A MOF-on-MOF material, preparation method and electrochemical energy storage application thereof

Abstract

The present invention relates to the technical field of MOF composite materials, and discloses a MOF-on-MOF material, a preparation method and its electrochemical energy storage application. The method uses terephthalic acid and 2,3,6,7,10,11-hexaaminotriphenylene as organic ligands, and in situ grows two-dimensional Ni-BDC nanosheets on the surface of nickel foam by a solvent thermal method; then uses a gas-liquid interface method to load the two-dimensional conjugated MOF material Co-HITP on its surface to form a Co-HITP-on-Ni-BDC composite material, that is, a MOF-on-MOF material. The preparation process is green and environmentally friendly, easy to operate, and can successfully prepare MOF-on-MOF metal-organic framework materials under lattice mismatch conditions. The obtained MOF-on-MOF material has both the rich active sites of Ni-BDC ultra-thin nanosheets and the excellent conductivity of the Co-HITP two-dimensional conjugated structure. The synergistic effect of the two makes it exhibit good electrochemical properties, and it has significant application potential in the field of energy storage.

Description

Technical Field

[0001] The present invention relates to the technical field of MOF composite materials, and in particular to a MOF-on-MOF material, a preparation method and electrochemical energy storage application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are a class of porous materials with periodic network structures formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination bonds. Their pore structure, specific surface area, and functional groups can be precisely controlled through the rational selection of metal nodes and organic ligands. Therefore, they hold broad application prospects in a wide range of fields, including sensing, gas adsorption, separation, catalysis, and drug delivery. However, traditional MOFs are often electrical insulators, a drawback that severely limits their application in areas requiring efficient charge transport.

[0003] Two-dimensional conjugated metal-organic frameworks (2D c-MOFs), an emerging class of conductive metal-organic framework materials, have attracted considerable attention due to their efficient in-plane conjugation and strong interlayer coupling, demonstrating broad application prospects. Although 2D conductive MOFs have improved their conductivity compared to traditional MOFs, their conductivity remains relatively low compared to traditional metal conductors and some high-performance conductive materials.

[0004] MOF-on-MOF materials are nanocomposites assembled from MOF units of varying structures and morphologies. Constructing MOF-on-MOF composites by assembling two or more different MOF units is an effective strategy for preparing MOF composites with complex nanostructures. Compared to single two-dimensional conductive MOF materials, the tunability and multi-layered nanostructures of MOF-on-MOF composites offer valuable development potential for applications in supercapacitor energy storage devices. However, most MOF materials differ in their unit cell parameters and coordination modes. The lattice-matching MOF-on-MOF synthesis strategy requires similar lattice parameters and crystal plane matching between the two MOFs, a requirement that significantly limits its application. Therefore, the simple and efficient synthesis of MOF-on-MOF structures has become a research hotspot and a key challenge in chemistry and materials science in recent years. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a MOF-on-MOF material, a preparation method and electrochemical energy storage applications thereof.

[0006] The process for preparing the MOF-on-MOF material in the present invention is simple, easy to operate, and requires mild conditions. The prepared MOF-on-MOF material can be applied to electrochemical energy storage. When the material is used as a supercapacitor electrode material, it has excellent storage capacity, good specific capacitance and rate performance, and is suitable for use as a supercapacitor electrode material.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a MOF-on-MOF material comprises the following steps:

[0009] Step (1): treating nickel foam (NF) with acetone, water, and ethanol in sequence, and drying the treated NF to obtain pretreated nickel foam;

[0010] Step (2): Mix and dissolve nickel metal salt and water to obtain an aqueous solution of nickel metal salt; mix and dissolve terephthalic acid (BDC) and N,N-dimethylformamide (DMF) to obtain an N,N-dimethylformamide solution of terephthalic acid;

[0011] Under stirring conditions, slowly add the aqueous solution of nickel metal salt to the N,N-dimethylformamide solution of terephthalic acid, mix well, add ethanol, and continue stirring to obtain a mixed solution;

[0012] The pretreated nickel foam is immersed in the mixed solution, reacted, cooled, washed, and dried after the reaction is completed to obtain the nickel foam loaded with Ni-BDC;

[0013] Step (3): 2,3,6,7,10,11-hexaaminotriphenylene (HITP), cobalt metal salt and water are mixed, ultrasonically dissolved, and ammonia water is added to react. After the reaction is completed, a Co-HITP film is obtained at the gas-liquid interface;

[0014] The nickel foam loaded with Ni-BDC was horizontally laminated on the Co-HITP film, cycled several times, washed, and dried to obtain MOF-on-MOF material.

