Metal organic framework modified graphite felt electrode material and preparation method thereof

Abstract

The invention discloses a metal organic framework modified graphite felt electrode material and a preparation method thereof. In the invention, the metal organic framework is constructed on the surface of the graphite felt fiber by adopting a loading-coordination mode, and the composite graphite felt material with the high overpotential metal loaded in the carbon skeleton is prepared by utilizing the relatively high specific surface area and adjustable physicochemical properties of the structure. The composite electrode material prepared by the invention has the advantages of high conductivity, large specific surface area, ultrahigh hydrophilicity and the like; the composite electrode material is assembled into an iron-chromium flow battery, and the average energy efficiency of the iron-chromium flow battery reaches 80% or above.

Description

Technical Field

[0001] This invention belongs to the field of electrode material preparation for iron-chromium redox flow batteries (ICFB), specifically relating to a method for preparing a superhydrophilic graphite felt electrode material by constructing a metal-organic framework. Background Technology

[0002] With the development of the world economy, people's demand for energy is increasing day by day, and energy shortages are becoming increasingly severe. "Renewable energy + energy storage" is considered to be the main way to achieve this goal. Due to the intermittent and random characteristics of renewable energy power generation such as wind and solar power, large-scale integration into the power grid will seriously impact the safe and stable operation of the grid. Therefore, large-scale energy storage technology, especially long-term energy storage technology, is urgently needed to achieve peak shaving and valley filling of the power grid, thereby improving the grid's ability to absorb renewable energy power generation, solving problems such as wind and solar curtailment, and helping to achieve the goal of "carbon peaking and carbon neutrality".

[0003] Electrodes are one of the key materials in iron-chromium flow batteries. During charge and discharge, they do not participate in electrochemical reactions but only provide a site for redox reactions of the active materials in the electrolyte. Ideal electrode materials should possess characteristics such as high conductivity, high activity, high stability, high wettability, and high specific surface area. Carbon-based materials are considered ideal electrode materials for iron-chromium flow batteries due to their low cost, high chemical stability, and large potential window in highly oxidizing media. Researching highly active and efficient electrode materials to reduce electrochemical polarization is of great significance and commercial value, becoming a research hotspot in this field. In recent years, many scientists have devoted themselves to improving the electrocatalytic activity of electrodes. Various modification methods have been proposed, leading to significant progress, including the introduction of functional groups, the formation of porous structures, and the loading of electrocatalysts. Modified carbon materials exhibit better electrochemical performance. Studies have shown that modified carbon materials have rougher surfaces, increased specific surface area, and abundant pore size.

[0004] CN111392821A discloses a method for preparing a graphite felt-supported metal-organic framework (MOF) cathode material and its application, comprising the following steps: using iron salts, Pluronic F127, a weak acid, 2-aminoterephthalic acid, and carbon felt, the method involves adding the iron salts and Pluronic F127 to deionized water, stirring, and then adding the weak acid and 2-aminoterephthalic acid in the stated molar ratio, stirring to obtain a MOF precursor solution, which is then placed together with pretreated carbon felt in a reaction vessel, sealed, and subjected to a hydrothermal reaction. After washing and vacuum drying, the cathode material is obtained. This patent uses water as a solvent to synthesize MOFs via a hydrothermal reaction; however, if the metal ions used are prone to hydrolysis with water, it can lead to crystal defects, thus limiting the scope of MOF synthesis using water as a solvent. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing iron-chromium redox flow battery technology and provide a method for synthesizing graphite felt electrode materials. By constructing a metal-organic framework, a superhydrophilic graphite felt electrode material is prepared, solving problems such as low current density, few active sites, low specific surface area, and severe hydrogen evolution side reactions in existing graphite felt technologies. Using the method of this invention, a composite graphite felt material with advantages such as low cost, high conductivity, large specific surface area, and ultra-high hydrophilicity can be obtained, achieving high energy efficiency in flow batteries.

[0006] According to the first objective of the present invention, the present invention provides a method for preparing a metal-organic framework modified graphite felt electrode material.

