Preparation method of flexible phosphoric acid type covalent organic framework doped perfluorosulfonic acid proton exchange membrane
By preparing a flexible phosphoric acid-based covalent organic framework-doped perfluorosulfonic acid proton exchange membrane, the trade-off problem between proton conductivity and mechanical stability of perfluorosulfonic acid membranes was solved, achieving improvements in both proton conductivity and mechanical strength, making it suitable for fuel cells and compressed hydrogen devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-03-27
AI Technical Summary
Existing perfluorosulfonic acid membranes exhibit a trade-off effect between proton conductivity and mechanical stability during proton exchange. Traditional inorganic fillers cannot provide additional ordered proton conduction pathways, and sulfonated COF proton carriers have poor water binding capacity, affecting the proton conductivity of composite membranes.
Flexible phosphoric acid-based covalent organic framework nanosheets (TpMbh-PO3H2 and TpPa-PO3H2) were prepared by single-liquid-phase synthesis. Perfluorosulfonic acid (Nafion) was blended with the phosphoric acid-based nanosheets by casting to regulate the local flexibility of the composite film, enhance the local mobility of the conductive groups, and form a continuous hydrogen bond network.
It improves the proton conductivity and mechanical stability of the composite membrane, enhances the local flexibility and mechanical strength of the membrane, and exhibits excellent ductility and adaptability, making it suitable for fuel cells and compressed hydrogen devices.
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Figure CN121736342A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of proton exchange membrane material preparation technology. Specifically, it relates to a method for preparing a flexible phosphoric acid-based covalent organic framework composite proton exchange membrane. Background Technology
[0002] Hydrogen energy, as a clean energy source, has an energy density three times that of petroleum and 4.5 times that of coal. The hydrogen energy industry chain comprises four main segments: hydrogen production, storage, transportation, and utilization. In each segment, efficient electrochemical processes are becoming mainstream. In hydrogen production, proton exchange membrane (PEM) water electrolysis technology exhibits wide adaptability to power fluctuations, allowing it to be matched with rapidly fluctuating renewable energy sources and achieve millisecond-level response. In hydrogen storage, electrochemical compression hydrogen storage technology is characterized by high efficiency and low energy consumption. In hydrogen utilization, PEMFCs can directly and efficiently convert hydrogen energy into electrical energy and are considered one of the most promising technologies in hydrogen energy applications. In the electrochemical process, the proton exchange membrane (PEM) is a core component, and its performance directly determines the overall efficiency and long-term operational stability of the device. Currently, the widely used perfluorosulfonic acid membranes (such as Nafion) rely on the hydration of hydrophilic ionic groups for proton conduction. However, excessive ionic groups lead to over-swelling of the membrane, resulting in a trade-off between proton conductivity and mechanical stability, which severely restricts commercial applications. To address these challenges, researchers attempted to dope Nafion with fillers to prepare hybrid matrix films.
[0003] Although the performance of composite membranes has been improved, traditional inorganic fillers cannot provide additional ordered proton conduction pathways, so their effect on improving proton conductivity is limited.
[0004] Covalent organic frameworks (COFs) are a class of crystalline porous materials with tunable periodic pore structures and extremely high specific surface areas. By functionalizing these highly ordered structures, long-range ordered ion channels can be fabricated, while the rigid framework provides excellent mechanical stability. Based on these properties, COFs are increasingly being selected as fillers for incorporating into polymers to regulate local flexibility and prepare proton exchange membranes with high conductivity and excellent stability.
[0005] Reference [1] synthesized a sulfonated covalent organic nanosheet (TpPa-SO3H) via interfacial polymerization and incorporated it into a sulfonated polyether ether ketone (SPEEK) matrix to prepare a proton exchange membrane (PEM). The tightly ordered sulfonic acid groups in the rigid framework of the TpPa-SO3H nanosheets, along with their high aspect ratio and well-defined porous structure, provide channels for proton conduction in the membrane. The doping of TpPa-SO3H nanosheets led to an increase in ion exchange capacity but a 2-fold decrease in swelling rate, significantly alleviating the trade-off between high ion exchange capacity and excessive swelling rate. However, compared to phosphorylated COF, sulfonated COF has a poorer ability to bind water to the proton carrier, which is not conducive to improving the proton conduction capacity of the composite membrane.