[0015] Preferably, in step (1), the ultrasonic treatment conditions are as follows: placing the nickel foam (NF) in acetone, ultrasonically treating it for 10-20 minutes, taking it out, transferring it to water, ultrasonically treating it 1-2 times, each time for 5-10 minutes, taking it out, transferring it to ethanol and ultrasonically treating it 1-2 times, each time for 10-20 minutes, and taking it out; the drying conditions are as follows: drying it at a temperature of 60-90°C for 8-12 hours.

[0016] Furthermore, the size of the nickel foam is 2cm×2cm.

[0017] Preferably, in step (2), the nickel metal salt is any one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate.

[0018] Furthermore, the nickel metal salt is nickel chloride.

[0019] Preferably, in step (2), the solid-liquid ratio of nickel metal salt to water is 16-79 mg:1 mL; and the solid-liquid ratio of terephthalic acid to N,N-dimethylformamide is 2-8.3 mg:1 mL.

[0020] Preferably, in step (2), the stirring condition is: stirring at a temperature of 20-80° C. and a rotation speed of 100-500 rpm; the slow addition condition is: slowly adding at a speed of 1-5 d / s.

[0021] Preferably, in step (2), the molar ratio of nickel metal salt to terephthalic acid is 3.66:1; and the volume ratio of the aqueous solution of nickel metal salt, the N,N-dimethylformamide solution of terephthalic acid, and ethanol is 3:10:10.

[0022] Preferably, in step (2), the stirring time is continued for 0.5-2 hours.

[0023] Preferably, in step (2), the solid-liquid ratio of the pretreated nickel foam to the mixed solution is 1 g:50 mL; and the reaction conditions are: reaction at a temperature of 120° C. for 0.5-3 h.

[0024] Preferably, in step (3), the cobalt metal salt is any one of cobalt acetate, cobalt chloride, cobalt nitrate or cobalt sulfate.

[0025] Furthermore, the cobalt metal salt is cobalt acetate.

[0026] Preferably, in step (3), the molar ratio of 2,3,6,7,10,11-hexaaminotriphenylene to the cobalt metal salt is 1.28:1.

[0027] Preferably, in step (3), the solid-liquid ratio of 2,3,6,7,10,11-hexaaminotriphenylene, water, and ammonia water is 1 mg:3 mL:0.03 mL.

[0028] Preferably, in step (3), the reaction conditions are: reaction at a temperature of 20-80° C. for 0.5-2 h.

[0029] Preferably, in step (3), the number of cycles is 1-3 times.

[0030] Preferably, a MOF-on-MOF material is prepared using the MOF-on-MOF material preparation method as described above.

[0031] Preferably, an application of the MOF-on-MOF material as described above in the field of electrochemical energy storage.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention uses a simple two-step synthesis method. First, Ni-BDC is grown on a nickel foam substrate by a solvothermal method. Then, Co-HITP-on-Ni-BDC material, i.e., MOF-on-MOF material, is obtained on the surface of the nickel foam loaded with Ni-BDC by a gas-liquid interface method. The two-dimensional sheet structure of Ni-BDC is conducive to the exposure of more active sites, which is conducive to improving the Faradaic capacitance contribution of the energy storage reaction. Its two-dimensional nanosheets grow vertically on the surface of the nickel foam, forming an open three-dimensional array structure. This open pore structure is also more conducive to sufficient contact between the electrolyte and the active sites. The conductive two-dimensional conjugated MOF Co-HITP is loaded onto the Ni-BDC surface. The two-dimensional conjugated skeleton of its Co-HITP gives the material a high electron transfer rate and reduces the charge transfer impedance. The above factors work synergistically, so that the MOF-on-MOF metal organic framework material prepared by the present invention can achieve dual optimization of capacitance performance and rate characteristics in the application of supercapacitors.

[0034] 2. The preparation method of the present invention avoids the limitations of lattice matching strategies, eliminating the need for similar lattice parameters and crystal plane matching between the two MOFs. This provides a new approach to the design of MOF composites. Furthermore, in the MOF-on-MOF material formed by adsorption, Ni-BDC and Co-HITP can produce a stronger synergistic effect, significantly optimizing the material's energy storage performance.

[0035] 3. When preparing MOF-on-MOF materials, the present invention has mild preparation conditions, does not require extreme temperature, pressure and other conditions, and the process is energy-saving and simple.