[0007] Specifically, the preparation method of the superhydrophilic graphite felt electrode material includes the following:

[0008] S1. Ultrasonic cleaning is performed on the graphite felt to remove various organic and inorganic impurities inside the graphite felt, and then it is dried.

[0009] S2. The graphite felt obtained in step S1 is subjected to heat pretreatment.

[0010] S3. Weigh the metal salt and polyvinylpyrrolidone (PVP), add an appropriate amount of solvent N,N-dimethylformamide (DMF) and stir. After it is completely dissolved, use the solution to impregnate the graphite felt material that has undergone heat pretreatment in step S2, stirring thoroughly and continuously.

[0011] S4. Weigh 2,5-dihydroxyterephthalic acid (DHTA), dissolve it in an appropriate amount of DMF solution, and then add it to the graphite felt system obtained in step S3 to carry out a solvothermal reaction.

[0012] S5. The graphite felt material obtained in step S4 is dried and calcined to obtain a metal-organic framework-based graphite felt electrode material.

[0013] Furthermore, the cleaning method in step S1 specifically involves sequentially soaking and ultrasonicating with acetone, ethanol, and deionized water; the soaking time is generally 0.5-4 hours, and the ultrasonication time is 0.5-4 hours. The drying process employs vacuum drying at a temperature of 60-80°C.

[0014] Furthermore, the temperature of the heat pretreatment in step S2 is generally 400–600℃, and the holding time is 3–6 hours. The heating rate during the heating process is generally 5–10℃ / min.

[0015] Furthermore, in step S3, the amounts of each material are added according to the following proportions: depending on the type of metal salt added, the amount is 1–3.6 g; the mass of PVP is 2–4 g; the molecular weight of PVP is 5000–100000; and the amount of DMF is 10–50 mL. The impregnation treatment time is generally 0.5–5 minutes.

[0016] Furthermore, in step S4, the amounts of each material are added in the following proportions: DHTA is 0.1–0.3 g, and DMF is 10–50 mL.

[0017] Furthermore, the temperature of the solvothermal reaction in step S4 is generally 80–120°C, and the reaction time is generally 12–36 h.

[0018] Furthermore, in step S5, the graphite felt is dried in a vacuum oven at 60–80°C for 12–48 hours.

[0019] Furthermore, the calcination in step S5 is carried out under an inert atmosphere. The graphite felt is heated to 800–1000°C under an inert atmosphere for 1–4 hours. The heating rate during the heating process is generally 5–10°C / min.

[0020] Furthermore, the metal salt mentioned in step S3 includes, but is not limited to, compounds of metal ions with high superpotential such as Bi(NO3)3·5H2O, Co(NO3)2·6H2O, and PbCl2.

[0021] According to a second objective of the present invention, the present invention also provides a superhydrophilic graphite felt electrode material, which is prepared by the method described above.

[0022] The electrode material prepared by this invention is particularly suitable for the field of iron-chromium redox flow batteries.

[0023] In this invention, a metal-organic framework is constructed on the surface of graphite felt fibers using a loading-coordination approach. Utilizing the high specific surface area and tunable physicochemical properties of this structure, a composite graphite felt material with a high-potential metal loaded within a carbon framework is prepared. Its surface provides numerous active sites, catalyzing redox reactions and suppressing hydrogen evolution side reactions. Furthermore, the material prepared in this invention exhibits superhydrophilicity, enabling it to fully wet the electrolyte, reducing ohmic polarization losses within the battery, and forming a highly active composite electrode.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention uses commercially produced graphite felt, PVP (40000), DHTA, metal salts and other raw materials as raw materials, and adopts a loading-coordination method to prepare superhydrophilic graphite felt electrode materials by constructing metal-organic frameworks. The resulting composite electrode materials have the advantages of high conductivity, large specific surface area and ultra-high hydrophilicity.

[0026] 2. The technical route of this invention is simple, the process steps are suitable for large-scale commercial production, the process cost is low, and the operation is simple, which helps to realize the large-scale energy storage application of iron-chromium redox flow batteries.

