CoNP-coated HNC hollow porous material prepared by etching-pyrolysis strategy and method

Abstract

The invention discloses a Co NP-coated HNC hollow porous material prepared by an etching-pyrolysis strategy and a preparation method of the Co NP-coated HNC hollow porous material. The method mainly comprises the following steps: constructing a hollow rod-shaped ZIF-67HR with rich defects by a solvothermal method, and then performing pyrolysis in an inert atmosphere through etching treatment to obtain the Co NP-coated HNC material. Co metal nanoparticles in the obtained framework material are uniformly distributed on the outer layer, so that high exposure of active sites is facilitated, and efficient mass transfer can be realized. The method has the advantages of being easy to operate, good in universality and the like, due to introduction of in-situ metal active sites, the material shows excellent activity and selectivity in the reaction for preparing benzoic acid through toluene oxidation, and potential industrial application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the field of porous materials, and particularly to a Co NP@HNC hollow rod-shaped porous material prepared by an etching-pyrolysis strategy. Background Art

[0002] Metal-Organic Frameworks (MOFs) are a class of materials self-assembled through coordination bonds between metal ions and organic ligands, having a periodic microporous structure similar to zeolites. By pyrolyzing MOFs in an inert or reducing atmosphere, metal@carbon and other composite materials with excellent thermal stability and chemical stability can be prepared. Such derived materials can not only increase the metal loading amount, but also maintain the good dispersion of the metal, and inherit the diverse morphologies and rich chemical compositions of the original MOFs materials.

[0003] MOF-derived hollow porous nanomaterials exhibit broad application prospects in the catalytic field due to their high specific surface area, abundant active sites, and excellent charge transfer ability. However, during the high-temperature sintering process, the framework of MOFs often collapses, resulting in the aggregation of metals and being encapsulated inside the carbon layer. Although strong acids or bases can be used to destroy the carbon layer to remove excess metals and expose the active sites, this process is difficult to precisely control and may cause partial loss of metals, thereby reducing the activity of the catalyst. In addition, the existing preparation steps are usually relatively complex, limiting their wide application. Therefore, designing an efficient and simple catalyst synthesis method and developing MOF-derived hollow material catalysts have become the key challenges faced by current research.

[0004] The preparation strategies of MOF-derived hollow porous materials can be divided into MOFs as self-sacrificial templates, MOFs as both sacrificial templates and precursors, MOF core-shell composites as precursors, and hollow MOFs and their composites as precursors. He et al. coated a layer of SiO 2 uniformly on ZIF nanocrystals of soluble TEOS precursors to generate ZIF-8@SiO 2 core-shell materials. Subsequently, by calcining the ZIF-8@SiO 2 core-shell materials in air at 500 °C, ZnO@SiO 2Yolk–shell composites. Additionally, hollow NPs can be obtained by hydrothermally etching the ZIF-8 core in an acidic aqueous environment at 100 °C. (He, L.; Li, L.; Zhang, L.; Xing, S.; Wang, T.; Li, G.; Wu, X.; Su, Z.; Wang, C. ZIF-8 Templated Fabrication of Rhombic Dodecahedron-Shaped ZnO@SiO2, ZIF-8@SiO2 Yolk–Shell and SiO2 Hollow Nanoparticles. CrystEngComm 2014, 16(29), 6534–6537.) Zhang et al. used ZIF-8 as a sacrificial template and precursor to fabricate hollow carbon matrices. First, the interior of the ZIF-8 template was etched with tannic acid solution, then the hollow ZIF-8 was pyrolyzed at 600 °C in an inert atmosphere, and subsequently the resulting sample was etched with an acid solution to remove the remaining Zn species, obtaining a hollow carbon matrix. (Tang, C.; Rao, H.; Li, S.; She, P.; Qin, J. A Review of Metal–Organic Frameworks Derived Hollow-Structured Photocatalysts: Synthesis and Applications. Small 2024, 20(48), 2405533). Liu et al. fabricated NC@Co-NGC nanocages by epitaxially growing a ZIF-67 shell on the surface of a ZIF-8 core, pyrolyzing the obtained ZIF-8@ZIF-67 core–shell composite in an inert atmosphere at 800 °C, and subsequently etching away the unstable Co nanoparticles with sulfuric acid. (Liu, X.; Verma, G.; Chen, Z.; Hu, B.; Huang, Q.; Yang, H.; Ma, S.; Wang, X. Metal-Organic Framework Nanocrystal-Derived Hollow Porous Materials: Synthetic Strategies and Emerging Applications. The Innovation 2022, 3(5), 100281.). Yu et al. prepared hierarchical CoS using ZIF-67 as a precursor 2 Hollow prisms. The hollow ZIF-67 prisms were sulfided with thioacetamide in an ethanol solution to prepare nanoscale CoS 4 Bubble-like subunits. During the sulfidation process, Co 2+ cations in ZIF-67 were converted into hollow CoS 4Nanocrystals. After pyrolysis under an N 2 atmosphere, hierarchical CoS with a multi-level hollow interior was obtained 2 . (Yu, L.; Yang, J. F.; Lou, X. W. (David). Formation of CoS2 Nanobubble Hollow Prisms for Highly Reversible Lithium Storage. Angew. Chem. 2016, 128(43), 13620–13624.)