[0036] 4. The MOF-on-MOF material prepared by the present invention has excellent energy storage performance due to its multi-component synergistic properties: the abundant redox active sites of the Ni-BDC nanosheets and the highly conductive network of the Co-HITP conjugated skeleton form a three-dimensional charge transfer channel, exhibiting a specific capacitance of 2986.8 F / g at a current density of 1 A / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a scanning electron microscope image of the nickel foam material loaded with Ni-BDC prepared in Examples 1-4 of the present invention;

[0038] Figure 2is a scanning electron microscope image of the MOF-on-MOF material Co-HITP-1c-on-Ni-BDC-1h prepared in Example 2;

[0039] Figure 3 The constant current charge-discharge (CP) curve and specific capacitance diagram of the MOF-on-MOF material prepared in Example 1 of the present invention at different current densities in the energy storage performance test;

[0040] Figure 4 The constant current charge-discharge (CP) curve and specific capacitance diagram of the MOF-on-MOF material prepared in Example 2 of the present invention at different current densities in the energy storage performance test;

[0041] Figure 5 The constant current charge-discharge (CP) curve and specific capacitance diagram of the MOF-on-MOF material prepared in Example 3 of the present invention at different current densities in the energy storage performance test;

[0042] Figure 6 The constant current charge-discharge (CP) curve and specific capacitance diagram of the MOF-on-MOF material prepared in Example 4 of the present invention at different current densities in the energy storage performance test;

[0043] Figure 7 The constant current charge-discharge (CP) curve and specific capacitance diagram of the MOF-on-MOF material prepared in Example 5 of the present invention at different current densities in the energy storage performance test;

[0044] Figure 8 The constant current charge-discharge (CP) curve and specific capacitance diagram of the MOF-on-MOF material prepared in Example 6 of the present invention at different current densities in the energy storage performance test;

[0045] Figure 9 The constant current charge-discharge (CP) curve and specific capacitance diagram of the Ni-BDC-loaded nickel foam material prepared in Comparative Example 1 of the present invention at different current densities in the energy storage performance test;

[0046] Figure 10 The constant current charge-discharge (CP) curve and specific capacitance diagram of the Co-HITP-loaded nickel foam material prepared in Comparative Example 2 of the present invention at different current densities in the energy storage performance test;

[0047] Figure 11 The constant current charge-discharge (CP) curve and specific capacitance diagram of the nickel foam material loaded with Co-HITP / Ni-BDC mixed material prepared in Comparative Example 3 of the present invention at different current densities in the energy storage performance test;

[0048] Figure 12Schematic diagram of the synthesis of MOF-on-MOF materials prepared in the present invention;

[0049] In the picture:

[0050] Figure 1 In the figure, (a) is a scanning electron microscope image of the nickel foam loaded with Ni-BDC-0.5h prepared in Example 1; (b) is a scanning electron microscope image of the nickel foam loaded with Ni-BDC-1h prepared in Example 2; (c) is a scanning electron microscope image of the nickel foam loaded with Ni-BDC-2h prepared in Example 3; (d) is a scanning electron microscope image of the nickel foam loaded with Ni-BDC-3h prepared in Example 4;

[0051] Figure 2 In the figure, (a) is a plan view of the MOF-on-MOF material Co-HITP-1c-on-Ni-BDC-1h prepared in Example 2; (b) is a cross-sectional view of the MOF-on-MOF material Co-HITP-1c-on-Ni-BDC-1h prepared in Example 2;

[0052] Figure 3-11 In the figure, (a) is the constant current charge and discharge (CP) curve; (b) is the specific capacitance diagram. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0054] Example 1

[0055] This embodiment discloses a method for preparing a MOF-on-MOF material, comprising the following steps:

[0056] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, take it out, transfer it to water, ultrasonically treat it twice, each time for 5 minutes, take it out, transfer it to ethanol and ultrasonically treat it once, each time for 15 minutes, take it out, and dry it at 85°C for 12 hours to obtain pretreated nickel foam;

[0057] Step (2): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0058] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0059] The pretreated 2×2 cm nickel foam was placed in a 50 ml autoclave, and the above mixture was added. The mixture was reacted at 120°C for 0.5 h. After the reaction, the mixture was cooled to room temperature, washed with ethanol and water, and dried at 60°C for 12 h to obtain nickel foam loaded with Ni-BDC-0.5h.

[0060] The solid-liquid ratio of the pretreated nickel foam to the mixed solution was 1 g:50 mL;

[0061] Step (3): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed and dissolved by ultrasonication. 0.3 mL of ammonia water was added at 50 °C and reacted for 0.5 h. After the reaction was completed, a Co-HITP film was obtained at the gas-liquid interface.

