A triazine-based imidazole porous covalent organic polymer material and its preparation and application in a proton exchange membrane of a vanadium redox flow battery

Abstract

The application provides a triazine-based imidazole porous covalent organic polymer material and a preparation and application thereof in a proton exchange membrane of a vanadium redox flow battery. A triazine-based imidazole covalent organic polymer with high specific surface area, porosity and high structural stability is synthesized, and the triazine-based imidazole covalent organic polymer is modified by sulfonation and then loaded with a proton carrier to obtain a triazine-based imidazole porous covalent organic polymer material with high proton conductivity. The triazine-based imidazole porous covalent organic polymer material is prepared into a composite membrane together with sulfonated polyether ether ketone, and the composite membrane exhibits excellent vanadium resistance and high ion selectivity, and can be stably operated in the vanadium redox flow battery, so that the comprehensive performance of the vanadium redox flow battery is significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of novel energy material all-vanadium redox flow battery proton exchange membrane material, and particularly relates to a triazine-based imidazole porous covalent organic polymer material and preparation and application thereof in all-vanadium redox flow battery proton exchange membrane. BACKGROUND

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

[0003] Chinese patent document CN107978769A discloses a vanadium battery based on triazine derivative diaphragm 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 uniformly, stirred and refluxed at 30-40 DEG C for 6-8 hours, then the solvent is removed by rotary evaporation at 40-50 DEG C, then washed with ether and ethyl acetate for 3-5 times respectively, and finally the solvent is removed by rotary evaporation at 40-50 DEG C to prepare a polymer type triazine derivative. Then the polymer type triazine derivative, polymer monomer, perfluoro-n-propyl vinyl ether, emulsifier and photoinitiator are mixed and dropped on a glass plate, and then placed under a 200-250 nm ultraviolet lamp in a nitrogen or inert gas atmosphere for 45-55 minutes to generate a polymer film. The polymer film prepared by the method has excellent mechanical properties, ultraviolet aging resistance and chemical stability; but the polymer film prepared by the method has low proton conductivity due to lack of sufficient proton carriers, the reaction is relatively complex, and the comprehensive performance of the composite membrane is not tested in the all-vanadium redox flow battery, so it is particularly important to find other materials to prepare a composite membrane.

[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 functional material, so as to meet the needs of certain functions, and thus it has attracted 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 the all-vanadium redox flow battery. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a triazine-based imidazole porous covalent organic polymer material and its preparation and application in a proton exchange membrane of a vanadium redox flow battery. The present application synthesizes a triazine-based imidazole covalent organic polymer with high specific surface area, porosity and high structural stability, and sulfonates and modifies the triazine-based imidazole covalent organic polymer to obtain a triazine-based imidazole porous covalent organic polymer material with high proton conductivity. The present application prepares a composite membrane by combining the triazine-based imidazole porous covalent organic polymer material and sulfonated polyether ether ketone, which exhibits excellent vanadium resistance and high ion selectivity, and can be stably operated in a vanadium redox flow battery, thereby significantly improving the comprehensive performance of the vanadium redox flow battery.

[0006] The technical scheme of the present application is as follows:

[0007] A triazine-based imidazole porous covalent organic polymer material, wherein the organic polymer material is a triazine-based imidazole COPs, a sulfonated and modified triazine-based imidazole COPs, or a sulfonated and modified triazine-based imidazole COPs loaded with a proton carrier.

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

[0009]

[0010]

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

[0012] According to the present application, preferably, the proton carrier is a sulfonic acid, a phosphoric acid, or a compound containing a triazine ring.

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

[0014] The preparation method of the triazine-based imidazole COPs includes the following steps: 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-based imidazole COPs.

[0015] According to the application, preferably, 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 pyrene-4,5,9,10-tetraone and the organic solvent A is 0.02-0.05 mol / L.

[0016] According to the application, preferably, 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] According to the application, preferably, the reaction of pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine also needs one to three freeze-pumping-thaw cycles before the reaction, so that the reaction system is kept in a vacuum state, to ensure that the reaction is carried out under the conditions of no oxygen and no water.

[0018] According to the application, preferably, the reaction temperature is 130-160℃, and the reaction time is 6-7 days, and the reaction is carried out under the conditions of no oxygen, no water and vacuum; preferably, the reaction temperature is 150℃, and the reaction time is 7 days.

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

[0020] According to the application, preferably, the washing is sequentially carried out 2-4 times with DMF and THF respectively, and then Soxhlet extraction is carried out with THF for 45-50 hours.

