Triazinyl imidazole porous covalent organic polymer material, preparation thereof and application of triazinyl imidazole porous covalent organic polymer material in proton exchange membrane of all-vanadium redox flow battery

Abstract

The invention provides a triazinyl imidazole porous covalent organic polymer material, preparation thereof and application of the triazinyl imidazole porous covalent organic polymer material in an all-vanadium redox flow battery proton exchange membrane. The triazinyl imidazole covalent organic polymer with high specific surface area, porosity and high structural stability is synthesized, sulfonation modification is performed on the triazinyl imidazole covalent organic polymer, a proton carrier is loaded after sulfonation modification, and the triazinyl imidazole porous covalent organic polymer material with high proton conductivity is obtained. According to the invention, the triazinyl imidazole porous covalent organic polymer material and sulfonated polyetheretherketone are jointly used for preparing the composite membrane, so that the composite membrane shows excellent vanadium resistance and relatively high ion selectivity, and can stably operate in the all-vanadium redox flow battery, so that the comprehensive performance of the all-vanadium redox flow battery is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of new energy material all-vanadium liquid flow battery proton exchange membrane material, and specifically relates to a triazine imidazole porous covalent organic polymer material and its preparation and application in all-vanadium liquid flow battery proton exchange membrane. Background Art

[0002] As an energy conversion device, all-vanadium liquid flow battery can reduce the pollution problems caused by the combustion of traditional energy, and has the advantages of high safety and cleanliness. It is a new generation of energy storage technology with great application prospects. As one of the most important components in all-vanadium liquid flow battery, the performance of the diaphragm directly affects the overall performance of the liquid flow battery. The most commonly used proton exchange membrane in liquid flow battery is perfluorosulfonic acid series, but it has a high vanadium ion permeability, resulting in poor overall performance of the liquid flow battery. Therefore, it is particularly important to prepare a proton exchange membrane with low vanadium ion permeability.

[0003] Chinese patent document CN107978769A discloses a triazine derivative-based diaphragm for vanadium batteries and a preparation method thereof. First, 2,4-diamino-6-phenyl-1,3,5-triazine and 2-chloroethyl vinyl ether are added to an organic solvent and mixed evenly, stirred and refluxed at 30-40°C for 6-8 hours, then the solvent is removed by rotary evaporation at 40-50°C, and then washed with ether and ethyl acetate for 3-5 times respectively, and finally the solvent is removed by rotary evaporation at 40-50°C to obtain a polymerized triazine derivative; then the above-mentioned polymerized triazine derivative, polymerized monomer, perfluoro-n-propyl vinyl ether, emulsifier and photoinitiator are mixed, dropped on a glass plate, and placed under a 200-250nm ultraviolet lamp under a nitrogen or inert gas atmosphere for 45-55 minutes to cause a polymerization reaction to obtain a polymer film. The polymer membrane prepared by this invention has excellent mechanical properties, anti-ultraviolet aging performance and chemical stability; however, the polymer membrane prepared by this method has low proton conductivity due to the lack of sufficient proton carriers, the reaction is more complicated, and it has not been used in all-vanadium liquid flow batteries to test the comprehensive performance of its composite membrane. Therefore, it is particularly important to find other materials to prepare composite membranes.

[0004] As a porous covalent organic polymer material connected by covalent bonds, functional groups with specific functions can be introduced into the polymer material by pre-design, or a certain group can be post-modified to obtain a functionalized material to meet the needs of certain functions, so it has received more and more attention. Therefore, it is of great significance to develop a porous polymer proton exchange membrane material with high proton conductivity and excellent vanadium resistance to significantly improve the comprehensive performance of all-vanadium redox flow batteries. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a triazine-based imidazole porous covalent organic polymer material and its preparation and application in the proton exchange membrane of an all-vanadium liquid flow battery. The present invention synthesizes a triazine-based imidazole covalent organic polymer with high specific surface area, porosity, and high structural stability, and performs sulfonation modification on the triazine-based imidazole and then loads a proton carrier after the sulfonation modification to obtain a triazine-based imidazole porous covalent organic polymer material with high proton conductivity. The present invention prepares a composite membrane by co-preparing the triazine-based imidazole porous covalent organic polymer material with sulfonated polyetheretherketone, which exhibits excellent vanadium resistance and high ion selectivity, and can stably operate in an all-vanadium liquid flow battery, thereby significantly improving the comprehensive performance of the all-vanadium liquid flow battery.

[0006] The technical solution of the present invention is as follows:

[0007] A triazine imidazole porous covalent organic polymer material, wherein the organic polymer material is triazine imidazole COPs, sulfonated triazine imidazole COPs or sulfonated triazine imidazole COPs loaded with a proton carrier;

[0008] The triazine imidazole COPs and sulfonated triazine imidazole COPs are two-dimensional porous polymers having structural units represented by the following formulas (I) and (II), respectively;

[0009]

[0010]

[0011] Wherein, in formula (II), R1 is a propyl sulfonic acid anion group, and R2 is propyl sulfonic acid.