[0062] The nickel foam loaded with Ni-BDC-0.5h was horizontally laminated on the Co-HITP film, cycled once, washed with ethanol and water, and dried at 60°C for 12h to obtain a MOF-on-MOF material, which was recorded as Co-HITP-1c-on-Ni-BDC-0.5h.

[0063] Example 2

[0064] This embodiment discloses a method for preparing a MOF-on-MOF material, comprising the following steps:

[0065] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, take it out, transfer it to water, ultrasonically treat it twice, each time for 5 minutes, take it out, transfer it to ethanol and ultrasonically treat it once, each time for 15 minutes, take it out, and dry it at 85°C for 12 hours to obtain pretreated nickel foam;

[0066] Step (2): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0067] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0068] The pretreated 2×2 cm nickel foam was placed in a 50 ml autoclave, and the above mixture was added. The mixture was reacted at 120°C for 1 h. After the reaction, the mixture was cooled to room temperature, washed with ethanol and water, and dried at 60°C for 12 h to obtain nickel foam loaded with Ni-BDC-1h.

[0069] The solid-liquid ratio of the pretreated nickel foam to the mixed solution was 1 g:50 mL;

[0070] Step (3): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed and dissolved by ultrasonication. 0.3 mL of ammonia water was added at 50 °C and reacted for 0.5 h. After the reaction was completed, a Co-HITP film was obtained at the gas-liquid interface.

[0071] The nickel foam loaded with Ni-BDC-1h was horizontally laminated on the Co-HITP film, cycled once, washed with ethanol and water, and dried at 60°C for 12h to obtain a MOF-on-MOF material, which was recorded as Co-HITP-1c-on-Ni-BDC-1h.

[0072] Example 3

[0073] This embodiment discloses a method for preparing a MOF-on-MOF material, comprising the following steps:

[0074] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, take it out, transfer it to water, ultrasonically treat it twice, each time for 5 minutes, take it out, transfer it to ethanol and ultrasonically treat it once, each time for 15 minutes, take it out, and dry it at 85°C for 12 hours to obtain pretreated nickel foam;

[0075] Step (2): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0076] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0077] The pretreated 2×2 cm nickel foam was placed in a 50 ml autoclave, and the above mixture was added. The mixture was reacted at 120°C for 2 h. After the reaction, the foam was cooled to room temperature, washed with ethanol and water, and dried at 60°C for 12 h to obtain nickel foam loaded with Ni-BDC-2h.

[0078] The solid-liquid ratio of the pretreated nickel foam to the mixed solution was 1 g:50 mL;

[0079] Step (3): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed and dissolved by ultrasonication. 0.3 mL of ammonia water was added at 50 °C and reacted for 0.5 h. After the reaction was completed, a Co-HITP film was obtained at the gas-liquid interface.

[0080] The nickel foam loaded with Ni-BDC-2h was horizontally laminated on the Co-HITP film, cycled once, washed with ethanol and water, and dried at 60°C for 12h to obtain a MOF-on-MOF material, which was recorded as Co-HITP-1c-on-Ni-BDC-2h.

[0081] Example 4

[0082] This embodiment discloses a method for preparing a MOF-on-MOF material, comprising the following steps:

[0083] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, take it out, transfer it to water, ultrasonically treat it twice, each time for 5 minutes, take it out, transfer it to ethanol and ultrasonically treat it once, each time for 15 minutes, take it out, and dry it at 85°C for 12 hours to obtain pretreated nickel foam;

[0084] Step (2): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0085] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0086] The pretreated 2×2 cm nickel foam was placed in a 50 ml autoclave, and the above mixture was added. The mixture was reacted at 120°C for 3 h. After the reaction, the foam was cooled to room temperature, washed with ethanol and water, and dried at 60°C for 12 h to obtain nickel foam loaded with Ni-BDC-3h.

[0087] The solid-liquid ratio of the pretreated nickel foam to the mixed solution was 1 g:50 mL;

[0088] Step (3): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed and dissolved by ultrasonication. 0.3 mL of ammonia water was added at 50 °C and reacted for 0.5 h. After the reaction was completed, a Co-HITP film was obtained at the gas-liquid interface.

[0089] The nickel foam loaded with Ni-BDC-3h was horizontally laminated on the Co-HITP film, cycled once, washed with ethanol and water, and dried at 60°C for 12h to obtain a MOF-on-MOF material, which was recorded as Co-HITP-1c-on-Ni-BDC-3h.