[0021] According to the application, preferably, the drying temperature is 80-120℃.

[0022] The preparation method of the sulfonated modified triazine-based imidazole COPs includes the steps of: dispersing the prepared triazine-based imidazole COPs in the organic solvent B, adding a 1,3-propanesultone solution dropwise, reacting, filtering, washing and drying to obtain the sulfonated modified triazine-based imidazole COPs (Im-TFPT-2SO3H).

[0023] According to the application, preferably, the organic solvent B is acetonitrile; the mass of the triazine-based imidazole COPs and the volume of the organic solvent B are 5-8 g / L.

[0024] According to the application, preferably, the solvent used by the 1,3-propanesultone solution is acetonitrile, and the mass concentration of the 1,3-propanesultone solution is 0.5-2 g / mL.

[0025] According to the application, the mass ratio of the triazinyl imidazole COPs and 1,3-propanesultone is preferably 1:20-40; and the mass ratio of the triazinyl imidazole COPs and 1,3-propanesultone is preferably 1:20-30.

[0026] According to the application, the reaction temperature is preferably 40-80℃, and the reaction time is preferably 1-3 days; and the reaction temperature is preferably 60-70℃, and the reaction time is preferably 2-3 days.

[0027] According to the application, the washing is preferably with acetone; and the drying temperature is preferably 60-100℃.

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

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

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

[0031] According to the application, the mass of the sulfonated modified triazinyl imidazole COPs and the volume of the proton carrier solution are preferably in a ratio of 5-10 g / L.

[0032] According to the application, the reaction conditions are as follows: vacuum condition, stirring at 60-80℃ for 12-24h; and then normal pressure, stirring at 60-80℃ for 12-24h.

[0033] According to the application, the longer the reaction time, the higher the proton conductivity of the proton carrier-loaded sulfonated modified triazinyl imidazole COPs. When the material is reacted for more than 12h under vacuum or normal pressure conditions, the proton conductivity no longer increases.

[0034] The above-mentioned triazinyl imidazole porous covalent organic polymer material is applied to a proton exchange membrane for a full vanadium redox flow battery.

[0035] According to the application, the triazinyl imidazole porous covalent organic polymer material is applied to a method for preparing a proton exchange membrane for a full vanadium redox flow battery, which comprises the following steps: the triazinyl imidazole porous covalent organic polymer material is fully dispersed in a treated sulfonated polyether ether ketone solution, reacted, formed into a film, and washed to obtain the proton exchange membrane for the full vanadium redox flow battery.

[0036] Preferably, the solvent used in the treated sulfonated polyether ether ketone solution is DMF, and the concentration of the treated sulfonated polyether ether ketone solution is 0.05-0.5 g / mL.

[0037] Preferably, the treated sulfonated polyether ether ketone is prepared as follows: dry sulfonated polyether ether ketone is added to a concentrated sulfuric acid solution with a mass concentration of 98%, and stirred at 50-70℃ for 5-7 h, then poured into deionized water, and the obtained solid is washed with deionized water until neutral, and dried to obtain the treated sulfonated polyether ether ketone. The mass ratio of the sulfonated polyether ether ketone to the volume of the concentrated sulfuric acid solution is 0.05-1 g / 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 polyether ether ketone, 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 polyether ether ketone, the overall performance is better, and the surface is more 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 polyether ether ketone, the overall performance of the composite film is best.

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

[0040] Preferably, the film forming method is as follows: the reaction solution obtained by reaction is poured on tin paper after removing air, naturally dried, and then immersed in deionized water to obtain a thin film by peeling.

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

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

[0043] 1. The COPs containing imidazole and triazine ring structures are prepared by one-pot three-component reaction from pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine as raw materials, the preparation method is simple and suitable for industrial production. The ratio of pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and the used organic solvent A need to be appropriate, otherwise the triazine-based imidazole COPs with the structure and performance of the application cannot be obtained. At the same time, the temperature and time of the reaction also need to be appropriate, so as to obtain the triazine-based imidazole COPs with the structure and performance of the application.

[0044] 2. The triazine-based imidazole COPs obtained in the application can be sulfonated by 1,3-propane sultone to obtain sulfonated modified triazine-based imidazole COPs. The sulfonated modified triazine-based imidazole COPs have sulfonic acid functional groups on the skeleton, and the presence of such groups makes these functionalized COPs have proton conductive ability. In addition, the presence of triazine ring structure and sulfonic acid group can strengthen the adsorption performance of COPs material to proton carrier, and the sulfonated modified triazine-based imidazole COPs can be further loaded with proton carrier to further enhance the mass transfer performance of the material.

