Hollow ZIF-8 nanosphere and preparation method thereof

Abstract

The invention relates to the field of hollow ZIF-8 nanospheres, in particular to a hollow ZIF-8 nanosphere and a preparation method thereof. The hollow ZIF-8 nanosphere is of a sodalite structure, the specific surface area of the hollow ZIF-8 nanosphere is not smaller than 1300m < 2 > / g, and the pore volume of the hollow ZIF-8 nanosphere is not smaller than 0.75 cm < 3 > / g. The sodalite structure, the high specific surface area and the pore volume of the hollow ZIF-8 nanosphere are limited, the structural stability is maintained through a rigid framework of a sodalite topological structure, the large specific surface area provides rich gas adsorption sites, and the molecular diffusion efficiency and the storage capacity are improved through cooperation of a hollow cavity and the pore volume. By means of the hierarchical structure of the cavities and the micropores, efficient capture and separation of gas molecules such as CO2 are achieved, meanwhile, it is guaranteed that the material is not prone to collapse in the cyclic adsorption / desorption process through a rigid framework, and the material is suitable for a long-term stable operation gas separation scene.

Description

Technical Field

[0001] The present invention relates to the field of hollow ZIF-8 nanospheres, and in particular to hollow ZIF-8 nanospheres and a preparation method thereof. Background Art

[0002] With the acceleration of global industrialization, atmospheric carbon dioxide concentrations continue to rise, triggering a severe greenhouse effect and climate crisis. To address this challenge, the development of efficient CO2 capture and separation technologies has become a research hotspot in the field of environmental materials. Metal-organic frameworks (MOFs) are widely considered one of the most promising CO2 adsorbents due to their ultra-large specific surface area, tunable pore structure, and excellent gas adsorption performance. Zeolitic imidazolate frameworks, a key branch of MOFs, are assembled from metal ions and imidazole ligands through coordination bonds, combining high chemical stability with structural designability. Among them, ZIF-8 has become a star material in the field of CO2 capture due to its sodalite topology, 3.4Å pore size, and excellent thermal stability. To further enhance its adsorption performance, hollow ZIF-8 nanostructures are constructed by constructing internal cavities and thin shell structures to simultaneously optimize storage capacity and diffusion efficiency, demonstrating unique advantages in gas separation, catalysis, and other fields.

[0003] The synthesis of hollow ZIF-8 primarily relies on template methods, including hard and soft template methods. While the hard template method can precisely control the morphology, it requires high-temperature calcination or strong acid etching to remove the template, which can easily lead to damage to the shell structure. It also has a long synthesis cycle and high energy consumption. The soft template method forms a microemulsion template through surfactant self-assembly, avoiding tedious post-processing steps. However, traditional single surfactants suffer from problems such as insufficient micelle stability and a wide particle size distribution, making it difficult to control the uniformity of the hollow structure. Furthermore, existing soft template systems often use a single oil phase and high surfactant concentrations, which not only increases production costs but can also reduce the thermal stability of the material due to residual organic matter.

[0004] In response to the above-mentioned existing technologies, the inventors found that although the specific surface area of ​​the existing hollow ZIF-8 materials is improved, the pore volume is generally poor, and the CO2 / N2 selectivity is insufficient and the cyclic adsorption stability is poor, which makes it difficult to meet the needs of industrial-grade CO2 capture. Summary of the Invention

[0005] Based on the technical problems existing in the above-mentioned prior art, the present invention provides a hollow ZIF-8 nanosphere and a preparation method thereof.

[0006] In the first aspect, the present application provides a hollow ZIF-8 nanosphere, which adopts the following technical solution: A hollow ZIF-8 nanosphere having a sodalite structure and a specific surface area of ​​not less than 1300 m 2 / g, the pore volume of the hollow ZIF-8 nanospheres is not less than 0.75cm 3 / g.

[0007] Through the above technical solution, this application defines the sodalite structure, high specific surface area, and pore volume of hollow ZIF-8 nanospheres. The rigid skeleton of the sodalite topology maintains structural stability, and the large specific surface area provides abundant gas adsorption sites. The hollow cavity and pore volume synergistically improve molecular diffusion efficiency and storage capacity. Through the hierarchical structure of cavities and micropores, efficient capture and separation of gas molecules such as CO2 are achieved. At the same time, the rigid skeleton ensures that the material does not collapse during the cyclic adsorption / desorption process, making it suitable for long-term stable operation of gas separation scenarios.

