Quaternary ammonium type covalent organic framework doped sulfonated polyetheretherketone proton exchange membrane and preparation method thereof

Abstract

The invention discloses a preparation method of a quaternary ammonium type covalent organic framework doped sulfonated polyetheretherketone proton exchange membrane, which is characterized by comprising the following steps: firstly, synthesizing a quaternary ammonium type amine monomer under a mild condition, then synthesizing quaternary ammonium type covalent organic framework powder by a solvothermal method, and finally, preparing the quaternary ammonium type covalent organic framework doped sulfonated polyetheretherketone proton exchange membrane. Sulfonated polyetheretherketone and quaternary ammonium type covalent organic framework powder are blended through a tape casting method, and the proton exchange membrane is obtained after membrane casting. The preparation method is simple and convenient to operate and convenient to implement. According to the preparation method disclosed by the invention, a quaternary ammonium group in the quaternary ammonium type amine monomer is used for inducing ordered arrangement and distribution of sulfonic acid groups in the sulfonated polyether-ether-ketone, so that high proton conductivity is realized. Meanwhile, the micro-phase separation structure of the membrane is improved through interaction of static electricity and hydrogen bonds formed between the quaternary ammonium type amine monomer and the sulfonated polyetheretherketone matrix, and the mechanical stability of the membrane is enhanced. The prepared proton exchange membrane is used for electrochemical hydrogen compression and shows excellent electrochemical hydrogen compression performance.

Description

Technical Field

[0001] The present invention relates to the preparation of a proton exchange membrane material, and particularly to the preparation of a covalent organic framework proton exchange membrane. Background Art

[0002] Electrochemical compression of hydrogen has received increasing attention as it can safely, quietly, and efficiently compress and store hydrogen without mechanical moving parts, becoming an essential part of the hydrogen energy supply chain. As a key component in an electrochemical hydrogen compression system, the proton exchange membrane must meet the strict requirements of commercial applications, including high proton conductivity for efficient compression, excellent mechanical strength to withstand high-pressure conditions, and low hydrogen permeability to minimize energy loss and ensure operational safety and durability. Sulfonated polyether ether ketone has received extensive attention due to its superior heat resistance and mechanical properties compared to the commonly used Nafion membrane. However, due to the random distribution of proton-conducting groups and electrostatic repulsion in sulfonated polyether ether ketone, there is a trade-off effect between proton conductivity and mechanical stability.

[0003] Ionic covalent organic porous framework materials (iCOF) are formed by connecting light elements (such as C, H, O, N, B, Si, S, etc.) through reversible dynamic covalent chemical bonds to form a two-dimensional or three-dimensional framework structure. Due to their highly ordered and uniformly distributed proton-conducting groups, excellent thermal stability, and chemical stability, these materials are commonly used as fillers in polymer matrices to enhance the proton conductivity and mechanical stability of proton exchange membranes. By maximizing the filler loading without particle agglomeration, the hybrid membrane can more closely mimic the excellent properties of the filler itself, thereby improving proton conductivity and / or enhancing multiple interactions within the membrane matrix. However, the practical application of such fillers is often restricted by the complexity of monomer design, the synthesis difficulty, and the high cost of porous materials. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides a preparation method of a quaternary ammonium-type covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane, so as to solve the technical problems of complex monomer design, high synthesis difficulty, and high cost in the prior art.

[0005] To solve the above technical problems, the present invention proposes a preparation method of a quaternary ammonium-type covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane. First, the synthesis of the quaternary ammonium-type amine monomer is completed under mild conditions. Then, the quaternary ammonium-type covalent organic framework powder is synthesized by a solvothermal method. Finally, sulfonated polyether ether ketone and the quaternary ammonium-type covalent organic framework powder are blended by a casting method, and the obtained proton exchange membrane is obtained after casting. The specific steps are as follows:

