Method for improving cycle stability of MOF electrode material and application thereof

Abstract

This invention relates to the field of nanocomposite materials technology, specifically to a method for improving the cycling stability of MOF electrode materials and its application. The method of this invention uses aromatic hydrocarbons with hydroxyl or amino groups as organic ligands and MOFs that regulate the ligands. UPy-NCO molecules are grafted onto the hydroxyl or amino ends of the MOF material, and then dimers are formed through quadruple hydrogen bonds to obtain a cross-linked network. The preparation method disclosed in this invention is novel, and the MOF material prepared using this method exhibits high cycling stability, which can greatly improve the material's lifespan. This material can be used as an energy storage electrode material for supercapacitors, exhibiting excellent electrochemical performance and long service life.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite materials technology, and more specifically to a method for improving the cycling stability of MOF electrode materials and its application. Background Technology

[0002] MOF materials, or Metal-Organic Frameworks, possess extremely high specific surface areas and abundant pore structures, thus showing broad application prospects in fields such as gas adsorption and electrochemistry. The structure of MOF materials can be controlled by adjusting the selection and ratio of metal ions and organic ligands, thereby regulating their pore structure and chemical properties, offering strong tunability and design potential. Therefore, MOF materials have become one of the research hotspots in materials science and energy fields.

[0003] However, in practical applications, the nanostructure of MOF materials collapses with increasing usage time, reducing the specific surface area and leading to a decline in electrochemical performance. To improve the structural stability and lifespan of two-dimensional MOFs, introducing self-healing groups to prepare two-dimensional MOF hybrid materials has proven to be an effective method. Li et al. introduced quadruple hydrogen bonds (UPy) during the preparation of two-dimensional MOFs, synthesizing a series of Cu-MOF hybrid materials, including Cu-MOF@Ti3C2T x -UPy in 1A g -1 After 5000 cycles at a current density, its capacitance retention was 10% higher than that of Cu-MOF, indicating that quadruple hydrogen bonding endows Cu-MOF@Ti3C2T with... X -UPy exhibits stronger cycle stability because the binding energy of hydrogen bonds is lower than that of coordinate bonds. Under internal stress during electrochemical processes, hydrogen bonds preferentially break as sacrificial bonds, while new hydrogen bonds are regenerated at room temperature. This not only protects the MOF framework from damage but also improves the cycle stability of the material. (Li,S.;Zhang,L.;Ye,P.;Zhu,M.;Nie,Y.;Dai,Y.;Yang,F.,Construction ofBattery-Like Hierarchical MOF@MXeneHeterostructures for HybridSupercapacitors.Crystal Growth&Design 2024,24(18),7445-7454.)

[0004] However, due to the limited functional groups of MOFs themselves, the content of self-healing groups introduced is low, resulting in limited improvement in their stability. Therefore, a method is needed to improve the cycling stability of MOF electrode materials. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for improving the cycle stability of MOF electrode materials and its application.

[0006] The method of this invention utilizes the strong tunability of MOF materials to introduce quadruple hydrogen bonds. After cycling, the damage to the nanostructure of the electrode material can be self-repaired through quadruple hydrogen bonds. On this basis, a regulating ligand is added to adjust the content of groups that react with UPy-NCO units, thereby adjusting the content of quadruple hydrogen bonds, thus improving the cycling stability of the material and extending its service life.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect of the present invention, a method for improving the cycling stability of MOF electrode materials is provided, comprising the following steps:

[0009] 1) Dissolve the UPy-NCO unit in solvent a at 70-100℃ and stir for 30 minutes to obtain solution A with a concentration of 2.5-3.6 mg / ml;

[0010] 2) Dissolve the metal salt in solvent b and stir for 5-20 minutes to form solution B; dissolve the organic ligand, regulating ligand and surfactant polyvinylpyrrolidone (PVP) in solvent c and add it to solution B to obtain the reaction system. React at 30-120℃ for 2-20 hours; centrifuge the reaction product, wash and dry it to obtain the initial MOF material.