[0090] Example 5

[0091] This embodiment discloses a method for preparing a MOF-on-MOF material, comprising the following steps:

[0092] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, remove, transfer to water, ultrasonically treat twice, each time for 5 minutes, remove, transfer to ethanol and ultrasonically treat once, each time for 15 minutes, remove, and dry at 85°C for 12 hours to obtain pretreated nickel foam;

[0093] Step (2): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0094] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0095] The pretreated 2×2 cm nickel foam was placed in a 50 ml autoclave, and the above mixture was added. The mixture was reacted at 120°C for 1 h. After the reaction, the mixture was cooled to room temperature, washed with ethanol and water, and dried at 60°C for 12 h to obtain nickel foam loaded with Ni-BDC-1h.

[0096] The solid-liquid ratio of the pretreated nickel foam to the mixed solution was 1 g:50 mL;

[0097] Step (3): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed and dissolved by ultrasonication. 0.3 mL of ammonia water was added at 50 °C and reacted for 0.5 h. After the reaction was completed, a Co-HITP film was obtained at the gas-liquid interface.

[0098] The nickel foam loaded with Ni-BDC-1h was horizontally laminated on the Co-HITP film for two cycles, washed with ethanol and water, and dried at 60°C for 12h to obtain a MOF-on-MOF material, which was recorded as Co-HITP-2c-on-Ni-BDC-1h.

[0099] Example 6

[0100] This embodiment discloses a method for preparing a MOF-on-MOF material, comprising the following steps:

[0101] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, remove, transfer to water, ultrasonically treat twice, each time for 5 minutes, remove, transfer to ethanol and ultrasonically treat once, each time for 15 minutes, remove, and dry at 85°C for 12 hours to obtain pretreated nickel foam;

[0102] Step (2): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0103] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0104] The pretreated 2×2 cm nickel foam was placed in a 50 ml autoclave, and the above mixture was added. The mixture was reacted at 120°C for 1 h. After the reaction, the mixture was cooled to room temperature, washed with ethanol and water, and dried at 60°C for 12 h to obtain nickel foam loaded with Ni-BDC-1h.

[0105] The solid-liquid ratio of the pretreated nickel foam to the mixed solution was 1 g:50 mL;

[0106] Step (3): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed and dissolved by ultrasonication. 0.3 mL of ammonia water was added at 50 °C and reacted for 0.5 h. After the reaction was completed, a Co-HITP film was obtained at the gas-liquid interface.

[0107] The nickel foam loaded with Ni-BDC-1h was horizontally laminated on the Co-HITP film for three cycles, washed with ethanol and water, and dried at 60°C for 12 hours to obtain a MOF-on-MOF material, which was named Co-HITP-3c-on-Ni-BDC-1h.

[0108] Comparative Example 1

[0109] This comparative example discloses a method for preparing a nickel foam material loaded with Ni-BDC, comprising the following steps:

[0110] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, take it out, transfer it to water, ultrasonically treat it twice, each time for 5 minutes, take it out, transfer it to ethanol and ultrasonically treat it once, each time for 15 minutes, take it out, and dry it at 85°C for 12 hours to obtain pretreated nickel foam;

[0111] Step (2): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0112] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0113] The pretreated 2×2 cm nickel foam was placed in a 50 ml autoclave, and the above mixture was added. The mixture was reacted at 120°C for 1 h. After the reaction, the foam was cooled to room temperature, washed with ethanol and water, and dried at 60°C for 12 h to obtain a nickel foam material loaded with Ni-BDC, which was recorded as Ni-BDC.

[0114] The solid-liquid ratio of the pretreated nickel foam to the mixed solution was 1 g:50 mL;

[0115] Comparative Example 2

[0116] This comparative example discloses a method for preparing a nickel foam material loaded with Co-HITP, comprising the following steps:

[0117] Step (1): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, take it out, transfer it to water, ultrasonically treat it twice, each time for 5 minutes, take it out, transfer it to ethanol and ultrasonically treat it once, each time for 15 minutes, take it out, and dry it at 85°C for 12 hours to obtain pretreated nickel foam;

[0118] Step (2): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed and dissolved by ultrasonication. 0.3 mL of ammonia water was added at 50 °C and reacted for 0.5 h. After the reaction was completed, a Co-HITP film was obtained at the gas-liquid interface.

[0119] The pretreated nickel foam was horizontally laminated on the Co-HITP film, and the cycle was repeated once. The nickel foam was washed with ethanol and water, and dried at 60°C for 12 hours to obtain a nickel foam material loaded with Co-HITP, which was recorded as Co-HITP.

