A MOFs derived N-rich doped three-dimensional porous Co / NC-D composite material and a preparation method thereof

Abstract

The application discloses a MOFs derived N-rich doped three-dimensional porous Co / NC-D composite material and a preparation method thereof. The method comprises the following steps: adding an organic ligand into methanol and ultrasonically dissolving to obtain an organic ligand solution; adding Co(NO3)2.6H2O, Zn(NO3)2.6H2O and dicyandiamide (DCDA) into methanol and ultrasonically dissolving to obtain a metal salt solution; adding the organic ligand solution into the metal salt solution, stirring, centrifuging, washing and drying to obtain a ZIF-67-D or ZnCo-ZIF-D material; and performing calcination, acid washing, filtering, drying and vacuum drying to obtain the material. Compared with Co / AC, Co / rGO and a material obtained by directly calcining ZIF-67, the material has good dispersity and small Co nanoparticles and a synergistic effect between Co and N species, exhibits excellent performance in catalyzing dimethyl sulfide oxidation under mild conditions and has recyclability and a good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of porous materials, in particular to a MOFs derived N-rich doped three-dimensional porous Co / NC-D composite material and a preparation method thereof. BACKGROUND

[0002] Metal-Organic Frameworks (MOFs) is a new type of porous zeolite material that has emerged in recent years, which is a three-dimensional porous material with regular channels formed by self-assembly of central metal ions or metal clusters and organic ligands through coordination bonds. Compared with traditional porous materials, MOFs materials have high specific surface area, controllable pore size and adjustable morphology. MOFs materials can be pyrolyzed to prepare porous metal-carbon composite materials with good thermal stability and chemical stability, which have broad application prospects in the field of catalysis. ZIF-67 is a sub-class of MOF, which has excellent properties of MOF. As a common template for constructing cobalt-based hybrids, it has good thermal stability, high carbon content and zero oxygen content. Co@CN (carbon-nitrogen embedded cobalt nanoparticles) materials are often obtained by pyrolysis of ZIF-67, which have adjustable functions, high pore volume and high metal content, and are widely used in various catalytic reactions. For example: Zhong et al. used Co@CN materials obtained by high-temperature calcination of ZIF-67 to catalyze the oxidation of alcohols to esters, which showed good catalytic activity [Zhong W., Liu H., Bai C., et al. Base-Free Oxidation of Alcohols to Esters at Room Temperature and Atmospheric Conditions using Nanoscale Co-Based Catalysts [J]. ACS Catalysis, 2015, 5(3): 1850-1856]; similarly, Wang et al. used metal-organic framework ZIF-67 as a self-template, which was acid washed and etched after high-temperature calcination to obtain N-doped porous carbon materials, which were excellent catalysts for aerobic catalytic oxidation [Wang X., Li Y. Nanoporous carbons derived from MOFs as metal-free catalysts for selective aerobic oxidations [J]. Journal of Materials Chemistry A, 2016, 4(14): 5247-5257].

[0003] One of the main problems currently faced is that when some MOFs, including ZIF-67, are used as templates to obtain carbon-supported metal nanoparticles by high-temperature calcination, the high temperature can cause the agglomeration of metal nanoparticles. To address this issue, a bimetallic (Zn and Co) MOF material was pyrolyzed to prepare Co particles supported on N-doped carbon. The introduction of Zn allows the active site Co to be well dispersed as nanoparticles, which can be used as an effective catalyst for oxidative desulfurization [Bhadra B.N., Khan N.A., Jhung S.H. Co supported on N-doped carbon, derived from bimetallic azolate framework-6: a highly effective oxidative desulfurization catalyst [J]. Journal of Materials Chemistry A, 2019, 7(30): 17823-17833]. As carbon-based catalysts for supporting metal nanoparticles, heteroatom doping (e.g., N, B, P, etc.) into sp 2 Hybrid carbon skeletons are effective methods for adjusting electronic properties or electrical conductivity and inducing significant catalytic effects, thereby facilitating their applications. For example, ZIF-67 was used as a precursor, and dicyandiamide and sodium hypophosphite were used as external N and P sources, respectively, to successfully prepare a three-functional electrocatalyst composed of Co / CoP nanoparticles, N-doped carbon nanotubes, and hollow polyhedral carbon assembled by two calcination processes for N and P doping, respectively [Hao Y., Xu Y., Liu W., et al. Co / CoP embedded in a hairy nitrogen-doped carbon polyhedron as an advanced tri-functional electrocatalyst [J]. Materials Horizons, 2018, 5(1): 108-115]. Therefore, seeking simple and effective methods to prevent the agglomeration of metal nanoparticles supported on porous carbon, achieve small and uniform particle distribution, and achieve rich and uniform N or P heteroatom doping on the carbon skeleton to promote the coordination of metal nanoparticles and heteroatoms is a challenge for material researchers and a higher demand from social development for the field of MOFs materials SUMMARY