[0006] [References]
[0007] [1] Zhuo YY, Hao BG, Peng FY, et al. Improved proton conduction of sulfonated poly (ether ether ketone) membrane by sulfonated covalent organicframework nanosheets [J]. International Journal of Hydrogen Energy 46.52(2021): 26550-26559; July 29, 2021. Summary of the Invention
[0008] In view of the above-mentioned prior art, based on the advantages of short hydrogen bonds and flexible linkages in the hydrated proton domain around the phosphate group to enhance the local mobility of the conduction unit, the present invention provides a method for preparing a flexible phosphate-type covalent organic framework doped with perfluorosulfonic acid proton exchange membrane.
[0009] To address the aforementioned technical problems, this invention proposes a method for preparing a flexible phosphoric acid-type covalent organic framework-doped perfluorosulfonic acid proton exchange membrane, comprising the following steps:
[0010] Step 1, Synthesis of Phosphate-Based Covalent Organic Frameworks: Phosphate-based amine monomers were dissolved in dimethyl sulfoxide to obtain concentrations of 0.03–0.04 mmol / mL. -1 The amine monomer solution was prepared; a mixed solution with a volume ratio of 1:10 of 36% aqueous acetic acid and dimethyl sulfoxide was prepared, denoted as solution A. 1,3,5-Trihydroxypyrrolizaldehyde was dissolved in solution A to obtain a concentration of 0.018–0.024 mmol / mL. -1The aldehyde monomer solution was prepared by slowly adding the amine monomer solution to the aldehyde monomer solution at a volume ratio of 1:1.1 and reacting at 60°C for 4-7 days to obtain a phosphoric acid covalent organic framework nanosheet dispersion.
[0011] Step 2, Preparation of Phosphoric Acid Covalent Organic Framework Doped Perfluorosulfonic Acid Proton Exchange Membrane: Weigh the phosphoric acid covalent organic framework nanosheet dispersion and perfluorosulfonic acid polymer prepared in Step 1 at a mass ratio of 1:49 to 1:9, and dissolve them in dimethylformamide, wherein the mass-to-volume ratio of perfluorosulfonic acid polymer to dimethylformamide is 1 g / 50 mL. Stir for 12-24 h to obtain the casting solution; according to the volume-to-area ratio of 1 mL:5 cm²... 2 The casting solution was transferred to a glass plate and dried in an oven at 80°C for 1-3 days, followed by drying in an oven at 120°C for 1 hour to obtain the proton exchange membrane.
[0012] Furthermore, in the preparation method of the present invention, the phosphoric acid amine monomer is 3,5-dihydrazide carbonyl phenylphosphonic acid or 2,5-diaminophenylphosphonic acid.
[0013] The synthesis of the 3,5-dihydrazide carbonyl phenylphosphonic acid comprises: weighing dimethyl 5-aminoisophthalate and sodium tetrafluoroborate at a mass ratio of 1:0.89 and dispersing them in deionized water, wherein the concentration of sodium tetrafluoroborate is 0.093 mg / mL. -1 Stir for 3 hours to obtain solution A. Then, add concentrated hydrochloric acid and sodium nitrite solution in a volume ratio of 1.7:1 to solution A, wherein the volume ratio of sodium nitrite solution to solution A is 1:25. Stir for 1 hour, filter, wash, and dry to obtain a yellow powder. Prepare a mixed solution of phosphorus trichloride and ethyl acetate in a volume ratio of 1:4, denoted as solution B. Weigh the above-prepared yellow powder and cuprous bromide in solution B at a mass ratio of 1:0.6 to obtain solution C. The mass concentration of cuprous bromide in solution C is 0.045 g / mL. -1 After stirring for 3 hours, deionized water was added, with a volume ratio of deionized water to phosphorus trichloride of 1:0.2. The reaction was continued for 3 hours, followed by filtration, vacuum distillation, and recrystallization to obtain a white solid. This white solid was dispersed in a mixed solution of hydrazine hydrate and ethanol at a volume ratio of 4:1 to obtain a solid concentration of 0.6 g / mL. -1 Solution D was reacted at 80℃ for 36 h, and then filtered, washed and dried to obtain the phosphate-type amine monomer 3,5-dihydrazide carbonylphenylphosphoric acid.
