Metal modified covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a metal modified covalent organic framework material as well as a preparation method and application thereof, relates to the technical field of electrochemistry, and is used for solving the technical problems that metal introduction is incomplete, metal assembly is not firm and the performance of the prepared MCOF is unstable in an existing preparation method of a metal-covalent organic framework (MCOF) material. The preparation method of the metal modified covalent organic framework material comprises the following steps: adding 2, 4, 6-triformyl phloroglucinol and a coordination monomer into a solvent, and uniformly dispersing; wherein the molar ratio of the 2, 4, 6-triformyl phloroglucinol to the coordination monomer is (1: 4)-(4: 1), and the volume ratio of the coordination monomer to the solvent is 1: (1000-2200); the preparation method comprises the following steps: adding a catalyst and metal salt into a solvent, freezing and vacuumizing, reacting for 48-72 hours at the temperature of 100-130 DEG C, cleaning and drying to obtain a target product. The technical scheme of the invention is used for providing the metal modified covalent organic framework material as well as the preparation method and the application thereof.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and more specifically to a metal-modified covalent organic framework material and a preparation method and application thereof. Background Art

[0002] Metal-organic framework (MOF) materials and covalent organic framework (COF) materials are two common types of porous materials. Both have high specific surface area and adjustable structure, so they are widely used in many fields such as gas separation and catalytic sensing. However, due to its weak coordination bond effect, MOF has weak chemical stability to organic solvents, acids and bases, which greatly affects its application performance. COF is considered to be an alternative structure to MOF, but its physical and chemical structure is limited by the constituent elements. A feasible strategy is to introduce open metal sites into the highly stable COF framework to construct metal-covalent organic framework (MCOF) materials, forming complementary advantages, combining the characteristics of MOF and COF, and achieving a balance between crystallinity, stability and multifunctionality.

[0003] The existing methods for preparing metal covalent organic framework (MCOF) materials mainly include direct synthesis, sub-component self-assembly and post-synthesis metallization. Among them, the sub-component self-assembly and post-synthesis metallization methods require a cumbersome multi-step reaction process, and the post-modification method will also lead to incomplete metal introduction and unstable metal assembly. The direct synthesis method is simple and convenient, and different metal precursors can be used to expand the performance of COF, so it is the main synthesis method for most MCOFs. The introduction of metals can effectively broaden the functional applications of COF, but when preparing MCOF by direct synthesis, the existence form of metals in COF is usually uncertain. Metals can exist in various forms such as single atoms, clusters, single substances, ions, oxides, etc. Different existence forms make the prepared MCOF performance unstable. It can be seen that the existing MCOF preparation methods have technical problems such as incomplete metal introduction, unstable metal assembly, and unstable performance of the prepared MCOF. Summary of the invention

[0004] The purpose of the present invention is to provide a metal-modified covalent organic framework material, a preparation method and an application thereof, so as to solve the technical problems of incomplete metal introduction, weak metal assembly and unstable performance of the prepared MCOF in the existing MCOF preparation method. In view of this, the present invention is implemented by the following scheme.

[0005] In the first aspect, the present invention provides a metal-modified covalent organic framework material, the structural formula of which is: ; Wherein, M represents the existence form of the metal, and the existence form of the metal includes single atom, cluster and single substance.

[0006] Compared with the prior art, in the metal-modified covalent organic framework material of the present invention, the covalent bond between the nitrogen and oxygen elements in the COF matrix and the metal realizes the fixation of metal single atoms, clusters or single substances in the COF matrix. The covalent bond has the advantage of high strength, and the COF matrix has a large specific surface area and a unique pp stacking structure. These advantages make the metal completely introduced into the COF matrix and firmly fixed without falling off, so there is no secondary pollution problem caused by the shedding of heavy metal ions; further, since the metal in the metal-modified covalent organic framework material of the present invention exists in a stable form, the covalent organic framework material of the present invention has stable performance. Through the above technical solution of the present invention, the technical problems of incomplete metal introduction, unstable metal assembly, and unstable MCOF performance in the existing MCOF are solved.

