Core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks and their preparation methods
By adjusting the concentration and pH of the organic ligand solution, a core-shell material of nickel manganese oxide/nickel manganese organic framework was prepared, solving the problems of inhomogeneity and high temperature and pressure in the core-shell material of the prior art. This enabled low-energy-consumption large-scale production and efficient charge transport, and is suitable for energy storage, microwave absorption and catalytic conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING XIAOZHUANG UNIV
- Filing Date
- 2026-03-31
- Publication Date
- 2026-05-26
Smart Images
Figure CN122080433A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks and their preparation methods, belonging to the field of core-shell material technology. Background Technology
[0002] Core-shell nanomaterials, as an important branch of functional materials, have seen significant progress in their preparation technology in recent years, but still face multiple technical bottlenecks in practical applications. Currently, their preparation methods are mainly divided into three categories: stepwise synthesis, one-step coprecipitation, and interfacial self-assembly. While one-step coprecipitation simplifies the process, the reaction kinetics are difficult to balance during the simultaneous deposition of multiple components, often resulting in elemental segregation and impurity phase formation, directly leading to uneven shell thickness. Stepwise synthesis has become the mainstream technology due to its advantage of precise control over the core-shell interface; however, this method is prone to interdiffusion of core and shell components during high-temperature processing, leading to interfacial lattice distortion and electronic structure destruction, significantly reducing the stability of the nanostructure. While interfacial self-assembly is suitable for organic-inorganic composite materials, its reliance on surfactants results in poor shell uniformity, and nanoparticles are prone to agglomeration during large-scale production, requiring the introduction of dispersants such as PVP (polyvinylpyrrolidone) to increase process complexity. Furthermore, existing technologies generally suffer from high energy consumption at high temperatures and strong dependence on precious metal precursors. For example, the preparation cost of ruthenium / nickel oxide graphene aerogel far exceeds the standard for commercial catalysts. A deeper challenge lies in the lagging research on its synthesis mechanism; the dynamic evolution mechanism of core-shell synergy lacks in-situ characterization support, such as the lack of a quantitative relationship between microstructure characteristics and their physical properties. These technical deficiencies severely restrict the practical application of core-shell materials in energy storage, microwave absorption, catalytic conversion, and other fields. There is an urgent need to overcome these limitations through interface engineering optimization, green synthesis technology innovation, and intelligent preparation methods to improve the physical properties of core-shell nanomaterials. Summary of the Invention
[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a core-shell material based on nickel manganese oxide / nickel manganese organic framework and its preparation method. By precisely controlling the concentration of the organic ligand solution and the pH value of the reaction system, and by optimizing the synthesis conditions, uniform and controllable growth of the nickel manganese organic framework core is achieved.
[0004] To achieve the above objectives, the present invention is implemented using the following technical solution: On one hand, this invention discloses a method for preparing core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks, comprising the following steps: Nickel-manganese organic framework precursors were synthesized by mixing nickel and manganese salts with organic ligand solutions and carrying out a hydrothermal reaction under alkaline conditions. The nickel-manganese organic framework precursor is subjected to programmed temperature heating in a mixture of inert gas and oxygen to obtain a core-shell material of nickel-manganese oxide / nickel-manganese organic framework with a heterogeneous nanostructure.
[0005] Furthermore, the nickel salt includes at least one of nickel nitrate, nickel chloride, nickel acetate, and their hydrates; The manganese salt includes at least one of manganese nitrate, manganese chloride, manganese acetate, and their hydrates; The molar ratio of the metal cations in the nickel salt and manganese salt is from 1:1 to 5:1.
[0006] Furthermore, the preparation step of the organic ligand solution is as follows: dissolve the eicosapentaenoic acid organic ligand in a hexafluoroisopropanol solution to prepare an organic ligand solution with a concentration of 50-150 mg / mL. The pH value of the organic ligand solution is 4-5.
[0007] Furthermore, the method for synthesizing the nickel-manganese organic framework precursor includes the following steps: Nickel and manganese salts were dissolved in deionized water, and an organic ligand solution was added under continuous stirring to form a first mixed solution. Add an alkaline solution to the first mixed solution, and mix to obtain a second mixed solution; The second mixed solution was placed in a closed reactor for hydrothermal reaction to obtain hydrothermal products; The hydrothermal products were cooled and separated, and then washed and purified using organic solvents and deionized water, followed by drying to obtain a nickel-manganese organic framework precursor.