[0045] 3. The triazine-based imidazole porous covalent organic polymer material prepared in the application has a porous structure, a large specific surface area, regular pore channels and crystallinity. The triazine-based imidazole porous covalent organic polymer material prepared in the application 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 the sulfonated modified triazine-based imidazole COPs are prepared, the mass ratio of 1,3-propane sultone to triazine-based imidazole COPs needs to be greater than or equal to 20, otherwise the sulfonic acid groups cannot be completely grafted in the framework material, affecting the proton conductivity of the material.

[0047] 5. The triazine-based imidazole porous covalent organic polymer material prepared in the application exhibits good proton conduction ability under a wide range of temperature and humidity conditions; the proton conductive ability can reach 7.78 x 10 -2 S cm -1 ; the activation energy of proton conduction is low, indicating that the barrier of proton conduction of the material is small.

[0048] 6. The triazine-based imidazole porous covalent organic polymer material and the sulfonated polyether ether ketone prepared in the application can be used to prepare a proton exchange membrane with good vanadium blocking performance and high proton conductivity, and the proton exchange membrane can be stably operated in a full vanadium redox flow battery, so as to significantly improve the comprehensive performance of the full vanadium redox flow battery. The proton conductivity of the proton exchange membrane is as low as 1.77 x 10 -1S cm -1 , and because the triazine-based imidazole covalent organic framework has a rigid structure, the swelling rate of the proton exchange membrane is reduced, the vanadium blocking performance is excellent, and the ion selectivity reaches 7.45*10 10 mS s cm -3 , and has good comprehensive performance.

[0049] 7、The prepared proton exchange membrane has excellent vanadium blocking performance and increased proton conductivity as the mass ratio of the triazine-based imidazole porous covalent organic polymer material increases, and the performance is optimal when the mass of the triazine-based imidazole porous covalent organic polymer material accounts for 30% of the total mass of the triazine-based imidazole porous covalent organic polymer material and the sulfonated polyether ether ketone, and the composite membrane is easy to break and has poor mechanical properties when the mass exceeds 30%. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

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

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

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

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

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

[0058] Figure 9 is the conductivity plot 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, Nafion 212 membrane.

[0059] Figure 10 is the vanadium ion permeability and ion selectivity spectrum of PA@Im-TFPT-2SO3H / SPEEK(X) synthesized in Example 4, SPEEK, Nafion 212 membrane.

[0060] Figure 11 is the Coulomb efficiency (a), voltage efficiency (b), energy efficiency spectrum (c) of PA@Im-TFPT-2SO3H / SPEEK(30%) synthesized in Example 4, Nafion 212 membrane.

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

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

[0063] In the examples, the sulfonated polyether ether ketone of 1200 purpose used is purchased from Beijing Mai Ruida Technology Co., Ltd.

[0064] Example 1

[0065] A method for preparing a triazine-based imidazole COP, namely Im-TFPT-COP, is as follows: pyrene-4,5,9,10-tetraone (0.045 mmol), ammonium acetate (0.27 mmol) and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (0.03 mmol) are mixed in a glass tube, then solvent toluene (0.6 mL), mesitylene (0.4 mL), glacial acetic acid (0.2 mL) are added, and the mixture is ultrasonically mixed uniformly. The reaction material is frozen into a solid at -78°C under liquid nitrogen, and is pumped to vacuum, and then thawed to a liquid, and the above-mentioned three freezing-pumping-thawing cycles are repeated three times. After the three freezing-pumping-thawing cycles, the glass tube is kept in a vacuum state, is sealed, and then is placed in an oven at 150°C for reaction for 7 days (the reaction material is gradually warmed from low temperature after thawing to 150°C for reaction). The solid is filtered, washed with DMF and THF three times in turn, and then is transferred into a Soxhlet extractor and washed with THF for 48 hours. The product Im-TFPT-COP is obtained by drying at 100°C, and the molar yield is 89%, which is brown.

[0066] The Fourier infrared spectra of the synthesized Im-TFPT-COP and raw materials pyrene-4,5,9,10-tetraone (PyTO), ammonium acetate (NH4OAc) and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT) are shown in Figure 2 The figure shows that the target product is successfully prepared.