[0004] In order to solve the problems existing in the prior art, the purpose of the present application is to provide a MOFs derived N-rich doped three-dimensional porous Co / NC-D composite material and a preparation method thereof. Due to the introduction of dicyandiamide or low-boiling-point Zn, the coordination of Co and N is increased during the calcination process, and the spacing effect of Zn reduces the agglomeration of Co nanoparticles at high temperature. Compared with Co / AC, Co / rGO and the material obtained by directly calcining ZIF-67, the material has good dispersion and small Co nanoparticles, and the synergistic effect between Co and N species, exhibits excellent performance in catalyzing dimethyl sulfide oxidation under mild conditions, and can be recycled, and has good application prospect.

[0005] The purpose of the present application is achieved at least by one of the following technical solutions.

[0006] The preparation method of the MOFs derived N-rich doped three-dimensional porous Co / NC-D composite material provided by the present application comprises the following steps:

[0007] (1) adding an organic ligand into methanol, ultrasonic dissolving uniformly to obtain an organic ligand solution; dissolving Co(NO3)2.6H2O and dicyandiamide in methanol to obtain a metal salt solution A, and dissolving Co(NO3)2.6H2O, Zn(NO3)2.6H2O and dicyandiamide in methanol to obtain a metal salt solution B;

[0008] (2) mixing the metal salt solution in step (1) with the organic ligand solution, stirring uniformly, standing, centrifuging to obtain a precipitate, washing, and drying to obtain ZIF-67-D or ZnCo-ZIF-D materials, respectively;

[0009] (3) calcining the ZIF-67-D and ZnCo-ZIF-D materials in step (2) under an inert atmosphere, then washing with acid, filtering and washing, and vacuum drying to obtain a three-dimensional porous Co / NC-D composite material.

[0010] Further, the organic ligand in step (1) is 2-methylimidazole, the concentration of the organic ligand solution is 0.2-0.26 mol / L, and the ultrasonic dissolving time is 3-5 min.

[0011] Further, the concentration of Co(NO3)2.6H2O in the metal salt solution A in step (1) is 0.033 mol / L; the concentration of Co(NO3)2.6H2O in the metal salt solution B is 0.0066-0.033 mol / L, and the concentration of Zn(NO3)2.6H2O is 0.1-0.126 mol / L.

[0012] Further, the concentration of dicyandiamide in the metal salt solution A is 3.3 mol / L, and the concentration of dicyandiamide in the metal salt solution B is 6.6 mol / L.

[0013] Further, the volume ratio of the metal salt solution to the organic ligand solution in step (2) is 1:1, the standing time is 0-24 h, and the drying temperature is 60-80℃.

[0014] Preferably, the stirring temperature in step (2) is 25-30℃, and the stirring time is 2 min-12 h.

[0015] Preferably, the centrifugation rate in step (2) is 4000-6000 r / min, and the centrifugation time is 2-4 min.

[0016] Further, in step (3), the inert atmosphere is argon atmosphere, the gas flow rate is 40-60 mL / h, the calcination temperature is 700℃ or 950℃, the calcination time is 2-3 h, and the temperature rising rate is 2-5℃ / min.

[0017] Further, in step (3), the acid for pickling is 0.8 M H2SO4 or aqua regia, and the pickling time is 12 h.

[0018] Further, in step (3), the vacuum drying temperature is 150℃, and the time is 12 h.

[0019] The application provides a MOFs-derived N-rich doped three-dimensional porous Co / NC-D composite material prepared by the above preparation method.