[0005] Through the above strategy, various MOF-derived hollow porous material composites including metal carbides, metal oxides, metal sulfides, and porous carbon materials can be prepared. However, existing literature reports all involve further post-treatment to obtain the final hollow porous material catalyst, and it cannot show good generality for different reactions, which limits its application in the field of heterogeneous catalysis. Summary of the Invention

[0006] To solve the problems existing in the prior art, the purpose of the present invention is to provide a Co NP@HNC hollow rod-shaped porous material prepared by an etching-pyrolysis strategy and its preparation method.

[0007] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0008] A preparation method of a Co NP@HNC hollow rod-shaped porous material prepared by an etching-pyrolysis strategy provided by the present invention includes the following steps:

[0009] (1) Dissolve a Co salt and a surfactant in ethanol to obtain a mixed solution, heat and stir the mixed solution, and centrifuge and dry it to obtain a Co precursor;

[0010] (2) Add the Co precursor obtained in step (1) to ethanol, ultrasonically disperse it evenly to obtain a Co precursor suspension; disperse an alkaline organic ligand in ethanol to obtain an organic ligand solution; mix the Co precursor suspension and the organic ligand solution, heat and stir, and centrifuge and dry it to obtain a ZIF-67HR material;

[0011] (3) Add the ZIF-67HR material obtained in step (2) to ethanol, ultrasonically disperse it evenly to obtain a ZIF-67HR suspension; dissolve an organic acid in ethanol to obtain an etching solution;

[0012] Mix the ZIF-67

[0013] The HR-CA material is calcined to obtain the MOFs-derived hollow porous Co NP@HNC material.

[0014] Further, in step (1), the surfactant is urea, and the mass ratio of the metal salt to the surfactant is 1:1 - 4.

[0015] Further, in step (1), the temperature of heating and stirring is 60 - 80 °C, and the time of heating and stirring is 1 - 5 h.

[0016] Further, in step (2), the temperature of heating and stirring is 100 - 140 °C, and the time of heating and stirring is 10 - 50 min.

[0017] Further, in step (2), the concentration of the Co precursor suspension is 8.0 g / L - 16.0 g / L.

[0018] Further, in step (2), the organic ligand is 2-methylimidazole, and the concentration is 0.81 - 1.13 mol / L.

[0019] Further, in step (3), the organic acid is cyanuric acid, and the concentration of the cyanuric acid solution is 0.008 - 0.14 mol / L.

[0020] Further, in step (3), the temperature of heating and stirring is 50 - 90 °C, and the time of heating and stirring is 1 - 6 h.

[0021] Further, in step (3), the calcination treatment is carried out under an inert atmosphere; the calcination temperature is 550 - 750 °C, the time of calcination treatment is 1 - 3 h, and the heating rate is 2 - 6 °C / min.

[0022] The present invention provides a Co NP@HNC hollow rod-shaped porous material prepared by the above preparation method.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] (1) In the preparation method provided by the present invention, the self-template used is a nanomaterial with a very mature and low-cost preparation method at present, which is easy to operate, green and environmentally friendly;

[0025] (2) In the preparation method provided by the present invention, using the rod-shaped ZIF-67 as a template, through the etching step, the size of the Co nanoparticles in the obtained Co NP@HNC material can be regulated to a certain extent. After pyrolysis at high temperature, rich mesopores can be formed, which helps to improve the catalytic reaction activity and shows excellent activity and selectivity in the catalytic toluene oxidation experiment;

[0026] (3) The MOFs-derived hollow rod-shaped porous Co NP@HNC material provided by the present invention has a higher specific surface area and richer mesopores compared with the Co NP@HNC material obtained by directly calcining ZIF-67HR, can expose active sites to a greater extent, and has good practical application value. Description of the Drawings

[0027] Figure 1 Scanning electron microscopy (SEM) images of the Co precursor materials obtained in Examples 1 to 9;

[0028] Figure 2 SEM images of the ZIF-67HR materials obtained in Examples 1, 10, 11 to 17;

[0029] Figure 3 Transmission electron microscopy (TEM) images of the related products in Examples 1 and 18.

[0030] Figure 4 Powder X-ray diffraction (PXRD) curves of the 1# Co NP@HNC material obtained in Example 1 and the ZIF-67HR-650 material obtained by directly calcining ZIF-67HR in Example 1;

[0031] Figure 5 Nitrogen adsorption-desorption isotherms of the 1# Co NP@HNC material obtained in Example 1 and the ZIF-67HR-650 material obtained by directly calcining ZIF-67HR in Example 1;

[0032] Figure 6 Performance test result graph of the 1# Co NP@HNC material obtained in Example 1 for catalytic toluene oxidation reaction. Detailed Description of the Invention

[0033] The following further illustrates the specific implementation of the present invention in combination with examples, but the implementation and protection of the present invention are not limited thereto.