[0006] Step 1) Synthesis of quaternary ammonium monomer: A mixture A was obtained by adding an anhydrous ethanol solution of methyl 5-(bromomethyl)isophthalate and trimethylamine solution into a container, where the ratio of methyl 5-(bromomethyl)isophthalate:trimethylamine solution:anhydrous ethanol was 1 g / 2 mL / 10 mL. The above mixture A was continuously stirred in a 40 °C water bath, and the anhydrous ethanol and unreacted trimethylamine solution were rotary evaporated. Then, anhydrous ethanol and hydrazine hydrate solution were added according to a volume ratio of 6.25:1 to obtain mixture B, where the amount of anhydrous ethanol was the same as that in mixture A. The mixture B was refluxed at a high temperature, then the solvent was concentrated, and the resulting pale yellow oily liquid was precipitated in ethyl acetate. The precipitate was filtered, washed with ethyl acetate, and dried to obtain the white powder 3,5-diformylhydrazide-benzyltrimethylammonium bromide as the quaternary ammonium monomer, denoted as MBh-QA-C1;

[0007] Step 2) Synthesis of quaternary ammonium covalent organic framework powder: MBh-QA-C1 prepared in Step 1), phloroglucinol trisaldehyde, 6 M acetic acid aqueous solution, mesitylene, and dioxane were added to a reaction tube to obtain mixture C, where the ratio of MBh-QA-C1:phloroglucinol trisaldehyde:6 M acetic acid aqueous solution:mesitylene:dioxane was 0.6 mmol:0.4 mmol:2 mL:4.5 mL:1.5 mL. After the mixture C was ultrasonically treated for 15 min, it was degassed by 3 freeze-pump-thaw cycles. After sealing and reacting at a high temperature, it was washed successively with DMF / water / methanol and dried in vacuo to obtain the quaternary ammonium covalent organic framework powder, denoted as TpMBh-QA-C1;

[0008] Step 3) Preparation of quaternary ammonium covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane: The TpMBh-QA-C1 powder prepared in Step 2) and SPEEK were dissolved in DMF to obtain mixture D, where the mass ratio of TpMBh-QA-C1 powder to sulfonated polyether ether ketone (SPEEK) was 0.5 - 4:100, and the mass-volume ratio of TpMBh-QA-C1 to DMF was 1 - 8 mg / 5 mL. The mixture D was stirred for 24 h to obtain a casting solution. The casting solution was poured onto a glass plate and subjected to heat preservation treatment to obtain the proton exchange membrane, denoted as SPEEK / TpMBh-QA-C1-1.

[0009] Furthermore, in the preparation method of the proton exchange membrane of the present invention, where:

[0010] In Step 1), the temperature of the high-temperature reflux was 85 °C and the time was 36 h; the time of continuous stirring under the water bath was 36 h.

[0011] In Step 2), the temperature of the high-temperature reaction after sealing was 120 °C and the time was 96 h; the temperature of the vacuum drying was 80 °C and the time was 48 h.

[0012] In step 3), the mass ratio of TpMBh-QA-C1 powder to SPEEK is 2:100; the dosage of the casting solution is 1 mL / 5 cm according to the volume-area ratio. 2 The process conditions for heat preservation treatment are: heat preservation at 60 °C for 12 h, and then the temperature is raised to 80 °C for heat preservation for 12 h.

[0013] The proton conductivity of the quaternary ammonium type covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane prepared according to the above preparation method is 289-469 mS cm. -1 , the mechanical strength is 84.9-97.0 MPa, and when this proton exchange membrane is used for electrochemical compression of hydrogen, the outlet pressure on the cathode side can reach 3.31 MPa.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] (1) The quaternary ammonium type covalent organic framework powder mentioned in this technical solution is synthesized by the solvothermal method, and then the SPEEK / TpMBh-QA-C1 proton exchange membrane is prepared by the casting method. The preparation method is simple in operation and easy to implement.

[0016] (2) By adjusting the mass ratio of TpMBh-QA-C1 to SPEEK in this technical solution, the strength of hydrogen bonds and electrostatic interactions can be adjusted, and further the trade-off relationship between the proton conductivity and mechanical properties of the membrane can be regulated.