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

[0068] The crystallinity of Im-TFPT-COP is tested by a powder diffractometer, and the powder X-ray diffraction spectra of the simulated AA stacking and AB stacking are shown in Figure 1 The figure shows that Im-TFPT-COP has crystallinity.

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

[0070] Im-TFPT-COP is soaked in DMF, MeCN, THF, acetone, ethanol solution and water at room temperature for 12 hours respectively, and the chemical stability of Im-TFPT-COP after soaking in the above-mentioned solutions is tested by a powder diffractometer, and the X-ray diffraction spectra are shown in Figure 3 The results show that the peak shape of Im-TFPT-COP powder can be well maintained after being treated by these organic solvents, which shows that they have good structural stability.

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

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

[0073] Example 2

[0074] A preparation method of a sulfonated modified triazine-based imidazole COP (referred to as Im-TFPT-2SO3H) is as follows:

[0075] Take 200 mg of Im-TFPT-COP powder prepared by the method of Example 1 and disperse it in 30 mL of acetonitrile solution, drop 1,3-propanesulfonic acid lactone (5 g) and acetonitrile (5 mL) mixture dropwise, after dropwise addition, react at 70°C for 48 hours, filter, then wash the solid with acetone, and finally dry the obtained sample at 100°C for 24 hours under vacuum to obtain dried Im-TFPT-2SO3H.

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

[0077] The nitrogen adsorption-desorption isotherm is as shown in Figure 4 From the figure, it can be seen that the specific surface area is 85.94 m 2 / g.

[0078] Example 3

[0079] A preparation method of a sulfonated modified triazine-based imidazole COP (referred to as 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 at 70°C for 12 h, then continue to stir at 70°C under normal pressure for 12 h, filter, then wash the solid with distilled water until the eluent reaches pH = 7, then dry the obtained sample at 120°C for 24 hours to obtain dried PA@Im-TFPT-2SO3H.

[0081] The Fourier infrared spectrum of the PA@Im-TFPT-2SO3H synthesized in this example is as shown in Figure 5As shown, compared with Im-TFPT-COP, Im-TFPT-2SO3H, it can be seen that the triazine-based imidazole COPs loaded with phosphoric acid-sulfonated modification are successfully prepared.

[0082] Nitrogen adsorption-desorption isotherms are as shown in the following figure: Figure 4 As shown, the specific surface area of the prepared PA@Im-TFPT-2SO3H is 8.72 m 2 / g.

[0083] Example 4

[0084] A preparation method of a composite membrane of the triazine-based imidazole COPs loaded with phosphoric acid-sulfonated modification and SPEEK, i.e. PA@Im-TFPT-2SO3H / SPEEK (30%) is 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 prepared treated sulfonated polyether ether ketone solution is added into the round-bottom flask, and the mixed solution is uniformly mixed by ultrasonic and stirred at 60°C for 6 h. After air is exhausted, the solution is poured on a tin paper, and the membrane is peeled off after natural drying by soaking in deionized water. Then, the membrane is sequentially soaked in 3 mol / L dilute sulfuric acid, deionized water and 3 mol / L phosphoric acid solution for 24 h, and finally stored in deionized water for standby.

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

[0086] Example 5

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

[0088] Example 6

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

[0090] Example 7

[0091] A method for preparing a composite membrane of phosphoric acid-sulfonated modified triazine-based imidazole COPs and SPEEK, i.e. PA@Im-TFPT-2SO3H / SPEEK (25%), was as described in Example 4, except that the mass of PA@Im-TFPT-2SO3H added was 0.086 g.

[0092] Comparative Example 1

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

[0094] From this comparative example, it can be seen that the selection of the 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-based imidazole COPs was as described in Example 1, except that the heating time was 5 days; other steps and conditions were the same as in Example 1. The molar yield was 75%, and no obvious peak signal was observed in the powder diffraction peak test.

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

[0098] Comparative Example 3

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

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

[0101] Comparative Example 4

[0102] A method for preparing triphenyl imidazole COPs, i.e. Im-TFPB-COP, was as described in Example 1, except that 1,3,5-tris(p-formylphenyl)benzene monomer was used instead of 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 tested to be 1.16 x 10 -6 S / cm at 353 K and 98% humidity.

[0103] From the present comparative example, it can be seen that the selection of monomer has an important influence on the proton conductivity of the target product.