[0008] Furthermore, the pH value of the first mixed solution is 6-9; the pH value of the second mixed solution is 6-9.
[0009] Furthermore, the heating temperature of the hydrothermal reaction is 160-200℃; the reaction time of the hydrothermal reaction is 8 to 16 hours.
[0010] Furthermore, the steps of the programmed heating heat treatment are as follows: The nickel-manganese organic framework precursor was placed in a high-temperature resistant reactor and then transferred to a heat treatment furnace. After the heat treatment furnace is evacuated to a vacuum, it is filled with a mixture of inert gas and oxygen to atmospheric pressure. The temperature inside the heat treatment furnace is then raised to 400°C to 800°C using a programmed heating method, and maintained at this temperature for 4 to 8 hours. After natural cooling, a core-shell material of nickel manganese oxide / nickel manganese organic framework with a heterogeneous nanostructure was obtained.
[0011] Furthermore, in the mixed gas, oxygen accounts for 1% to 5% of the volume; the inert gas is any one or a mixture of nitrogen, argon or helium.
[0012] Furthermore, the temperature rise rate is 0.5°C / min to 2°C / min, and the heating time is 20 to 40 minutes.
[0013] On the other hand, the present invention discloses a core-shell material based on nickel manganese oxide / nickel manganese organic framework prepared according to the above-described method for preparing a core-shell material based on nickel manganese oxide / nickel manganese organic framework, wherein the core of the core-shell material is a nickel manganese metal-organic framework and the outer shell of the core-shell material is a nickel manganese bimetallic oxide. Beneficial effects
[0014] This invention relates to a core-shell material based on nickel-manganese oxide / nickel-manganese organic framework and its preparation method. By precisely controlling the concentration of the organic ligand solution and the pH value of the reaction system, combined with optimization of synthesis conditions, the uniform and controllable growth of the nickel-manganese organic framework core is achieved. This method employs mild experimental conditions, requires no additional high-pressure gas equipment, consumes little energy, and effectively avoids the adverse effects of high-temperature and high-pressure processes on the microstructure of the material. It exhibits good process repeatability and potential for large-scale production.
[0015] The preparation method of this invention achieves a tight chemical bond at the atomic scale between the oxide shell and the metal-organic framework core. This strong interfacial coupling provides an ideal channel for rapid charge and energy transport, which is impossible to achieve with traditional physical hybrid materials. The preparation process of this invention is simple, easy to operate, and low in cost, which is conducive to its industrial application. Attached Figure Description
[0016] Figure 1 This is a flowchart of the preparation method of the core-shell material based on nickel manganese oxide / nickel manganese organic framework provided by the present invention; Figure 2 This is a scanning electron microscope image of the nickel-manganese organic framework precursor provided in Embodiment 1 of the present invention; Figure 3 This is a scanning electron microscope image of the nickel-manganese organic framework precursor provided in Embodiment 2 of the present invention; Figure 4 This is a scanning electron microscope image of the core-shell material of nickel-manganese oxide / nickel-manganese organic framework provided in Embodiment 1 of the present invention. Figure 5 This is a scanning electron microscope image of the core-shell material of nickel-manganese oxide / nickel-manganese organic framework provided in Embodiment 3 of the present invention; Figure 6 These are electrocatalytic performance test diagrams of the nickel-manganese oxide / nickel-manganese organic framework core-shell materials provided in Examples 1 and 4-7 of this invention. Detailed Implementation
[0017] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.
[0018] This invention provides a method for preparing a core-shell material of nickel-manganese oxide / nickel-manganese organic framework, such as... Figure 1 As shown, it includes the following steps: Nickel-manganese organic framework precursors were synthesized by mixing nickel and manganese salts with organic ligand solutions and carrying out a hydrothermal reaction under alkaline conditions. In a mixture of inert gas and oxygen, a nickel-manganese organic framework precursor is subjected to programmed temperature heat treatment to obtain a core-shell material of nickel-manganese oxide / nickel-manganese organic framework with a heterogeneous nanostructure.
[0019] The technical concept of this invention is as follows: by precisely controlling the concentration of the organic ligand solution and the pH value of the reaction system, combined with the optimization of synthesis conditions, uniform and controllable growth of the nickel-manganese organic framework core is achieved. This method has mild experimental conditions, requires no additional high-pressure gas equipment, has low energy consumption, and can effectively avoid the adverse effects of high-temperature and high-pressure processes on the microstructure of materials, exhibiting good process repeatability and potential for large-scale production.