[0012] Preferably according to the present invention, the proton carrier is sulfonic acid, phosphoric acid or a compound containing a triazine ring.

[0013] According to the preferred embodiment of the present invention, the specific surface area of ​​the organic polymer material is 8-245m 2 / g; the organic polymer material is a crystalline material composed of regular organic structural units.

[0014] The preparation method of the triazine imidazole COPs comprises the steps of: reacting pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine in an organic solvent A, and then filtering, washing and drying to obtain the triazine imidazole COPs.

[0015] Preferably according to the present invention, the organic solvent A is a mixed solvent of toluene, mesitylene and glacial acetic acid; the volume ratio of toluene, mesitylene and glacial acetic acid is 2-20:2:1, preferably 3:2:1; the volume ratio of the amount of pyrene-4,5,9,10-tetraketone to the organic solvent A is 0.02-0.05 mol / L.

[0016] Preferably according to the present invention, the molar ratio of pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine is 1-2:8-10:1, preferably 1.5:9:1.

[0017] Preferably according to the present invention, one to three freeze-pump-thaw cycles are required before the reaction of pyrene-4,5,9,10-tetraketone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine to keep the reaction system in a vacuum state, so as to ensure that the reaction is carried out under oxygen-free and water-free conditions.

[0018] According to the preferred embodiment of the present invention, the reaction temperature is 130-160° C., the reaction time is 6-7 days, and the reaction is carried out under anaerobic, anhydrous and vacuum conditions; preferably, the reaction temperature is 150° C., and the reaction time is 7 days.

[0019] According to the present invention, pyrene-4,5,9,10-tetraone and ammonium acetate need to fully react with 2,4,6-tris(4-formylphenyl)-1,3,5-triazine containing a triazine ring structure to ensure that the synthesized material has a higher proton conductivity.

[0020] Preferably, according to the present invention, the washing is performed by washing with DMF and THF 2-4 times respectively in sequence, and then performing Soxhlet extraction with THF for 45-50 hours.

[0021] Preferably according to the present invention, the drying temperature is 80-120°C.

[0022] The preparation method of the sulfonated triazine imidazole COPs comprises the steps of: fully dispersing the prepared triazine imidazole COPs in an organic solvent B, dropping a 1,3-propane sultone solution, reacting, filtering, washing and drying to obtain the sulfonated triazine imidazole COPs (Im-TFPT-2SO3H).

[0023] Preferably according to the present invention, the organic solvent B is acetonitrile; and the mass ratio of the triazine imidazole COPs to the organic solvent B is 5 g / L-8 g / L.

[0024] Preferably according to the present invention, the solvent used for the 1,3-propane sultone solution is acetonitrile, and the mass concentration of the 1,3-propane sultone solution is 0.5-2 g / mL.

[0025] Preferably, according to the present invention, the mass ratio of the triazine imidazole COPs to 1,3-propane sultone is 1:20-40; preferably, the mass ratio of the triazine imidazole COPs to 1,3-propane sultone is 1:20-30.

[0026] According to the present invention, preferably, the reaction temperature is 40-80°C, and the reaction time is 1 day to 3 days; preferably, the reaction temperature is 60-70°C, and the reaction time is 2 days to 3 days.

[0027] Preferably according to the present invention, the washing is done with acetone; and the drying temperature is 60-100°C.

[0028] The preparation method of the above-mentioned sulfonated triazine imidazole COPs loaded with proton carrier comprises the steps of:

[0029] The sulfonated triazine imidazole COPs prepared above are mixed with a proton carrier solution, reacted, filtered, washed and dried to obtain the sulfonated triazine imidazole COPs loaded with the proton carrier.

[0030] According to the preferred embodiment of the present invention, the proton carrier solution is a 2-4 mol / L phosphoric acid aqueous solution. The phosphoric acid molecules and the nitrogen atoms or sulfonate groups in the triazine ring structure are anchored in the COPs pores through hydrogen bonds. The obtained product is referred to as PA@Im-TFPT-2SO3H.

[0031] Preferably according to the present invention, the mass ratio of the sulfonated triazine imidazole COPs to the volume ratio of the proton carrier solution is 5-10 g / L.

[0032] According to the preferred embodiment of the present invention, the reaction conditions are as follows: stirring and reacting at 60-80° C. for 12-24 h under vacuum conditions; then stirring and reacting at 60-80° C. under normal pressure for 12-24 h.

[0033] According to the present invention, the longer the reaction time, the higher the proton conductivity of the sulfonated triazine imidazole COPs loaded with proton carriers, and when the material is reacted for more than 12 hours under vacuum or normal pressure conditions, respectively, the proton conductivity no longer increases.

[0034] Application of the above triazine imidazole porous covalent organic polymer material in the proton exchange membrane of all-vanadium liquid flow battery.

[0035] Preferably, according to the present invention, a method for applying triazine-based imidazole porous covalent organic polymer material to prepare a proton exchange membrane for an all-vanadium liquid flow battery comprises the steps of: fully dispersing the triazine-based imidazole porous covalent organic polymer material in a treated sulfonated polyetheretherketone solution, reacting, forming a membrane, and washing to obtain a proton exchange membrane for an all-vanadium liquid flow battery.