[0034] Example 1

[0035] (1) 0.20 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, 0.30 g of urea was added to 50 mL of ethanol to obtain solution B, and solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0036] (2) The mixed solution from step (1) is placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed 2 - 3 times with ethanol, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C is obtained; 2-Methylimidazole (12.0 g) is added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; The suspension C is mixed with solution D, placed in an oil bath at 120 °C and heated for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0037] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, continue heating for 3 h after ultrasonic dispersion for 5 min to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is washed 2 - 3 times with ethanol and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; The obtained ZIF-67HR-CA material is placed in a quartz boat, put into a tubular furnace, and argon is used as the calcination atmosphere. After purging at room temperature for 30 min, it is heated to 650 °C at a rate of 2 °C / min and calcined at 650 °C for 2 h. After cooling to room temperature, it is taken out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (marked as 1# Co NP@HNC material) is obtained, which is a black solid.

[0038] Figure 1 In (a) is the SEM image of the Co precursor obtained in this example. From Figure 1 in (a), it can be seen that the material is rod-shaped and has a moderate aspect ratio.

[0039] Figure 2 In (a) is the SEM image of the ZIF-67HR material obtained in the example. From Figure 2 in (a), it can be seen that the structural unit of the material is relatively moderate.

[0040] Figure 3 In (a) is the TEM image of the ZIF-67HR-CA material obtained in this example. From Figure 3 in (a), a porous hollow structure inside can be observed; Figure 3 In (d) is the SEM image of the 1# Co NP@HNC material obtained in this example. FromFigure 3 It can be seen from Fig. (d) that the 1# Co NP@HNC material well retains the rod-shaped hollow structure; Figure 3 Fig. (e) is the SEM image of the ZIF-67HR-650 material obtained by directly calcining ZIF-67HR. It can be seen that the ZIF-67HR-650 material also retains the rod-shaped hollow structure; Figure 3 Fig. (g) is the TEM image of the 1# Co NP@HNC material obtained in this example. Figure 3 Fig. (h) is the TEM image of ZIF-67HR-650 obtained by directly calcining ZIF-67HR. The comparison shows that the rod-shaped hollow structure can effectively prevent metal aggregation during the pyrolysis process.

[0041] Figure 4 are the PXRD spectra of the 1# Co NP@HNC material obtained in this example and the ZIF-67HR-650 material obtained by directly calcining ZIF-67HR. From Figure 6 it can be seen that the PXRD peaks of 1# Co NP@HNC are at 44.3°, 51.6° and 75.9°, corresponding to the diffraction peaks of Co.

[0042] Figure 5 are the nitrogen adsorption-desorption test results of the 1# Co NP@HNC material obtained in this example and the ZIF-67HR-650 material obtained by directly calcining ZIF-67HR. It can be Figure 5 seen that the nitrogen adsorption capacity of the 1# Co NP@HNC material obtained by etching-pyrolysis increases significantly. From the hysteresis loop, it can be seen that the 1# Co NP@HNC material is rich in mesopores, proving that it is a porous material.

[0043] Example 2

[0044] (1) 0.40 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, and 0.30 g of urea was added to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, they were mixed to obtain a mixed solution;

[0045] (2) The mixed solution from step (1) is placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed 2 - 3 times with ethanol, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C is obtained; 12.0 g of 2-methylimidazole is added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; The suspension C and the solution D are mixed and heated in an oil bath at 120 °C for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0046] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, and preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, ultrasonicate for 5 min and then continue heating for 2 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is washed 2 - 3 times with ethanol and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; Place the obtained ZIF-67HR-CA material in a quartz boat, put it into a tubular furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and take it out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (marked as 2# Co NP@HNC material) is obtained, which is a black solid.

[0047] Example 3

[0048] (1) Add 0.60 g of cobalt acetate to 50 ml of ethanol to obtain solution A, add 0.30 g of urea to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, they are mixed to obtain a mixed solution;

[0049] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain the Co precursor material; (3) 120 mg of the Co precursor material obtained in step (2) was weighed and dispersed in 10 mL of ethanol, and ultrasonically dispersed for 5 min to obtain a light pink suspension C; 2 - methylimidazole (12.0 g) was added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; the suspension C was mixed with the solution D, placed in an oil bath at 120 °C and heated for 30 min to obtain a ZIF - 67HR suspension. The obtained ZIF - 67HR suspension was centrifuged at 9000 r / min for 2 min, and the precipitate was washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain the ZIF - 67HR material;