[0014] The synthesis of 2,5-diaminophenylphosphonic acid includes: preparing a mixed solution of diethyl phosphonite, triethylamine, and toluene in a volume ratio of 2.24:2.2:1, denoted as solution E; weighing 2-bromophenyl-1,4-diamine and tetrakis(triphenylphosphine)palladium in a mass ratio of 1:0.25 and dispersing them in solution E to obtain a concentration of 0.18 g / mL of 2-bromophenyl-1,4-diamine. -1 Solution F was reacted at 90℃ for 48 h. After vacuum evaporation and chromatography purification, a purple liquid was obtained; a solution with a concentration of 0.02 g / mL was prepared. -1 A mixture of a purple liquid and anhydrous acetonitrile, denoted as solution G, was prepared by adding trimethylbromosilane to solution G, wherein the volume ratio of trimethylbromosilane to anhydrous acetonitrile was 1:9.1. The mixture was stirred in an N2 environment for 12 h to form a white suspension. Anhydrous methanol was then added to the white suspension, wherein the volume ratio of anhydrous methanol to anhydrous acetonitrile was 1:6, to produce an orange solid. After extraction, recrystallization, filtration, and drying, the phosphoric acid amine monomer 2,5-diaminophenylphosphoric acid was obtained.
[0015] Compared with the prior art, the beneficial effects of the present invention are:
[0016] The membrane fabrication process of this invention mainly includes preparing flexible phosphoric acid-based covalent organic framework nanosheets (TpMbh-PO3H2 and TpPa-PO3H2) via a single-liquid-phase synthesis method, and preparing composite proton exchange membranes (Nafion / TpMbh-PO3H2 and Nafion / TpPa-PO3H2) by blending perfluorosulfonic acid (Nafion) and phosphoric acid-based nanosheets via a casting method. This preparation method is simple to operate and easy to implement. In the preparation method of this invention, the local flexibility of the composite membrane is controlled by adjusting the flexibility of the doped COF, enhancing the local mobility of the conductive groups, improving the adaptability of the hydrogen bond network, and strengthening proton conduction. At the same time, the local flexibility of the composite membrane provides excellent ductility and mechanical stability, allowing it to maximize the membrane performance in practical applications. The composite membrane was assembled into a fuel cell and a hydrogen compression device for testing, exhibiting excellent performance. Attached Figure Description
[0017] Figure 1 This is a graph showing the change in proton conductivity of the membrane prepared in Example 1 as a function of temperature.
[0018] Figure 2 This is a stress-strain curve of the membrane prepared in Example 1;
[0019] Figure 3 The graph shows the change in proton conductivity of the membrane prepared in the comparative example as a function of temperature.
[0020] Figure 4 This is a stress-strain curve of the membrane prepared in the comparative example;
[0021] Figure 5 The graphs show the electrochemical hydrogen compression performance of the membranes prepared in Example 1 and Comparative Example 1. Detailed Implementation
[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention.
[0023] Example 1
[0024] A flexible phosphoric acid-type covalent organic framework-doped perfluorosulfonic acid proton exchange membrane was prepared. In this embodiment, the phosphoric acid-type amine monomer was 3,5-dihydrazide carbonyl phenylphosphonic acid, and the aldehyde monomer was 1,3,5-trihydroxytriphenylmethanealdehyde (Tp). The preparation steps of the membrane are as follows:
[0025] Step 1: Synthesis of 3,5-dihydrazide carbonyl phenylphosphonic acid: 20.92 mg of dimethyl 5-aminoisophthalate and 18.62 mg of sodium tetrafluoroborate were weighed and dispersed in 200 mL of deionized water, and stirred for 2 h. Then, 13.6 mL of concentrated hydrochloric acid and 8 mL of sodium nitrite solution were added, and the mixture was stirred for 1 h. After filtration, washing, and drying, a yellow powder was obtained. 3 g of the yellow powder and 1.8 g of cuprous bromide were weighed and dispersed in a mixed solution of 8 mL of phosphorus trichloride and 32 mL of ethyl acetate, and stirred for 3 h. Then, 40 mL of deionized water was added, and the reaction was allowed to proceed for 3 h. After filtration, vacuum distillation, and recrystallization, a white solid was obtained. 3 g of the white solid was dispersed in a mixed solution of 4 mL of hydrazine hydrate and 1 mL of ethanol, and reacted at 80 °C for 36 h. After the reaction was completed, 3,5-dihydrazide carbonyl phenylphosphonic acid was obtained after filtration, washing, and drying, denoted as Mbh-PO3H2.