[0036] Preferably, the solvent used for the treated sulfonated polyetheretherketone solution is DMF, and the concentration of the treated sulfonated polyetheretherketone solution is 0.05-0.5 g / mL.

[0037] Preferably, the preparation method of the treated sulfonated polyetheretherketone is as follows: adding dried sulfonated polyetheretherketone to a concentrated sulfuric acid solution with a mass concentration of 98%, stirring and reacting at 50-70°C for 5-7h, pouring into deionized water, washing the obtained solid with deionized water until neutral, and drying to obtain the treated sulfonated polyetheretherketone. The mass ratio of the sulfonated polyetheretherketone to the volume ratio of the concentrated sulfuric acid solution is 0.05-1g / mL.

[0038] Preferably, the mass of the triazine-based imidazole porous covalent organic polymer material is 1% to 30% of the total mass of the triazine-based imidazole porous covalent organic polymer material and the treated sulfonated polyetheretherketone, preferably 10% to 30%, and most preferably 30%. When the mass of the triazine-based imidazole porous covalent organic polymer material is 10% to 30% of the total mass of the triazine-based imidazole porous covalent organic polymer material and the treated sulfonated polyetheretherketone, the overall performance is good and the surface is relatively complete; when the mass of the triazine-based imidazole porous covalent organic polymer material is 30% of the total mass of the triazine-based imidazole porous covalent organic polymer material and the treated sulfonated polyetheretherketone, the overall performance of the composite membrane is the best.

[0039] Preferably, the reaction temperature is 40-80° C., the reaction time is 5-7 h, and the reaction is carried out under stirring conditions.

[0040] Preferably, the film forming method is as follows: the reaction solution obtained by the reaction is poured onto tin foil after air is removed, dried naturally, and then immersed in deionized water to peel off to obtain a thin film.

[0041] Preferably, the washing method is as follows: the film obtained by film formation is soaked in a sulfuric acid aqueous solution with a mass concentration of 2-4 mol / L, deionized water, and a 2-4 mol / L phosphoric acid aqueous solution for 12 to 36 hours respectively to obtain a proton exchange membrane for an all-vanadium redox flow battery. The longer the soaking time, the higher the proton conductivity. When the film is soaked in the phosphoric acid aqueous solution for more than 24 hours, the proton conductivity no longer increases.

[0042] The technical features and beneficial effects of the present invention are as follows:

[0043] 1. The present invention uses pyrene-4,5,9,10-tetraketone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine as raw materials to prepare COPs containing imidazole and triazine ring structures through a three-component reaction one-pot method. The preparation method is simple and suitable for industrial production. The ratio of pyrene-4,5,9,10-tetraketone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and the organic solvent A used need to be appropriate. If the ratio or the type of organic solvent A is not appropriate, the triazine-based imidazole COPs with the structure and performance of the present invention cannot be obtained. At the same time, the reaction temperature and time also need to be appropriate to obtain the triazine-based imidazole COPs with the structure and performance of the present invention.

[0044] 2. The triazine imidazole COPs obtained by the present invention can be sulfonated with 1,3-propane sultone to obtain sulfonated triazine imidazole COPs. The sulfonated triazine imidazole COPs have sulfonate functional groups on their skeletons. The presence of such groups makes these functionalized COPs have proton conductivity. In addition, the presence of triazine ring structure and sulfonic acid group can enhance the adsorption performance of COPs material for proton carriers. In order to further enhance the mass transfer performance of the material, the sulfonated triazine imidazole COPs can continue to load proton carriers.

[0045] 3. The triazine-based imidazole porous covalent organic polymer material prepared by the present invention has a porous structure, a large specific surface area, regular pores, and crystallinity. The triazine-based imidazole porous covalent organic polymer material prepared by the present invention has high structural stability and excellent chemical stability, and can stably exist in various common organic solvents (N, N-dimethylformamide, tetrahydrofuran, acetone, acetonitrile, ethanol, etc.) and water.

[0046] 4. When preparing the sulfonated triazine imidazole COPs, the mass ratio of 1,3-propane sultone to triazine imidazole COPs must be greater than or equal to 20, otherwise the sulfonic acid groups cannot be completely grafted into the framework material, affecting the proton conductivity of the material.

[0047] 5. The triazine-based imidazole porous covalent organic polymer material prepared by the present invention exhibits good proton conductivity under a wide range of temperature and humidity conditions; the proton conductivity can reach 7.78×10 -2 S cm -1 ; The activation energy of proton conduction is low, indicating that the barrier to proton conduction of this type of material is small.

[0048] 6. The triazine imidazole porous covalent organic polymer material of the present invention and sulfonated polyetheretherketone are used to prepare a proton exchange membrane with good vanadium resistance and high proton conductivity, and can be stably operated in an all-vanadium redox flow battery to significantly improve the comprehensive performance of the all-vanadium redox flow battery. The proton conductivity of the proton exchange membrane is as low as 1.77×10 -1S cm -1 , and because the triazine imidazole covalent organic framework has a rigid structure, the swelling rate of the proton exchange membrane is reduced, the vanadium barrier performance is excellent, and the ion selectivity reaches 7.45×10 10 mS s cm -3 , the overall performance is good.