[0007] In a second aspect, the present invention provides a method for preparing the above-mentioned metal-modified covalent organic framework material, comprising: Add 2,4,6-triformylphloroglucinol and a coordination monomer into a solvent and disperse them uniformly; Wherein, the molar ratio of the 2,4,6-triformylphloroglucinol to the coordination monomer is (1:4) to (4:1), and the volume ratio of the coordination monomer to the solvent is 1: (1000 to 2200); A catalyst and a metal salt are added to the solvent, and after freezing and vacuuming, the reaction is carried out at a temperature of 100 to 130° C. for 48 to 72 hours, and the target product is obtained after washing and drying.

[0008] Compared with the prior art, the beneficial effects of the preparation method of the metal-modified covalent organic framework material of the present invention are the same as the beneficial effects of the metal-modified covalent organic framework material described in the above technical solution, which will not be repeated here.

[0009] Furthermore, in the preparation method of the metal-modified covalent organic framework material of the present invention, the coordination monomers include hydrazine hydrate, 2,5-diethoxyterephthaloylhydrazide, 2,5-dimethyl-1,4-phenylenediamine, 2,6-diaminoanthraquinone, p-phenylenediamine and 2,5-dimethylp-phenylenediamine.

[0010] Furthermore, in the preparation method of the metal-modified covalent organic framework material of the present invention, the solvent includes one or more of 1,3,5-trimethylbenzene, 1,4-dioxane, 1,2-o-dichlorobenzene, N,N-dimethylformamide, dimethylacetamide and DL-lactide.

[0011] Furthermore, in the method for preparing the metal-modified covalent organic framework material of the present invention, the catalyst comprises acetic acid; and / or, The metal salts include acetates, nitrates, sulfates and chlorides.

[0012] Furthermore, in the preparation method of the metal-modified covalent organic framework material of the present invention, the acetate includes zinc acetate, cobalt acetate, nickel acetate, copper acetate and iron acetate; The nitrates include zinc nitrate, cobalt nitrate, nickel nitrate, copper nitrate and iron nitrate; The sulfates include zinc sulfate, cobalt sulfate, nickel sulfate, copper sulfate and iron sulfate; The chloride salts include zinc chloride, cobalt chloride, nickel chloride, copper chloride and ferric chloride.

[0013] Furthermore, in the method for preparing the metal-modified covalent organic framework material of the present invention, the concentration of the acetic acid is 4-7 mol / L; and / or, The volume ratio of the acetic acid to the coordination monomer is 1:(1-2).

[0014] Furthermore, in the preparation method of the metal-modified covalent organic framework material of the present invention, after the cleaning and drying, the method further comprises: Activation treatment with methanol; and / or, The drying process is carried out in a vacuum environment, the drying temperature is 110-130° C., and the drying time is 12-72 hours.

[0015] Furthermore, in the preparation method of the metal-modified covalent organic framework material of the present invention, during the cleaning process, the cleaning agent includes acetone, tetrahydrofuran and ethanol.

[0016] In a third aspect, the present invention provides the use of the above-mentioned metal-modified covalent organic framework material as a positive electrode sulfur storage material or a diaphragm modification material for a lithium-sulfur battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 This is a schematic diagram of the structure of Zn-COF according to Example 1 of the present invention; Figure 2 This is a schematic diagram of a field emission scanning electron microscope of Zn-COF according to Example 1 of the present invention; Figure 3 This is a high-resolution transmission electron microscopy schematic diagram of Zn-COF in Example 1 of the present invention; Figure 4 This is the energy spectrum picture of Zn-COF of Example 1 of the present invention; Figure 5This is a schematic diagram of the rate performance of a lithium-sulfur battery assembled with a Zn-COF modified separator according to Example 1 of the present invention; Figure 6 The charge and discharge curves of the lithium-sulfur battery assembled with the Zn-COF modified separator of Example 1 of the present invention at various rates; Figure 7 The lithium symmetric battery assembled with the Zn-COF modified separator of Example 1 of the present invention is 1 mA cm -2 Voltage-time curves at current density. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0020] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. "Several" means one or more, unless otherwise clearly and specifically defined.