[0050] (4) 50 mg of cyanuric acid was weighed and added to 50 ml of ethanol, and preheated under stirring in an oil bath at 50 °C for 30 min. The ZIF - 67HR material obtained in step (3) was dispersed in 60 mL of ethanol, ultrasonically treated for 5 min and then heated for 2 h to obtain a ZIF - 67HR - CA suspension. The obtained ZIF - 67HR - CA suspension was centrifuged at 5000 r / min for 1 min, and the precipitate was washed with ethanol 2 - 3 times and dried in an oven at 60 °C for 12 h to obtain the ZIF - 67HR - CA material; The obtained ZIF - 67HR - CA material was placed in a quartz boat, put into a tubular furnace, and purged with argon as the calcination atmosphere. After purging at room temperature for 30 min, it was heated to 650 °C at a rate of 2 °C / min and calcined at 650 °C for 2 h. After cooling to room temperature, it was taken out, and finally the Co NP@HNC hollow rod - shaped porous material prepared by the etching - pyrolysis strategy (labeled as 3# Co NP@HNC material) was obtained, which was a black solid.

[0051] Example 4

[0052] (1) 0.40 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, and 0.50 g of urea was added to 50 mL of ethanol to obtain solution B. Solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0053] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) 120 mg of the Co precursor material obtained in step (2) was weighed and dispersed in 10 mL of ethanol, and ultrasonically dispersed for 5 min to obtain a light pink suspension C; 2-methylimidazole (12.0 g) was added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; the suspension C and the solution D were mixed and heated in an oil bath at 120 °C for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension was centrifuged at 9000 r / min for 2 min, and the precipitate was washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0054] (4) 50 mg of cyanuric acid was weighed and added to 50 ml of ethanol, and preheated under stirring in an oil bath at 50 °C for 30 min. The ZIF-67HR material obtained in step (3) was dispersed in 60 mL of ethanol, ultrasonically dispersed for 5 min and then heated for 2 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension was centrifuged at 5000 r / min for 1 min, and the precipitate was washed with ethanol 2 - 3 times and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; The obtained ZIF-67HR-CA material was placed in a quartz boat, put into a tube furnace, and purged with argon as the calcination atmosphere. After purging at room temperature for 30 min, it was heated to 650 °C at a rate of 2 °C / min and calcined at 650 °C for 2 h. After cooling to room temperature, it was taken out, and finally the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (labeled as 4# Co NP@HNC material) was obtained, which was a black solid.

[0055] Example 5

[0056] (1) 0.40 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, and 0.70 g of urea was added to 50 mL of ethanol to obtain solution B. Solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0057] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) 120 mg of the Co precursor material obtained in step (2) was weighed and dispersed in 10 mL of ethanol, and ultrasonically dispersed for 5 min to obtain a light pink suspension C; 2-methylimidazole (12.0 g) was added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; the suspension C and the solution D were mixed and heated in an oil bath at 120 °C for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension was centrifuged at 9000 r / min for 2 min, and the precipitate was washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0058] (4) 50 mg of cyanuric acid was weighed and added to 50 ml of ethanol, and preheated under stirring in an oil bath at 50 °C for 30 min. The ZIF-67HR material obtained in step (3) was dispersed in 60 mL of ethanol, ultrasonically treated for 5 min and then heated for 2 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension was centrifuged at 5000 r / min for 1 min, and the precipitate was washed with ethanol 2 - 3 times and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; The obtained ZIF-67HR-CA material was placed in a quartz boat, put into a tubular furnace, and purged with argon as the calcination atmosphere. After purging at room temperature for 30 min, it was heated to 650 °C at a rate of 2 °C / min and calcined at 650 °C for 2 h. After cooling to room temperature, it was taken out, and finally the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (labeled as 4# Co NP@HNC material) was obtained, which was a black solid.

[0059] Example 6

[0060] (1) 0.20 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, and 0.30 g of urea was added to 50 mL of ethanol to obtain solution B. Solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0061] (2) The mixed solution from step (1) is placed in an oil bath at 70 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. Ultrasonic dispersion for 5 min gives a light pink suspension C; Dissolve 2-methylimidazole (12.0 g) in 150 mL of ethanol to obtain a colorless transparent solution D; Mix the suspension C and the solution D, place it in an oil bath at 120 °C and heat for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0062] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, ultrasonic for 5 min and then continue heating for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; Place the obtained ZIF-67HR-CA material in a quartz boat, put it into a tubular furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and then take it out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by an etching-pyrolysis strategy (labeled as 6# Co NP@HNC material) is obtained, which is a black solid.