[0027] 3. The key to this invention lies in the fact that metal-organic frameworks possess high specific surface area and flexible, tunable physicochemical properties. Based on these frameworks, a stable carbon skeleton can be formed after calcination. This catalyst with high specific surface area can significantly increase the number of active sites. Furthermore, the high-potential metal ions coordinated internally provide sufficient activity for redox reactions while suppressing hydrogen evolution side reactions, resulting in a highly active composite graphite felt electrode material. More importantly, the stable structure of the metal-organic framework allows for a more robust metal loading.

[0028] 4. In summary, this invention uses commercially produced graphite felt, PVP (40000), DHTA, metal salts, etc. as raw materials. It adopts a loading-coordination method to first prepare a polyvinylpyrrolidone (PVP) solution containing metal salts, and then immerse it in pretreated graphite felt. After the metal ions are fully loaded, it is transferred to a hydrothermal reactor and subjected to a solvothermal reaction with a 2,5-dihydroxyterephthalic acid (DHTA) ligand solution. The addition of PVP can make the graphite felt electrode have better hydrophilicity. Attached Figure Description

[0029] Figure 1 Cyclic voltammetry results of the superhydrophilic graphite felt electrode material prepared in Example 1 and a blank graphite felt.

[0030] Figure 2 The graph shows the efficiency of the superhydrophilic graphite felt electrode material prepared in Example 1 after 40 cycles.

[0031] Figure 3 This is a schematic diagram of the hydrophilicity test of the materials obtained in Examples 2 and 3. Detailed Implementation

[0032] The present invention will be described in detail below through specific embodiments. However, the purpose and use of these exemplary embodiments are only for illustrating the present invention and do not constitute any limitation on the actual protection scope of the present invention, nor are they intended to limit the protection scope of the present invention to these embodiments.

[0033] Example 1

[0034] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 400°C for 3 hours at a heating rate of 5°C / min.

[0035] Weigh 3.6g of Bi(NO3)3·5H2O and 2g of PVP (molecular weight 40000), add 30mL of DMF and stir until completely dissolved. Then, immerse the pre-treated graphite felt material in the solution and stir continuously for 4 hours. Weigh 0.1g of DHTA and 10mL of DMF and stir until completely dissolved. Transfer the solution to a 100mL hydrothermal reactor for later use. Add the graphite felt material and solution loaded with metal ions to the hydrothermal reactor. Then, place the hydrothermal reactor in a constant temperature chamber and keep it at 80℃ for 12 hours. After the reaction is complete, rinse the surface of the obtained graphite felt material with deionized water and dry it in a vacuum oven at 60℃ for 48 hours. Finally, calcine the obtained graphite felt in a high-temperature tube furnace and keep it at 800℃ for 1 hour with a heating rate of 5℃ / min to obtain a superhydrophilic graphite felt electrode material based on a metal-organic framework.

[0036] Depend on Figure 1 Cyclic voltammetry results show that the modified graphite felt electrode prepared in Example 1 has better redox reversibility and lower electrochemical polarization.

[0037] The modified graphite felt electrode material prepared in Example 1 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA / cm². -2 Cyclic testing was conducted at a current density of [value missing]. After 40 charge-discharge cycles, the average coulombic efficiency (CE) was greater than 95% and the energy efficiency (EE) was greater than 80%, demonstrating excellent battery performance.

[0038] Example 2

[0039] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 500°C for 5 hours at a heating rate of 10°C / min.

[0040] Weigh 1g of Bi(NO3)3·5H2O and 4g of PVP (molecular weight 5000), add 50mL of DMF and stir until completely dissolved. Then, immerse the pre-treated graphite felt material in the solution and stir continuously for a period of time. Weigh 0.3g of DHTA and 50mL of DMF and stir until completely dissolved. Transfer the solution to a 100mL hydrothermal reactor for later use. Add the graphite felt material and solution loaded with metal ions to the hydrothermal reactor. Then, place the hydrothermal reactor in a constant temperature chamber and keep it at 120℃ for 36h. After the reaction is complete, rinse the surface of the obtained graphite felt material with deionized water and dry it in a vacuum oven at 60℃ for 48h. Finally, calcine the obtained graphite felt in a high-temperature tube furnace and keep it at 1000℃ for 4h with a heating rate of 5℃ / min to obtain a superhydrophilic graphite felt electrode material based on a metal-organic framework.