[0020] Furthermore, nickel salts include at least one of nickel nitrate, nickel chloride, nickel acetate, and their hydrates; Manganese salts include at least one of manganese nitrate, manganese chloride, manganese acetate, and their hydrates; The molar ratio of metal cations in nickel salts and manganese salts is 1:1 to 5:1.
[0021] Furthermore, the preparation steps for the organic ligand solution are as follows: dissolve the eicosapentaenoic acid organic ligand in a hexafluoroisopropanol solution to prepare an organic ligand solution with a concentration of 50-150 mg / mL. The pH value of the organic ligand solution is 4-5.
[0022] In this invention, a weakly acidic pH of 4-5 is used to precisely promote the deprotonation of the carboxyl group of docosapentaenoic acid, transforming it into a more coordinating carboxylate ion. Simultaneously, excessive alkalinity is avoided, preventing the formation of hydroxide precipitates from nickel and manganese ions, thus ensuring that the coordination reaction dominates and resulting in a pure nickel-manganese organic framework. Because nickel and manganese ions have different coordination abilities with the same organic ligand, this kinetic difference helps to form bimetallic nodes with uniform component distribution in the early stages of nucleation, rather than simple physical mixing; the synergistic effect of the bimetals further ensures the homogeneity of the nucleus.
[0023] This invention precisely controls the coordination reaction rate and equilibrium by controlling ligand concentration and pH value, thereby obtaining uniform, non-agglomerated nickel-manganese organic framework precursors under mild conditions. The entire process is based on conventional solution reactions, requiring no high-temperature or high-pressure equipment, resulting in low energy consumption, avoiding damage to the microstructure, and exhibiting good reproducibility and industrial production potential.
[0024] Furthermore, the synthetic steps of the nickel-manganese organic framework precursor are as follows: Nickel and manganese salts were dissolved in deionized water, and an organic ligand solution was added under continuous stirring to form a first mixed solution. Add alkali solution to the first mixed solution, and after mixing, obtain the second mixed solution; The second mixed solution was placed in a closed reactor for hydrothermal reaction to obtain hydrothermal products; The hydrothermal products were cooled and separated, and then washed and purified with organic solvents and deionized water before drying to obtain the nickel-manganese organic framework precursor.
[0025] Furthermore, the pH value of the first mixed solution is 6-9; the pH value of the second mixed solution is 6-9.
[0026] Furthermore, the heating temperature for the hydrothermal reaction is 160-200℃; the reaction time for the hydrothermal reaction is 8 to 16 hours.
[0027] This invention effectively controls the rate of deprotonation by stepwise pH adjustment, avoiding instantaneous burst nucleation and promoting the formation of a moderate number of uniformly sized crystal nuclei. Maintaining a pH within the range of 6-9 effectively inhibits the formation of impurity phases such as metal hydroxides or basic salts, ensuring the precursor is a pure-phase metal-organic framework structure. Simultaneously, this pH environment maintains the high coordination activity of carboxylate ions, guaranteeing sufficient bonding between metal ions and organic ligands.
[0028] This invention employs high-temperature hydrothermal conditions of 160-200℃ to ensure high crystallinity of the product, which is crucial for maintaining morphology and constructing clear heterogeneous interfaces during subsequent heat treatment. During the sustained high-temperature reaction, nickel and manganese ions migrate and rearrange extensively within the crystal, ultimately forming a solid solution structure with a uniform nickel / manganese ratio at the nodes. This achieves a truly uniform distribution of bimetallic compounds at the atomic scale, rather than a simple physical mixture. By controlling the reaction time to 8-16 hours, the crystal growth process can be precisely controlled, resulting in metal-organic framework precursor particles with uniform particle size and regular morphology.
[0029] Furthermore, the steps of the programmed temperature rise heat treatment are as follows: The precursor is placed in a high-temperature resistant reactor and then transferred to a heat treatment furnace. After the heat treatment furnace is evacuated to a vacuum, it is filled with a mixture of inert gas and oxygen until it reaches atmospheric pressure. The temperature inside the heat treatment furnace is then raised to 400°C to 800°C using a programmed heating method, and maintained at this temperature for 4 to 8 hours. After natural cooling, a core-shell material of nickel manganese oxide / nickel manganese organic framework with a heterogeneous nanostructure was obtained.
[0030] Furthermore, in the gas mixture, oxygen accounts for 1% to 5% of the volume; the inert gas is any one or a mixture of nitrogen, argon, or helium.