[0017] (3) Compared with the traditional SPEEK polymer membrane, for the SPEEK / TpMBh-QA-C1 proton exchange membrane prepared by this technical solution, the quaternary ammonium groups in the SPEEK / TpMBh-QA-C1 membrane induce the sulfonic acid groups on SPEEK to be arranged in an orderly manner, realizing excellent proton conduction. The hydrogen bonds and electrostatic interactions between TpMBh-QA-C1 and SPEEK improve the mechanical properties of the membrane. These synergistic effects enable the SPEEK / TpMBh-QA-C1 proton exchange membrane to exhibit excellent performance in electrochemical compression of hydrogen, thus promoting the further development of electrochemical compression of hydrogen.

[0018] (4) The filling amount of the quaternary ammonium type covalent organic framework powder used in this technical solution is relatively low, reducing the membrane preparation cost. Description of the Drawings

[0019] Figure 1 It is a graph showing the change of proton conductivity of the SPEEK / TpMBh-QA-C1-2 membrane prepared in Example 3 with temperature;

[0020] Figure 2 It is a stress-strain curve graph of the SPEEK / TpMBh-QA-C1-2 membrane;

[0021] Figure 3 is the scanning electron microscope photograph of the SPEEK / TpMBh-QA-C1-2 membrane;

[0022] Figure 4 is the atomic force microscope photograph of the SPEEK / TpMBh-QA-C1-2 membrane;

[0023] Figure 5 is the transmission electron microscope photograph of the SPEEK / TpMBh-QA-C1-2 membrane;

[0024] Figure 6 is the graph of the proton conductivity of the SPEEK membrane prepared in Comparative Example 1 varying with temperature;

[0025] Figure 7 is the stress-strain curve graph of the SPEEK membrane;

[0026] Figure 8 is the graph of the electrochemical compression hydrogen performance of the SPEEK membrane;

[0027] Figure 9 is the graph of the electrochemical compression hydrogen performance of the SPEEK / TpMBh-QA-C1-2;

[0028] Figure 10 is the test process of the electrochemical compression hydrogen performance. Detailed implementation manners

[0029] The design concept of a quaternary ammonium type covalently organic framework doped sulfonated polyether ether ketone proton exchange membrane proposed by the present invention is based on the advantages of the ordered arrangement of sulfonic acid groups induced by quaternary ammonium groups and the enhancement of mechanical strength by the electrostatic and hydrogen bond interactions between them; the ordered arrangement and distribution of sulfonic acid groups in SPEEK are induced by the quaternary ammonium groups in the quaternary ammonium type amine monomer, so as to achieve high proton conductivity. At the same time, the electrostatic and hydrogen bond interactions formed between the quaternary ammonium type amine monomer and the SPEEK matrix can the microphase separation structure of the membrane and enhance the mechanical stability of the membrane. The proton exchange membrane prepared by the present invention is used for electrochemical compression hydrogen and shows excellent electrochemical compression hydrogen performance. The preparation method of the present invention mainly includes: first, the synthesis of the quaternary ammonium type amine monomer (MBh-QA-C1) is completed under mild conditions, then, the quaternary ammonium type covalently organic framework powder (TpMBh-QA-C1) is synthesized by a solvothermal method, and finally, SPEEK and TpMBh-QA-C1 are blended by a casting method, and the proton exchange membrane is obtained after casting the film.

[0030] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings, comparative examples and specific examples. The specific examples described are only used to explain the present invention and are not intended to limit the present invention. In the present invention, the proton conductivity of the membrane is tested based on the double-electrode alternating current impedance method, and the mechanical strength of the membrane is tested by a universal tensile testing machine.

[0031] Example 1

[0032] Preparation of a quaternary ammonium-type covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane, the steps are as follows:

[0033] Step 1, synthesis of quaternary ammonium-type amine monomer: Add 5 g (17.4 mmol) of methyl 5-bromomethyl-isophthalate, 10 mL of trimethylamine solution, and 50 mL of absolute ethanol into a 100 mL round-bottom flask, and continuously stir in a water bath environment at 40 °C for 36 h. Rotate and evaporate the absolute ethanol and the unreacted trimethylamine solution, then add 50 mL of absolute ethanol and 8 mL of hydrazine hydrate solution. Reflux this solution at 85 °C for 36 h, then concentrate the solvent to obtain a pale yellow oily liquid, and precipitate the pale yellow oily liquid in ethyl acetate. Filter the precipitate, wash and dry it with ethyl acetate, and finally obtain white powdery 3,5-diformylhydrazide-benzyltrimethylammonium bromide, denoted as MBh-QA-C1.

