Cyclodextrin metal-organic framework nanoparticles and their preparation methods

Abstract

A method for preparing a cyclodextrin-metal-organic framework (MOF) nano-sustained-release pesticide, the cyclodextrin-metal-organic framework nano-sustained-release pesticide prepared by this method, and the application of this cyclodextrin-metal-organic framework nano-sustained-release pesticide in fruit preservation. The preparation method includes 1) the preparation of γ-CD-MOF; 2) the preparation of a mixture of γ-CD and azoxystrobin; and 3) the preparation of a γ-CD-MOF / azoxystrobin nano-sustained-release pesticide. Biocompatible γ-cyclodextrin is used as the organic ligand, with K... + γ-CD-MOF materials were prepared using ion centers. The synthesis process conditions were optimized, and a universal synthesis method was established. Azoxystrobin fungicide was loaded into γ-CD-MOF materials to prepare a slow-release pesticide. The process conditions were optimized, and when the solvent ratio was 10:6, the material morphology was a uniform cubic shape with an average particle size of 1.93 μm.

Description

Technical Field

[0001] This invention relates to the field of pesticide preparation technology, specifically to a nano-slow-release pesticide based on cyclodextrin metal-organic framework compounds and its synthesis method, and more specifically to a method for preparing pyraclostrobin nano-slow-release fungicide using cyclodextrin metal-organic framework compounds. Background Technology

[0002] Strawberries are one of the most widely cultivated berries in my country. Currently, the main problems in strawberry production include excessive pesticide application and excessive pesticide residues. In recent years, the Ministry of Agriculture and Rural Affairs has proposed reducing pesticide and fertilizer use while increasing efficiency to develop high-quality agriculture. Therefore, the preparation of nano-controlled-release pesticides with strong stability and long-lasting effects is of great significance for solving the problems of low pesticide utilization and excessive pesticide use in strawberry cultivation.

[0003] In recent years, strawberry diseases have become increasingly frequent, mainly caused by fungal infections and pests, including gray mold, wilt, anthracnose, powdery mildew, and nematode diseases. Therefore, fungicides such as azoxystrobin are necessary in strawberry cultivation. However, azoxystrobin has poor water solubility, and most commercially available azoxystrobin fungicides are in the form of aqueous suspensions and water-dispersible particles. This results in a short residual effect, requiring multiple applications and low utilization rates. Excessive application leads to increased azoxystrobin residues, impacting environmental safety and human health. Therefore, developing azoxystrobin nano-controlled-release pesticides can extend the residual effect, improve fungicide utilization, and reduce application rates, holding significant research value in the field of green pesticide development for the strawberry industry.

[0004] Cyclodextrin (CD) is a natural cyclic oligosaccharide produced by enzymatic hydrolysis of starch or starch derivatives. Its basic component is D-(+)-pyranose groups linked by α-1,4-glycosidic bonds, primarily including α-, β-, and γ-CD types. Metal-organic frameworks (MOFs) are organic-inorganic hybrid materials with intramolecular pores, formed by coordination bonds between organic ligands and metal ions or clusters. Cyclodextrin-based metal-organic frameworks (CD-MOFs) are porous nanomaterials self-assembled from food-grade cyclodextrin ligands and biocompatible metal ions. The combination of cyclodextrin and metal ions gives CD-MOFs the excellent properties of both cyclodextrin and MOF materials, including good encapsulation ability, solubility, and porosity. Furthermore, unlike traditional MOF materials which are toxic, CD-MOFs are edible. The abundant pores of CD-MOFs can encapsulate different types of guest molecules, such as gas molecules, drug molecules, and metal nanoclusters, and have wide applications in catalysis, electronics, drug delivery, biosensing, and medicine. Cyclodextrin metal-organic frameworks, as porous framework materials, can be used in the synthesis of sustained-release pesticides due to their good biocompatibility, degradability, and non-toxicity. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a method for synthesizing cyclodextrin-metal-organic framework (MOF) nano-controlled-release pesticides. Specifically, it addresses the problems of low efficacy and poor utilization of traditional azoxystrobin fungicides used in strawberry cultivation. The method synthesizes a biocompatible and non-toxic cyclodextrin-MOF material loaded with azoxystrobin fungicide, resulting in a novel nano-controlled-release pesticide with strong stability and long-lasting effect. The cyclodextrin MOF-azoxystrobin controlled-release pesticide also has a certain preservative effect on strawberry fruit, effectively delaying the decrease in fruit weight and firmness and preventing decay, similar to azoxystrobin suspension, and promoting an increase in the soluble sugar content of strawberry fruit.