[0008] In a second aspect, the present application provides a method for preparing hollow ZIF-8 nanospheres, comprising the following preparation steps: The oil phase and surfactant are added to a deionized water solution of 2-methylimidazole, ultrasonically treated for 1-3 hours, and zinc nitrate solution is added dropwise to the ultrasonicated microemulsion; The temperature is raised and added, and the temperature is kept for reaction. After centrifugation, washing and drying, hollow ZIF-8 nanospheres are obtained.

[0009] Through the above technical solution, this application adopts a soft template system of oil phase-surfactant-ligand solution, promotes the uniform dispersion of microemulsion template through ultrasonic treatment, and directionally coordinates the growth of metal ions and ligands at the template interface. Combined with low-temperature hydrothermal reaction and post-processing purification, it realizes the controllable synthesis of hollow structures. Compared with the hard template method, this method omits the high-temperature calcination or strong acid etching steps, avoiding the risk of damage to the hollow structure. At the same time, ultrasound assistance shortens the reaction cycle and improves synthesis efficiency. The centrifugal washing process effectively removes residual impurities, ensuring material purity and structural integrity.

[0010] Furthermore, the oil phase is n-hexane, and the volume proportion of the added n-hexane is 0~23v / v%.

[0011] Through the above technical solution, this application uses n-hexane as the oil phase, and controls the droplet size and stability of the oil-in-water microemulsion by adjusting its volume ratio. A low proportion of oil phase inhibits over-emulsification, and a high proportion promotes the formation of polydisperse droplets. The droplets act as soft templates to directly determine the cavity size and distribution of the hollow nanospheres. The low polarity and volatility of n-hexane avoid interference with subsequent coordination reactions. Effect: Precise control of the oil phase ratio can achieve a gradient design of the cavity size, solving the problem of template agglomeration caused by the traditional oil phase; the easy removal of n-hexane reduces surfactant residues, improves the chemical purity of the material, and at the same time broadens the adjustable range of the hollow structure to meet the needs of different application scenarios. Furthermore, the surfactant is perfluorodecyltriethoxysilane, and the added concentration of the perfluorodecyltriethoxysilane is 0.05-0.10 g / mL.

[0012] Through the above technical solution, the perfluorodecyltriethoxysilane used in this application forms a stable monolayer at the oil-water interface through superhydrophobic chain segments and siloxy groups. The siloxy groups form hydrogen bonds with ligands, guiding the directional growth of ZIF-8 crystals along the template interface. The superhydrophobic properties of perfluorodecyltriethoxysilane enhance the stability of the microemulsion and prevent template breakage caused by aqueous phase interference. The coordination effect of the siloxy groups enhances the binding force between the crystals and the template, reducing nonspecific nucleation, thereby improving the yield and structural regularity of the hollow nanospheres. At the same time, the fluorocarbon segments can impart hydrophobicity to the material surface, expanding its application in oil-water separation.

[0013] Furthermore, the surfactant also includes a compound surfactant, which is formed by compounding cetyltrimethylammonium bromide and Pluronic F127 surfactant in a mass ratio of 1: (1-3).

[0014] Through the above technical solution, the present application selects a compound of cationic surfactants and nonionic surfactants, and forms mixed micelles through charge complementarity and entanglement with hydrophobic segments. The positive charge of the cationic surfactant adsorbs the ligand anion, and the polyoxyethylene segment of the nonionic surfactant provides steric hindrance, synergistically reducing the critical micelle concentration and optimizing the micelle size distribution. Compared with a single surfactant, the compound system broadens the template stability range, and the synergistic effect of the mixed micelles inhibits the ripening effect during crystal growth, making the nanosphere particle size distribution more uniform; at the same time, it improves the interfacial adsorption efficiency, enhances the ability to regulate the ZIF-8 crystal morphology, and realizes the controllable synthesis of various morphologies from cubic to rod-shaped.

[0015] Furthermore, the molar ratio of the compound surfactant to zinc ions is (0.01-0.4):1.

[0016] Through the above technical solution, the present application regulates the coordination equilibrium between metal ions and surfactant micelles by limiting the molar ratio of the compound surfactant to zinc ions. At low ratios, insufficient micelle templates lead to the formation of solid particles, while at high ratios, excess surfactants induce micelle aggregation, interfering with the formation of hollow structures. Optimizing the molar ratio can achieve the coordinated assembly of "template-metal-ligand", ensuring that the surface of each micelle template is evenly loaded with metal ions, avoiding crystal agglomeration caused by local oversaturation; at the same time, it improves the controllability of the coordination reaction, making the shell thickness and pore size distribution of the hollow structure more uniform, and improving the batch stability of the material.