[0034] Step 2, synthesis of quaternary ammonium-type covalent organic framework powder: Add 206.62 mg (0.6 mmol) of MBh-QA-C1 obtained in Step 1, 84 mg (0.4 mmol) of phloroglucinol trialdehyde, 2 mL of 6 M acetic acid aqueous solution, 4.5 mL of mesitylene, and 1.5 mL of dioxane into a Pyrex tube; after ultrasonic treatment for 15 min, degas with 3 freeze-pump cycles, then seal and react at 120 °C for 96 h, and then wash successively with DMF / water / methanol and dry in vacuum at 80 °C for 48 h. Obtain quaternary ammonium-type covalent organic framework powder, denoted as TpMBh-QA-C1.

[0035] Step 3, preparation of quaternary ammonium-type covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane: Dissolve 1 mg of the TpMBh-QA-C1 powder prepared in Step 2 and 200 mg of SPEEK (the mass ratio of TpMBh-QA-C1 to SPEEK is 0.5%) in 5 mL of DMF, stir for 24 h to obtain a casting solution; pour the casting solution onto a 25 cm2 glass plate, keep it warm at 60 °C for 12 h, and then raise the temperature to 80 °C and keep it warm for 12 h to obtain a proton exchange membrane, denoted as SPEEK / TpMBh-QA-C1-0.5.

[0036] After testing, as shown in Table 1, the proton conductivity of the SPEEK / TpMBh-QA-C1-0.5 membrane prepared in Example 1 is 313.4 mS cm-1 (80 °C, 100% RH), and the mechanical strength is 84.9 MPa.

[0037] Example 2

[0038] The preparation of a quaternary ammonium-type covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane is basically the same as that in Example 1, except that: in Step 3, the addition amount of TpMBh-QA-C1 is increased from 1 mg to 2 mg (the mass ratio of TpMBh-QA-C1 to SPEEK is 1%), and the finally obtained membrane is denoted as SPEEK / TpMBh-QA-C1-1.

[0039] After testing, as shown in Table 1, the proton conductivity of the SPEEK / TpMBh-QA-C1-1 membrane prepared in Example 2 is 358.5 mS cm-1 (80 °C, 100% RH), and the mechanical strength is 88.6 MPa.

[0040] Example 3

[0041] To prepare a quaternary ammonium-type covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane, the preparation process is basically the same as that in Example 1, except that: in Step 3, the addition amount of TpMBh-QA-C1 is increased from 2 mg to 4 mg (the mass ratio of TpMBh-QA-C1 to SPEEK is 2%), and the finally obtained membrane is denoted as SPEEK / TpMBh-QA-C1-2.

[0042] Figure 3 Showing the scanning electron microscope photograph of the membrane, Figure 4 Showing the atomic force microscope photograph of the membrane, Figure 5 Showing the transmission electron microscope photograph of the membrane. Figure 3 The cross-section of the membrane is dense and defect-free, and SPEEK and TpMBh-QA-C1 have good compatibility. Figure 4 and Figure 5 The membrane has a uniform surface morphology, distinct phase separation regions, and clear phase separation characteristics, indicating that the membrane has a good microphase separation structure.

[0043] After testing, as shown in Table 1, the proton conductivity of the SPEEK / TpMBh-QA-C1-2 membrane prepared in Example 3 is 469.0 mS cm-1 (80 °C, 100% RH), and the mechanical strength is 91.3 MPa.

[0044] Example 4

[0045] Prepare a quaternary ammonium covalent organic framework doped sulfonated polyether ether ketone proton exchange membrane. The preparation process is basically the same as that of Example 1, except that: in Step 3, the addition amount of SPEEK is increased from 4 mg to 8 mg (the mass ratio of TpMBh-QA-C1 to SPEEK is 4%). The finally obtained membrane is denoted as SPEEK / TpMBh-QA-C1-4.