[0011] 3) Under stirring at 60-70℃ and N2 protection, the initial MOF material obtained in step 2) is dispersed in solvent d at a concentration of 1.5-2 mg / ml. Then, solution A obtained in step 1) is added to it to obtain a mixed system. The catalyst dibutyltin dilaurate is added to it, and then the temperature is raised to 90-150℃ and stirred for 12-20 hours. The reaction product is centrifuged, washed and dried to obtain MOF material with high cycle stability.

[0012] Further, in step 1), the preparation method of the UPy-NCO unit is as follows: UPy and HDI are mixed at a mass ratio of 1:10, and then the mixture is reacted at 100°C under N2 protection for 15 hours. After the reaction is completed, the reaction product is washed with n-hexane and then dried to obtain the UPy-NCO unit.

[0013] Furthermore, in step 1), solvent a is N,N-dimethylformamide.

[0014] Further, in step 2), the organic ligand is selected from 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-diaminoterephthalic acid, or 1,2,4,5-benzenetetracarboxylic acid; the regulating ligand is selected from 2,6-diaminopyridine or 2,4,6-triaminopyrimidine; and the metal salt is one or two of the nitrates, acetates, or chlorides of zinc, copper, nickel, cobalt, iron, titanium, and zirconium.

[0015] Further, in step 2), the mass ratio of metal salt: organic ligand: regulatory ligand: PVP is 1:(0.25~2):(0.1~0.5);(0.5~3).

[0016] Furthermore, in step 2), the content of the metal salt in solution B is 1-5 mg / ml.

[0017] Furthermore, in step 2), solvent b is selected from one or more of ethanol, deionized water, and N,N-dimethylformamide (DMF), and solvent c is selected from one or more of ethanol, deionized water, and N,N-dimethylformamide (DMF).

[0018] Furthermore, in step 3), the mass ratio of MOFs:UPy-NCO is 1:(0.375~1).

[0019] Furthermore, in step 3), the solvent d is N,N-dimethylformamide.

[0020] In a second aspect of the invention, the application of MOFs materials prepared by the method described in the first aspect as electrode materials in supercapacitors is provided.

[0021] The present invention has the following beneficial effects:

[0022] 1) The method of the present invention utilizes organic ligands and groups that regulate the ligands in MOFs materials to graft UPy-NCO units and controls the content of UPy-NCO units. The addition of regulated ligands can increase the content of UPy groups, so that the UPy system can form more dimers through quadruple hydrogen bonds, thereby obtaining a cross-linked network. When the MOFs structure is damaged, the structure can be restored through dynamic hydrogen bonds to obtain MOFs materials with high cycling stability.

[0023] 2) This invention introduces self-healing groups into MOF materials, fully utilizing the strong controllability of MOF materials and maximizing the role of each component. UPy (2-urea-4[H]-pyrimidinone) endows oligomers or polymers with reversible, self-complementary quadruple hydrogen bonds and a high association constant, enabling the oligomers or polymers to exhibit bulk material properties similar to high molecular weight covalent polymers or cross-linked elastic rubbers. By reacting the amino or hydroxyl groups of the organic ligands in the MOF materials with isonitrile ester groups, UPy-NCO is grafted into the MOF materials, allowing the MOF materials to be repaired through dynamic hydrogen bonding when damaged, restoring the initial nanostructure.

[0024] 3) Comparative experiments of specific embodiments of the present invention show that the MOFs material obtained by the present invention has good electrochemical cycling performance. When used as an electrode material to form a capacitor, the capacitor can be repaired by the electrode material instead of by the electrolyte after damage, which can greatly improve the service life of the capacitor. Attached Figure Description

[0025] Figure 1 This is a SEM image of Zn-MOF-DAP-UPy-NCO-1 prepared in Example 1.

[0026] Figure 2 This is a SEM image of Zn-MOF-UPy-NCO prepared in Comparative Example 1.

[0027] Figure 3 This is a comparison chart of the cycle performance of Zn-MOF-DAP-UPy-NCO-1 prepared in Example 1 and Zn-MOF-UPy-NCO prepared in Comparative Example 1. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0029] The sources of the materials involved in this invention are as follows:

[0030] Reagents: N,N-dimethylformamide (DMF), anhydrous ethanol, 2,5-diaminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2-aminoterephthalic acid (H2BDC-NH2), 2,6-diaminopyridine (DAP), copper nitrate trihydrate, zinc acetate, nickel chloride hexahydrate, cobalt chloride hexahydrate, and polyvinylpyrrolidone K-30 (PVP) were all purchased from Shanghai Husheng. 2-Amino-6-methylpyrimidin-4(1H)-one (UPy) and hexamethylene diisocyanate (HDI) were purchased from East China Chemical & Glassware Co., Ltd. All chemical substances used in the experiment were not further purified.