[0041] The modified graphite felt electrode material prepared in Example 2 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA / cm². -2 Cyclic testing was conducted at a current density of [value missing], and the average energy efficiency was 78%, coulombic efficiency was 93%, and voltage efficiency was 84%. Additionally, [details missing]. Figure 3 The superhydrophilic properties of the material in Example 2 were demonstrated.

[0042] Example 3

[0043] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 500°C for 3 hours at a heating rate of 5°C / min.

[0044] Weigh 2.0 g of Bi(NO3)3·5H2O and 3 g of PVP (molecular weight 100,000), add 30 mL of DMF and stir until completely dissolved. Then, immerse the pre-treated graphite felt material in the solution and stir continuously for a period of time. Weigh 0.2 g of DHTA and 30 mL of DMF and stir until completely dissolved. Transfer the solution to a 100 mL hydrothermal reactor for later use. Add the graphite felt material and solution loaded with metal ions to the hydrothermal reactor. Then, place the hydrothermal reactor in a constant temperature chamber and keep it at 100 °C for 24 h. After the reaction is complete, rinse the surface of the obtained graphite felt material with deionized water and dry it in a vacuum oven at 60 °C for 48 h. Finally, calcine the obtained graphite felt in a high-temperature tube furnace and keep it at 900 °C for 2 h with a heating rate of 5 °C / min to obtain a superhydrophilic graphite felt electrode material based on a metal-organic framework.

[0045] The superhydrophilic graphite felt electrode material prepared in Example 3 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA cm⁻¹. -2 Cyclic tests were conducted at a current density, and the average energy efficiency was 84%, the coulombic efficiency was 95%, and the voltage efficiency was 88%.

[0046] Example 4

[0047] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 500°C for 3 hours at a heating rate of 5°C / min.

[0048] Weigh 2.0 g of PbCl2 and 3 g of PVP (molecular weight 40000), add 30 mL of DMF and stir until completely dissolved. Then, immerse the pre-treated graphite felt material in the solution and stir continuously for a period of time. Weigh 0.2 g of DHTA and 30 mL of DMF and stir until completely dissolved. Transfer the solution to a 100 mL hydrothermal reactor for later use. Add the graphite felt material and solution loaded with metal ions to the hydrothermal reactor. Then, place the hydrothermal reactor in a constant temperature chamber and keep it at 100 °C for 24 h. After the reaction is complete, rinse the surface of the obtained graphite felt material with deionized water and dry it in a vacuum oven at 60 °C for 48 h. Finally, calcine the obtained graphite felt in a high-temperature tube furnace and keep it at 900 °C for 2 h with a heating rate of 5 °C / min to obtain a superhydrophilic graphite felt electrode material based on a metal-organic framework.

[0049] The superhydrophilic graphite felt electrode material prepared in Example 4 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA cm⁻¹. -2 Cyclic tests were conducted at a current density, and the average energy efficiency was 77%, the coulombic efficiency was 92%, and the voltage efficiency was 84%.

[0050] Example 5

[0051] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 400°C for 3 hours at a heating rate of 5°C / min.

[0052] Weigh 2g of Co(NO3)2·6H2O and 3.5g of PVP (molecular weight 40000), add 30mL of DMF and stir until completely dissolved. Then, immerse the pre-treated graphite felt material into the solution and stir continuously for a period of time. Weigh 0.2g of DHTA and 30mL of DMF and stir until completely dissolved. Transfer the solution to a 100mL hydrothermal reactor for later use. Add the graphite felt material and solution loaded with metal ions to the hydrothermal reactor. Then, place the hydrothermal reactor in a constant temperature chamber and keep it at 100℃ for 24h. After the reaction is complete, rinse the surface of the obtained graphite felt material with deionized water and dry it in a vacuum oven at 60℃ for 48h. Finally, calcine the obtained graphite felt in a high-temperature tube furnace and keep it at 900℃ for 2h with a heating rate of 5℃ / min to obtain a superhydrophilic graphite felt electrode material based on a metal-organic framework.