[0031] Furthermore, the programmed heating rate is 0.5℃ / min to 2℃ / min, and the heating time is 20 to 40 minutes.
[0032] This programmed heating heat treatment step successfully achieved the precise construction of heterogeneous nanostructures, resulting in core-shell materials with the following significant advantages: the outer shell is composed of tightly packed nickel-manganese oxide nanocrystals, endowing the material with excellent electrochemical or catalytic activity; the core retains the porous framework of the metal-organic framework precursor and, due to partial carbonization, also possesses a certain degree of conductivity; the two phases form a tightly contacting heterogeneous interface through chemical bonding, exhibiting low interfacial resistance and high structural stability, which is conducive to synergistic effects. Due to the use of slow heating and controlled oxidation processes, the original morphology of the precursor is completely preserved, and the core-shell material essentially replicates the geometry of the metal-organic framework precursor, laying the structural foundation for performance in subsequent applications. By adjusting the heat treatment parameters, the composition and microstructure of the product can be finely controlled: changing the temperature can adjust the oxide grain size and organic residue ratio, and changing the atmosphere can adjust the shell thickness and oxidation degree, thereby obtaining a series of materials with tunable performance and designable functions. Furthermore, this process is compatible with existing industrial heat treatment equipment, requires no high pressure or special conditions, and has good scalability and industrial application potential.
[0033] Example 1: This Example 1 provides a method for preparing a core-shell material of nickel manganese oxide / nickel manganese organic framework, including the following steps:
[0034] Step 1: Preparation of organic ligand solution: Dissolve the organic ligand docosapentaenoic acid at a concentration of 100 mg / mL in hexafluoroisopropanol solution to obtain the organic ligand solution. The pH value of the organic ligand solution is 4.6.
[0035] Step 2: Preparation of the first mixed solution: Add 10 mL of deionized water to a pressure-resistant tube, then add 20 μL of a 1 mol / L Ni(NO3)2·6H2O aqueous solution and 20 μL of a 1 mol / L Mn(NO3)2·4H2O aqueous solution, wherein the molar ratio of nickel ions to manganese ions is 4:1. While stirring continuously, add 80 μL of the organic ligand solution prepared in Step 1 dropwise, continuing stirring to prevent the organic ligands from self-assembling, to obtain the first mixed solution. The pH value of the first mixed solution is 7.0.
[0036] Step 3: Preparation of the second mixed solution: Slowly add 30 μL of 1 mol / L sodium hydroxide solution to the first mixed solution obtained in step 2, and shake continuously to ensure that the reactants are fully mixed and homogeneous, thus obtaining the second mixed solution.
[0037] Step 4, hydrothermal reaction: Transfer the second mixed solution obtained in step 3 to a high-pressure reactor, seal it, and place it in an oven at 180°C for 12 hours to heat and react.
[0038] Step 5, Post-processing: After the reaction is complete, the product is naturally cooled to room temperature, collected, and repeatedly washed with ethanol and deionized water. Then, it is dried in an oven at 60°C for 24 hours to obtain the nickel-manganese organic framework precursor.
[0039] Step 6: Programmed heating heat treatment: Transfer the precursor sample collected in Step 5 into a quartz boat. After slight shaking, spread the precursor evenly and compact it with a spatula. Then place the quartz boat in the center of a high-temperature annealing furnace. Evacuate the annealing furnace to remove air from the chamber, and then introduce a mixed gas of 97% nitrogen and 3% oxygen to atmospheric pressure. Heat uniformly to 700℃ within 30 minutes and maintain this temperature for 6 hours. Then allow it to cool naturally to room temperature to obtain a core-shell material of a heterogeneous nanostructured nickel-manganese oxide / nickel-manganese organic framework.
[0040] Example 2: This Example 2 is basically the same as Example 1, except that the hydrothermal reaction temperature in step 4 is 200℃. The remaining steps and parameters are the same as in Example 1.
[0041] Example 3: This Example 3 is basically the same as Example 1, except that the pH value of the first mixed solution in step 2 is 9.0. The remaining steps and parameters are the same as in Example 1.
[0042] Example 4: This Example 4 is basically the same as Example 1, except that in step 2, the molar ratio of Ni(NO3)2·6H2O to Mn(NO3)2·4H2O is 5:1, that is, the molar ratio of nickel ions to manganese ions is 5:1. The remaining steps and parameters are the same as in Example 1.