[0017] Furthermore, the conditions for the heating and heat preservation reaction are: 25-35° C., 400-600 rpm, and reaction time of 0.5-24 h.

[0018] Through the above technical solution, this application optimizes the reaction conditions to avoid ligand decomposition caused by high temperature; low rotation speed ensures template stability, and time gradient regulation achieves a balance between morphology and crystallinity; the obtained material has both high crystallinity and a complete hollow structure, and is suitable for catalysis and sensing fields that have strict requirements on structural integrity.

[0019] Furthermore, the compounded surfactant further comprises graphene oxide, and the graphene oxide accounts for 0.5-2.0% of the mass of the compounded surfactant.

[0020] Through the above technical solution, the present application adds graphene oxide, whose π-π stacking combines with the hydrophobic segments of the surfactant. The surface hydroxyl and carboxyl groups form hydrogen bonds with the ligands, synergistically stabilizing the microemulsion template. The two-dimensional GO layered structure is interspersed with the ZIF-8 shell to construct a "hollow sphere-GO" composite framework, enhancing the material's mechanical strength. The addition of GO enhances the mechanical strength of the template system and inhibits the structural shrinkage of the nanospheres during drying or adsorption.

[0021] In summary, this application has the following beneficial effects: First, this technical solution significantly optimizes the structural controllability of ZIF-8 nanospheres by combining the sodalite topological structure with the hollow design, supplemented by the synergistic effect of the surfactant compound system and graphene oxide. The compound surfactant forms stable mixed micelles through charge complementarity and entanglement with the hydrophobic chain segments, suppressing the problems of easy aggregation and wide particle size distribution of micelles in the traditional single surfactant system, making the nanosphere morphology more regular and the size distribution more uniform. The introduction of GO enhances the template stability through π-π stacking and hydrogen bonding. At the same time, its two-dimensional lamellar structure is interspersed in the ZIF-8 shell to construct a hollow sphere / GO composite skeleton, effectively improving the mechanical strength of the material and avoiding structural collapse during recycling. In addition, the superhydrophobic properties of perfluorodecyltriethoxysilane further consolidate the stability of the oil-water interface film, reduce nonspecific nucleation, ensure the integrity and repeatability of the hollow structure, and lay the foundation for subsequent functional modification.

[0022] Second, compared to the traditional hard template method that requires a complex process of high-temperature calcination or strong acid etching, this application adopts a soft template method combined with ultrasound-assisted technology to achieve a gentle and efficient synthesis of hollow ZIF-8 nanospheres. Ultrasonic treatment promotes the uniform dispersion of the microemulsion template, shortens the reaction cycle, and avoids the damage of the template to the high shear force; low-temperature reaction conditions reduce energy consumption, inhibit ligand decomposition, and improve material purity; the simple post-processing process of centrifugal washing and drying effectively removes residual impurities, eliminates the tedious template removal steps, and reduces environmental pollution. The low boiling point characteristics of the oil phase allow it to be removed by simple volatilization, reducing the risk of surfactant residues. At the same time, the compounded surfactant system reduces the critical micelle concentration, reduces the dosage, and broadens the template stability range, significantly reducing production costs, and providing feasibility for large-scale industrial production.

[0023] Third, this application uses collaborative innovation in structure and process to enable hollow ZIF-8 nanospheres to demonstrate excellent performance in the fields of gas adsorption, catalysis, and separation. The rigid skeleton of the sodalite structure and the hierarchical design of the hollow cavity optimize the material diffusion path and storage capacity, and improve the selective adsorption capacity of target molecules; the surfactant compounding and GO composite enhance the chemical stability of the material, ensuring that the performance attenuation rate during recycling is reduced and the service life is extended. In addition, the fluorocarbon chain segment of HFS gives the material surface hydrophobicity, which can be used in oil-water separation; the conductivity and catalytic activity of GO expand the application of the material in electrocatalysis, energy storage and other fields. This integrated design of "structure-performance-function" breaks through the limitations of the single function of traditional ZIF materials and realizes cross-domain expansion from gas capture to multi-scenario applications. DETAILED DESCRIPTION

[0024] The present application is further described in detail below with reference to the embodiments.

[0025] Preparation Example 1 Cetyltrimethylammonium bromide and Pluronic F127 were mixed in a mass ratio of 1:1 to prepare a compound surfactant 1.

[0026] Preparation Example 2 Cetyltrimethylammonium bromide and Pluronic F127 were mixed in a mass ratio of 1:2 to prepare a compound surfactant 2.