[0063] Example 7

[0064] (1) Add 0.20 g of cobalt acetate to 50 ml of ethanol to obtain solution A, add 0.30 g of urea to 50 mL of ethanol to obtain solution B. Ultrasonic disperse solution A and solution B for 5 min and then mix them to obtain a mixed solution;

[0065] (2) The mixed solution from step (1) is placed in an 80 °C oil bath and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed 2 - 3 times with ethanol, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C is obtained; 2-Methylimidazole (12.0 g) is added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; The suspension C and the solution D are mixed and heated in an oil bath at 120 °C for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0066] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, and preheat it under stirring in a 50 °C oil bath for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, continue heating for 3 h after ultrasonic treatment for 5 min to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is taken and washed 2 - 3 times with ethanol, and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; Place the obtained ZIF-67HR-CA material in a quartz boat, put it into a tubular furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and take it out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (marked as 7# Co NP@HNC material) is obtained, which is a black solid.

[0067] Example 8

[0068] (1) Add 0.20 g of cobalt acetate to 50 ml of ethanol to obtain solution A, add 0.30 g of urea to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, they are mixed to obtain a mixed solution;

[0069] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 1 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) 120 mg of the Co precursor material obtained in step (2) was weighed and dispersed in 10 mL of ethanol, and ultrasonically dispersed for 5 min to obtain a light pink suspension C; 2-methylimidazole (12.0 g) was added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; the suspension C and the solution D were mixed, placed in an oil bath at 120 °C and heated for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension was centrifuged at 9000 r / min for 2 min, the precipitate was taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0070] (4) 50 mg of cyanuric acid was weighed and added to 50 ml of ethanol, preheated under stirring in an oil bath at 50 °C for 30 min. The ZIF-67HR material obtained in step (3) was dispersed in 60 mL of ethanol, ultrasonically treated for 5 min and then heated for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension was centrifuged at 5000 r / min for 1 min, the precipitate was taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; The obtained ZIF-67HR-CA material was placed in a quartz boat, put into a tube furnace, purged with argon as the calcination atmosphere, purged at room temperature for 30 min, then heated to 650 °C at a rate of 2 °C / min, calcined at 650 °C for 2 h, cooled to room temperature and taken out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (labeled as 8# Co NP@HNC material) was obtained, which was a black solid.

[0071] Example 9

[0072] (1) 0.20 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, 0.30 g of urea was added to 50 mL of ethanol to obtain solution B. Solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0073] (2) The mixed solution from step (1) is placed in an oil bath at 60 °C and stirred for 5 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C is obtained; Dissolve 2-methylimidazole (12.0 g) in 150 mL of ethanol to obtain a colorless transparent solution D; Mix the suspension C and the solution D, place it in an oil bath at 120 °C and heat for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0074] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, and preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, continue heating for 3 h after ultrasonic dispersion for 5 min to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; Place the obtained ZIF-67HR-CA material in a quartz boat, put it into a tubular furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and take it out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (marked as 9# Co NP@HNC material) is obtained, which is a black solid.

[0075] Example 10

[0076] (1) Add 0.20 g of cobalt acetate to 50 ml of ethanol to obtain solution A, add 0.30 g of urea to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, mix them to obtain a mixed solution;

[0077] (2) The mixed solution from step (1) is placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed 2 - 3 times with ethanol, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 80 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. Ultrasonic dispersion for 5 min gives a light pink suspension C; 2-methylimidazole (12.0 g) is added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; The suspension C is mixed with solution D, placed in an oil bath at 120 °C and heated for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0078] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, ultrasonic for 5 min and then continue heating for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is washed 2 - 3 times with ethanol and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; Place the obtained ZIF-67HR-CA material in a quartz boat, put it into a tubular furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and take it out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (marked as 10# Co NP@HNC material) is obtained, which is a black solid.

[0079] Example 11

[0080] (1) Add 0.20 g of cobalt acetate to 50 ml of ethanol to obtain solution A, add 0.30 g of urea to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, mix them to obtain a mixed solution;

[0081] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain the Co precursor material; (3) 160 mg of the Co precursor material obtained in step (2) was weighed and dispersed in 10 mL of ethanol, and ultrasonically dispersed for 5 min to obtain a light pink suspension C; 2 - methylimidazole (12.0 g) was added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; the suspension C was mixed with the solution D, placed in an oil bath at 120 °C and heated for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension was centrifuged at 9000 r / min for 2 min, the precipitate was taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain the ZIF-67HR material;

[0082] (4) 50 mg of cyanuric acid was weighed and added to 50 ml of ethanol, and preheated under stirring in an oil bath at 50 °C for 30 min. The ZIF-67HR material obtained in step (3) was dispersed in 60 mL of ethanol, ultrasonically dispersed for 5 min and then heated for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension was centrifuged at 5000 r / min for 1 min, the precipitate was taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain the ZIF-67HR-CA material; The obtained ZIF-67HR-CA material was placed in a quartz boat, put into a tubular furnace, and purged with argon as the calcination atmosphere. After purging at room temperature for 30 min, it was heated to 650 °C at a rate of 2 °C / min and calcined at 650 °C for 2 h. After cooling to room temperature, it was taken out, and finally the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (labeled as 11# Co NP@HNC material) was obtained, which was a black solid.