[0043] Example 5: This Example 5 is basically the same as Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Mn(NO3)2·4H2O in step 2 is 3:1, that is, the molar ratio of nickel ions to manganese ions is 3:1. The remaining steps and parameters are the same as in Example 1.
[0044] Example 6: This Example 6 is basically the same as Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Mn(NO3)2·4H2O in step 2 is 2:1, that is, the molar ratio of nickel ions to manganese ions is 2:1. The remaining steps and parameters are the same as in Example 1.
[0045] Example 7: This Example 7 is basically the same as Example 1, except that the molar ratio of Ni(NO3)2·6H2O to Mn(NO3)2·4H2O in step 2 is 1:1, that is, the molar ratio of nickel ions to manganese ions is 1:1. The remaining steps and parameters are the same as in Example 1.
[0046] The nickel-manganese organic framework precursors prepared in Examples 1 and 2 were subjected to scanning electron microscopy, and their morphologies were compared as follows: Figure 2 and Figure 3 As shown.
[0047] The sample in Example 1 was a product obtained at 180°C. Its morphology showed uniformly sized, densely distributed cubic nanoparticles with smooth surfaces and no obvious agglomeration. At this temperature, the crystal nucleation rate and growth rate were in dynamic equilibrium. The crystal nuclei could grow uniformly into regular cubic crystals, and the slow growth rate avoided particle agglomeration and overgrowth, ultimately forming a uniform and dense array of nanoparticles.
[0048] The sample in Example 2 was a product from 200°C. Its morphology showed a mixed morphology of large, plate-like crystals with significant size differences and fine particles. The large crystals had rough surfaces and obvious stacking. This corresponds to a crystal growth rate much greater than the nucleation rate at higher hydrothermal temperatures, with a few nuclei preferentially and rapidly growing into large, plate-like crystals. Simultaneously, the high temperature intensified solvothermal convection, causing small particles to adhere and stack on the surface of the large crystals, thus disrupting the uniformity of the morphology.
[0049] The test results show that the hydrothermal reaction temperature has a significant impact on the morphology of the precursor. A reaction temperature of 180℃ is conducive to uniform nucleation and slow growth, resulting in nanoparticles with regular morphology and uniform size. High temperatures accelerate growth and induce directional aggregation, forming a heterogeneous morphology in which large-sized plate-like crystals and fine particles coexist. This principle provides a theoretical basis for the precise control of the morphology of nanomaterials using the hydrothermal method.
[0050] The core-shell materials of nickel-manganese oxide / nickel-manganese organic frameworks prepared in Examples 1 and 3 were subjected to scanning electron microscopy, and their morphologies were compared to those in Examples 1 and 3. Figure 4and Figure 5 As shown.
[0051] The sample in Example 1 corresponds to a neutral or weakly alkaline environment with pH=7. Under these conditions, the hydrolysis rate of precursor ions is moderate, the crystals grow uniformly along all crystal directions, the thermodynamic stability of the cubic crystal form is maintained, and a smooth, regular cubic crystal is formed.
[0052] The sample in Example 3 corresponds to an alkaline environment with pH=9. Under these alkaline conditions, the precursor ion hydrolysis rate increases sharply, and a large number of unstable hydroxyl intermediates are rapidly generated on the crystal surface, initiating local heterogeneous nucleation and ultimately forming a rough, wrinkled layered structure.
[0053] The test results show that different pH environments can regulate the precursor hydrolysis rate and crystal face adsorption behavior, directly affecting the anisotropy of crystal growth. Neutral or weakly alkaline environments are conducive to uniform growth, forming regular and smooth cubic crystals; excessive alkalinity leads to morphological deterioration. This principle provides a theoretical basis for precisely controlling the morphology of nanomaterials through pH.
[0054] The electrocatalytic performance of the nickel-manganese oxide / nickel-manganese organic framework core-shell materials prepared in Examples 1 and 4-7 was tested under alkaline conditions, and the results are as follows: Figure 6 As shown, the electrocatalytic performance initially increases and then decreases with increasing nickel to manganese molar ratio in the catalyst. When the nickel to manganese molar ratio is 4:1, the metal and ligand form an optimal coordination structure, resulting in the best performance. At this point, the nickel ion active sites are uniformly dispersed, enabling efficient adsorption of reactant molecules and promoting electron transfer.
[0055] When the nickel content increases to 5:1, excess nickel ions disrupt the coordination balance, leading to the aggregation of active sites and reducing the effective exposure of catalytic sites. At the same time, excess nickel changes the electron cloud density of the catalyst, causing the d-band center of the nickel active sites to shift, thereby reducing the reaction kinetic efficiency.