[0006] The technical solution of this invention mainly includes the preparation, performance testing, and bioactivity determination of cyclodextrin-MOF-pyraclostrobin slow-release pesticide.

[0007] Embodiments of the present invention provide a method for preparing a cyclodextrin metal-organic framework nanoparticle sustained-release pesticide, the method comprising:

[0008] 1) Preparation of γ-CD-MOF

[0009] γ-CD and KOH were dissolved in deionized water and sonicated for 30 minutes. The mixed solution was then filtered using an organic filter membrane. The resulting solution was mixed with methanol at a solvent ratio of 10:(2-10) and heated at 60°C for 1 hour in a constant temperature water bath. 8 mg / mL of PEG-20000 was added to the obtained clear solution. The precipitate was washed three times with methanol and ethanol, soaked in dichloromethane for 3 days, centrifuged, and then vacuum dried. γ-CD-MOF was neutralized with ethanol and acetic acid and then vacuum dried for later use.

[0010] 2) Preparation of a mixture of γ-CD and azoxystrobin

[0011] Weighing according to a 1:1 molar ratio, a certain amount of γ-cyclodextrin was first dissolved in deionized water in a beaker, and then stirred at 750 rpm with a magnetic stirrer to ensure complete dissolution. At the same time, a certain amount of azoxystrobin was weighed and dissolved in ethanol, and then the azoxystrobin solution was added to the γ-CD aqueous solution, and the mixture was stirred continuously. The compound was stirred in the dark at 60℃ for 2 hours to evaporate the ethanol. Subsequently, the solution was centrifuged at 10000 rpm for 10 minutes and the supernatant was collected. The precipitate was frozen at -20℃ for 24 hours, and then dried at -50℃ for 24 hours using a freeze dryer. The inclusion complex of γ-CD and azoxystrobin was collected, dried and stored for later use.

[0012] 3) Preparation of γ-CD-MOF / pyraclostrobin nano-release pesticide

[0013] First, a 1.0 mg / mL-5.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of (1-10):1, and then magnetically stirred at 750 rpm for 3 hours in the dark. Subsequently, the mixture was centrifuged at 10,000 rpm for 1 hour, and the resulting precipitate was washed twice with methanol and ethanol, respectively, to remove the unencapsulated portion of azoxystrobin. Finally, all samples were vacuum dried overnight in the dark. The supernatant was recovered to obtain the cyclodextrin metal-organic framework nano-controlled-release pesticide.

[0014] According to one embodiment of the present invention, for example, in step 1), the resulting solution is mixed with methanol at a solvent ratio of 10:(3-8); preferably, the resulting solution is mixed with methanol at a solvent ratio of 10:6.

[0015] According to one embodiment of the present invention, for example, in step 3), a pyraclostrobin methanol solution with a concentration of 1.2 mg / mL to 4.0 mg / mL is mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of (1-10):1; preferably, a pyraclostrobin methanol solution with a concentration of 2.0 mg / mL is mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of (1-10):1.

[0016] According to one embodiment of the present invention, for example, in step 3), a pyraclostrobin methanol solution with a concentration of 1.2 mg / mL to 4.0 mg / mL is mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of (1-6):1; preferably, a pyraclostrobin methanol solution with a concentration of 2.0 mg / mL is mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 2:1.

[0017] According to one embodiment of the present invention, for example, the cyclodextrin metal-organic framework nanoparticles of sustained-release pesticides have a uniform cubic morphology with an average particle size of 1.93 μm.

[0018] An embodiment of the present invention also provides an application of cyclodextrin metal-organic framework nano-slow-release pesticides for fruit preservation, comprising: preparing a 0.15 mg / mL γ-CD-MOF / pyraclostrobin solution, immersing the fruit in the prepared solution for 5 min, and then removing the fruit for proper storage. Attached Figure Description

[0019] Figure 1 These are scanning electron microscope images of γ-CD-MOF prepared under different solvent ratios: a. solvent ratio 10:4; b. solvent ratio 10:6; c. solvent ratio 10:8; d. solvent ratio 10:10.