[0031] The preparation of UPy-NCO units can be carried out with reference to existing technologies, specifically the following literature: Liang Zhaopeng. Design, preparation and performance study of self-healing polyurethane elastomers [D]. Jiangsu University, 2021. DOI:10.27170 / d.cnki.gjsuu.2021.002025.

[0032] Example 1

[0033] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. At 70°C with stirring, 15 mg UPy-NCO was uniformly dispersed in 5 ml N,N-dimethylformamide and stirred for 30 min, denoted as solution A; 25 mg (CH3COO)2Zn was added to 12.5 ml ethanol and stirred for 10 min to obtain solution B; 4 mg 2,6-diaminopyridine, 25 mg 2-aminoterephthalic acid, and 75 mg polyvinylpyrrolidone were dissolved in 12.5 ml N,N-dimethylformamide and then added to solution B to obtain the reaction system, which was stirred at 35°C for 2 h; after the reaction was completed, the sample was centrifuged and washed, and dried at 60°C for 12 h to obtain the initial MOF material, labeled as Zn-MOF-DAP-1. Under stirring at 65℃ and N2 protection, 40 mg of Zn-MOF-DAP-1 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 90℃ and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 35℃ for 12 h to obtain the Zn-MOF-DAP-UPy-NCO-1 product.

[0034] Figure 1 SEM image of Zn-MOF-DAP-UPy-NCO-1 prepared in Example 1. Figure 1 It can be seen that after the UPy-NCO component is grafted onto the MOF framework, due to the intervention of the regulatory ligand, the number of UPy groups increases, the number of quadruple hydrogen bonds between molecules increases, and Zn-MOF-DAP-UPy-NCO-1 exhibits a cross-linked network structure.

[0035] The Zn-MOF-UPy-NCO-1 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Zn-MOF-DAP-UPy-NCO-1 sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 89.7%.

[0036] Example 2

[0037] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. At 80℃ with stirring, 15 mg UPy-NCO was uniformly dispersed in 5 mL of N,N-dimethylformamide and stirred for 30 min, denoted as solution A. 25 mg Cu(NO3)2·3H2O was dispersed in 10 mL of water under ultrasonication and stirred for 20 min, denoted as solution B. Then, 3 mg 2,6-diaminopyridine, 30 mg 2-aminoterephthalic acid, and 50 mg polyvinylpyrrolidone were dissolved in a mixed solvent consisting of 1 mL N,N-dimethylformamide, 1 mL water, and 1 mL ethanol, and added to solution B. The mixture was ultrasonicated for 10 min to obtain the reaction system, which was then transferred to an autoclave and solvated at 100℃ for 20 h. After the reaction, the mixture was centrifuged and washed, and then soaked in methanol for one day. Finally, the product was centrifuged, the sample was collected, and vacuum dried at 80℃ for 12 h to obtain the initial MOF material, labeled as Cu-MOF-DAP-2. Under stirring at 70℃ and N2 protection, 36 mg of Cu-MOF-DAP-2 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 90℃ and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 35℃ for 12 h to obtain the Cu-MOF-DAP-UPy-NCO-2 product.

[0038] The Cu-MOF-DAP-UPy-NCO-2 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Cu-MOF-DAP-UPy-NCO-2 sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 84.4%.