[0104] Comparative Example 5

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

[0106] From the present comparative example, it can be seen that the amount of 1,3-propanesultone has an important influence on the proton conductivity of the target product.

[0107] Comparative Example 6

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

[0109] Comparative Example 7

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

[0111] Test Example

[0112] Test of proton conductive properties:

[0113] The AC impedance of the as-pressed sheet of the material prepared in Examples 1-3 is tested at a certain humidity and temperature using an electrochemical workstation, and the conductivity value is calculated using the formula σ = L / (RA), wherein σ is the proton conductivity, L is the thickness of the sheet film, A is the area of the film, and R is the resistance.

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

[0115] While maintaining a constant humidity (98% RH), the temperature was varied at 303 K, 313 K, ..., 353 K, and the AC impedance diagrams of the materials prepared in Examples 1-3 were measured, as shown below. Figure 6 As shown in (a), (b), and (c), the corresponding resistance values ​​can be read 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, reaching 7.78 × 10⁻⁶. -2 The proton conductivity is measured in S / cm. The proton conductivity of the Im-TFPT-COP synthesized in Example 1 is 8.83 × 10⁻⁶. -6 S / cm, the proton conductivity of Im-TFPT-2SO3H synthesized in Example 2 is 3.38 × 10⁻⁶. -3 S / cm. On the other hand, by Figure 7 It can also be seen that the activation energies of proton conduction in this type of material are all low, and none are higher than 0.4 eV. This indicates that the barrier to proton conduction in this type of material is small, and the mass transfer process is mainly carried out through a hopping mechanism.

[0117] Depend on Figure 8 It can be seen that, after replacing 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine with 1,3,5-tris(p-formylphenyl)benzene monomer, the proton conductivity of Im-TFPB-COP is 1.16 × 10⁻⁶. -6 The S / cm ratio demonstrates that the choice of monomer has a significant impact on the proton conduction properties of the target product.

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

[0119] Vanadium ion permeability test:

[0120] Vanadium ion permeability (P) represents the vanadium-blocking ability of the membrane and directly affects the coulombic efficiency of the vanadium redox flow battery (VFB). The VO of the membrane was measured using an H-type diffusion cell. 2+ To determine the permeability, add 30 mL of 1.5 mol L to the left diffusion cell. -1 VO 2+ 3 mol L -1To balance the osmotic pressure, 30 mL of 1.5 mol / L H2SO4 aqueous solution was added to the right-side diffusion cell. -1 3 mol L of MgSO4 -1 Aqueous H2SO4 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. (Volumetric analysis follows.) 2+ The standard curve of concentration and absorbance can be used to obtain the VO that diffuses to the MgSO4 side at different times. 2+ Concentration. Furthermore, VO can be calculated using the formula. 2+ Penetration rate.

[0121]

[0122] Among them, V B Let C represent the volume of the MgSO4 solution, A and L be the effective area and thickness of the membrane, respectively, and C be the volume of the MgSO4 solution. A VO in the left diffusion cell 2+ Concentration, t is diffusion time, C B (t) represents 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 vanadium ion permeability, representing the difference in the rate of proton and vanadium ion transport within the membrane. S can be calculated using the formula: S = σ / P, where σ is the proton conductivity and P is the ion transfer rate (V / V). 2+ Penetration rate.

[0123] Depend on Figure 10 It can be seen that the PA@Im-TFPT-2SO3H / SPEEK (30%) synthesized in Example 4 has excellent vanadium blocking ability and high ion selectivity, reaching 2.37 × 10⁻⁶. -9 cm 2 s -1 Vanadium ion permeability and 7.45×10 10 mS s cm -3 Ion selectivity. As the weight percentage of PA@Im-TFPT-2SO3H increases, the vanadium blocking performance and proton conductivity increase. When the weight percentage of PA@Im-TFPT-2SO3H in the composite membrane increases, the membrane becomes easily broken, and the mechanical properties decrease.

[0124] Depend on Figure 11 It can be seen that when the composite membrane is assembled into a vanadium ion electrolyte at both the positive and negative electrodes, and nitrogen gas is introduced into the negative electrode for 10 minutes, the electrolyte is then subjected to a current density of 80 mA / cm². -2 The first activation was performed with cutoff voltages of 0.8V and 1.65V, respectively. After activation, the prepared membrane was subjected to a current density of 60–100 mA / cm². -2The PA@Im-TFPT-2SO3H / SPEEK(30%) synthesized in Example 4 has higher energy efficiency and better comprehensive performance than the Nafion 212 membrane when running.