[0083] Example 12

[0084] (1) 0.20 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, 0.30 g of urea was added to 50 mL of ethanol to obtain solution B. Solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0085] (2) The mixed solution from step (1) is placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C is obtained; Dissolve 2-methylimidazole (12.0 g) in 150 mL of ethanol to obtain a colorless transparent solution D; Mix the suspension C and the solution D, place it in an oil bath at 100 °C and heat for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0086] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, continue to heat for 3 h after ultrasonic treatment for 5 min to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; Place the obtained ZIF-67HR-CA material in a quartz boat, put it into a tube furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and take it out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (marked as 12# Co NP@HNC material) is obtained, which is a black solid.

[0087] Example 13

[0088] (1) Add 0.20 g of cobalt acetate to 50 ml of ethanol to obtain solution A, add 0.30 g of urea to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, mix them to obtain a mixed solution;

[0089] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) 120 mg of the Co precursor material obtained in step (2) was weighed and dispersed in 10 mL of ethanol, and ultrasonically dispersed for 5 min to obtain a light pink suspension C; 2-methylimidazole (12.0 g) was added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; the suspension C and the solution D were mixed, placed in an oil bath at 140 °C and heated for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension was centrifuged at 9000 r / min for 2 min, the precipitate was taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0090] (4) 50 mg of cyanuric acid was weighed and added to 50 ml of ethanol, preheated under stirring in an oil bath at 50 °C for 30 min. The ZIF-67HR material obtained in step (3) was dispersed in 60 mL of ethanol, ultrasonically dispersed for 5 min and then heated for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension was centrifuged at 5000 r / min for 1 min, the precipitate was taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; The obtained ZIF-67HR-CA material was placed in a quartz boat, put into a tube furnace, purged with argon as the calcination atmosphere for 30 min at room temperature, then heated to 650 °C at a rate of 2 °C / min, calcined at 650 °C for 2 h, cooled to room temperature and taken out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (labeled as 13# Co NP@HNC material) was obtained, which was a black solid.

[0091] Example 14

[0092] (1) 0.20 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, 0.30 g of urea was added to 50 mL of ethanol to obtain solution B. Solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0093] (2) The mixed solution from step (1) is placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C is obtained; Dissolve 2 - methylimidazole (12.0 g) in 150 mL of ethanol to obtain a colorless transparent solution D; Mix the suspension C and the solution D, place it in an oil bath at 120 °C and heat for 10 min to obtain a ZIF - 67HR suspension. The obtained ZIF - 67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF - 67HR material;

[0094] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, and preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF - 67HR material obtained in step (3) in 60 mL of ethanol, continue to heat for 3 h after ultrasonic dispersion for 5 min to obtain a ZIF - 67HR - CA suspension. The obtained ZIF - 67HR - CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain a ZIF - 67HR - CA material; Place the obtained ZIF - 67HR - CA material in a quartz boat, put it into a tubular furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and then take it out. Finally, the Co NP@HNC hollow rod - shaped porous material prepared by the etching - pyrolysis strategy (labeled as 14# Co NP@HNC material) is obtained, which is a black solid.

[0095] Example 15

[0096] (1) Add 0.20 g of cobalt acetate to 50 ml of ethanol to obtain solution A, add 0.30 g of urea to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, mix them to obtain a mixed solution;

[0097] (2) The mixed solution from step (1) is placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension is centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C is obtained; 2-Methylimidazole (12.0 g) is added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; The suspension C and the solution D are mixed and placed in an oil bath at 120 °C and heated for 50 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension is centrifuged at 9000 r / min for 2 min, and the precipitate is washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0098] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, and preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, ultrasonicate for 5 min and then continue heating for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension is centrifuged at 5000 r / min for 1 min, and the precipitate is washed with ethanol 2 - 3 times and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; The obtained ZIF-67HR-CA material is placed in a quartz boat and put into a tube furnace. Using argon as the calcination atmosphere, after purging at room temperature for 30 min, it is heated to 650 °C at a rate of 2 °C / min and calcined at 650 °C for 2 h. After cooling to room temperature, it is taken out, and finally the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (marked as 15# Co NP@HNC material) is obtained, which is a black solid.