[0049] 7. When the present invention prepares a proton exchange membrane, as the proportion of the mass of the triazine imidazole porous covalent organic polymer material increases, the vanadium resistance is excellent and the proton conductivity increases. When the mass of the triazine imidazole porous covalent organic polymer material accounts for 30% of the total mass of the triazine imidazole porous covalent organic polymer material and the sulfonated polyetheretherketone, the performance is optimal. When it exceeds 30%, the composite membrane is easy to break and the mechanical properties are poor. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The powder X-ray diffraction spectrum of Im-TFPT-COP synthesized in Example 1 and the powder X-ray diffraction spectrum of simulated AA stacking, AB stacking and ABC stacking;

[0051] Figure 2 is the Fourier infrared spectrum of Im-TFPT-COP and raw materials synthesized in Example 1;

[0052] Figure 3 is a comparative powder X-ray diffraction spectrum of Im-TFPT-COP synthesized in Example 1 after solvent treatment;

[0053] Figure 4 It is the nitrogen adsorption-desorption isotherms of Im-TFPT-COP synthesized in Example 1, Im-TFPT-2SO3H synthesized in Example 2, and PA@Im-TFPT-2SO3H synthesized in Example 3;

[0054] Figure 5 It is the Fourier transform infrared spectra of Im-TFPT-2SO3H synthesized in Example 2, PA@Im-TFPT-2SO3H synthesized in Example 3 and Im-TFPT-COP synthesized in Example 1;

[0055] Figure 6 These are the Nyquist diagrams of Im-TFPT-COP synthesized in Example 1 at different temperatures (a), the Nyquist diagrams of Im-TFPT-2SO3H synthesized in Example 2 at different temperatures (b), and the Nyquist diagrams of PA@Im-TFPT-2SO3H synthesized in Example 3 at different temperatures (c).

[0056] Figure 7It is the Arrhenius plot of proton conduction and temperature of Im-TFPT-COP synthesized in Example 1, Im-TFPT-2SO3H synthesized in Example 2, and PA@Im-TFPT-2SO3H synthesized in Example 3.

[0057] Figure 8 It is the Nyquist plot of Im-TFPB-COP synthesized in Comparative Example 4 at different temperatures.

[0058] Fig. 9 It is the conductivity diagram of PA@Im-TFPT-2SO3H / SPEEK(X) (X represents the weight ratio of PA@Im-TFPT-2SO3H in the composite membrane) synthesized in Example 4, SPEEK, and Nafion 212 membrane.

[0059] Fig.10 These are the vanadium ion permeability and ion selectivity spectra of the PA@Im-TFPT-2SO3H / SPEEK(X), SPEEK, and Nafion 212 membranes synthesized in Example 4.

[0060] Fig.11 The coulombic efficiency (a), voltage efficiency (b), and energy efficiency spectra (c) of the PA@Im-TFPT-2SO3H / SPEEK (30%) and Nafion 212 membrane synthesized in Example 4 are shown.

[0061] Fig.12 This is the long-term test spectrum of the PA@Im-TFPT-2SO3H / SPEEK (30%) membrane and Nafion 212 membrane synthesized in Example 4. DETAILED DESCRIPTION

[0062] The present invention is further described below by specific examples in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited thereto. The raw materials used in the examples can be obtained from commercial sources unless otherwise specified; the methods used are conventional methods unless otherwise specified, and the equipment used are conventional equipment unless otherwise specified.

[0063] In the examples, the 1200-mesh sulfonated polyetheretherketone used was purchased from Beijing Mairida Technology Co., Ltd.

[0064] Example 1

[0065] A preparation method of triazine imidazole COPs, namely Im-TFPT-COP, is as follows: pyrene-4,5,9,10-tetraketone (0.045 mmol), ammonium acetate (0.27 mmol) and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (0.03 mmol) are mixed and placed in a glass tube, and then solvent toluene (0.6 mL), mesitylene (0.4 mL) and glacial acetic acid (0.2 mL) are added, and ultrasonic mixing is performed. The reaction material was frozen into a solid under liquid nitrogen at -78°C, evacuated to a vacuum, and then thawed until the reaction material was a liquid. This process was repeated three times. After the three freeze-evacuate-thaw cycles, the glass tube was kept in a vacuum state, the tube was sealed, and then reacted in an oven at 150°C for 7 days (the reactant was gradually heated from the low temperature after thawing to 150°C for reaction). The solid was filtered, washed three times with DMF and THF respectively, then transferred to a Soxhlet extractor and washed with THF for 48 hours, and dried at 100°C to obtain a brown Im-TFPT-COP product with a molar yield of 89%.

[0066] The Fourier transform infrared spectra of Im-TFPT-COP synthesized in this example and the raw materials pyrene-4,5,9,10-tetraketone (PyTO), ammonium acetate (NH4OAc) and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT) are shown in Figure 2. Figure 2 As shown in the figure, it can be seen that the target product is successfully prepared by the present invention.