[0120] Comparative Example 3

[0121] This comparative example discloses a method for preparing a nickel foam material loaded with a Co-HITP / Ni-BDC mixed material, comprising the following steps:

[0122] Step (1): 237 mg of NiCl2·6H2O and 3 mL of water were mixed and dissolved to obtain a nickel chloride hexahydrate aqueous solution; 83 mg of terephthalic acid (BDC) and 10 mL of N,N-dimethylformamide (DMF) were mixed and dissolved to obtain a terephthalic acid N,N-dimethylformamide solution;

[0123] Under stirring conditions of 25°C and 400 rpm, an aqueous solution of nickel chloride hexahydrate was slowly added to a solution of terephthalic acid in N,N-dimethylformamide at a rate of 3 d / s. After mixing evenly, 10 mL of ethanol was added and stirring was continued for 30 min to obtain a mixed solution.

[0124] The mixture was reacted at 120°C for 1 hour. After the reaction, it was cooled to room temperature, centrifuged, filtered, washed with ethanol and water, and dried at 60°C for 12 hours to obtain Ni-BDC.

[0125] Step (2): 10 mg of 2,3,6,7,10,11-hexaaminotriphenylene (HITP), 6 mg of cobalt acetate, and 30 mL of water were mixed, 10 mg of Ni-BDC was added for ultrasonic dispersion, 0.3 mL of ammonia water was added, and the mixture was reacted at 50°C for 0.5 h. After the reaction, the mixture was washed by centrifugation with ethanol and water for 3 times, and dried in an oven at 60°C for 12 h to obtain a Co-HITP / Ni-BDC mixed material;

[0126] Step (3): Place nickel foam (NF) with a size of 2×2 cm in acetone, ultrasonically treat for 15 minutes, take it out, transfer it to water, ultrasonically treat it twice, each time for 5 minutes, take it out, transfer it to ethanol and ultrasonically treat it once, each time for 15 minutes, take it out, and dry it at 85°C for 12 hours to obtain pretreated nickel foam;

[0127] 13 mg of Co-HITP / Ni-BDC mixed material, 2.4 mg of acetylene black powder, and 0.8 mg of PVDF binder were mixed and ground for 30 min and dispersed in isopropanol solution to obtain Co-HITP / Ni-BDC mixed material slurry;

[0128] Using the pretreated nickel foam as the substrate, the Co-HITP / Ni-BDC mixed material slurry was evenly coated on the 2cm×2cm pretreated nickel foam. After coating, it was dried, washed with ethanol and water, and dried again at 60°C for 12h to obtain a nickel foam material loaded with Co-HITP / Ni-BDC mixed material.

[0129] Experimental data characterization and performance testing

[0130] like Figure 1 、 Figure 2 As shown, the nickel foam materials loaded with Ni-BDC prepared in Examples 1-4 were tested by scanning electron microscopy;

[0131] Figure 1The scanning electron microscope images of the nickel foam material loaded with Ni-BDC prepared at different reaction times in Examples 1-4 are shown. Figure 1 The test results show that the Ni-BDC nanosheets synthesized in the examples grow vertically on the surface of nickel foam, staggered, and form an open three-dimensional array structure. By comparing Examples 1-4, it can be seen that the thickness of the Ni-BDC two-dimensional nanosheets gradually increases with the increase of reaction time, and excessive reaction time will lead to densification of the structure. Therefore, the solvothermal reaction time plays a crucial role in the construction of MOF-on-MOF nanomaterials.

[0132] Figure 2 This is a scanning electron microscope image of Co-HITP-1c-on-Ni-BDC-1h prepared in Example 2. Figure 2 The test results show that Co-HITP is in the form of a two-dimensional film, which is attached to the surface of the nickel foam material loaded with Ni-BDC.

[0133] like Figure 3-11 As shown in Table 1, the energy storage performance tests were performed on the materials prepared in Examples 1-6 and Comparative Examples 1-3 respectively;

[0134] The energy storage performance test process specifically involved using a standard three-electrode system. The materials prepared in Examples 1-6 and Comparative Examples 1-3 were pressed into electrode sheets at a pressure of 10.0 MPa using a tablet press. These sheets served as the working electrode, a Hg / HgO electrode served as the reference electrode, and a platinum sheet served as the counter electrode. A 1 mol / L KOH aqueous solution was used as the electrolyte for capacitance performance testing. All tests were conducted on a CHI760F electrochemical workstation. Constant current charge-discharge (CP) curves were measured at different current densities, and specific capacitance and rate performance were calculated.