[0021] The existing methods for preparing metal covalent organic framework (MCOF) materials mainly include direct synthesis, sub-component self-assembly and post-synthesis metallization. Among them, the sub-component self-assembly and post-synthesis metallization methods require a cumbersome multi-step reaction process, and the post-modification method will also lead to incomplete metal introduction and unstable metal assembly. The direct synthesis method is simple and convenient, and different metal precursors can be used to expand the performance of COF. Therefore, it is the main synthesis method for most MCOFs. The introduction of metals can effectively broaden the functional application of COF. When preparing MCOF by direct synthesis, the existence form of metals in COF is uncertain. Metals can exist in various forms such as single atoms, clusters, simple substances, ions, oxides, etc. Different existence forms make the prepared MCOF have different catalytic properties. It can be seen that the existing MCOF preparation methods have technical problems such as incomplete metal introduction, unstable metal assembly, and unstable performance of the prepared MCOF.

[0022] In order to solve the above technical problems, in the first aspect, the present invention provides a metal-modified covalent organic framework material, the structural formula of which is: ; Wherein, M represents the existence form of the metal, and the existence form of the metal includes single atom, cluster and single substance.

[0023] In the case of adopting the above technical scheme, in the metal-modified covalent organic framework material of the present invention, the covalent bond between the nitrogen and oxygen elements in the COF matrix and the metal realizes the fixation of metal single atoms, clusters or single substances in the COF matrix. The covalent bond has the advantage of high strength, and the COF matrix has a large specific surface area and a unique pp stacking structure. These advantages make the metal completely introduced into the COF matrix and firmly fixed without falling off. Therefore, there is no secondary pollution problem caused by the shedding of heavy metal ions; further, since the metal in the metal-modified covalent organic framework material of the present invention exists in a stable form, the covalent organic framework material of the present invention has stable performance. Through the above technical scheme of the present invention, the technical problems of incomplete metal introduction, unstable metal assembly, and unstable performance of MCOF in the existing MCOF are solved.

[0024] In a second aspect, the present invention provides a method for preparing the above-mentioned metal-modified covalent organic framework material, comprising: Add 2,4,6-triformylphloroglucinol and a coordination monomer into a solvent and disperse them uniformly; Wherein, the molar ratio of the 2,4,6-triformylphloroglucinol to the coordination monomer is (1:4) to (4:1), and the volume ratio of the coordination monomer to the solvent is 1: (1000 to 2200); A catalyst and a metal salt are added to the solvent, and after freezing and vacuuming, the reaction is carried out at a temperature of 100 to 130° C. for 48 to 72 hours, and the target product is obtained after washing and drying.

[0025] In the case of adopting the above technical scheme, the preparation method of the metal-modified covalent organic framework material of the present invention is used to prepare the above metal-modified covalent organic framework material, specifically a metal-modified β-ketoenamine covalent organic framework material; in the preparation method, 2,4,6-triformyl phloroglucinol and a coordination monomer are added to a solvent, and a metal salt is added after uniform dispersion, and the above metal-modified covalent organic framework material can be obtained after reaction. In the metal-modified covalent organic framework material obtained by the preparation method, the fixation of metal single atoms, clusters or single substances in the COF matrix is ​​achieved through the covalent bonds between nitrogen and oxygen elements in the COF matrix and the metal, and the covalent bonds have the advantage of high strength, and the COF matrix has a large specific surface area and a unique pp stacking structure. These advantages make the metal completely introduced into the COF matrix, and fixed firmly, and there will be no shedding phenomenon, so there is no secondary pollution problem caused by the shedding of heavy metal ions; further, since the existence form of the metal in the metal-modified covalent organic framework material of the present invention is stable, the covalent organic framework material of the present invention has stable performance. For example, the molar ratio of the 2,4,6-triformylphloroglucinol to the coordination monomer may be 1:4 or 4:1, the volume ratio of the coordination monomer to the solvent may be 1:1000, 1:1600 or 1:2200, the reaction temperature may be 100°C, 120°C or 130°C, and the reaction time may be 48 hours, 60 hours or 72 hours.