[0039] Example 3

[0040] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. At 90℃ with stirring, 15 mg UPy-NCO was uniformly dispersed in 5 mL N,N-dimethylformamide and stirred for 30 min, denoted as solution A; 30 mg NiCl2·6H2O and 30 mg CoCl2·6H2O were dispersed in 12 mL N,N-dimethylformamide under ultrasonication and stirred for 20 min, denoted as solution B; then 7 mg 2,6-diaminopyridine, 40 mg 2-aminoterephthalic acid and 80 mg polyvinylpyrrolidone were dissolved in a mixed solvent of 1 mL N,N-dimethylformamide, 1 mL water and 1 mL ethanol, denoted as solution C. Solution B and solution C were then mixed and stirred for 30 min to obtain the reaction system, which was transferred to an autoclave and solvothermal reacted at 120℃ for 20 h. After the reaction, the sample was centrifuged, washed, collected, and vacuum dried at 60℃ for 12 h to obtain the initial MOF material, labeled as Ni / Co-MOF-DAP-3. Under stirring at 70℃ and N2 protection, 30 mg of Ni / Co-MOF-DAP-3 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 90℃ and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 35℃ for 12 h to obtain the Ni / Co-MOF-DAP-UPy-NCO-3 product.

[0041] The Ni / Co-MOF-DAP-UPy-NCO-3 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which a Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Ni / Co-MOF-DAP-UPy-NCO-3 sample was used as the working electrode. Electrochemical cycling was performed in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 83.4%.

[0042] Example 4

[0043] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. At 80℃ with stirring, 30 mg UPy-NCO was uniformly dispersed in 10 ml N,N-dimethylformamide and stirred for 30 min, denoted as solution A; 30 mg (CH3COO)2Zn was added to 14 ml ethanol and stirred for 10 min to obtain solution B; 3 mg 2,6-diaminopyridine, 15 mg 2,5-dihydroxyterephthalic acid and 30 mg polyvinylpyrrolidone were dissolved in 8 ml N,N-dimethylformamide and then added to solution B to obtain the reaction system, which was stirred at 35℃ for 2 h; after the reaction was completed, the sample was centrifuged and washed, and dried at 60℃ for 12 h to obtain the initial MOF material, which was labeled as Zn-MOF-DAP-4. Under stirring at 65℃ and N2 protection, 36 mg of Zn-MOF-DAP-4 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 150℃ and reacted for 20 h. After the reaction was completed, the product was centrifuged and washed, and then vacuum dried at 35℃ for 12 h to obtain the Zn-MOF-DAP-UPy-NCO-4 product.

[0044] The Zn-MOF-DAP-UPy-NCO-4 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Zn-MOF-DAP-UPy-NCO-4 sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 85.5%.

[0045] Example 5

[0046] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. Under stirring at 100℃, 36 mg UPy-NCO was uniformly dispersed in 10 mL N,N-dimethylformamide and stirred for 30 min, denoted as solution A. 40 mg Cu(NO3)2·3H2O was dispersed in 16 mL water and stirred for 20 min under ultrasonication, denoted as solution B. Then, 10 mg 2,6-diaminopyridine, 30 mg 2,5-dihydroxyterephthalic acid, and 50 mg polyvinylpyrrolidone were dissolved in a mixed solvent consisting of 1 mL N,N-dimethylformamide, 1 mL water, and 1 mL ethanol, and added to solution B. The mixture was ultrasonicated for 10 min to obtain the reaction system, which was then transferred to an autoclave and solvated at 120℃ for 20 h. After the reaction, the mixture was centrifuged and washed, then soaked in methanol for one day. Finally, the product was centrifuged, the sample was collected, and vacuum dried at 80℃ for 12 h to obtain the initial MOF material, labeled as Cu-MOF-DAP-5. Under stirring at 70℃ and N2 protection, 36 mg of Cu-MOF-DAP-5 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 150℃ and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 60℃ for 12 h to obtain the Cu-MOF-DAP-UPy-NCO-5 product.

[0047] The Cu-MOF-DAP-UPy-NCO-5 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Cu-MOF-DAP-UPy-NCO-5 sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 84.4%.

[0048] Example 6

[0049] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. At 90℃ with stirring, 25 mg UPy-NCO was uniformly dispersed in 10 mL N,N-dimethylformamide and stirred for 30 min, denoted as solution A; 36 mg NiCl2·6H2O and 36 mg CoCl2·6H2O were dispersed in 15 mL N,N-dimethylformamide under ultrasonication and stirred for 20 min, denoted as solution B; then 16 mg 2,6-diaminopyridine, 18 mg 2,5-dihydroxyterephthalic acid and 80 mg polyvinylpyrrolidone were dissolved in a mixed solvent consisting of 1 mL N,N-dimethylformamide, 1 mL water and 1 mL ethanol, denoted as solution C. Solution B and solution C were then mixed and stirred for 30 min to obtain the reaction system, which was transferred to an autoclave and solvothermal reacted at 120℃ for 20 h. After the reaction, the sample was centrifuged, washed, collected, and vacuum dried at 60℃ for 12 h to obtain the initial MOF material, labeled as Ni / Co-MOF-DAP-6. Under stirring at 70℃ and N2 protection, 40 mg of Ni / Co-MOF-DAP-6 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 150℃ and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 65℃ for 12 h to obtain the Ni / Co-MOF-DAP-UPy-NCO-6 product.