[0099] Example 16

[0100] (1) Add 0.20 g of cobalt acetate to 50 ml of ethanol to obtain solution A, and add 0.30 g of urea to 50 mL of ethanol to obtain solution B. After ultrasonic dispersion of solution A and solution B for 5 min, they are mixed to obtain a mixed solution;

[0101] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. After ultrasonic dispersion for 5 min, a light pink suspension C was obtained; 2-Methylimidazole (10.0 g) was added to 150 mL of ethanol and dissolved to obtain a colorless transparent solution D; The suspension C was mixed with the solution D, placed in an oil bath at 120 °C and heated for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension was centrifuged at 9000 r / min for 2 min, and the precipitate was washed thoroughly with ethanol and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0102] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, and preheat it under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, ultrasonicate for 5 min and then continue heating for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension was centrifuged at 5000 r / min for 1 min, and the precipitate was washed with ethanol 2 - 3 times and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; The obtained ZIF-67HR-CA material was placed in a quartz boat, put into a tube furnace, and purged with argon as the calcination atmosphere. After purging at room temperature for 30 min, it was heated to 650 °C at a rate of 2 °C / min and calcined at 650 °C for 2 h. After cooling to room temperature, it was taken out, and finally the Co NP@HNC hollow rod-shaped porous material prepared by the etching-pyrolysis strategy (labeled as 16# Co NP@HNC material) was obtained, which is a black solid.

[0103] Example 17

[0104] (1) 0.20 g of cobalt acetate was added to 50 ml of ethanol to obtain solution A, and 0.30 g of urea was added to 50 mL of ethanol to obtain solution B. Solution A and solution B were ultrasonically dispersed for 5 min and then mixed to obtain a mixed solution;

[0105] (2) The mixed solution from step (1) was placed in an oil bath at 60 °C and stirred for 3 h to obtain a Co precursor suspension. The obtained Co precursor suspension was centrifuged and washed with ethanol 2 - 3 times, and finally dried in an oven at 60 °C for 12 h to obtain a Co precursor material; (3) Weigh 120 mg of the Co precursor material obtained in step (2) and disperse it in 10 mL of ethanol. Ultrasonically disperse for 5 min to obtain a light pink suspension C; Dissolve 2-methylimidazole (14.0 g) in 150 mL of ethanol to obtain a colorless transparent solution D; Mix the suspension C with solution D, place it in an oil bath at 120 °C and heat for 30 min to obtain a ZIF-67HR suspension. The obtained ZIF-67HR suspension was centrifuged at 9000 r / min for 2 min, and the precipitate was taken and washed thoroughly with ethanol, and dried at 60 °C for 12 h to obtain a ZIF-67HR material;

[0106] (4) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, preheat under stirring in an oil bath at 50 °C for 30 min. Disperse the ZIF-67HR material obtained in step (3) in 60 mL of ethanol, ultrasonically disperse for 5 min and then continue heating for 3 h to obtain a ZIF-67HR-CA suspension. The obtained ZIF-67HR-CA suspension was centrifuged at 5000 r / min for 1 min, and the precipitate was taken and washed with ethanol 2 - 3 times, and dried in an oven at 60 °C for 12 h to obtain a ZIF-67HR-CA material; Place the obtained ZIF-67HR-CA material in a quartz boat, put it into a tubular furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat up to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, cool to room temperature and then take it out. Finally, the Co NP@HNC hollow rod-shaped porous material prepared by an etching-pyrolysis strategy (labeled as 17# Co NP@HNC material) was obtained, which is a black solid.

[0107] Example 18

[0108] (1) Add cobalt nitrate hexahydrate (0.873 g) to 75 mL of methanol and ultrasonically disperse evenly to obtain a metal salt solution. Add 2-methylimidazole (0.984 g) to 75 mL of methanol solution and ultrasonically disperse evenly to obtain an organic ligand solution. Pour the metal salt solution into the organic ligand solution, age for 1 day, centrifuge and wash to obtain ZIF-67RD.

[0109] (2) Weigh 50 mg of cyanuric acid, add 50 ml of ethanol, preheat it for 30 min under stirring in an oil bath at 50 °C. Disperse the ZIF-67RD material obtained in step (1) into 60 mL of ethanol, ultrasonicate for 5 min and then continue heating for 2 h to obtain a ZIF-67RD-CA suspension. Centrifuge the obtained ZIF-67HR-RD suspension at 5000 r / min for 1 min, take the precipitate and wash it with ethanol 2 - 3 times, and dry it in an oven at 60 °C for 12 h to obtain the ZIF-67HR-CA material.

[0110] (3) Place the obtained ZIF-67RD-CA material in a quartz boat, put it into a tube furnace, use argon as the calcination atmosphere, purge at room temperature for 30 min, then heat it to 650 °C at a rate of 2 °C / min, calcine at 650 °C for 2 h, take it out after cooling to room temperature, and finally obtain the hollow dodecahedron porous Co NP@HNC material (labeled as 30# Co NP@HNC material) prepared by the etching - pyrolysis strategy, which is a black solid.