[0026] It should be understood that in order to improve the performance of MCOF materials and broaden their application scope, in the preparation method of the metal-modified covalent organic framework material of the present invention, the type of coordination monomer should also be controlled. For example, the coordination monomer includes hydrazine hydrate, 2,5-diethoxyterephthaloylhydrazide, 2,5-dimethyl-1,4-phenylenediamine, 2,6-diaminoanthraquinone, p-phenylenediamine and 2,5-dimethyl-p-phenylenediamine; for another example, the coordination monomer can be hydrazine hydrate, 2,5-diethoxyterephthaloylhydrazide, 2,5-dimethyl-1,4-phenylenediamine, 2,6-diaminoanthraquinone, p-phenylenediamine or 2,5-dimethyl-p-phenylenediamine.

[0027] It should also be understood that in order to further optimize the reaction environment, improve the solubility and dispersibility of the reactants, ensure the smooth progress of the reaction process, and make the structure and performance of the final product meet expectations, the type of solvent should also be controlled in the preparation method of the metal-modified covalent organic framework material of the present invention. For example, the solvent includes one or more of 1,3,5-trimethylbenzene, 1,4-dioxane, 1,2-o-dichlorobenzene, N,N-dimethylformamide, dimethylacetamide and DL-lactide. For another example, the solvent can be one or more of 1,3,5-trimethylbenzene, 1,4-dioxane, 1,2-o-dichlorobenzene, N,N-dimethylformamide, dimethylacetamide and DL-lactide.

[0028] It should also be understood that in order to accelerate the reaction process, improve the reaction efficiency, ensure the selectivity of the reaction, and enable the metal to be more uniformly introduced into the covalent organic framework, the preparation method of the metal-modified covalent organic framework material of the present invention should also control the type of catalyst. For example, the catalyst includes acetic acid. Further, in order to introduce a specific type of metal and form a stable coordination relationship between it and the covalent organic framework, thereby giving the material a specific catalytic activity or functionality, the present invention should also control the type of metal salt. For example, the metal salt includes acetate, nitrate, sulfate and chloride. For another example, the acetate can be zinc acetate, cobalt acetate, ethyl acetate, etc. The catalyst may be acetic acid, nickel acetate, cupric acetate or ferric acetate, the nitrate may include zinc nitrate, cobalt nitrate, nickel nitrate, copper nitrate and ferric nitrate, the sulfate may be zinc sulfate, cobalt sulfate, nickel sulfate, copper sulfate and ferric sulfate, and the chloride may be zinc chloride, cobalt chloride, nickel chloride, cupric chloride and ferric chloride; exemplarily, the catalyst is acetic acid, the concentration of the acetic acid may be 4-7 mol / L, and the volume ratio of the acetic acid to the coordination monomer may be 1:(1-2); as another example, the concentration of the acetic acid may be 4 mol / L, 5 mol / L or 7 mol / L, and the volume ratio of the acetic acid to the coordination monomer may be 1:1, 1:1.5 or 1:2.

[0029] As a possible implementation manner, in the preparation method of the metal-modified covalent organic framework material of the present invention, after the cleaning and drying, the method further comprises: Activation treatment with methanol; and / or, The drying process is carried out in a vacuum environment, the drying temperature is 110-130° C., and the drying time is 12-72 hours.