[0020] Compared with the prior art, the application has the following beneficial effects and advantages:

[0021] (1) The application is simple to operate, low in cost, and green and environmentally friendly, and the dicyandiamide used is a low-cost and effective N source;

[0022] (2) The preparation method provided by the application can prevent the aggregation of Co nanoparticles and promote uniform distribution to a certain extent by adding zinc ions in the synthesis of the MOFs precursor, and can improve the porosity and specific surface area of the material after evaporation at high temperature, which helps to improve the catalytic reaction activity;

[0023] (3) The MOFs-derived porous Co / NC-D composite material provided by the application has a higher specific surface area, more abundant and uniformly distributed Co and N active species, and excellent performance in the catalytic dimethyl sulfide oxidation reaction compared with the material obtained by directly synthesizing ZIF-67 and calcining and the traditional Co / AC and Co / rGO materials, and has good practical application value. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 PXRD patterns of 1#Co / NC-D and Co / NC composite material obtained from Example 1, 2#Co / NC-D composite material obtained from Example 2 and 3#Co / NC-D composite material obtained from Example 3;

[0025] Figure 2a SEM images of 1#Co / NC-D obtained from Example 1;

[0026] Figure 2b SEM images of Co / NC composite material obtained from Example 1;

[0027] Figure 3 TEM images of 1#Co / NC-D composite material obtained from Example 1;

[0028] Figure 4a and 4b SEM images of 2#Co / NC-D composite material obtained from Example 2 and 3#Co / NC-D composite material obtained from Example 3, respectively;

[0029] Figure 5a and 5b TEM images of 2#Co / NC-D composite material obtained from Example 2 and 3#Co / NC-D composite material obtained from Example 3, respectively;

[0030] Figure 6 N2sorption-desorption isotherms of 1#Co / NC-D and Co / NC composite material obtained from Example 1, 2#Co / NC-D composite material obtained from Example 2 and 3#Co / NC-D composite material obtained from Example 3;

[0031] Figure 7 Graphs of performance test results of 1#Co / NC-D and Co / NC composite material obtained from Example 1, 2#Co / NC-D composite material obtained from Example 2 and 3#Co / NC-D composite material obtained from Example 3 for catalyzing the oxidation of dimethyl sulfide to dimethyl sulfoxide.

[0032] Figure 8 Graph of 4 cycles performance test results of 1#Co / NC-D composite material obtained from Example 2 for catalyzing the oxidation of dimethyl sulfide to dimethyl sulfoxide. DETAILED DESCRIPTION

[0033] The following further describes the specific implementation of the present application with reference to examples, but the implementation and protection of the present application are not limited thereto. It should be noted that if the following process is not specifically described in detail, it can be implemented or understood by referring to the prior art. If the reagent or instrument used is not marked with the manufacturer, it is considered to be a conventional product that can be obtained by commercial purchase.

[0034] Example 1

[0035] The present embodiment provides a preparation method of MOFs derived N-richly doped three-dimensional porous Co / NC-D composite material, comprising the following steps:

[0036] (1) 2-methylimidazole (4.92 g) was added to methanol (150 mL) and dissolved by ultrasonic for 5 min to obtain an organic ligand solution; Co(NO3)2·6H2O (2.91 g) and dicyandiamide (0.5 g) were dissolved in methanol (150 mL) to obtain a metal salt solution;

[0037] (2) The organic ligand solution in step (1) was added to the metal salt solution to obtain a mixed solution, which was stirred at 25°C for 2 min and stood for 24 h to obtain a ZIF-67-D suspension. The obtained ZIF-67-D suspension was centrifuged at 4000 r / min for 8 min, and the precipitate was taken and washed with methanol. After drying at 60°C for 12 h, ZIF-67-D material was obtained;

[0038] (3) 500 mg of ZIF-67-D material obtained in step (2) was weighed in a quartz boat and placed in a tube furnace. Argon was used as the calcination atmosphere, and the temperature was raised to 700°C at a rate of 2°C / min. The black solid was obtained after calcination at 700°C for 2 h and cooling to room temperature. The black solid was ground into a powder with a jade mortar and then used for the next step;

[0039] (4) The black powder obtained in step (3) was placed in a round-bottom flask containing 50 mL of concentrated sulfuric acid with a concentration of 0.8 mol / L. After refluxing at 80°C for 12 h to remove non-active Co species, the mixture was filtered and washed with deionized water until neutral. Finally, the mixture was vacuum dried at 150°C for 12 h to obtain the MOFs derived N-richly doped three-dimensional porous Co / NC-D composite material (labeled as 1#Co / NC-D composite material), which was a black solid. The obtained 1#Co / NC-D composite material can be directly applied to heterogeneous catalysis;

[0040] (5) In step (1), only Co(NO3)2·6H2O (2.91 g) was added to methanol (150 mL) to form a metal salt solution, and the other processes were the same as steps (2), (3), and (4) to finally obtain a black solid Co / NC composite material.