[0020] Figure 2 These are particle size distribution diagrams of γ-CD-MOF prepared under different solvent ratios: a. solvent ratio of 10:4; b. solvent ratio of 10:6; c. solvent ratio of 10:8; d. solvent ratio of 10:10.

[0021] Figure 3 The adsorption rate and drug loading of γ-CD-MOF on azoxystrobin.

[0022] Figure 4 The adsorption rate and drug loading of γ-CD-MOF / pyraclostrobin prepared under different feed ratios are shown.

[0023] Figure 5 These are the XRD patterns of azoxystrobin, γ-CD-MOF, and γ-CD-MOF / azoxystrobin.

[0024] Figure 6 This is a scanning electron microscope image of the γ-CD-MOF prepared in Example 9 of this invention.

[0025] Figure 7 It refers to the solubility of azoxystrobin, γ-CD / azoxystrobin, and γ-CD-MOF / azoxystrobin.

[0026] Figure 8 This is the cumulative release curve of γ-CD-MOF / pyraclostrobin.

[0027] Figure 9 The antibacterial effect of γ-CD-MOF / pyraclostrobin nano-slow-release pesticide was observed six days after application.

[0028] Figure 10 The effect of γ-CD-MOF / pyraclostrobin nano-slow-release pesticide on the degree of strawberry fruit decay. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. However, those skilled in the art will understand that this invention is not limited to the accompanying drawings and the following embodiments.

[0030] Example 1

[0031] An embodiment of the present invention provides a method for preparing a cyclodextrin-MOF sustained-release azoxystrobin pesticide, the method comprising:

[0032] 1) Preparation of γ-CD-MOF

[0033] 3.24 g γ-CD and 1.12 g KOH were dissolved in 100 mL deionized water, sonicated for 30 minutes, and the mixture was filtered through an organic filter membrane. The resulting solution was mixed with methanol at a solvent ratio of 10:4 and heated at 60 °C for 1 hour in a constant temperature water bath. 8 mg / mL PEG-20000 was added to the obtained clear solution. The precipitate was washed three times with methanol and ethanol, soaked in dichloromethane for 3 days, centrifuged, and then vacuum dried. γ-CD-MOF was neutralized with 40 mL ethanol and 4 mL acetic acid, then vacuum dried for later use.

[0034] 2) Preparation of a mixture of γ-CD and azoxystrobin

[0035] Weigh out the γ-cyclodextrin in a 1:1 molar ratio. First, dissolve a certain amount of γ-cyclodextrin in deionized water in a beaker, and then stir with a magnetic stirrer at 750 rpm until fully dissolved. Simultaneously, weigh out a certain amount of azoxystrobin and dissolve it in ethanol. Then, add the azoxystrobin solution to the γ-CD aqueous solution and stir continuously. Stir the compound in the dark at 60°C for 2 hours to evaporate the ethanol. Subsequently, centrifuge the solution at 10,000 rpm for 10 minutes and collect the supernatant. Freeze the precipitate at -20°C for 24 hours, and then freeze-dry it (at -50°C) for 24 hours. Collect the inclusion complex of γ-CD and azoxystrobin, dry and store for later use.

[0036] 3) Preparation of γ-CD-MOF / pyraclostrobin nano-release pesticide

[0037] First, a 1.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 1:1, and then magnetically stirred at 750 rpm for 3 hours in the dark. Subsequently, the mixture was centrifuged at 10,000 rpm for 1 hour, and the resulting precipitate was washed twice with methanol and ethanol, respectively, to remove the unencapsulated portion of azoxystrobin. Finally, all samples were vacuum-dried overnight in the dark. The supernatant was recovered, and its drug loading and adsorption rate were determined by high-performance liquid chromatography (HPLC).

[0038] Example 2

[0039] In step 1), the resulting solution was mixed with methanol at a solvent ratio of 10:6, and other experimental conditions were the same as in Example 1.

[0040] Example 3

[0041] In step 1, the resulting solution was mixed with methanol at a solvent ratio of 10:8, and other experimental conditions were the same as in Example 1.

[0042] Example 4

[0043] In step 1), the resulting solution was mixed with methanol at a solvent ratio of 10:10, and other experimental conditions were the same as in Example 1.