[0030] In the case of adopting the above technical scheme, in the preparation method of the metal-modified covalent organic framework material of the present invention, after cleaning and drying, the MCOF material is activated. During the activation process, methanol can effectively penetrate into the pore structure of the MCOF material, and further purify the internal environment of the MCOF material by dissolving or replacing residual moisture, unreacted raw materials or other impurities; further, by controlling the drying process to be carried out in a vacuum environment, and controlling the temperature and time within the above reasonable range, on the one hand, the oxidation or hydrolysis of the MCOF material by oxygen or moisture can be avoided, and the structure of the MCOF material can be protected from damage. On the other hand, it can also ensure that the solvent and unreacted products in the MCOF material are fully volatilized, while avoiding the destruction of the MCOF material structure or the degradation of its performance due to excessive temperature; illustratively, the drying temperature can be 110°C, 120°C or 130°C, and the time can be 12 hours, 48 ​​hours or 72 hours; illustratively, during the cleaning process, the cleaning agent includes acetone, tetrahydrofuran and ethanol, and in another example, the cleaning agent can be acetone, tetrahydrofuran or ethanol.

[0031] In a third aspect, the present invention provides the use of the above-mentioned metal-modified covalent organic framework material as a positive electrode sulfur storage material or a diaphragm modification material for a lithium-sulfur battery.

[0032] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific embodiments, but the content of the present invention is not limited to the following embodiments.

[0033] Unless otherwise specified, the raw materials used in the following examples are commercially available. Example 1

[0034] This embodiment provides a method for preparing a metal-modified covalent organic framework material, comprising: S100, weigh 42 mg of 2,4,6-triformylphloroglucinol, add it into a 10 mL ampoule, add 2 mL of solvent into the ampoule, and ultrasonicate for 15 min to make it evenly dispersed; Wherein, the solvent is a mixed solution of equal volumes of 1,3,5-trimethylbenzene and 1,4-dioxane; S200, adding 200 μL of hydrazine hydrate into the ampoule bottle, and ultrasonicating for 15 min to make it evenly dispersed; S300, adding 200 μL of acetic acid and 0.15 mol of zinc acetate dihydrate into the ampoule, and performing ultrasonic treatment for 15 min to make them dispersed evenly; wherein the concentration of acetic acid is 6 mol / L; S400, clamp the ampoule on the double-row tube, freeze-vacuum-thaw in liquid nitrogen three times in a row, and seal it with a fire gun; S500, placing the ampoule in an oven at 120°C and reacting for 72 hours; S600, after the reaction is completed, the product is washed with acetone, tetrahydrofuran and ethanol respectively, and activated with methanol three times, and the time interval between each activation in the methanol activation process is 2 hours; The amounts of acetone, tetrahydrofuran and ethanol used in the cleaning process were (50) mL respectively, and the amount of methanol used was (150) mL; S700, drying the product after methanol activation in a vacuum oven for 72 hours to obtain a target product, which is labeled as Zn-COF; wherein the temperature of the vacuum oven is 120°C.

[0035] This embodiment also provides a metal-modified covalent organic framework material, which is prepared by the preparation method of the metal-modified covalent organic framework material in this embodiment, namely the above-mentioned Zn-COF, and its structural formula is as follows: Figure 3 . Example 2

[0036] The preparation method of the metal-modified covalent organic framework material provided in this embodiment is basically the same as that in Example 1, except that the zinc acetate dihydrate in step S300 of Example 1 is replaced by copper acetate monohydrate, the amount of copper acetate monohydrate is kept unchanged at 0.15 mol, and the ultrasonic time is 30 min.

[0037] The target product prepared in this example is labeled Cu-COF1.

[0038] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Cu-COF1. Example 3

[0039] The preparation method of the metal-modified covalent organic framework material provided in this embodiment is basically the same as that in Example 1, except that the zinc acetate dihydrate in step S300 of Example 1 is replaced by cobalt acetate tetrahydrate, the amount of cobalt acetate tetrahydrate is kept unchanged at 0.15 mol, and the ultrasonic time is 30 min.