[0041] Figure 1 are PXRD patterns of 1#Co / NC-D and Co / NC obtained in this example, from Figure 1 It can be seen from the figure that the peaks of 1#Co / NC-D and Co / NC PXRD are at 44°, 51° and 76°, which correspond to the diffraction peaks of elemental Co, and the diffraction peaks of Co of 1#Co / NC-D are sharper than those of Co / NC, indicating that the Co particles in 1#Co / NC-D material are finer.

[0042] Figure 2a and Figure 2b are SEM images of 1#Co / NC-D and Co / NC composite materials obtained in this example, it can be observed that the two materials retain the size and morphology of the precursor rhombic dodecahedron, and it can be seen that many fine Co nanoparticles are loaded on the surface of 1#Co / NC-D composite material, and there are carbon nanotubes on the surface of Co / NC composite material.

[0043] Figure 3 is a TEM image of 1#Co / NC-D composite material obtained in this example, from Figure 3 It can be seen that Co nanoparticles of about 15nm are uniformly loaded on the carbon skeleton.

[0044] Figure 6 are BET test results of 1#Co / NC-D composite material and Co / NC composite material obtained in this example, from Figure 6 It can be seen that the N2 adsorption amount of 1#Co / NC-D material obtained by adding N source dicyandiamide during the synthesis of ZIF-67 and then calcining is more than that of Co / NC composite material without introducing N source, and it can be seen from the hysteresis loop that 1#Co / NC-D composite material contains mesoporous, which is a hierarchical porous carbon material.

[0045] Example 2

[0046] The present example provides a preparation method of MOFs derived N-rich doped three-dimensional porous Co / NC-D composite material, comprising the following steps:

[0047] (1) 2-methylimidazole (3.28g) was added to methanol (75mL) and dissolved by ultrasonic for 5min to obtain an organic ligand solution; Zn(NO3)2·6H2O (2.23g) and Co(NO3)2·6H2O (0.73g) and dicyandiamide (1g) were dissolved in methanol (75mL) to obtain a metal salt solution;

[0048] (2) The organic ligand solution in step (1) is added to the metal salt solution to obtain a mixed solution, which is stirred at 25℃ for 12h to obtain a ZnCo-ZIF-D suspension. The obtained ZnCo-ZIF-D suspension is centrifuged at 6000r / min for 2min, and the precipitate is taken and washed with methanol. After drying at 60℃ for 12h, the ZnCo-ZIF-D material is obtained.

[0049] (3) 500mg of the ZnCo-ZIF-D material obtained in step (2) is weighed into a quartz boat, which is placed in a tube furnace. Argon is used as the calcination atmosphere, and the temperature is raised to 950℃ at a rate of 5℃ / min. The sample is calcined at 950℃ for 2h, and then cooled to room temperature. The black solid is obtained and ground into powder with a jade mortar for further processing.

[0050] (4) The solid powder material obtained in step (3) is immersed in 6mL aqua regia, and soaked and acid washed for 12h to remove non-active Co species. After filtration and washing with deionized water until neutral, the material is vacuum dried at 150℃ for 12h to obtain a MOFs-derived N-doped three-dimensional porous Co / NC-D composite material (labeled as 2#Co / NC-D composite material), which is a black solid. The obtained 2#Co / NC-D composite material can be directly used.

[0051] Figure 1 is the PXRD spectrum of the 2#Co / NC-D composite material obtained in this example, and it can be seen from Figure 1 that the diffraction characteristic peaks of elemental Co of the 2#Co / NC-D composite material are sharper than those of the 1#Co / NC-D material, which indicates that the Co particles in the 2#Co / NC-D material are finer

[0052] Figure 4a is the SEM image of the 2#Co / NC-D composite material obtained in this example, and it can be observed that the 2#Co / NC-D material retains the structure and morphology of the precursor, and the surface of the 2#Co / NC-D composite material is smoother than that of the 1#Co / NC-D composite material, and the loaded Co nanoparticles are fine, which is consistent with the PXRD test results of the material