[0046] After testing, as shown in Table 1, the proton conductivity of the SPEEK / TpMBh-QA-C1-4 membrane prepared in Example 4 is 289.5 mS cm-1 (80 °C, 100% RH), and the mechanical strength is 97.0 MPa.

[0047] Comparative Example 1

[0048] Prepare a SPEEK proton exchange membrane. Dissolve an appropriate amount of SPEEK in DMF and stir for 24 h to obtain a casting solution; pour the casting solution onto a 25 cm2 glass plate, keep it at 60 °C for 12 h, and then raise the temperature to 80 °C and keep it for 12 h to obtain a proton exchange membrane, denoted as SPEEK.

[0049] After testing, as shown in Table 1, the proton conductivity of the SPEEK membrane prepared in Comparative Example 1 is 127.2 mS cm-1 (80 °C, 100% RH), and the mechanical strength is 63.9 MPa.

[0050] Figure 1 Shows the graph of the proton conductivity of the SPEEK / TpMBh-QA-C1-2 membrane prepared in Example 3 varying with temperature; Figure 2 Shows the stress-strain curve of this membrane, Figure 9 Shows the electrochemical compression hydrogen performance graph of this membrane. The electrochemical compression hydrogen performance test process is as Figure 10 shown; Figure 6 Shows the graph of the proton conductivity of the SPEEK membrane prepared in Comparative Example 1 varying with temperature, Figure 7 Shows the stress-strain curve of this SPEEK membrane, Figure 8 Shows the electrochemical compression hydrogen performance graph of this SPEEK membrane. Table 1 is the test data of the conductivity and mechanical strength of the membranes prepared in Examples 1-4 and Comparative Examples of the present invention.

[0051] Table 1 Test data of Examples and Comparative Examples of the present invention

[0052] Sample <![CDATA[Proton conductivity (mS cm -1 )]]> Mechanical strength (MPa) SPEEK 127.2±2.7 63.9 SPEEK / TpMBh - QA - C1 - 0.5 313.4±0.8 84.9 SPEEK / TpMBh - QA - C1 - 1 358.5±1.8 88.6 SPEEK / TpMBh - QA - C1 - 2 469.0±7.8 91.3 SPEEK / TpMBh - QA - C1 - 4 289.5±9.5 97.0

[0053] According to Figure 1 、 Figure 2 、 Figures 6 to 9From Table 1, it can be concluded that: by doping the quaternary ammonium-type covalent organic framework into the SPEEK proton exchange membrane, the preparation method provided by the present invention plays a role in inducing the ordered arrangement of sulfonic acid groups on SPPEK and enhancing the mechanical strength through electrostatic and hydrogen bond interactions between SPEEKs. The comparison results show that both the proton conductivity and mechanical properties of the quaternary ammonium-type covalent organic framework-doped sulfonated polyether ether ketone proton exchange membrane are improved, overcoming to a certain extent the trade-off effect between the proton conductivity and mechanical properties of the polymer. Among them, SPEEK / TpMBh-QA-C1-2 (the mass ratio of TpMBh-QA-C1 powder to SPEEK is 4%) has the best comprehensive performance. Therefore, SPEEK / TpMBh-QA-C1-2 and SPEEK were respectively tested for electrochemical compression hydrogen performance. The results show that the outlet pressure on the cathode side of SPEEK / TpMBh-QA-C1-2 is 3.31 MPa, which is 272% higher than 0.89 MPa of SPEEK. This is due to the enhanced proton conductivity and strong mechanical stability of SPEEK / TpMBh-QA-C1-2.

[0054] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many improvements and changes without departing from the purpose of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a quaternary ammonium covalent organic framework doped sulfonated polyetheretherketone proton exchange membrane, characterized in that: Firstly, the synthesis of quaternary ammonium amine monomers is completed under mild conditions, then the quaternary ammonium covalent organic framework powder is synthesized by a solvent thermal method, and finally, the sulfonated polyetheretherketone and the quaternary ammonium covalent organic framework powder are blended by a casting method, and the proton exchange membrane is obtained after film casting.