[0026] Step 2, Synthesis of Phosphoric Acid Covalent Organic Framework: 82 mg of MBh-PO3H2 obtained in Step 1 was weighed and dissolved in 10 mL of dimethyl sulfoxide (DMSO) to obtain an amine monomer solution. 42 mg of Tp was weighed and dissolved in a mixed solution of 10 mL DMSO and 1 mL 36% acetic acid to obtain an aldehyde monomer solution. The amine monomer solution was slowly added to the aldehyde monomer solution, and the reaction was carried out at 60 °C for 7 days to obtain a phosphoric acid covalent organic framework nanosheet dispersion, denoted as TpMBh-PO3H2.
[0027] Step 3: Preparation of a phosphoric acid-type covalent organic framework-doped perfluorosulfonic acid proton exchange membrane: Weigh 0.35 mL of the TpMBh-PO3H2 nanosheet solution prepared in Step 2 and 100 mg of the perfluorosulfonic acid polymer (Nafion), dissolve them in 5 mL of DMF, and stir for 24 h to obtain the casting solution. Transfer 5 mL of the casting solution to a membrane with an area of 25 cm². 2The proton exchange membrane was dried on a glass plate at 80°C for 1 day, and then dried at 120°C for 1 hour to obtain the membrane, denoted as Nafion / TpMBh-PO3H2.
[0028] The proton conductivity of the Nafion / TpMBh-PO3H2 membrane prepared in Example 1 was tested to be 447.9 mS / cm. -1 (90℃, 100% RH), mechanical strength is 44.17 MPa, elongation at break is 203.6%, such as Figure 1 and Figure 2 As shown.
[0029] Example 2
[0030] A flexible phosphoric acid-type covalent organic framework-doped perfluorosulfonic acid proton exchange membrane was prepared. In this embodiment, the phosphoric acid-type amine monomer was 2,5-diaminophenylphosphonic acid, and the aldehyde monomer was 1,3,5-trihydroxytriphenylmethanealdehyde (Tp). The preparation steps of the membrane are as follows:
[0031] Step 1: Synthesis of 2,5-diaminophenylphosphine: 2 g of 2-bromophenyl-1,4-diamine and 0.5 g of tetrakis(triphenylphosphine)palladium were dispersed in a mixed solution of 4.48 mL diethyl phosphonite, 4.4 mL triethylamine, and 2 mL toluene, and reacted at 90 °C for 48 h. After the reaction, the solution was purified by vacuum evaporation and chromatography to obtain a purple liquid. 0.06 g of the purple liquid and 3 mL of anhydrous acetonitrile were added to a reaction tube, followed by 0.33 mL of trimethylbromosilane. The mixture was stirred in a N2 environment for 12 h to form a white suspension. 0.5 mL of anhydrous methanol was added to the white suspension to produce an orange solid. After extraction, recrystallization, filtration, and drying, 2,5-diaminophenylphosphine was obtained, denoted as Pa-PO3H2.
[0032] Step 2, Synthesis of Phosphoric Acid Covalent Organic Framework: 75.2 mg of Pa-PO3H2 obtained in Step 1 was weighed and dissolved in 10 mL of DMSO to obtain an amine monomer solution. 56 mg of Tp was weighed and dissolved in a mixed solution of 10 mL of DMSO and 1 mL of 36% acetic acid to obtain an aldehyde monomer solution. The amine monomer solution was slowly added to the aldehyde monomer solution, and the reaction was carried out at 60 °C for 4 days to obtain a phosphoric acid covalent organic framework nanosheet dispersion, denoted as TpPa-PO3H2.
[0033] Step 3: Preparation of a phosphoric acid-type covalent organic framework-doped perfluorosulfonic acid proton exchange membrane: Weigh 0.93 mL of the TpPa-PO3H2 nanosheet solution prepared in Step 2 and 100 mg of the perfluorosulfonic acid polymer (Nafion), dissolve them in 5 mL of DMF, and stir for 12 h to obtain the casting solution. Transfer 5 mL of the casting solution to a membrane with an area of 25 cm². 2 The proton exchange membrane was dried on a glass plate at 80°C for 3 days, followed by drying at 120°C for 1 hour to obtain the membrane, denoted as Nafion / TpPa-PO3H2.