[0135] Table 1

[0136]

[0137] exist Figure 3-11 middle, Figure 3 The three-electrode system constructed with the MOF-on-MOF material prepared in Example 1 has a specific capacitance of 1266.0 F / g at a current density of 1 A / g and a rate performance of 51.1% at a current density of 10 A / g. Figure 4 The three-electrode system constructed with the MOF-on-MOF material prepared in Example 2 has a specific capacitance of 2986.8 F / g at a current density of 1 A / g and a rate performance of 52.7% at a current density of 10 A / g. Figure 5The three-electrode system constructed with the MOF-on-MOF material prepared in Example 3 has a specific capacitance of 1832.7 F / g at a current density of 1 A / g and a rate performance of 28.1% at a current density of 10 A / g. Figure 6 The three-electrode system constructed with the MOF-on-MOF material prepared in Example 4 has a specific capacitance of 1229.3 F / g at a current density of 1 A / g and a rate performance of 13.5% at a current density of 10 A / g. Figure 7 The three-electrode system constructed with the MOF-on-MOF material prepared in Example 5 has a specific capacitance of 1272.3 F / g at a current density of 1 A / g and a rate performance of 49.7% at a current density of 10 A / g. Figure 8 The three-electrode system constructed with the MOF-on-MOF material prepared in Example 6 has a specific capacitance of 1986.8 F / g at a current density of 1 A / g and a rate performance of 20.3% at a current density of 10 A / g. Figure 9 The three-electrode system constructed with the nickel foam material loaded with Ni-BDC prepared in Comparative Example 1 has a specific capacitance of 988.2 F / g at a current density of 1 A / g and a rate performance of 15.1% at a current density of 10 A / g; Figure 10 The three-electrode system constructed with the Co-HITP-loaded nickel foam prepared in Comparative Example 2 has a specific capacitance of 343.8 F / g at a current density of 1 A / g and a rate performance of 81.6% at a current density of 10 A / g. Figure 11 It shows that the three-electrode system constructed with nickel foam material loaded with Co-HITP / Ni-BDC mixed material prepared in Comparative Example 3 has a specific capacitance of 885.7 F / g at a current density of 1 A / g and a rate performance of 9.6% at a current density of 10 A / g.

[0138] Depend on Figure 3-11As shown in Table 1, the nickel foam material loaded with Ni-BDC prepared in Comparative Example 1 has good specific capacitance but poor rate performance. The specific capacitances at current densities of 1, 2, 3, 5, 7, and 10 A / g are 988.2, 774.7, 657.3, 520.0, 376.4, and 148.9 F / g, respectively. When the specific capacitance increases 10-fold from a low current density of 1 A / g to 10 A / g, the capacitance retention rate is only 15.1%. The nickel foam material loaded with Co-HITP prepared in Comparative Example 2 has good rate performance, but its capacitance value is relatively low. The MOF-on-MOF nanomaterials obtained in Examples 1-6 are prepared by controlling different reaction times and different film thicknesses. It can be seen that the specific capacitance values ​​of the MOF-on-MOF materials prepared in Examples 1-6 are all higher than those of the materials obtained in Comparative Examples 1 and 2, and relative to the MOF-on-MOF material in Comparative Example 1, the rate performance of the MOF-on-MOF material obtained in Example 2 is greatly improved. This shows that in the MOF-on-MOF material, the synergistic effect between Ni-BDC and Co-HITP materials can effectively improve the capacitance performance of the material.

[0139] By comparing the specific capacitance values ​​of the MOF-on-MOF materials prepared in Examples 1-6, it was found that the MOF-on-MOF material prepared in Example 2 had the highest specific capacitance value, and the difference in the preparation process of Examples 1-4 was the different reaction times. This shows that when preparing the MOF-on-MOF material with optimal performance, an increase in reaction time results in a greater number of Ni-BDC MOFs, which is beneficial to the improvement of specific capacitance; however, with the increase in reaction time, the thickness of the Ni-BDC MOF on the surface of the nickel foam material loaded with Ni-BDC increases, resulting in structural densification, hindering ion diffusion, and affecting the specific capacitance value of the material. Compared to Example 2, the nickel foam material loaded with the Co-HITP / Ni-BDC hybrid prepared in Comparative Example 3 exhibited a specific capacitance of 885.7 F / g at a current density of 1 A / g, and a rate capability of only 9.6% at a current density of 10 A / g, both significantly lower than the corresponding values ​​in Example 2. This indicates that the composite material formed by the adsorption of Co-HITP and Ni-BDC MOF can produce a stronger synergistic effect than a simple mixture of the two materials, thereby significantly optimizing the material's energy storage performance. Overall, the MOF-on-MOF nanomaterial prepared in Example 2 exhibits superior electrical energy storage performance.