2. The method for preparing a proton exchange membrane according to claim 1, characterized in that: The following steps are involved: Step 1) Synthesis of quaternary ammonium monomer: Add an anhydrous ethanol solution of 5-bromomethyl-methyl isophthalate and trimethylamine solution into a container to obtain a mixture A, wherein the ratio of 5-bromomethyl-methyl isophthalate: trimethylamine solution: anhydrous ethanol is 1 g / 2 mL / 10 mL; continuously stir the mixture A in a 40° C. water bath, and evaporate the anhydrous ethanol and unreacted trimethylamine solution; then add anhydrous ethanol and hydrazine hydrate solution in a volume ratio of 6.25:1 to obtain a mixture B, wherein the amount of anhydrous ethanol is the same as that in the mixture A; reflux the mixture B at a high temperature, and then concentrate the solvent, and precipitate the obtained light yellow oily liquid in ethyl acetate; filter the precipitate, wash it with ethyl acetate, and dry it, and the obtained white powder 3,5-diformylhydrazide-benzyltrimethylammonium bromide is a quaternary ammonium monomer; Step 2) Synthesis of quaternary ammonium covalent organic framework powder: Add the quaternary ammonium monomer prepared in step 1), trialdehyde phloroglucinol, 6M acetic acid aqueous solution, mesitylene and dioxane to the reaction tube to obtain a mixture C, wherein the quaternary ammonium monomer: trialdehyde phloroglucinol: 6M acetic acid aqueous solution: mesitylene: dioxane is 0.6mmol: 0.4mmol: 2mL: 4.5mL: 1.5mL, and the mixture C is ultrasonically treated for 15min, and then degassed by 3 freeze-vacuum cycles; after sealing and reacting at high temperature, the mixture is washed with N,N-dimethylformamide / water / methanol in sequence, and vacuum dried; a quaternary ammonium covalent organic framework powder is obtained; Step 3) Preparation of quaternary ammonium covalent organic framework doped sulfonated polyetheretherketone proton exchange membrane: The quaternary ammonium covalent organic framework powder and sulfonated polyetheretherketone prepared in step 2) are dissolved in N,N-dimethylformamide to obtain a mixture D, wherein the mass ratio of the quaternary ammonium covalent organic framework powder to the sulfonated polyetheretherketone is 0.5-4:100, and the mass volume ratio of the quaternary ammonium covalent organic framework powder to N,N-dimethylformamide is 1-8 mg / 5 mL. The mixture D is stirred for 24 hours to obtain a casting solution; the casting solution is poured onto a glass plate, and a proton exchange membrane is obtained after heat preservation treatment.

3. The method for preparing a proton exchange membrane according to claim 2, characterized in that: In step 1), the temperature of high temperature reflux is 85° C. and the time is 36 h; and the time of continuous stirring in the water bath is 36 h.

4. The method for preparing a proton exchange membrane according to claim 2, characterized in that: In step 2), the temperature of the high temperature reaction after sealing is 120° C. and the time is 96 h; the temperature of the vacuum drying is 80° C. and the time is 48 h.

5. The method for preparing a proton exchange membrane according to claim 2, characterized in that: In step 3), the mass ratio of TpMBh-QA-C1 powder to SPEEK is 2:

100.

6. The method for preparing a proton exchange membrane according to claim 2, characterized in that: In step 3), the amount of the casting solution is 1 mL / 5 cm 2 The process conditions of the heat preservation treatment are: keep warm at 60℃ for 12h, then increase the temperature to 80℃ and keep warm for 12h.

7. A proton exchange membrane, characterized in that: The invention relates to a quaternary ammonium covalent organic framework doped sulfonated polyetheretherketone proton exchange membrane prepared according to any one of the preparation methods described in claims 1 to 6, wherein the proton conductivity of the proton exchange membrane is 289 to 469 mScm -1 , the mechanical strength is 84.9 ~ 97.0MPa, and the proton exchange membrane is used for electrochemical compression of hydrogen.

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