[0034] The proton conductivity of the Nafion / TpPa-PO3H2 membrane prepared in Example 2 was tested to be 290.13 mS / cm. -1 (90℃, 100% RH), mechanical strength is 29.28 MPa, and elongation at break is 148.2%.
[0035] Comparative Example
[0036] Preparation of perfluorosulfonic acid proton exchange membrane: 100 mg of Nafion was dissolved in 5 mL of DMF and stirred for 24 h to obtain the casting solution. 5 mL of the casting solution was transferred to a membrane with an area of 25 cm². 2 The proton exchange membrane, denoted as Nafion membrane, was dried in an oven at 80°C for 3 days on a glass plate and then dried in an oven at 120°C for 1 hour.
[0037] The proton conductivity of the Nafion membrane prepared in the comparative example was tested to be 154 mS / cm. -1 (90℃, 100% RH), mechanical strength is 20.1 MPa, elongation at break is 104.1%, such as Figure 3 and Figure 4 As shown.
[0038] Table 1 Test data of Examples 1-2 and Comparative Examples
[0039]
[0040] Based on the preparation conditions of all the above embodiments and Table 1, it can be concluded that, compared with the comparative example, the COF-doped composite film exhibits higher proton conductivity and mechanical strength, confirming that adding COF filler can overcome the trade-off effect between proton conductivity and mechanical strength to a certain extent. Furthermore, with the increase of COF doping flexibility, the local flexibility of the prepared composite film is enhanced, the local mobility of chain segments is improved, the hydrogen bond network exhibits excellent self-regulation ability, forming a continuous hydrogen bond network, and the proton conduction rate is increased. Simultaneously, the excellent local flexibility of the composite film endows it with good ductility and mechanical strength.
[0041] The Nafion / TpMbh-PO3H2 membrane prepared in Example 1 exhibited the best overall performance. Both the Nafion / TpMbh-PO3H2 membrane and the Nafion membrane were assembled into a hydrogen compression device, and their electrochemical hydrogen compression performance was tested. Figure 5 As shown, the results indicate that the cathode output pressure of Nafion / TpMbh-PO3H2 is 1.94 MPa, which is attributed to the good local flexibility of Nafion / TpMbh-PO3H2, which improves the proton conductivity and mechanical stability of the composite membrane.
[0042] In summary, the phosphate-type nanosheets (TpMbh-PO3H2 and TpPa-PO3H2) used in the preparation method of this invention are synthesized via a single-liquid-phase synthesis method. Then, a series of phosphate-type covalent organic framework-doped perfluorosulfonic acid proton exchange membranes (Nafion / TpMbh-PO3H2 and Nafion / TpPa-PO3H2) are prepared by a casting method. The preparation method is simple and easy to implement. In the preparation method of this invention, the local flexibility of the composite membrane is controlled by adjusting the flexibility of the doped COF, thereby enhancing the adaptiveness of the hydrogen bond network and improving the proton conduction rate. Compared with traditional Nafion polymer membranes, the phosphate-type covalent organic framework-doped perfluorosulfonic acid proton exchange membranes (Nafion / TpMbh-PO3H2 and Nafion / TpPa-PO3H2) prepared by this invention exhibit superior performance in electrochemically compressed hydrogen and fuel cell devices due to the enhanced flexibility and ductility of the composite membranes with flexible COF fillers.
[0043] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many improvements and changes under the guidance of the present invention without departing from the spirit of the present invention, and these improvements and changes are all within the protection scope of the present invention.