[0053] Figure 5a is the TEM image of the 2#Co / NC-D composite material obtained in this example, and it can be seen from Figure 5a that Co nanoparticles of about 10nm are uniformly loaded on the carbon skeleton, and the Co nanoparticles are more finely and uniformly distributed, but the loading amount is less than that of the 1#Co / NC-D material

[0054] Figure 6 is the BET test result of the 2#Co / NC-D composite material obtained in this example, and it can be seen from Figure 6It can be seen that compared with the 1#Co / NC-D composite material, the 2#Co / NC-D composite material has more N2 adsorption amount and larger hysteresis loop, indicating that it contains more mesopores

[0055] Example 3

[0056] The present embodiment provides a preparation method of MOFs derived N-richly doped three-dimensional porous Co / NC-D composite material, comprising the following steps:

[0057] (1) 2-methylimidazole (3.28 g) was added to methanol (75 mL) and dissolved by ultrasonic for 5 min to obtain an organic ligand solution; Zn(NO3)2·6H2O (2.82 g) and Co(NO3)2·6H2O (0.146 g) and dicyandiamide (1 g) were dissolved in methanol (75 mL) to obtain a metal salt solution;

[0058] (2) The organic ligand solution in step (1) was added to the metal salt solution to obtain a mixed solution, which was stirred at 25°C for 12 h to obtain a ZnCo-ZIF-D suspension. The obtained ZnCo-ZIF-D suspension was centrifuged at 7000 r / min for 2 min, and the precipitate was taken and washed with methanol. After drying at 60°C for 12 h, ZnCo-ZIF-D material was obtained.

[0059] (3) 500 mg of the ZnCo-ZIF-D material obtained in step (2) was weighed into a quartz boat and placed in a tube furnace. Argon was used as the calcination atmosphere, and the temperature was raised to 950°C at a rate of 5°C / min. The sample was calcined at 950°C for 2 h, and then cooled to room temperature. The black solid was ground into a powder with a jade mortar for further processing.

[0060] (4) The solid powder material obtained in step (3) was immersed in 12 mL of aqua regia and soaked for 12 h for acid washing to remove non-active Co species. After filtration and washing with deionized water to neutral, the sample was vacuum dried at 150°C for 12 h to obtain a MOFs derived N-richly doped three-dimensional porous Co / NC-D composite material (labeled as 3#Co / NC-D composite material), which was a black solid. The prepared 3#Co / NC-D composite material can be directly used.

[0061] Figure 1 is the PXRD spectrum of the 3#Co / NC-D composite material obtained in the present embodiment, and it can be seen from Figure 1 that the diffraction characteristic peak of elemental Co in the 3#Co / NC-D composite material is very weak, indicating that the surface of the 3#Co / NC-D material hardly has loaded elemental Co particles

[0062] Figure 4bFigure 6 is a SEM image of the 3#Co / NC-D composite material obtained in this example, and it can be observed that the 3#Co / NC-D material retains the structural morphology of its precursor, and the surface is smooth and flat, without Co particle loading, which is consistent with the PXRD test results of the material

[0063] Figure 5b Figure 7 is a TEM image of the 3#Co / NC-D composite material obtained in this example, and it can be seen that no Co nanoparticles are loaded on the carbon skeleton of the 3#Co / NC-D composite material Figure 5b

[0064] Figure 6 Figure 8 is the BET test results of the 3#Co / NC-D composite material obtained in this example, and it can be seen that, compared with the 2#Co / NC-D composite material, the 3#Co / NC-D composite material has more N2 adsorption capacity, and there is no hysteresis loop, indicating that the material does not have mesopores Figure 6

[0065] Example 4 Test reaction of the N-doped porous carbon material loaded with cobalt nanoparticles catalyzing dimethyl sulfide oxidation

[0066] In a 150 mL three-necked flask, 40 mg of catalyst (1#Co / NC-D composite material prepared in Example 1 or Co / NC composite material or 2#Co / NC-D composite material prepared in Example 2 or 3#Co / NC-D composite material prepared in Example 3) was added, and a serpentine condenser was connected to the middle neck of the three-necked flask for sealing (the other end of the condenser was connected to a two-way valve, and an oxygen-filled gas bag was connected to the two-way valve for supplying oxygen to the system), and a two-way valve and a rubber plug were connected to the two oblique necks of the three-necked flask (for vacuumizing and liquid sample feeding, respectively, on the basis of good sealing), the system was vacuumized and then oxygen was supplied, a syringe was used to add sample (0.5 mL of dimethyl sulfide and 4 mL of acetone), and an oil bath was used to react at a reaction temperature of 40℃ for 10 min to 3 h, after the reaction was completed, the system was naturally cooled to room temperature, and solid-liquid separation was achieved by centrifugation. The liquid phase product obtained was subjected to qualitative and quantitative analysis by nuclear magnetic resonance hydrogen spectrum technology, and the yield of the oxidation product dimethyl sulfoxide (DMSO) was finally obtained.