[0040] The target product prepared in this example is labeled as Co-COF.

[0041] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Co-COF. Example 4

[0042] The preparation method of the metal-modified covalent organic framework material provided in this embodiment is basically the same as that in Example 1, except that the zinc acetate dihydrate in step S300 of Example 1 is replaced by nickel acetate tetrahydrate, the amount of nickel acetate tetrahydrate is kept unchanged at 0.15 mol, and the ultrasonic time is 30 min.

[0043] The target product prepared in this example is labeled as Ni-COF.

[0044] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Ni-COF. Example 5

[0045] The preparation method of the metal-modified covalent organic framework material provided in this embodiment is basically the same as that in Example 1, except that the zinc acetate dihydrate in step S300 of Example 1 is replaced by copper nitrate, the amount of copper nitrate is kept unchanged at 0.15 mol, and the ultrasonic time is 30 min.

[0046] The target product prepared in this example is labeled Cu-COF2.

[0047] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Cu-COF2. Example 6

[0048] The preparation method of the metal-modified covalent organic framework material provided in this embodiment is basically the same as that in Example 1, except that the zinc acetate dihydrate in step S300 of Example 1 is replaced by copper sulfate, the amount of copper sulfate is kept unchanged at 0.15 mol, and the ultrasonic time is 30 min.

[0049] The target product prepared in this example is marked as Cu-COF3.

[0050] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Cu-COF3. Example 7

[0051] The preparation method of the metal-modified covalent organic framework material provided in this embodiment is basically the same as that in Example 1, except that the zinc acetate dihydrate in step S300 of Example 1 is replaced by copper chloride, the amount of copper chloride is kept unchanged at 0.15 mol, and the ultrasonic time is 30 min.

[0052] The target product prepared in this example is marked as Cu-COF4.

[0053] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Cu-COF4. Example 8

[0054] This embodiment provides a method for preparing a metal-modified covalent organic framework material, comprising: S100, weigh 63 mg of 2,4,6-triformylphloroglucinol, add it into a 10 mL ampoule, add 3 mL of solvent into the ampoule, and ultrasonicate for 15 min to make it evenly dispersed; Wherein, the solvent is a mixed solution of equal volumes of 1,3,5-trimethylbenzene and 1,4-dioxane; S200, 63 mg of 2,5-dimethyl-1,4-phenylenediamine is placed in the ampoule and ultrasonicated for 15 min to make it uniformly dispersed; S300, adding 200 μL of acetic acid and 0.15 mol of zinc acetate dihydrate into the ampoule, and performing ultrasonication for 15 min to make them dispersed evenly; wherein the concentration of acetic acid is 4 mol / L; S400, clamp the ampoule on the double-row tube, freeze-vacuum-thaw in liquid nitrogen three times in a row, and seal it with a fire gun; S500, placing the ampoule in an oven at 110°C to allow the components to react for 72 hours; S600, after the reaction is completed, the product is washed with acetone, tetrahydrofuran and ethanol respectively, and then activated with methanol three times, and the time interval between each activation in the methanol activation process is 2 hours; The amounts of acetone, tetrahydrofuran and ethanol used in the cleaning process were (50) mL respectively, and the amount of methanol used was (150) mL; S700, drying the product after methanol in a vacuum oven for 48 hours to obtain a target product, which is marked as Zn-TpPa2; wherein the temperature of the vacuum oven is 130°C.