[0111] Figure 3 In (c) is the TEM image of the ZIF-67RD-CA material obtained in this example. From Figure 3 it can be observed that the internal hollow structure; Figure 3 In (b) is the TEM image of the ZIF-67RD-650 material obtained by directly calcining ZIF-67RD; Figure 3 In (f) is the SEM image of the 18# Co NP@HNC material obtained in this example, Figure 3 In (i) is the TEM image of the 18# Co NP@HNC material obtained in this example. Collectively, it shows that the 18# Co NP@HNC material well retains the hollow structure after pyrolysis, and the etching treatment can, to a certain extent, prevent metal aggregation and promote the formation of the hollow structure, indicating that this etching - pyrolysis strategy has a certain generality and can be extended to the preparation of other MOF-derived hollow materials.

[0112] Example 1 Catalytic Oxidation Test of Porous Materials Loaded with Cobalt Nanoparticles for Toluene

[0113] In a high-pressure reactor, add 3 ml of toluene, and then add 20 mg of the catalyst (the 1# Co NP@HNC material prepared in Example 1). Purge the reactor with oxygen 5 - 10 times, and then fill it with 1 MPa O 2 , react at a reaction temperature of 170 °C, and at the same time perform magnetic stirring at a speed of 800 rpm. After the reaction is completed, naturally cool it to room temperature, and the catalyst can be separated from the reaction system by simple filtration. Analyze it using a gas chromatography - mass spectrometry (GC-MS) instrument to obtain the conversion rate of toluene and the yield of benzoic acid.

[0114] Figure 6 These are the performance test results of using the 1# Co NP@HNC material in this example to catalyze the oxidation of toluene to prepare benzoic acid. Figure 6 It shows that the hollow porous material has relatively high catalytic activity, with a conversion rate of >89% and a selectivity of >70% achievable within 12 h. This indicates that the hollow rod-shaped porous material loaded with Co nanoparticles can accelerate the mass transfer rate and increase the accessibility of active sites, thereby improving the conversion rate and the selectivity of the target product.

[0115] The above embodiments are only the preferred embodiments of the present invention, which are only used to explain the present invention rather than limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing Co@HNC hollow porous materials by etching-pyrolysis strategy, characterized in that: The steps include: (1) adding a Co salt to an ethanol solution of a surfactant, dissolving it by ultrasonication to obtain a mixed solution, heating and stirring the mixed solution, and centrifugally drying the mixed solution to obtain a Co precursor; (2) adding the Co precursor obtained in step (1) to ethanol, dissolving it by ultrasonication to obtain a Co precursor suspension, dissolving the nitrogen-containing organic ligand in ethanol to obtain an organic ligand solution; mixing the suspension with the organic ligand solution, heating and stirring, and centrifugally drying to obtain a ZIF-67 hollow nanorod material ZIF-67-HR; (3) adding ethanol to the ZIF-67 hollow nanorod material described in step (2), and dissolving it by ultrasonication to obtain a suspension; dissolving an organic acid in ethanol to obtain an etching solution; mixing the above-mentioned suspension with the etching solution, heating and stirring, and centrifugally drying to obtain a ZIF-67HR-CA material; (4) The ZIF-67HR-CA material of step (3) is heated and calcined in an air-isolated calcination atmosphere to obtain a CoNP@HNC material.

2. The method according to claim 1, characterized in that In step (1), the Co salt is cobalt nitrate, cobalt acetate or cobalt chloride; and the concentration of cobalt nitrate, cobalt acetate or cobalt chloride in the mixed solution is 2.0-6.0 g / L.

3. The method according to claim 1, characterized in that In step (1), the surfactant is urea or polyvinylpyrrolidone (PVP), and the concentration of urea or PVP in the ethanol solution of the surfactant is 3.0-7.0 g / L, respectively.

4. The method according to claim 1, characterized in that: In step (1), the stirring temperature is 60-80°C, the stirring time is 1h-5h; and the drying temperature is 60-80°C.

5. The method according to claim 1, characterized in that In step (2), the concentration of the Co precursor suspension is 8.0 g / L-16.0 g / L, the molar concentration of the alkaline organic ligand in the organic ligand solution is 0.81-1.13 mol / L; the nitrogen-containing organic ligand is 2-methylimidazole.

6. The method according to claim 1, characterized in that In step (2), the volume ratio of the Co precursor suspension to the organic ligand solution is 1:3-4; the stirring temperature is 100-140°C; the stirring time is 10min-50min; and the drying temperature is 60-80°C.

7. The method according to claim 1, characterized in that In step (3), the molar concentration of the organic acid in the etching solution is 0.008-0.14 mol / L; the organic acid is cyanuric acid, phytic acid or tannic acid.

8. The method according to claim 1, characterized in that In step (3), the volume ratio of the suspension to the etching acid solution is 1:3-4; the stirring temperature is 50-90°C, the stirring time is 1h-6h; and the drying temperature is 60-80°C.

9. The method according to claim 1, characterized in that: In step (4), the calcination atmosphere is an inert atmosphere; the calcination temperature is 550-750°C, the calcination time is 1-3h, and the heating rate is 2-6°C / min.

10. Co NP@HNC material prepared by the preparation method according to any one of claims 1 to 9.

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