[0050] The Ni / Co-MOF-DAP-UPy-NCO-6 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which a Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Ni / Co-MOF-DAP-UPy-NCO-6 sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 82.3%.

[0051] Example 7

[0052] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. At 90℃ with stirring, 30 mg UPy-NCO was uniformly dispersed in 10 ml N,N-dimethylformamide and stirred for 30 min, denoted as solution A; 25 mg (CH3COO)2Zn was added to 12.5 ml ethanol and stirred for 10 min to obtain solution B; 6 mg 2,6-diaminopyridine, 25 mg 2,5-diaminoterephthalic acid and 70 mg polyvinylpyrrolidone were dissolved in 12.5 ml N,N-dimethylformamide and then added to solution B to obtain the reaction system, which was stirred at 35℃ for 2 h; after the reaction was completed, the sample was centrifuged and washed, and dried at 60℃ for 12 h to obtain the initial MOF material, which was labeled as Zn-MOF-DAP-7. Under stirring at 65°C and N2 protection, 30 mg of Zn-MOF-DAP-1 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 90°C and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 65°C for 12 h to obtain the Zn-MOF-DAP-UPy-NCO-7 product.

[0053] The Zn-MOF-DAP-UPy-NCO-7 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Zn-MOF-DAP-UPy-NCO-7 sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 85.2%.

[0054] Example 8

[0055] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. Under stirring at 90℃, 30 mg UPy-NCO was uniformly dispersed in 10 mL of N,N-dimethylformamide and stirred for 30 min, denoted as solution A. 40 mg Cu(NO3)2·3H2O was dispersed in 16 mL of water under ultrasonication and stirred for 20 min, denoted as solution B. Then, 5 mg 2,6-diaminopyridine, 30 mg 2,5-dihydroxyterephthalic acid, and 70 mg polyvinylpyrrolidone were dissolved in a mixed solvent of 1 mL N,N-dimethylformamide, 1 mL water, and 1 mL ethanol, added to solution B, and ultrasonicated for 10 min to obtain the reaction system. This system was transferred to an autoclave and solvated at 100℃ for 20 h. After the reaction, the sample was centrifuged, washed, and then soaked in methanol for one day. Finally, the product was centrifuged, the sample was collected, and vacuum dried at 80℃ for 12 h to obtain the initial MOF material, labeled as Cu-MOF-DAP-8. Under stirring at 70℃ and N2 protection, 40 mg of Cu-MOF-DAP-8 was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 90℃ and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 65℃ for 12 h to obtain the Cu-MOF-DAP-UPy-NCO-8 product.

[0056] The Cu-MOF-DAP-UPy-NCO-8 prepared in this embodiment was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Cu-MOF-DAP-UPy-NCO-8 sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 84.2%.

[0057] Comparative Example 1: Preparation of Zn-MOF-UPy-NCO

[0058] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain UPy-NCO units. 15 mg of UPy-NCO was uniformly dispersed in 5 ml of N,N-dimethylformamide at 90 °C with stirring and stirred for 30 min, and this was labeled as solution A. 25 mg of (CH3COO)2Zn was added to 12.5 ml of ethanol and stirred for 10 min to obtain solution B. 25 mg of 2-aminoterephthalic acid and 75 mg of polyvinylpyrrolidone were dissolved in 12.5 ml of N,N-dimethylformamide and then added to solution B to obtain the reaction system. The reaction was stirred at 35 °C for 2 h. After the reaction, the mixture was centrifuged, washed, and dried at 60 °C for 12 hours to obtain the initial MOF material, which was labeled as Zn-MOF. Under stirring at 65℃ and N2 protection, 40 mg of Zn-MOF was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 90℃ and reacted for 20 h. After the reaction was completed, the product was centrifuged and washed, and then vacuum dried at 35℃ for 12 h to obtain the Zn-MOF-UPy-NCO product.