[0067] Figure 7 Figure 9 is the performance test results of the 1#Co / NC-D, Co / NC, 2#Co / NC-D and 3#Co / NC-D composite materials used in this example in catalyzing dimethyl sulfide oxidation into dimethyl sulfoxide (DMSO). Figure 7 ​​It is shown that 1#Co / NC-D and 2#Co / NC-D have higher catalytic activity, and the yield can reach 41% and 37% respectively within 10 min, and finally reach 51% and 54% respectively, which is higher than the catalytic performance of Co / NC and 3#Co / NC-D composite materials, indicating that the rich N species of the N-doped porous material loaded with Co nanoparticles and the small and uniformly distributed Co nanoparticles are beneficial to the catalytic activity of the material.

[0068] Figure 8 is the cycle performance test result of 1#Co / NC-D composite material used in the present embodiment. Figure 8 It is shown that the catalytic material can also maintain a yield of 41% after being used for 4 cycles, and the performance gap with the first use is not large, indicating that the N-doped porous material loaded with Co nanoparticles has good stability.

[0069] The above embodiments are only the preferred embodiments of the present application, and are only used to explain the present application, but not to limit the present application. The changes, replacements, modifications, etc. made by the person skilled in the art without departing from the spirit and essence of the present application shall belong to the protection scope of the present application.

Claims

1. Use of MOFs derived N-rich doped three-dimensional porous Co / NC-D composites in catalyzing dimethyl sulfide oxidation reaction, characterized in that, The preparation method of the MOFs derived N-doped three-dimensional porous Co / NC-D composite material comprises the following steps: (1) adding an organic ligand into methanol, uniformly dissolving by ultrasonic to obtain an organic ligand solution, the organic ligand is 2-methyl imidazole; dissolving Co(NO3)2·6H2O, Zn(NO3)2·6H2O and dicyandiamide in methanol to obtain a metal salt solution B; the concentration of dicyandiamide in the metal salt solution B is 6.6 mol / L; (2) adding the organic ligand solution in step (1) into the metal salt solution B, stirring and mixing, centrifuging after standing, washing and drying the precipitate to obtain a ZnCo-ZIF-D material; (3) calcining the ZnCo-ZIF-D material in step (2) under an inert atmosphere, then acid washing, filtering and washing, and vacuum drying to obtain a three-dimensional porous Co / NC-D composite material.

2. Use according to claim 1, characterized in that, In step (1), the concentration of the organic ligand solution is 0.2-0.26 mol / L.

3. Use according to claim 1, characterized in that, In step (1), the ultrasonic dissolving time is 3-5 min.

4. Use according to claim 1, characterized in that, In step (1), the concentration of Co(NO3)2·6H2O in the metal salt solution B is 0.0066-0.033 mol / L, and the concentration of Zn(NO3)2·6H2O is 0.1-0.126 mol / L.

5. The use according to claim 1, characterized in that, In step (2), the volume ratio of the metal salt solution to the organic ligand solution is 1:1; the stirring temperature is 25-30 ℃, and the stirring time is 2 min-12 h; the standing time is 0-24 h; and the drying temperature is 60-80 ºC.

6. Use according to claim 1, characterized in that, In step (3), the inert atmosphere is an argon atmosphere, and the gas flow rate is 40-60 mL / h; the calcination temperature is 700 or 950 ℃, the calcination time is 2-3 h, and the temperature rising rate is 2-5 ºC / min.

7. Use according to claim 1, characterized in that, In step (3), the acid for acid washing is 0.8 M H2SO4 or aqua regia, the amount of H2SO4 is 50 mL, the amount of aqua regia is 6 mL, and the acid washing time is 12 h.

8. The use according to claim 1, characterized in that, In step (3), the vacuum drying temperature is 150 ℃, and the drying time is 12 h.

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