[0053] The superhydrophilic graphite felt electrode material prepared in Example 5 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA cm⁻¹. -2 Cyclic tests were conducted at a current density, and the average energy efficiency was 75%, the coulombic efficiency was 91%, and the voltage efficiency was 82%.

[0054] Comparative Example 1

[0055] 179 mg FeCl3·6H2O and 160 mg Pluronic F127 were dissolved in 15 mL of deionized water and stirred for 1 h to obtain a mixed solution. 0.3 mL CH3COOH and 60 mg 2-aminoterephthalic acid were added to the mixed solution and stirred for 4 h to prepare a precursor solution for a metal-organic framework compound. Commercial graphite felt with a thickness of 0.5 cm was cut into 3 cm × 2 cm pieces, immersed in acetone, and ultrasonically cleaned for 0.5 h to remove oil stains. Then, it was rinsed with ultrapure water to obtain clean graphite felt (GF). The precursor solution of the metal-organic framework compound and the graphite felt (GF) were placed together in a reaction vessel, sealed, and subjected to a hydrothermal reaction at 110 °C for 24 h. After the reaction, the reaction vessel was allowed to cool naturally to room temperature. The product was first washed in ultrapure water at room temperature for 0.5 h, and then washed in ethanol at 60 °C for 0.5 h to remove impurities. The obtained product was vacuum dried at 60℃ for 10 h to obtain the graphite felt-supported metal-organic framework compound cathode material MOFs@GF.

[0056] The graphite felt loaded with metal-organic framework compounds prepared in Comparative Example 1 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA cm⁻¹. -2 Cyclic tests were conducted at a current density, and the average energy efficiency was 73%, the coulombic efficiency was 90%, and the voltage efficiency was 81%.

[0057] Comparative Example 2

[0058] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 400°C for 3 hours at a heating rate of 5°C / min.

[0059] The graphite felt loaded with metal-organic framework compounds prepared in Comparative Example 2 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA cm⁻¹. -2 Cyclic tests were conducted at a current density, and the average energy efficiency was 69%, the coulombic efficiency was 89%, and the voltage efficiency was 77%.

[0060] Comparative Example 3

[0061] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 400°C for 3 hours at a heating rate of 5°C / min.

[0062] Weigh 2g of PVP (molecular weight 40000), add 30mL of DMF and stir until completely dissolved. Then, immerse the PVP-modified graphite felt material in the solution and stir continuously for 4 hours. Add the graphite felt material and solution to a hydrothermal reactor, then place the reactor in a constant temperature chamber and keep it at 80℃ for 12 hours. After that, rinse the surface of the obtained graphite felt material with deionized water and dry it in a vacuum oven at 60℃ for 48 hours. Finally, place the obtained graphite felt in a high-temperature tube furnace for calcination and keep it at 800℃ for 1 hour with a heating rate of 5℃ / min to obtain the PVP-modified graphite felt electrode material.

[0063] The graphite felt loaded with metal-organic framework compounds prepared in Comparative Example 3 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA cm⁻¹. -2 Cyclic tests were conducted at a current density, and the average energy efficiency was 77%, the coulombic efficiency was 92%, and the voltage efficiency was 84%.

[0064] Comparative Example 4

[0065] The graphite felt was soaked in acetone, 95% ethanol solution, and deionized water sequentially, and then ultrasonically treated for 1 hour to remove various organic and inorganic impurities. Afterwards, residual moisture was removed using a vacuum pump, and the felt was dried in a vacuum oven at 60°C. The dried graphite felt was then placed in a ceramic boat and pre-treated in a high-temperature tube furnace at 500°C for 3 hours at a heating rate of 5°C / min.