[0059] Figure 2 SEM images of Zn-MOF-UPy-NCO prepared for Comparative Example 1. Figure 2 It can be seen that after the UPy-NCO component is grafted onto the MOF framework, there are quadruple hydrogen bonds between the molecules, which makes the sample partially connected.

[0060] The Zn-MOF-UPy-NCO prepared in this comparative example was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Zn-MOF-UPy-NCO sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 81.6%.

[0061] Comparative Example 2: Preparation of Cu-MOF-UPy-NCO

[0062] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 mL of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain UPy-NCO units. 15 mg of UPy-NCO was uniformly dispersed in 5 mL of N,N-dimethylformamide at 90 °C with stirring for 30 min, and this was recorded as solution A. 25 mg of Cu(NO3)2·3H2O was dispersed in 10 mL of water under ultrasonication and stirred for 20 min, and this was recorded as solution B. Then, 30 mg of 2-aminoterephthalic acid and 50 mg of polyvinylpyrrolidone were dissolved in a mixed solvent of 1 mL of N,N-dimethylformamide, 1 mL of water, and 1 mL of ethanol, and added to solution B. The mixture was ultrasonicated for 10 min to obtain the reaction system, which was then transferred to an autoclave and solvothermal reacted at 100 °C for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then soaked in methanol for one day. Finally, the product was centrifuged, the sample was collected, and vacuum dried at 80℃ for 12 h to obtain the initial MOF material, which was labeled as Cu-MOF. Under stirring at 70℃ and N2 protection, 40 mg of Cu-MOF was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate, to obtain the reaction system. The reaction system temperature was raised to 90℃ and reacted for 20 h. After the reaction, the product was centrifuged and washed, and then vacuum dried at 35℃ for 12 h to obtain the Cu-MOF-UPy-NC product.

[0063] The Cu-MOF-UPy-NC prepared in this comparative example was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which the Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and the Cu-MOF-UPy-NCO sample was used as the working electrode. The sample was subjected to electrochemical cycling in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 80.9%.

[0064] Comparative Example 3: Preparation of Ni / Co-MOF-UPy-NCO

[0065] 0.76 g of UPy was mixed with 7.6 g of HDI, and the mixture was reacted at 100 °C under N2 protection for 15 hours. After the reaction was completed, 20 ml of n-hexane was added, the precipitate was filtered, and the reaction was repeated three times. The mixture was then dried at 50 °C for 12 hours to obtain the UPy-NCO unit. At 90℃ with stirring, 36 mg UPy-NCO was uniformly dispersed in 10 mL N,N-dimethylformamide and stirred for 30 min, denoted as solution A; 30 mg NiCl2·6H2O and 30 mg CoCl2·6H2O were dispersed in 12 mL N,N-dimethylformamide under ultrasonication and stirred for 20 min, denoted as solution B; then 40 mg 2-aminoterephthalic acid and 80 mg polyvinylpyrrolidone were dissolved in a mixed solvent of 1 mL N,N-dimethylformamide, 1 mL water and 1 mL ethanol, denoted as solution C. Solution B and solution C were then mixed and stirred for 30 min to obtain the reaction system, which was transferred to an autoclave and solvothermal reacted at 120℃ for 20 h. After the reaction, the sample was centrifuged, washed, collected, and vacuum dried at 60℃ for 12 h to obtain the initial MOF material, which was labeled as Ni / Co-MOF. Under stirring at 70℃ and N2 protection, 40 mg of Ni / Co-MOF was uniformly dispersed in 20 ml of N,N-dimethylformamide, then solution A was added, followed by two drops of dibutyltin dilaurate to obtain the reaction system. The reaction system temperature was raised to 90℃ and reacted for 20 h. After the reaction was completed, the mixture was centrifuged and washed, and then vacuum dried at 35℃ for 12 h to obtain the Ni / Co-MOF-UPy-NCO product.