[0055] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Zn-TpPa2. Example 9

[0056] This embodiment provides a method for preparing a metal-modified covalent organic framework material, comprising: S100, weigh 42 mg of 2,4,6-triformylphloroglucinol, add it into a 10 mL ampoule, add 3 mL of solvent into the ampoule, and ultrasonicate for 15 min to make it evenly dispersed; Wherein, the solvent is a mixed solution of equal volumes of 1,2-o-dichlorobenzene and 1,4-dioxane; S200, 84 mg of 2,5-diethoxyterephthaloylhydrazide is placed in the ampoule and ultrasonicated for 15 min to make it uniformly dispersed; S300, adding 200 μL of acetic acid and 0.15 mol of zinc acetate dihydrate into the ampoule, and performing ultrasonication for 15 min to make them dispersed evenly; wherein the concentration of acetic acid is 7 mol / L; S400, clamp the ampoule on the double-row tube, freeze-vacuum-thaw in liquid nitrogen three times in a row, and seal it with a fire gun; S500, placing the ampoule in an oven at 130°C to allow the components to react for 48 hours; S600, after the reaction is completed, the product is washed with acetone, tetrahydrofuran and ethanol respectively, and then activated with methanol three times, and the time interval between each activation in the methanol activation process is 2 hours; The amounts of acetone, tetrahydrofuran and ethanol used in the cleaning process were (50) mL respectively, and the amount of methanol used was (150) mL; S700, drying the product after methanol in a vacuum oven for 60 hours to obtain a target product, which is marked as Zn-NUS3; wherein the temperature of the vacuum oven is 110°C.

[0057] This embodiment also provides a metal-modified covalent organic framework material, which is prepared using the preparation method of the metal-modified covalent organic framework material of this embodiment, namely the above-mentioned Zn-NUS3.

[0058] After preparing the metal-modified covalent organic framework materials of Examples 1 to 9, the present invention respectively carried out structural characterization and performance testing, and will be described in detail below using Example 1 as an example: The structure of Zn-COF of Example 1 is shown in Figure 1 After testing, the single-atom content of Zn in the Zn-COF of Example 1 of the present invention is 12.43%. Figure 1 , Figure 2 and Figure 3 , it can be seen that Zn-COF is a flower-like structure formed by the accumulation of smaller sheets; Figure 4 This is the TEM spectrum image of Zn-COF. It can be seen that elements such as C, N, O, and Zn are uniformly enriched, among which metallic Zn is uniformly distributed on the surface of the COF matrix. Zn exists in the form of single atoms, clusters, and single substances.

[0059] Furthermore, the target products prepared in the above embodiments of the present invention, namely, Zn-COF of embodiment 1, Cu-COF1 of embodiment 2, Co-COF of embodiment 3, Ni-COF of embodiment 4, Cu-COF2 of embodiment 5, Cu-COF3 of embodiment 6, Cu-COF4 of embodiment 7, Zn-TpPa2 of embodiment 8, and Zn-NUS3 of embodiment 9, can be used as positive electrode sulfur storage materials or diaphragm modification materials for lithium-sulfur batteries. Still taking Zn-COF of embodiment 1 for illustration, please refer to Figure 5 , Figure 5 Schematic diagram of the rate performance of lithium-sulfur batteries assembled with Zn-COF separator modified materials. Figure 5 It can be seen that the lithium-sulfur battery assembled with Zn-COF modified separator exhibits significantly better rate performance than that of PP separator, and its discharge specific capacity at 0.2, 0.5, 1 and 2C is 1215.7, 973.2, 860.2 and 693.2 mAh g -1 ; Figure 6 yes Figure 5 From the charge and discharge curves corresponding to each rate, we can see that the battery exhibits two complete discharge platforms at each rate, corresponding to the two-stage solid-liquid-solid conversion reaction process in the lithium-sulfur battery. Figure 7 The voltage-time curve of a lithium symmetric battery assembled with a Zn-COF modified separator. It can be seen that at 1 mA cm -2 At a current density of , the lithium symmetric battery assembled with Zn-COF modified diaphragm can achieve a stable cycle of up to 1000h, while the symmetric battery assembled with ordinary PP diaphragm has a sharp change in voltage within a cycle time of 600h. This comparison highlights the role of Zn-COF in homogenizing the lithium ion flow and achieving uniform lithium deposition by relying on its uniform pore structure. It should be noted that the batteries were assembled in an argon-filled glove box (water and oxygen values ​​were both less than 0.01PPm), and standard CR2032 button cells were obtained. The diaphragms used for the assembled batteries were Zn-COF modified PP diaphragms and commercial PP diaphragms; specifically, 4mg of Zn-COF was dispersed in an ethanol solution, fully ultrasonically dispersed, and then filtered onto the surface of the PP diaphragm to obtain a Zn-COF modified diaphragm. The positive electrode is Ketjen black-loaded sulfur (KJC / S, content is 70%), and pure lithium is used as the negative electrode. The preparation method of the positive electrode is: the active material KJC / S, conductive carbon black and PVDF with a mass ratio of 7:2:1 are mixed, and then ground in N-methylpyrrolidone solution, and then coated on the carbon-coated aluminum foil.