[0044] By comparing the results of Examples 1-4, the effect of different solvent ratios on the morphology of nano-controlled-release pesticides can be investigated. The γ-CD-MOF scanning electron microscopy and particle size analysis of Examples 1-4 are shown below. Figure 1 , Figure 2 As shown, the results indicate that when the solvent ratio is 10:6, the morphology of γ-CD-MOF is cubic, with a particle size range of 1.45–2.48 μm and an average particle size of 1.93 μm. When the solvent ratio is 10:8 and 10:10, its microstructure exhibits cross-growth and irregular shape, with average particle sizes of 600 nm and 2.34 μm, respectively. Excess methanol reduces the crystallinity of γ-CD-MOF.

[0045] The addition of methanol helps reduce particle size, which was also confirmed by SEM analysis of γ-CD-MOFs prepared at a solvent ratio of 10:4. Figure 1 a. When the solvent ratio is 10:4, the morphology of γ-CD-MOF is non-uniform cubic with a relatively irregular shape, and the average particle size is the largest at 2.51 μm compared to other solvent ratios. Scanning electron microscopy analysis shows that 10:6 is the optimal solvent ratio, which is more conducive to the formation of γ-CD-MOF grains with good morphology.

[0046] Example 5

[0047] In step 3), a 2.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 1:1, and other experimental conditions were the same as in Example 2.

[0048] Example 6

[0049] In step 3), a 3.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 1:1, and other experimental conditions were the same as in Example 2.

[0050] Example 7

[0051] In step 3), a 4.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 1:1, and other experimental conditions were the same as in Example 2.

[0052] Example 8

[0053] In step 3), a 5.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 1:1, and other experimental conditions were the same as in Example 2.

[0054] The effect of different pesticide concentrations on the performance of slow-release pesticides can be investigated by comparing the results of Examples 2 and 5-8. The content of azoxystrobin in the nano-scale slow-release pesticide was determined by high-performance liquid chromatography. Figure 3 As shown, the adsorption rate of γ-CD-MOF for azoxystrobin is negatively correlated with the pesticide concentration. The adsorption rate gradually decreases with increasing azoxystrobin concentration, ranging from 82.56% to 87.42%. The actual pesticide loading shows a trend of first increasing and then decreasing. When the azoxystrobin concentration is 2 mg / mL, the pesticide loading of γ-CD-MOF / azoxystrobin is 46.18%, which is the highest among slow-release pesticides. The pesticide loadings of the nano-pesticides prepared at azoxystrobin concentrations of 3, 4, and 5 mg / mL are 38.54%, 36.56%, and 35.32%, respectively. The lowest pesticide loading (32.15%) is achieved when the azoxystrobin concentration is 1 mg / mL. Considering both adsorption rate and pesticide loading, 2 mg / mL is selected as the optimal concentration of azoxystrobin for preparing nano-pesticides.

[0055] Example 9

[0056] In step 3), a 2.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 2:1, and other experimental conditions were the same as in Example 2.

[0057] Example 10

[0058] In step 3), a 2.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 4:1, and other experimental conditions were the same as in Example 2.

[0059] Example 11

[0060] In step 3), a 2.0 mg / mL azoxystrobin methanol solution was mixed with 60 mg of dried nano-γ-CD-MOF at a molar ratio of 8:1, and other experimental conditions were the same as in Example 2.

[0061] By comparing the results of Examples 2 and 9-11, the effect of different molar ratios of feedstock can be examined. The adsorption rate and loading of γ-CD-MOF-loaded azoxystrobin with different molar ratios are shown below. Figure 4 As shown, with the increase of azoxystrobin dosage, the adsorption rate and drug loading of γ-CD-MOF for azoxystrobin both increased, from 83.72% and 39.41% to 84.33% and 40.94%, respectively. When the azoxystrobin:γ-CD-MOF ratio increases, the azoxystrobin dosage is negatively correlated with the adsorption rate and drug loading. Therefore, the optimal molar ratio of azoxystrobin:γ-CD-MOF is 2:1.

[0062] Figure 5 These are the XRD patterns of azoxystrobin, γ-CD-MOF, and the γ-CD-MOF / azoxystrobin prepared in Example 9 of this invention. Figure 5 It can be seen that azoxystrobin has obvious characteristic peaks at 10.8°, 13.6°, and 14.2°, while γ-CD-MOF has obvious characteristic peaks at 11.3°, 13.5°, and 18.4°, confirming that azoxystrobin has been successfully loaded into γ-CD-MOF.