[0027] Preparation Example 3 Cetyltrimethylammonium bromide and Pluronic F127 were mixed in a mass ratio of 1:3 to prepare a compound surfactant 3.

[0028] Preparation Example 4 Cetyltrimethylammonium bromide and Pluronic F127 were compounded in a mass ratio of 1:2, and graphene oxide was added thereto at a mass ratio of 0.5% of the mass of the compounded surfactant to prepare compounded surfactant 4.

[0029] Preparation Example 5 Cetyltrimethylammonium bromide and Pluronic F127 were compounded in a mass ratio of 1:2, and graphene oxide was added so that the graphene oxide accounted for 1% of the mass of the compounded surfactant to prepare a compounded surfactant 5.

[0030] Preparation Example 6 Cetyltrimethylammonium bromide and Pluronic F127 were compounded in a mass ratio of 1:2, and graphene oxide was added so that the graphene oxide accounted for 2.0% of the mass of the compounded surfactant to prepare compounded surfactant 6.

[0031] Example 1 Weigh 5 g of 2-methylimidazole and dissolve it in 100 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 3.5 g of zinc nitrate and dissolve it in 50 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 3.3 g of n-hexane and 4.32 mL of HFS were added to the ligand solution and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0032] Example 2 Weigh 10 g of 2-methylimidazole and dissolve it in 200 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 7 g of zinc nitrate and dissolve it in 100 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 6.8 g of n-hexane and 9.2 mL of HFS were added to the ligand solution and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0033] Example 3 Weigh 22 g of 2-methylimidazole and dissolve it in 500 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 15 g of zinc nitrate and dissolve it in 200 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 16.5 g of n-hexane and 20 mL of HFS were added to the ligand solution and ultrasonicated at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0034] Example 4 Weigh 5 g of 2-methylimidazole and dissolve it in 100 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 3.5 g of zinc nitrate and dissolve it in 50 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 3.3 g of n-hexane and 2 g of the composite surfactant 1 were added to the ligand solution, and ultrasonic treatment was performed at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0035] Example 5 Weigh 5 g of 2-methylimidazole and dissolve it in 100 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 3.5 g of zinc nitrate and dissolve it in 50 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 3.3 g of n-hexane and 2 g of the composite surfactant 2 were added to the ligand solution, and ultrasonic treatment was performed at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0036] Example 6 Weigh 5 g of 2-methylimidazole and dissolve it in 100 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 3.5 g of zinc nitrate and dissolve it in 50 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 3.3 g of n-hexane and 2 g of the compound surfactant 3 were added to the ligand solution, and ultrasonic treatment was performed at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0037] Example 7 Weigh 5 g of 2-methylimidazole and dissolve it in 100 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 3.5 g of zinc nitrate and dissolve it in 50 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 3.3 g of n-hexane and 2 g of the composite surfactant 4 were added to the ligand solution, and ultrasonic treatment was performed at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0038] Example 8 Weigh 5 g of 2-methylimidazole and dissolve it in 100 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 3.5 g of zinc nitrate and dissolve it in 50 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 3.3 g of n-hexane and 2 g of the composite surfactant 5 were added to the ligand solution, and ultrasonic treatment was performed at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0039] Example 9 Weigh 5 g of 2-methylimidazole and dissolve it in 100 mL of deionized water. Stir until completely dissolved to obtain a ligand solution. Weigh 3.5 g of zinc nitrate and dissolve it in 50 mL of deionized water to obtain a metal salt solution. Use n-hexane as the oil phase and perfluorodecyltriethoxysilane as the surfactant. 3.3 g of n-hexane and 2 g of the composite surfactant 6 were added to the ligand solution, and ultrasonic treatment was performed at a power of 300 W and a frequency of 40 kHz for 1.5 h to form a uniform microemulsion; The metal salt solution was added dropwise to the microemulsion, stirred magnetically at 500 rpm, and kept at 30°C for 6 h. After the reaction, the precipitate was collected by centrifugation at 8000 rpm for 10 min, washed three times with deionized water and ethanol respectively, and dried in a vacuum at 60°C for 12 h to obtain hollow ZIF-8 nanospheres.

[0040] Performance testing Specific surface area: The surface area was determined using the Brunauer−Emmett−Teller method; Adsorption performance: at 1×10 −7 The adsorption / desorption behavior was tested in the pressure range from 0.1 bar to 1 bar with N2 at 77 K. Before the N2 adsorption studies, the powder samples were outgassed at 120 °C for 12 h.