[0067] Study on the crystallinity of Im-TFPT-COP:

[0068] The crystallinity of Im-TFPT-COP was tested by powder diffractometer. The powder X-ray diffraction spectrum was similar to the simulated AA stacking and AB stacking powder X-ray diffraction spectrum. Figure 1 As shown. This shows that Im-TFPT-COP has crystallinity.

[0069] Chemical stability test of Im-TFPT-COP:

[0070] Im-TFPT-COP was immersed in DMF, MeCN, THF, acetone, ethanol solution and water at room temperature for 12 h, and the chemical stability of Im-TFPT-COP after immersion in the above solutions was tested by powder diffractometer. The X-ray diffraction spectrum is shown in Figure 3 The results show that the peak shape of Im-TFPT-COP powder can be well maintained after being treated with these organic solvents, which shows their good structural stability.

[0071] Study on the Porosity of Im-TFPT-COP:

[0072] Weigh about 100 mg of sample, activate it at 120℃ for 12 hours, and then test the nitrogen 77K isotherm adsorption curve of the sample by gas adsorption instrument. The nitrogen adsorption and desorption isotherm is as follows: Figure 4 The results show that the synthesized Im-TFPT-COP has a higher specific surface area (245m 2 / g).

[0073] Example 2

[0074] A preparation method of a sulfonated triazine imidazole COPs (abbreviated as Im-TFPT-2SO3H) is as follows:

[0075] Take 200 mg of Im-TFPT-COP powder prepared by the method of Example 1 and fully disperse it in 30 mL of acetonitrile solution, and add a mixed solution of 1,3-propanesulfonate (5 g) and acetonitrile (5 mL) drop by drop. After the addition is completed, react at 70°C for 48 hours, filter, and then thoroughly wash the solid with acetone. Finally, the obtained sample is vacuum dried at 100°C for 24 hours to obtain dry Im-TFPT-2SO3H.

[0076] The Fourier transform infrared spectrum of Im-TFPT-2SO3H synthesized in this example is as follows Figure 5 As shown, compared with Im-TFPT-COP, it can be seen that the sulfonated triazine imidazole COPs were successfully prepared in this example.

[0077] Nitrogen adsorption-desorption isotherms Figure 4 As shown in the figure, its specific surface area is 85.94m 2 / g.

[0078] Example 3

[0079] A preparation method of a phosphoric acid-sulfonated triazine imidazole COPs (abbreviated as PA@Im-TFPT-2SO3H) is as follows:

[0080] Take 200 mg of Im-TFPT-2SO3H prepared by the method of Example 2, place the sample in 30 mL of 3 mol / L phosphoric acid aqueous solution under vacuum conditions and stir at 70°C for 12 h, then continue stirring at 70°C for 12 h at normal pressure, filter, and then thoroughly wash the solid with distilled water until the eluent reaches pH = 7, and then dry the obtained sample at 120°C for 24 hours to obtain dry PA@Im-TFPT-2SO3H.

[0081] The Fourier transform infrared spectrum of PA@Im-TFPT-2SO3H synthesized in this example is shown in Figure 5As shown, compared with Im-TFPT-COP and Im-TFPT-2SO3H, this example successfully prepared triazine imidazole COPs loaded with phosphoric acid-sulfonation modification.

[0082] Nitrogen adsorption-desorption isotherms Figure 4 As shown in the figure, its specific surface area is 8.72m 2 / g.

[0083] Example 4

[0084] A composite membrane loaded with phosphoric acid-sulfonated triazine imidazole COPs and SPEEK, namely PA@Im-TFPT-2SO3H / SPEEK (30%), is prepared as follows: 0.1106 g of PA@Im-TFPT-2SO3H prepared by the method of Example 3 is placed in a round-bottom flask, and then 2 mL of the treated sulfonated polyetheretherketone solution is added to the round-bottom flask, and ultrasonically mixed evenly. The mixed solution is stirred at 60°C for 6 hours, and after evacuating the air, it is poured onto tin foil. After natural drying, it can be soaked in deionized water to peel off the membrane, and then the membrane is soaked in dilute sulfuric acid with a mass concentration of 3 mol / L, deionized water, and 3 mol / L phosphoric acid aqueous solution for 24 hours each, and finally stored in deionized water for use.

[0085] The preparation method of the treated sulfonated polyetheretherketone solution is as follows: 5g of sulfonated polyetheretherketone (PEEK) solid is dried at 100°C for 24h, poured into 50mL of concentrated sulfuric acid solution with a mass concentration of 98%, stirred at 60°C for 6h, then poured into deionized water, and the solid is washed with a large amount of deionized water until neutral, and dried at 100°C for 12h to obtain the treated sulfonated polyetheretherketone solid. 1.29g of the treated sulfonated polyetheretherketone solid is dissolved in 10mL of DMF to prepare the treated sulfonated polyetheretherketone solution.