[0066] The Ni / Co-MOF-UPy-NCO prepared in this comparative example was used as the electrode material for a supercapacitor. After the supercapacitor was fabricated, a three-electrode testing system was adopted, in which Pt sheet was used as the auxiliary electrode, Hg / HgO was used as the reference electrode, and Ni / Co-MOF-UPy-NCO sample was used as the working electrode. Electrochemical cycling was carried out in 1M KOH electrolyte at a current density of 2A / g. After 5000 cycles, the capacity retention rate of the sample was 80.1%.

[0067] Figure 3 A comparison of the cycling performance of Zn-MOF-DAP-UPy-NCO-1 prepared in Example 1 and Zn-MOF-UPy-NCO prepared in Comparative Example 1. (From...) Figure 3 It can be seen that the cycling performance of the material improved by about 10% after the addition of the regulatory ligand.

[0068] Table 1 shows the cycling performance of supercapacitors made using the products prepared in Examples 1-8 and the comparative examples as electrode materials. When the MOFs materials obtained in Examples 1-8 are used as electrode materials for supercapacitors, under the same conditions, the cycling performance of the MOFs materials of this invention is about 10% higher than that of pure MOFs materials. The MOFs materials obtained in this invention have better electrochemical cycling performance because the addition of controlled ligands increases the number of UPy-NCO groups grafted and also increases the hydrogen bond content of the material, allowing the material to break more hydrogen bonds during cycling to protect the coordination bonds. When used as electrode materials to form capacitors, this can greatly improve the lifespan of the capacitors.

[0069] Table 1 shows the cycling performance of the supercapacitors in Examples 1-8 and the comparative examples.

[0070]

[0071] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for improving the cycling stability of MOF electrode materials, characterized in that, Includes the following steps: 1) Dissolve the UPy-NCO unit in solvent a at 70-100℃ and stir for 30 minutes to obtain solution A with a concentration of 2.5-3.6 mg / ml; 2) Dissolve the metal salt in solvent b and stir for 5-20 minutes to form solution B; dissolve the organic ligand, regulating ligand and surfactant polyvinylpyrrolidone (PVP) in solvent c and add them to solution B to obtain the reaction system, and react at 30-120℃ for 2-20 hours. The reaction products were centrifuged, washed, and dried to obtain the initial MOF materials. 3) Under the conditions of stirring at 60-70℃ and N2 protection, the initial MOF material obtained in step 2) is dispersed in solvent d at a concentration of 1.5-2 mg / ml. Then, the solution A obtained in step 1) is added to it to obtain a mixed system. The catalyst dibutyltin dilaurate is added to it, and then the temperature is raised to 90-150℃ and stirred for 12-20 hours. The reaction product was centrifuged, washed, and dried to obtain MOF materials with high cycling stability.

2. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 1), the preparation method of UPy-NCO unit is as follows: UPy and HDI are mixed at a mass ratio of 1:10, and then the mixture is reacted at 100°C under N2 protection for 15 hours. After the reaction is completed, the reaction product is washed with n-hexane and then dried to obtain UPy-NCO unit.

3. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 1), solvent a is N,N-dimethylformamide.

4. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 2), the organic ligand is selected from 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-diaminoterephthalic acid, or 1,2,4,5-benzenetetracarboxylic acid; the regulating ligand is selected from 2,6-diaminopyridine or 2,4,6-triaminopyrimidine; and the metal salt is one or two of the nitrates, acetates, or chlorides of zinc, copper, nickel, cobalt, iron, titanium, and zirconium.

5. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 2), the mass ratio of metal salt: organic ligand: regulatory ligand: PVP is 1:(0.25~2):(0.1~0.5). (0.5～3)。 6. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 2), the content of the metal salt in solution B is 1-5 mg / ml.

7. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 2), solvent b is selected from one or more of ethanol, deionized water, and N,N-dimethylformamide (DMF), and solvent c is selected from one or more of ethanol, deionized water, and N,N-dimethylformamide (DMF).

8. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 3), MOFs:UPy-NCO = 1:(0.375~1).

9. The method for improving the cycling stability of MOF electrode materials according to claim 1, characterized in that, In step 3), the solvent d is N,N-dimethylformamide.

10. The application of MOF materials prepared by the method according to any one of claims 1-9 as electrode materials in supercapacitors.

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