[0063] Figure 6 This is a scanning electron microscope image of the γ-CD-MOF prepared in Example 9 of this invention. Figure 6 As can be seen, when the solvent ratio is 10:6, the morphology of γ-CD-MOF is cubic, with a particle size range of 1.45–2.48 μm and an average particle size of 1.93 μm. When the solvent ratio is 10:8 and 10:10, its microstructure exhibits cross-growth and irregular shape, with average particle sizes of 600 nm and 2.34 μm, respectively. Excess methanol will reduce the crystallinity of γ-CD-MOF.

[0064] The addition of methanol helps reduce the particle size, which was also confirmed by SEM analysis of γ-CD-MOFs prepared at a solvent ratio of 10:4. When the solvent ratio was 10:4, the morphology of γ-CD-MOFs was non-uniform cubic with a relatively irregular shape, and the average particle size was the largest at 2.51 μm compared to other solvent ratios.

[0065] Regarding the solubility of slow-release pesticides. For example... Figure 7 As shown, azoxystrobin has very poor solubility, with a solubility of 5.83 mg / L in water. The results indicate that the solubility of the γ-CD / azoxystrobin mixture increased slightly, while the solubility of the γ-CD-MOF / azoxystrobin nanopesticide in Example 9 increased significantly, by nearly 25 times that of azoxystrobin and 6 times that of the γ-CD / azoxystrobin mixture, respectively.

[0066] The sustained-release effect and antibacterial properties of slow-release pesticides. For example... Figure 8 As shown, the γ-CD-MOF / pyraclostrobin nanopesticide prepared in Example 9 exhibits a significant slow-release effect. The loaded pyraclostrobin shows a burst release within the first 6 hours, with a release rate of approximately 20%, and approximately 45% on the first day, with almost complete release within two weeks. On the 4th day after application, the inhibition rate of the γ-CD-MOF / pyraclostrobin nanopesticide ranged from 28.96% to 42.08%, while the inhibition rate of the 25% pyraclostrobin suspension ranged from 30.05% to 43.44%. The experimental results indicate that in the initial release phase, the overall inhibition rate of the nanopesticide against *Botrytis cinerea* is lower than that of the 25% pyraclostrobin suspension, meaning that the burst release amount of the nanopesticide is significantly lower than that of the traditional pyraclostrobin suspension. On the 6th day after application, the inhibition rate of azoxystrobin nano-controlled-release pesticide against strawberry gray mold ranged from 25.09% to 38.64%, while the inhibition rate of 25% azoxystrobin suspension against strawberry gray mold ranged from 20.15% to 33.88%. The antibacterial activity of the nano-controlled-release pesticide was initially higher than that of the traditional formulation azoxystrobin suspension. On the 10th day after application, the antibacterial activity of the azoxystrobin nano-pesticide was significantly better than that of the suspension, indicating that the prepared material has good slow-release performance. Figure 9 The images show the antibacterial effects of azoxystrobin nano-release pesticide and 25% azoxystrobin suspension on the sixth day after application. Compared to the 25% azoxystrobin suspension, the colony diameter in the culture medium containing the nano-release pesticide was generally smaller, indicating that the azoxystrobin nano-release pesticide has good sustained-release properties and exhibits good antibacterial activity six days after application.

[0067] Example 12

[0068] Strawberry preservation experiment: Prepare 0.15 mg / mL azoxystrobin suspension, γ-CD-MOF / azoxystrobin solution, and γ-CD-MOF aqueous solution. Select good strawberry fruits and divide them into groups of 9. Immerse each group in the prepared solutions for 5 minutes, with deionized water as the control group. Repeat the treatment three times. Then, remove the soaked strawberries, air-dry them, and store them at room temperature for 10 days. On days 3, 5, 7, and 10 after treatment, measure the weight and firmness of the strawberry fruits, and record the rot rate and rot index. Figure 10During strawberry storage, both the rot rate and rot index showed a continuous upward trend. From the third to the seventh day of storage, the rot rate of the blank control group increased rapidly, while the rot rate of strawberries treated with azoxystrobin suspension and γ-CD-MOF / azoxystrobin nano-controlled release pesticide increased more slowly. After the tenth day, differences were observed between the azoxystrobin suspension and the γ-CD-MOF / azoxystrobin nano-controlled release pesticide, indicating that the γ-CD-MOF / azoxystrobin nano-controlled release pesticide had better preservation performance and could effectively reduce strawberry rot after harvesting.