[0041] The results are shown in Table 1 below: Table 1 Performance test table

[0042] From the comparison of the above Examples 1-9 and Comparative Example 1 in conjunction with the test results in Table 1, it can be found that: Combining the data from Examples 1-3, we found that the use of a soft-template system consisting of an oil phase, surfactant, and ligand solution, with ultrasonic treatment promoting uniform dispersion of the microemulsion template and directed coordinated growth of metal ions and ligands at the template interface, combined with a low-temperature hydrothermal reaction and post-processing purification, enabled the controlled synthesis of hollow structures. Compared to the hard-template method, this method eliminates the need for high-temperature calcination or strong acid etching, thus avoiding the risk of damage to the hollow structure. Ultrasound-assisted treatment also shortens the reaction cycle and improves synthesis efficiency. A centrifugal washing process effectively removes residual impurities, ensuring material purity and structural integrity.

[0043] By comparing Examples 4-6 with Examples 1-3, it is further illustrated that the technical solution of the present application uses a compound of cationic surfactants and nonionic surfactants, which are entangled with hydrophobic segments through charge complementarity to form mixed micelles. The positive charge of the cationic surfactant adsorbs the ligand anion, and the polyoxyethylene segment of the nonionic surfactant provides steric hindrance, synergistically reducing the critical micelle concentration and optimizing the micelle size distribution. Compared with a single surfactant, the compound system broadens the template stability range, and the synergistic effect of the mixed micelles inhibits the ripening effect during crystal growth, making the nanosphere particle size distribution more uniform; at the same time, it improves the interfacial adsorption efficiency, enhances the ability to regulate the ZIF-8 crystal morphology, and realizes the controllable synthesis of various morphologies from cubic to rod-shaped.

[0044] Comparing Examples 7-9 with Examples 4-6 demonstrates that the π-π stacking of graphene oxide added to the present invention combines with the hydrophobic segments of the surfactant, allowing its surface hydroxyl and carboxyl groups to form hydrogen bonds with the ligands, synergistically stabilizing the microemulsion template. Furthermore, the two-dimensional GO layered structure interspersed within the ZIF-8 shell creates a "hollow sphere-GO" composite framework, enhancing the material's mechanical strength. The addition of GO enhances the mechanical strength of the template system and inhibits structural shrinkage of the nanospheres during drying or adsorption.

[0045] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

[0046] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail.

[0047] When this specification uses the prefix "well known to those skilled in the art", "existing technology" or its similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix include those commonly used in the field when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the field to be suitable for similar purposes.

[0048] In the context of this specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A hollow ZIF-8 nanosphere, characterized in that The hollow ZIF-8 nanospheres have a sodalite structure and a specific surface area of ​​not less than 1300 m 2 / g, the pore volume of the hollow ZIF-8 nanospheres is not less than 0.75cm 3 / g.

2. The method for preparing hollow ZIF-8 nanospheres according to claim 1, wherein The method comprises the following preparation steps: The oil phase and surfactant are added to a deionized water solution of 2-methylimidazole, ultrasonically treated for 1-3 hours, and zinc nitrate solution is added dropwise to the ultrasonicated microemulsion; The temperature is raised and added, and the temperature is kept for reaction. After centrifugation, washing and drying, hollow ZIF-8 nanospheres are obtained.

3. The method for preparing hollow ZIF-8 nanospheres according to claim 2, wherein The oil phase is n-hexane, and the added volume proportion of the n-hexane is 0-23 v / v%.

4. The method for preparing hollow ZIF-8 nanospheres according to claim 2, wherein The surfactant is perfluorodecyltriethoxysilane, and the added concentration of the perfluorodecyltriethoxysilane is 0.05-0.10 g / mL.

5. The method for preparing hollow ZIF-8 nanospheres according to claim 2, wherein The surfactant further comprises a compound surfactant, wherein the compound surfactant comprises cetyltrimethylammonium bromide and Pluronic F127 surfactant in a mass ratio of 1: (1-3).

6. The method for preparing hollow ZIF-8 nanospheres according to claim 2, wherein The molar ratio of the compound surfactant to the zinc ion is (0.01-0.4):

1.

7. The method for preparing hollow ZIF-8 nanospheres according to claim 2, wherein: The heating and heat preservation reaction conditions are: 25-35° C., 400-600 rpm, and reaction time of 0.5-24 h.

8. The method for preparing hollow ZIF-8 nanospheres according to claim 2, wherein: The compound surfactant further comprises graphene oxide, and the graphene oxide accounts for 0.5-2.0% of the mass of the compound surfactant.

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