[0056] Test results show that the molar ratio of nickel to manganese has a significant regulatory effect on the electrochemical performance of nanostructures, with 4:1 being the optimal ratio. Excessive nickel doping reduces catalytic activity through both structural disruption and electronic effects. This finding provides theoretical guidance for optimizing the structural composition of subsequent energy storage materials.
Claims
1. A method for preparing a core-shell material based on a nickel-manganese oxide / nickel-manganese organic framework, characterized by, Includes the following steps: Nickel-manganese organic framework precursors were synthesized by mixing nickel and manganese salts with organic ligand solutions and carrying out a hydrothermal reaction under alkaline conditions. The nickel-manganese organic framework precursor is subjected to programmed temperature heating in a mixture of inert gas and oxygen to obtain a core-shell material of nickel-manganese oxide / nickel-manganese organic framework with a heterogeneous nanostructure.
2. The method for preparing a nickel-manganese oxide / nickel-manganese organic framework-based core-shell material according to claim 1, characterized in that, The nickel salt includes at least one of nickel nitrate, nickel chloride, nickel acetate, and their hydrates; The manganese salt includes at least one of manganese nitrate, manganese chloride, manganese acetate, and their hydrates; The molar ratio of the metal cations in the nickel salt and manganese salt is from 1:1 to 5:
1.
3. The method for preparing a nickel-manganese oxide / nickel-manganese organic framework-based core-shell material according to claim 1, characterized in that, The preparation steps of the organic ligand solution are as follows: dissolve the eicosapentaenoic acid organic ligand in hexafluoroisopropanol solution to prepare an organic ligand solution with a concentration of 50-150 mg / mL. The pH value of the organic ligand solution is 4-5.
4. The method of claim 1, wherein the nickel-manganese oxide / nickel-manganese organic framework-based core-shell material is prepared by the following steps of: (1) preparing a nickel-manganese organic framework; (2) preparing a nickel-manganese oxide; and (3) mixing the nickel-manganese organic framework and the nickel-manganese oxide. The method for synthesizing the nickel-manganese organic framework precursor includes the following steps: Nickel and manganese salts were dissolved in deionized water, and an organic ligand solution was added under continuous stirring to form a first mixed solution. Add an alkaline solution to the first mixed solution, and mix to obtain a second mixed solution; The second mixed solution was placed in a closed reactor for hydrothermal reaction to obtain hydrothermal products; The hydrothermal products were cooled and separated, and then washed and purified using organic solvents and deionized water, followed by drying to obtain a nickel-manganese organic framework precursor.
5. The method for preparing core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks according to claim 4, characterized in that, The pH value of the first mixed solution is 6-9; the pH value of the second mixed solution is 6-9.
6. The method for preparing core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks according to claim 4, characterized in that, The heating temperature of the hydrothermal reaction is 160-200℃; the reaction time of the hydrothermal reaction is 8 to 16 hours.
7. The method for preparing core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks according to claim 1, characterized in that, The steps of the programmed heating heat treatment are as follows: The nickel-manganese organic framework precursor was placed in a high-temperature resistant reactor and then transferred to a heat treatment furnace. After the heat treatment furnace is evacuated to a vacuum, it is filled with a mixture of inert gas and oxygen to atmospheric pressure. The temperature inside the heat treatment furnace is then raised to 400°C to 800°C using a programmed heating method, and maintained at this temperature for 4 to 8 hours. After natural cooling, a core-shell material of nickel manganese oxide / nickel manganese organic framework with a heterogeneous nanostructure was obtained.
8. The method for preparing core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks according to claim 1, characterized in that, In the mixed gas, oxygen accounts for 1% to 5% of the volume; the inert gas is any one or a mixture of nitrogen, argon or helium.
9. The method for preparing core-shell materials based on nickel-manganese oxide / nickel-manganese organic frameworks according to claim 1, characterized in that, The temperature rise rate is 0.5°C / min to 2°C / min, and the heating time is 20 to 40 minutes.
10. The core-shell material based on nickel manganese oxide / nickel manganese organic framework prepared by the method for preparing core-shell materials based on nickel manganese oxide / nickel manganese organic framework according to any one of claims 1-9, characterized in that, The core of the core-shell material is a nickel-manganese metal-organic framework; the outer shell of the core-shell material is a nickel-manganese bimetallic oxide.