[0069] Advantages and positive effects of the present invention:

[0070] This invention uses biocompatible γ-cyclodextrin as an organic ligand, with K + γ-CD-MOF materials were prepared using ion centers. The synthesis process was optimized, and a universal synthesis method was established. Azoxystrobin fungicide was loaded into the γ-CD-MOF materials to prepare a slow-release pesticide. The process conditions were optimized, and at a solvent ratio of 10:6, the material exhibited a uniform cubic morphology with an average particle size of 1.93 μm. When the pesticide loading concentration was 5 mg / mL and the molar ratio of azoxystrobin to γ-CD-MOF was 2:1, it showed high encapsulation efficiency and pesticide loading.

[0071] The solubility of the γ-CD-MOF / pyraclostrobin nano-controlled-release pesticide prepared in this invention is significantly increased, showing a marked advantage over pyraclostrobin. γ-CD-MOF / pyraclostrobin exhibits a good inhibitory rate against strawberry gray mold and excellent sustained-release properties. Starting from the sixth day after application, the antibacterial activity of the nano-controlled-release pesticide is significantly stronger than that of the traditional pyraclostrobin suspension. γ-CD-MOF / pyraclostrobin also has a certain preservative effect on strawberry fruit. The prepared γ-CD-MOF / pyraclostrobin nano-controlled-release pesticide can effectively delay the decrease in fruit weight and firmness and prevent rotting to a certain extent, and can also promote the increase of soluble sugar content in strawberry fruit. This indicates that this highly efficient, safe, and multifunctional sustained-release pesticide has good application prospects in the field of green agriculture.

Claims

1. A method for preparing a cyclodextrin metal organic framework nano-slow release pesticide, characterized in that, The method comprises: 1) Preparation of γ-CD-MOF Dissolve γ-CD and KOH in deionized water, after ultrasonic treatment for 30 minutes, filter the mixed solution using an organic filter membrane; mix the obtained solution with methanol at a solvent ratio of 10:6, heat in a constant temperature water bath at 60°C for 1 hour; add 8 mg / mL of PEG-20000 to the obtained clear solution; wash the precipitate with methanol and ethanol three times respectively, soak in dichloromethane for 3 days, and dry in vacuum after centrifugation; neutralize the γ-CD-MOF with ethanol and acetic acid, and dry in vacuum, ready for use; 2) Preparation of γ-CD and azoxystrobin mixture According to the molar ratio of 1:1, first dissolve a certain amount of γ-cyclodextrin in a beaker with deionized water, and then use a magnetic stirrer to stir at 750 rpm to fully dissolve it; at the same time, dissolve a certain amount of azoxystrobin in ethanol, then add the azoxystrobin solution to the γ-CD aqueous solution, and continuously stir and mix; stir the above mixture at 60°C in the dark for 2 hours to evaporate ethanol; then, centrifuge the solution at 10,000 rpm for 10 minutes and recover the supernatant, freeze the precipitate at -20°C for 24 hours, and then dry it in a freeze dryer at -50°C for 24 hours; collect the γ-CD and azoxystrobin inclusion complex, dry and store, ready for use; 3) Preparation of γ-CD-MOF / azoxystrobin nano slow-release pesticide First, mix the methanol solution of γ-CD and azoxystrobin inclusion complex with a concentration of 2.0 mg / mL with 60 mg of dried nano γ-CD-MOF according to a molar ratio of 2:1, then stir in the dark at 750 rpm for 3 hours; then, centrifuge the mixture at 10,000 rpm for 1 hour, and wash the obtained precipitate with methanol and ethanol twice respectively to remove the unencapsulated part of azoxystrobin; finally, all samples are dried in vacuum overnight in the dark; recover the supernatant, and the cyclodextrin metal organic framework nano slow-release pesticide is obtained.

2. The use of the cyclodextrin metal-organic framework nano-slow release pesticide prepared by the method of claim 1, characterized in that, The cyclodextrin metal organic framework nano slow-release pesticide has a uniform cubic shape, with an average particle size of 1.93 μm. The cyclodextrin metal organic framework nano slow-release pesticide is used for fruit preservation, including: configuring a 0.15 mg / mL γ-CD-MOF / azoxystrobin solution, immersing the fruit in the above configured solution for 5 minutes, and then taking out the fruit for proper storage.

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