[0066] Weigh 2.0 g of Bi(NO3)3·5H2O, add 30 mL of DMF and stir until completely dissolved. Then, immerse the pre-treated graphite felt material in the solution and stir continuously for a period of time. Weigh 0.2 g of DHTA and 30 mL of DMF and stir until completely dissolved. Transfer the solution to a 100 mL hydrothermal reactor for later use. Add the graphite felt material and solution loaded with metal ions to the hydrothermal reactor. Then, place the hydrothermal reactor in a constant temperature chamber and keep it at 100 °C for 24 h. After the reaction is complete, rinse the surface of the obtained graphite felt material with deionized water and dry it in a vacuum oven at 60 °C for 48 h. Finally, place the obtained graphite felt in a high-temperature tube furnace for calcination and keep it at 900 °C for 2 h with a heating rate of 5 °C / min to obtain a superhydrophilic graphite felt electrode material based on a metal-organic framework.

[0067] The superhydrophilic graphite felt electrode material prepared in Comparative Example 4 was used as an electrode to assemble an iron-chromium flow battery, which was tested at 60 mA cm⁻¹. -2 Cyclic tests were conducted at a current density, and the average energy efficiency was 78%, the coulombic efficiency was 91%, and the voltage efficiency was 86%.

Claims

1. A method for preparing a metal-organic framework modified graphite felt electrode material, characterized in that, Includes the following: S1. Ultrasonic cleaning is performed on the graphite felt to remove various organic and inorganic impurities inside the graphite felt, and then it is dried. S2. The graphite felt obtained in step S1 is subjected to heat pretreatment. S3. Weigh the metal salt and polyvinylpyrrolidone, add an appropriate amount of solvent N,N dimethylformamide and stir. After it is completely dissolved, use the solution to impregnate the graphite felt material that has undergone heat pretreatment in step S2, and stir thoroughly and continuously. S4. Weigh 2,5-dihydroxyterephthalic acid, dissolve it in an appropriate amount of N,N dimethylformamide solution, and then add it to the graphite felt system obtained in step S3 for a solvothermal reaction. S5. The graphite felt material obtained in step S4 is dried and calcined to obtain a superhydrophilic graphite felt electrode material based on a metal-organic framework.

2. The preparation method according to claim 1, characterized in that, The cleaning method in step S1 is as follows: acetone, ethanol, and deionized water are used in sequence for soaking and ultrasonic processes, respectively.

3. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the heat pretreatment is 400~600 ℃, and the holding time is 3~6 h.

4. The preparation method according to claim 1, characterized in that, In step S3, the amounts of each material are added according to the following proportions: the amount of metal salt is 1 ~ 3.6 g, the mass of polyvinylpyrrolidone is 2 ~ 4 g, and the amount of N,N-dimethylformamide is 10 ~ 50 mL.

5. The preparation method according to claim 1, characterized in that, The proportions of each material used in step S4 are as follows: 0.1 ~ 0.3 g of 2,5-dihydroxyterephthalic acid and 10 ~ 50 mL of N,N dimethylformamide solution.

6. The preparation method according to claim 1, characterized in that, The temperature of the solvothermal reaction in step S4 is 80~120 ℃, and the reaction time is 12~36 h.

7. The preparation method according to claim 1, characterized in that, In step S5, the drying temperature of the graphite felt is 60-80 ℃, and the drying time is 12-48 h.

8. The preparation method according to claim 1, characterized in that, The calcination described in step S5 is carried out under an inert atmosphere, at a temperature of 800 ~ 1000 ℃, and for a time of 1 ~ 4 h.

9. The preparation method according to claim 1, characterized in that, The metal salt mentioned in step S3 is selected from one or more of Bi(NO3)3·5H2O, Co(NO3)2·6H2O, and PbCl2.

10. The metal-organic framework modified superhydrophilic graphite felt electrode material obtained by any of the preparation methods described in claims 1-9.

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