[0125] The composite membrane was assembled into a 3.5-valence vanadium ion electrolyte with positive and negative electrodes, and the negative electrode was charged with nitrogen for 10 min, and then the electrolyte was subjected to a current density of 80 mA cm -2 -2 for the first activation, and after the activation was completed, the PA@Im-TFPT-2SO3H / SPEEK(30%) composite membrane synthesized in Example 4 was subjected to single cell performance test at a current density of 80 mA cm -2 -2 for the first activation, and after the activation was completed, the PA@Im-TFPT-2SO3H / SPEEK(30%) composite membrane synthesized in Example 4 was subjected to single cell performance test at a current density of 80 mA cm Figure 12 As shown in the table, the synthesized composite membrane can maintain a high energy efficiency within 50 cycles, which indicates that the material has high use stability and better performance than the Nafion 212 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 a proton carrier. The triazine imidazole COPs and the sulfonated triazine imidazole COPs are two-dimensional porous polymers having the structural units shown in formulas (I) and (II) respectively. (I) (II) In formula (II), R1 is a propyl sulfonic acid anionic 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 8-245 m². 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 described in claim 1 or 2, comprising the steps of: reacting pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine in organic solvent A, and then preparing triazine imidazole COPs by filtration, washing and drying.

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; the molar amount of pyrene-4,5,9,10-tetraone and the volume ratio of organic solvent A are 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-aldehydephenyl)-1,3,5-triazine is 1-2:8-10:1; iii. Before reacting with pyrene-4,5,9,10-tetraone, ammonium acetate and 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, one to three freezing-evacuation-thawing cycles are required to keep the reaction system under vacuum to ensure that the reaction is carried out under oxygen-free and anhydrous conditions. iv. The reaction temperature is 130-160 ℃, the reaction time is 6-7 days, and the reaction is carried out under oxygen-free, water-free, and vacuum conditions.

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

6. The method for preparing sulfonated modified 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 volume ratio of the organic solvent B is 5 g / L-8 g / L; ii. The solvent used for the 1,3-propanesulfonate lactone solution is acetonitrile, and the mass concentration of the 1,3-propanesulfonate lactone solution is 0.5-2 g / mL; iii. The mass ratio of the triazine imidazole COPs to 1,3-propanesulfonic acid lactone is 1:20-40; iv. The reaction temperature is 40-80 ℃, and the reaction time is 1-3 days.

7. A method for preparing sulfonated triazine imidazole COPs supported on a proton carrier as described in claim 1 or 2, comprising the steps of: The sulfonated triazine imidazole COPs were mixed with a proton carrier solution, reacted, filtered, washed, and dried to obtain the sulfonated triazine imidazole COPs loaded with the proton carrier.

8. The method for preparing sulfonated modified 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 aqueous solution of phosphoric acid; ii. The mass ratio of 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: under vacuum conditions, stir at 60-80 ℃ for 12-24 h; then under normal pressure, stir at 60-80 ℃ for 12-24 h.

9. The application of the triazine imidazole porous covalent organic polymer material as described in claim 1 or 2 in the proton exchange membrane of a vanadium redox flow battery.

10. The application according to claim 9, characterized in that, A method for preparing a proton exchange membrane for a vanadium redox flow battery using a triazine imidazole porous covalent organic polymer material includes the following steps: the triazine imidazole porous covalent organic polymer material is fully dispersed in a treated sulfonated polyether ether ketone solution, reacted, formed into a film, and washed to obtain the vanadium redox flow battery proton exchange membrane.

11. The application according to claim 10, characterized in that, The solvent used in the treated sulfonated polyether ether ketone solution is DMF, and the concentration of the treated sulfonated polyether ether ketone solution is 0.05-0.5 g / mL. The preparation method of the treated sulfonated polyether ether ketone is as follows: dry sulfonated polyether ether ketone is added to a 98% concentrated sulfuric acid solution, stirred at 50-70℃ for 5-7 hours, then poured into deionized water. The resulting solid is washed with deionized water until neutral and dried to obtain the treated sulfonated polyether ether ketone. The mass ratio of sulfonated polyether ether ketone to the volume ratio of concentrated sulfuric acid solution is 0.05-1 g / mL.

12. The application according to claim 10, characterized in that, 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 polyether ether ketone; the reaction temperature is 40 to 80 °C, the reaction time is 5 to 7 h, and the reaction is carried out under stirring conditions.

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