[0086] Example 5

[0087] A preparation method of a composite membrane loaded with phosphoric acid-sulfonated triazine imidazole COPs and SPEEK, namely PA@Im-TFPT-2SO3H / SPEEK (10%), is as described in Example 4, except that the mass of the added PA@Im-TFPT-2SO3H is 0.0286 g.

[0088] Example 6

[0089] A preparation method of a composite membrane loaded with phosphoric acid-sulfonated triazine imidazole COPs and SPEEK, namely PA@Im-TFPT-2SO3H / SPEEK (20%), is as described in Example 4, except that the mass of the added PA@Im-TFPT-2SO3H is 0.0645 g.

[0090] Example 7

[0091] A composite membrane loaded with phosphoric acid-sulfonated triazine imidazole COPs and SPEEK, namely, a preparation method of PA@Im-TFPT-2SO3H / SPEEK (25%), as described in Example 4, wherein the mass of the added PA@Im-TFPT-2SO3H is 0.086 g.

[0092] Comparative Example 1

[0093] A method for preparing triazine imidazole COPs is as described in Example 1, except that the solvent toluene is replaced by dioxane (0.6 mL); the other steps and conditions are the same as in Example 1. The molar yield is 50%, and the BET surface area is 180 m 2 / g, no obvious crystallization peak was observed.

[0094] It can be seen from this comparative example that the choice of solvent type has an important influence on the yield, BET surface area and crystallinity of the target product.

[0095] Comparative Example 2

[0096] A method for preparing triazine imidazole COPs is as described in Example 1, except that the heating time is 5 days; the other steps and conditions are the same as in Example 1. The molar yield is 75%, and no obvious peak signal is observed in the powder diffraction peak test.

[0097] It can be seen from this comparative example that the reaction time is not suitable, and the yield and crystallinity of the obtained target product are reduced.

[0098] Comparative Example 3

[0099] A method for preparing triazine imidazole COPs is as described in Example 1, except that the heating temperature is 120° C. and the other steps and conditions are the same as in Example 1. The molar yield is 69%, and no obvious peak signal is observed in the powder diffraction peak test.

[0100] It can be seen from this comparative example that the reaction temperature is not suitable, and the yield and crystallinity of the obtained target product are reduced.

[0101] Comparative Example 4

[0102] A triphenylimidazole COPs, namely Im-TFPB-COP, was prepared as follows: as described in Example 1, except that 1,3,5-tris(p-formylphenyl)benzene monomer replaced 2,4,6-tris(4-formylphenyl)-1,3,5-triazine; other steps and conditions were the same as in Example 1. The molar yield was 80%, and the conductivity was 1.16×10 -6 S / cm.

[0103] It can be seen from this comparative example that the selection of monomers has an important influence on the proton conductivity of the target product.

[0104] Comparative Example 5

[0105] A method for preparing sulfonated triazine imidazole COPs is as described in Example 2, except that a mixture of 1,3-propane sultone (2 g) and acetonitrile (5 mL) is added dropwise; the other steps and conditions are the same as those in Example 2. The conductivity of the COPs at 353 K and 98% humidity is 2.68×10 -3 S cm -1 .

[0106] It can be seen from this comparative example that the amount of 1,3-propane sultone used has an important influence on the proton properties of the target product.

[0107] Comparative Example 6

[0108] A SPEEK membrane, the preparation method is as described in Example 4, except that PA@Im-TFPT-2SO3H is not added; the other steps and conditions are the same as Example 4.

[0109] Comparative Example 7

[0110] A preparation method of a composite membrane loaded with phosphoric acid-sulfonated triazine imidazole COPs and SPEEK, namely PA@Im-TFPT-2SO3H / SPEEK (35%), is as described in Example 4, except that the mass of the added PA@Im-TFPT-2SO3H is 0.1389 g.

[0111] Test example

[0112] Test of proton conductivity properties:

[0113] The AC impedance of the original thin sheets pressed from the materials prepared in Examples 1-3 was tested at a certain humidity and temperature using an electrochemical workstation, and the conductivity value was calculated using the formula σ=L / (RA), where σ is the proton conductivity, L is the thickness of the thin sheet membrane, A is the area of ​​the membrane, and R is the resistance.

[0114] The AC impedance of the composite membrane material prepared in Example 4 was tested in deionized water at room temperature using an electrochemical workstation. The formula σ = d / (W s L s R) to calculate the conductivity value, where σ is the proton conductivity, d is the distance between the two platinum electrodes, and W s is the width of the membrane, L s is the thickness of the film and R is the resistance.

[0115] Keeping the humidity (98% RH) constant, changing the temperature to 303K, 313K, ..., 353K, etc., the AC impedance diagrams of the materials prepared in Examples 1-3 were measured, respectively as shown in Figure 6 (a), (b), and (c) are shown; the corresponding resistance values ​​can be read out through software fitting, and the proton conductivity can be calculated. Figure 6 The results showed that the higher the temperature, the higher the proton conductivity.