[0140] In summary, the MOF-on-MOF material preparation method provided by the present invention, through a two-step synthesis, produces a material with excellent specific capacitance when used as a supercapacitor electrode material, and has broad application prospects in electrochemical energy storage.

[0141] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a MOF-on-MOF material, characterized in that: The following steps are involved: Step (1): slowly adding an aqueous solution of nickel metal salt to an N,N-dimethylformamide solution of terephthalic acid under stirring, mixing evenly, adding ethanol, and continuing to stir to obtain a mixed solution; The pretreated nickel foam is immersed in the mixed solution, reacted, cooled, washed, and dried after the reaction is completed to obtain the nickel foam loaded with Ni-BDC; Step (2): 2,3,6,7,10,11-hexaaminotriphenylene, cobalt metal salt and water are mixed, ultrasonically dissolved, and ammonia water is added to react. After the reaction is completed, a Co-HITP film is obtained at the gas-liquid interface; The nickel foam loaded with Ni-BDC was horizontally laminated on the Co-HITP film, cycled several times, washed, and dried to obtain MOF-on-MOF material.

2. The method for preparing a MOF-on-MOF material according to claim 1, wherein: In step (1): The aqueous solution of the nickel metal salt is prepared by the following steps: mixing and dissolving the nickel metal salt and water to obtain an aqueous solution of the nickel metal salt; wherein the solid-to-liquid ratio of the nickel metal salt to the water is 16-79 mg:1 mL; The N,N-dimethylformamide solution of terephthalic acid is prepared by mixing and dissolving terephthalic acid and N,N-dimethylformamide to obtain the N,N-dimethylformamide solution of terephthalic acid; wherein the solid-to-liquid ratio of terephthalic acid to N,N-dimethylformamide is 2-8.3 mg:1 mL.

3. The method for preparing a MOF-on-MOF material according to claim 1, wherein: In the step (1), the nickel metal salt is any one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate; the molar ratio of the nickel metal salt to terephthalic acid is 3.66:1; and the volume ratio of the aqueous solution of the nickel metal salt, the N,N-dimethylformamide solution of terephthalic acid, and ethanol is 3:10:

10.

4. The method for preparing a MOF-on-MOF material according to claim 1, wherein: In the step (1), the stirring conditions are: stirring at a temperature of 20-80° C. and a rotation speed of 100-500 rpm; the slow addition conditions are: slowly adding at a speed of 1-5 d / s; and the stirring time is continued for 0.5-2 h.

5. The method for preparing a MOF-on-MOF material according to claim 1, characterized in that: In step (1), the pretreated nickel foam is prepared by the following steps: The nickel foam is ultrasonically treated with acetone, water, and ethanol in sequence, and then dried to obtain pretreated nickel foam; The ultrasonic treatment conditions are as follows: placing the nickel foam in acetone, ultrasonically treating for 10-20 minutes, taking it out, transferring it to water, ultrasonically treating it 1-2 times, each time for 5-10 minutes, taking it out, transferring it to ethanol, and ultrasonically treating it 1-2 times, each time for 10-20 minutes.

6. The method for preparing a MOF-on-MOF material according to claim 1, characterized in that: In the step (1), the solid-liquid ratio of the pretreated nickel foam to the mixed solution is 1 g:50 mL; and the reaction conditions are: reacting at a temperature of 120° C. for 0.5-3 h.

7. The method for preparing a MOF-on-MOF material according to claim 1, characterized in that: In step (2), the cobalt metal salt is any one of cobalt acetate, cobalt chloride, cobalt nitrate or cobalt sulfate; the molar ratio of 2,3,6,7,10,11-hexaaminotriphenylene to the cobalt metal salt is 1.28:1; and the solid-liquid ratio of 2,3,6,7,10,11-hexaaminotriphenylene, water and ammonia water is 1 mg:3 mL:0.03 mL.

8. The method for preparing a MOF-on-MOF material according to claim 1, wherein: In the step (2), the reaction conditions are: reaction at a temperature of 20-80° C. for 0.5-2 h; and the number of cycles is 1-3 times.

9. A MOF-on-MOF material prepared by the method for preparing a MOF-on-MOF material according to any one of claims 1 to 8.

10. Use of the MOF-on-MOF material according to claim 9 as a supercapacitor electrode material in the field of electrochemical energy storage.

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