Claims
1. A method for preparing a flexible phosphoric acid-type covalent organic framework-doped perfluorosulfonic acid proton exchange membrane, characterized in that, The steps are as follows: Step 1: Synthesis of phosphate-based covalent organic frameworks: The phosphate-type amine monomer was dissolved in dimethyl sulfoxide to obtain a concentration of 0.03–0.04 mmol / mL. -1 The amine monomer solution was prepared; a mixed solution with a volume ratio of 1:10 of 36% aqueous acetic acid and dimethyl sulfoxide was prepared, denoted as solution A. 1,3,5-Trihydroxypyrrolizaldehyde was dissolved in solution A to obtain a concentration of 0.018–0.024 mmol / mL. -1 The aldehyde monomer solution was prepared by slowly adding the amine monomer solution to the aldehyde monomer solution at a volume ratio of 1:1.1 and reacting at 60°C for 4-7 days to obtain a phosphoric acid covalent organic framework nanosheet dispersion. Step 2, Preparation of phosphoric acid-type covalent organic framework-doped perfluorosulfonic acid proton exchange membrane: Weigh the phosphoric acid-type covalent organic framework nanosheet dispersion and perfluorosulfonic acid polymer prepared in step one according to a mass ratio of 1:49 to 1:9, and dissolve them in dimethylformamide, wherein the mass-to-volume ratio of perfluorosulfonic acid polymer to dimethylformamide is 1 g / 50 mL. Stir for 12 to 24 h to obtain the casting solution; according to a volume-to-area ratio of 1 mL:5 cm²... 2 The casting solution was transferred to a glass plate and dried in an oven at 80°C for 1-3 days, followed by drying in an oven at 120°C for 1 hour to obtain the proton exchange membrane.
2. The preparation method according to claim 1, characterized in that, In step one, the phosphoric acid amine monomer is 3,5-dihydrazide carbonyl phenylphosphonic acid or 2,5-diaminophenylphosphonic acid.
3. The preparation method according to claim 2, characterized in that, In step one, the synthesis of the 3,5-dihydrazide carbonyl phenylphosphonic acid includes: Dimethyl 5-aminoisophthalate and sodium tetrafluoroborate were weighed at a mass ratio of 1:0.89 and dispersed in deionized water, wherein the concentration of sodium tetrafluoroborate was 0.093 mg / mL. -1 Stir for 3 h to obtain solution A; then, add concentrated hydrochloric acid and sodium nitrite solution in a volume ratio of 1.7:1 to solution A, wherein the volume ratio of sodium nitrite solution to solution A is 1:25, stir for 1 h, filter, wash and dry to obtain yellow powder; A mixed solution of phosphorus trichloride and ethyl acetate with a volume ratio of 1:4 was prepared, denoted as solution B. The yellow powder obtained above and cuprous bromide were weighed and dispersed in solution B at a mass ratio of 1:0.6 to obtain solution C. The mass concentration of cuprous bromide in solution C was 0.045 g / mL. -1 After stirring for 3 hours, deionized water was added, with a volume ratio of deionized water to phosphorus trichloride of 1:0.
2. After reacting for 3 hours, the mixture was filtered, distilled under reduced pressure, and recrystallized to obtain a white solid. The white solid obtained above was dispersed in a mixed solution of hydrazine hydrate and ethanol at a volume ratio of 4:1 to obtain a solid concentration of 0.6 g / mL. -1 Solution D was reacted at 80℃ for 36 h, and then filtered, washed and dried to obtain the phosphate-type amine monomer 3,5-dihydrazide carbonylphenylphosphoric acid.
4. The preparation method according to claim 2, characterized in that, Step one, the synthesis of 2,5-diaminophenylphosphonic acid, includes: A mixed solution of diethyl phosphonite, triethylamine, and toluene in a volume ratio of 2.24:2.2:1 was prepared and denoted as solution E. 2-Bromophenyl-1,4-diamine and tetrakis(triphenylphosphine)palladium were weighed and dispersed in solution E at a mass ratio of 1:0.25, yielding a concentration of 0.18 g / mL for 2-bromophenyl-1,4-diamine. -1 Solution F was reacted at 90℃ for 48 h, and after vacuum evaporation and chromatography purification, a purple liquid was obtained. Prepare a concentration of 0.02 g / mL -1 A mixture of a purple liquid and anhydrous acetonitrile, denoted as solution G, is added to solution G. Trimethylbromosilane is added to solution G, wherein the volume ratio of trimethylbromosilane to anhydrous acetonitrile is 1:9.
1. The mixture is stirred in an N2 environment for 12 h to form a white suspension. Anhydrous methanol was added to the above white suspension, wherein the volume ratio of anhydrous methanol to anhydrous acetonitrile was 1:6, and an orange solid was generated. After extraction, recrystallization, filtration and drying, the phosphoric acid amine monomer 2,5-diaminophenylphosphoric acid was obtained.