[0116] Depend on Figure 6 It can be seen that under the conditions of 353K and 98%RH, the PA@Im-TFPT-2SO3H synthesized in Example 3 has a very high proton conductivity, which can reach 7.78×10 -2 The proton conductivity of Im-TFPT-COP synthesized in Example 1 is 8.83×10 -6 S / cm, and the proton conductivity of Im-TFPT-2SO3H synthesized in Example 2 is 3.38×10 -3 S / cm. On the other hand, Figure 7 It can be seen that the activation energy of proton conduction of this type of material is relatively low, and is no higher than 0.4 eV, which indicates that the barrier to proton conduction of this type of material is relatively small, and the mass transfer process is mainly carried out through a jumping mechanism.

[0117] Depend on Figure 8 It can be seen that after using 1,3,5-tris(p-formylphenyl)benzene monomer instead of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, the proton conductivity of Im-TFPB-COP is 1.16×10 -6 S / cm, proving that the choice of monomer has an important influence on the proton conductivity of the target product.

[0118] Depend on Fig. 9 It can be seen that the PA@Im-TFPT-2SO3H / SPEEK (30%) synthesized in Example 4 has a very high proton conductivity, which can reach 1.77×10 -1 S / cm, which has a higher proton conductivity than Examples 5-7 and Comparative Example 6.

[0119] Vanadium ion permeability test:

[0120] The vanadium ion permeability (P) indicates the vanadium resistance of the membrane, which directly affects the coulombic efficiency of the all-vanadium flow battery (VFB). 2+ Permeability, add 30mL of 1.5mol L -1 VO 2+ 3molL -1To balance the osmotic pressure, add 30 mL of 1.5 mol L H2SO4 aqueous solution to the right diffusion cell. -1 3 mol L of MgSO4 -1 H2SO4 aqueous solution. The membrane sample was sandwiched in the middle of the diffusion cell, and the solutions on both sides were continuously magnetically stirred to reduce concentration polarization. Samples were taken from the right diffusion cell every 2 hours, and the absorbance of the samples was measured using a UV spectrophotometer. 2+ The standard curve of concentration and absorbance can be used to obtain the VO diffused to the MgSO4 side at different times. 2+ Concentration. Then, VO can be calculated by the formula 2+ Permeability.

[0121]

[0122] Among them, V B represents the volume of MgSO4 solution, A and L are the effective area and thickness of the membrane respectively, C A is the VO in the left diffusion cell 2+ concentration, t is the diffusion time, C B (t) is the VO in the right diffusion cell 2+ The concentration changes with diffusion time. The ion selectivity (S) of the membrane is determined by the proton conductivity and the vanadium ion permeability, which shows the difference in the speed of proton and vanadium ion transmission in the membrane. S can be calculated by the formula. S = σ / P, where σ is the proton conductivity and P is VO 2+ Permeability.

[0123] Depend on Fig.10 It can be seen that the PA@Im-TFPT-2SO3H / SPEEK (30%) synthesized in Example 4 has excellent vanadium resistance and high ion selectivity, reaching 2.37×10 -9 cm 2 s -1 The vanadium ion permeability is 7.45×10 10 mS s cm -3 As the weight of PA@Im-TFPT-2SO3H increases, the vanadium resistance and proton conductivity increase. When the weight accounts for 35% of the composite membrane, the membrane is easily broken and the mechanical properties are reduced.

[0124] Depend on Fig.11 It can be seen that the composite membrane was assembled into a 3.5-valent vanadium ion electrolyte for the positive and negative electrodes, and nitrogen was filled into the negative electrode for 10 min. Then, the electrolyte was charged at a current density of 80 mA cm -2 The first activation was carried out with cut-off voltages of 0.8 V and 1.65 V. After activation, the prepared membrane was able to withstand a current density of 60 to 100 mA cm -2When running at the same time, PA@Im-TFPT-2SO3H / SPEEK (30%) synthesized in Example 4 has high energy efficiency and excellent comprehensive performance compared with Nafion 212 membrane.

[0125] The composite membrane was assembled to the positive and negative electrodes in a 3.5-valent vanadium ion electrolyte, and nitrogen was filled into the negative electrode for 10 min. Then, the electrolyte was charged at a current density of 80 mA cm -2 The first activation was carried out with cut-off voltages of 0.8 V and 1.65 V. After activation, the -2 At a current density of , the single cell performance test of the PA@Im-TFPT-2SO3H / SPEEK (30%) composite membrane synthesized in Example 4 was carried out, and the Nafion 212 membrane was used for comparison. Fig.12 As shown, the synthesized composite membrane can maintain a high energy efficiency within 50 cycles, which indicates that this type of material has high stability in use and performs better than Nafion212 membrane.

Claims

1. A triazine imidazole porous covalent organic polymer material, characterized in that: The organic polymer material is triazine imidazole COPs, sulfonated triazine imidazole COPs or sulfonated triazine imidazole COPs loaded with proton carriers; The triazine imidazole COPs and sulfonated triazine imidazole COPs are two-dimensional porous polymers having structural units represented by the following formulas (I) and (II), respectively; Wherein, in formula (II), R1 is a propyl sulfonic acid anion group, and R2 is propyl sulfonic acid.

