction reaction, removing the solvent under vacuum, adding water, extracting with chloroform, collecting the chloroform phase, removing the solvent under vacuum, and obtaining the compound B; the chemical formula of compound B is [insert chemical formula here]. ,in It is selected from one or more of alicyclic, aromatic, aliheterocyclic, and aromatic heterocyclic groups.

9. The method for preparing the polymer film modified with organic molecular cages as described in claim 3, characterized in that, It also includes immersing the obtained organic molecular cage-modified polymer film in a dilute sulfuric acid solution until it is saturated with acid.

10. The application of the polymer membrane modified with organic molecular cages as described in claim 1 or 2, or the polymer membrane modified with organic molecular cages prepared by the preparation method as described in any one of claims 3-9, as a separator in a redox flow battery.

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