[0060] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0061] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A metal-modified covalent organic framework material, characterized in that: Its structural formula is: ； Wherein, M represents the existence form of the metal, and the existence form of the metal includes single atom, cluster and single substance.

2. A method for preparing a metal-modified covalent organic framework material according to claim 1, characterized in that: include: Add 2,4,6-triformylphloroglucinol and a coordination monomer into a solvent and disperse them uniformly; Wherein, the molar ratio of the 2,4,6-triformylphloroglucinol to the coordination monomer is (1:4) to (4:1), and the volume ratio of the coordination monomer to the solvent is 1: (1000 to 2200); A catalyst and a metal salt are added to the solvent, and after freezing and vacuuming, the reaction is carried out at a temperature of 100 to 130° C. for 48 to 72 hours, and the target product is obtained after washing and drying.

3. The method for preparing a metal-modified covalent organic framework material according to claim 2, characterized in that: The coordination monomers include hydrazine hydrate, 2,5-diethoxyterephthaloylhydrazide, 2,5-dimethyl-1,4-phenylenediamine, 2,6-diaminoanthraquinone, p-phenylenediamine and 2,5-dimethyl-p-phenylenediamine.

4. The method for preparing a metal-modified covalent organic framework material according to claim 3, characterized in that: The solvent includes one or more of 1,3,5-trimethylbenzene, 1,4-dioxane, 1,2-o-dichlorobenzene, N,N-dimethylformamide, dimethylacetamide and DL-lactide.

5. The method for preparing a metal-modified covalent organic framework material according to claim 4, characterized in that: The catalyst comprises acetic acid; and / or, The metal salts include acetates, nitrates, sulfates and chlorides.

6. The method for preparing a metal-modified covalent organic framework material according to claim 5, characterized in that: The acetates include zinc acetate, cobalt acetate, nickel acetate, copper acetate and iron acetate; The nitrates include zinc nitrate, cobalt nitrate, nickel nitrate, copper nitrate and iron nitrate; The sulfates include zinc sulfate, cobalt sulfate, nickel sulfate, copper sulfate and iron sulfate; The chloride salts include zinc chloride, cobalt chloride, nickel chloride, copper chloride and ferric chloride.

7. The method for preparing a metal-modified covalent organic framework material according to claim 6, characterized in that: The concentration of the acetic acid is 4-7 mol / L; and / or, The volume ratio of the acetic acid to the coordination monomer is 1:(1-2).

8. The method for preparing a metal-modified covalent organic framework material according to claim 7, characterized in that: After the cleaning and drying, the method further comprises: Activation treatment with methanol; and / or, The drying process is carried out in a vacuum environment, the drying temperature is 110-130° C., and the drying time is 12-72 hours.

9. The method for preparing a metal-modified covalent organic framework material according to claim 8, characterized in that: In the cleaning process, the cleaning agent includes acetone, tetrahydrofuran and ethanol.

10. Use of the metal-modified covalent organic framework material according to claim 1 as a positive electrode sulfur storage material or a diaphragm modification material for lithium-sulfur batteries.

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