2. The triazine imidazole porous covalent organic polymer material according to claim 1, characterized in that: Includes one or more of the following conditions: i. The proton carrier is sulfonic acid, phosphoric acid or a compound containing a triazine ring; ii. The specific surface area of ​​the organic polymer material is 8-245m 2 / g; the organic polymer material is a crystalline material composed of regular organic structural units.

3. The method for preparing triazine imidazole COPs as claimed in claim 1-2, comprising the steps of: reacting pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine in an organic solvent A, and then filtering, washing and drying to prepare triazine imidazole COPs.

4. The method for preparing triazine imidazole COPs according to claim 3, characterized in that: Includes one or more of the following conditions: i. The organic solvent A is a mixed solvent of toluene, mesitylene and glacial acetic acid; the volume ratio of toluene, mesitylene and glacial acetic acid is 2-20:2:1, preferably 3:2:1; the volume ratio of the amount of pyrene-4,5,9,10-tetraketone to the organic solvent A is 0.02-0.05 mol / L; ii. the molar ratio of pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine is 1-2:8-10:1, preferably 1.5:9:1; iii. Before the reaction of pyrene-4,5,9,10-tetraketone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, one to three freezing-evacuation-thawing cycles are required to keep the reaction system in a vacuum state to ensure that the reaction is carried out under oxygen-free and water-free conditions; iv. The reaction temperature is 130-160°C, the reaction time is 6-7 days, and the reaction is carried out under anaerobic, anhydrous and vacuum conditions; preferably, the reaction temperature is 150°C, and the reaction time is 7 days.

5. The method for preparing the sulfonated triazine imidazole COPs as claimed in claim 1 or 2, comprising the steps of: fully dispersing the triazine imidazole COPs in an organic solvent B, dropwise adding a 1,3-propane sultone solution, reacting, filtering, washing, and drying to obtain the sulfonated triazine imidazole COPs (Im-TFPT-2SO3H).

6. The method for preparing sulfonated triazine imidazole COPs according to claim 5, characterized in that: Includes one or more of the following conditions: i. The organic solvent B is acetonitrile; the mass ratio of the triazine imidazole COPs to the organic solvent B is 5 g / L-8 g / L; ii. The solvent used for the 1,3-propane sultone solution is acetonitrile, and the mass concentration of the 1,3-propane sultone solution is 0.5-2 g / mL; iii. The mass ratio of the triazine imidazole COPs to 1,3-propane sultone is 1:20-40; preferably, the mass ratio of the triazine imidazole COPs to 1,3-propane sultone is 1:20-30; iv. The reaction temperature is 40-80°C, and the reaction time is 1 day to 3 days; preferably, the reaction temperature is 60-70°C, and the reaction time is 2 days to 3 days.

7. The method for preparing the sulfonated triazine imidazole COPs loaded with proton carriers as claimed in claim 1 or 2, comprising the steps of: The sulfonated triazine imidazole COPs and the proton carrier solution are mixed, reacted, filtered, washed and dried to obtain the sulfonated triazine imidazole COPs loaded with the proton carrier.

8. The method for preparing sulfonated triazine imidazole COPs according to claim 7, characterized in that: Includes one or more of the following conditions: i. The proton carrier solution is a 2-4 mol / L phosphoric acid aqueous solution; ii. The mass ratio of the sulfonated triazine imidazole COPs to the volume ratio of the proton carrier solution is 5-10 g / L; iii. The reaction conditions are as follows: vacuum condition, stirring reaction at 60-80°C for 12-24h; then normal pressure, stirring reaction at 60-80°C for 12-24h.

9. Use of the triazine imidazole porous covalent organic polymer material as claimed in claim 1 or 2 in a proton exchange membrane of an all-vanadium liquid flow battery.

10. The use according to claim 9, characterized in that: The method for preparing a proton exchange membrane of an all-vanadium redox flow battery using a triazine-based imidazole porous covalent organic polymer material comprises the following steps: the triazine-based imidazole porous covalent organic polymer material is fully dispersed in a treated sulfonated polyetheretherketone solution, and the all-vanadium redox flow battery proton exchange membrane is obtained through reaction, film formation, and washing; Preferably, the solvent used for the treated sulfonated polyetheretherketone solution is DMF, and the concentration of the treated sulfonated polyetheretherketone solution is 0.05-0.5g / mL; the preparation method of the treated sulfonated polyetheretherketone is as follows: adding dried sulfonated polyetheretherketone to a concentrated sulfuric acid solution with a mass concentration of 98%, stirring and reacting at 50-70°C for 5-7h, pouring into deionized water, washing the obtained solid with deionized water until neutral, and drying to obtain the treated sulfonated polyetheretherketone; the mass ratio of sulfonated polyetheretherketone to concentrated sulfuric acid solution is 0.05-1g / mL; Preferably, the mass of the triazine imidazole porous covalent organic polymer material is 1% to 30% of the total mass of the triazine imidazole porous covalent organic polymer material and the treated sulfonated polyetheretherketone, preferably 10% to 30%, and most preferably 30%; The reaction temperature is 40-80°C, the reaction time is 5-7h, and the reaction is carried out under stirring conditions.

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