CN106614552B - A kind of silkworm excrement porous carbon MOFs composite material and its preparation method and application - Google Patents

Abstract

The invention discloses a kind of silkworm excrement porous charcoal MOFs composite material and preparation methods and application.First by silkworm excrement and ZnCl₂It is freeze-dried after solution mixing swelling, silkworm excrement after freeze-drying is carried out to activation reaming reaction in protective gas again, then it cleans again, silkworm excrement base multi-stage porous Carbon Materials are obtained after centrifugation and drying, it is centrifuged after metal salt solution is stirred with the material again, drying, it is passed through oxygen under the conditions of plasma modification and forms high dispersion metal oxide in silkworm excrement base multi-stage porous charcoal material surface, again by hydrothermal synthesis method using high dispersion metal oxide as precursor, MOFs is grown on silkworm excrement base charcoal material surface, it finally filters and dries to obtain silkworm excrement porous charcoal MOFs composite material.The obtained carbon composite of present invention specific surface area with higher and carboxylic group, can there is higher adsorption capacity and preferable slow-releasing and controlled-releasing action to pesticide.

Description

A kind of silkworm excrement porous carbon MOFs composite material and its preparation method and application

technical field

The invention belongs to the technical field of carbon materials, and in particular relates to a silkworm excrement porous carbon MOFs composite material and a preparation method and application thereof.

Background technique

Pesticides can effectively control the harm of diseases, insects, weeds and other harmful organisms to crops. As an important means of chemical control, pesticides play an irreplaceable role in agricultural production. However, only a small amount of pesticides can reach the crop target site in a specific time, and most of the pesticides are directly released into the natural environment, resulting in low pesticide utilization efficiency. These ineffective pesticides will cause many negative problems such as excessive pesticide residues in agricultural products, damage to non-target organisms, and environmental pollution. How to effectively improve the utilization efficiency and targeted release function of pesticides is one of the main problems to be solved in the field of pesticides.

Sustained and controlled release technology is a new type of drug delivery technology that can slowly release the active ingredients of pesticides to the target site within a given period of time by physical or chemical means, and maintain the drug concentration above the effective concentration for a long period of time. Bioporous carbon is one of the materials with better adsorption. Silkworm excrement-based biochar is derived from silkworm excrement, which is the main waste in the silkworm industry. It is often discarded randomly in rural areas and causes environmental pollution. From the observation of the electron microscope structure, it can be seen that silkworm excrement has natural It has a three-dimensional wrinkled structure and high carbon content. After high-temperature carbonization and activation, porous biochar with high specific surface area can be obtained, and its surface is also rich in N(O) groups. Its slow and controlled release ability can be improved by modifying it. .

Contents of the invention

The object of the present invention is to provide a kind of silkworm excrement porous carbon MOFs composite material and its preparation method and application. In the present invention, silkworm excrement is subjected to swelling and pore expansion treatment firstly, and then through activation treatment, immersion in metal salt solution, drying and plasma surface modification, the obtained carbon material has relatively high specific surface area and alkaline adsorption site, and can It has high adsorption capacity and good slow and controlled release effect on pesticides.

The purpose of the present invention is achieved through the following technical solutions:

The preparation method of silkworm excrement porous carbon MOFs composite material of the present invention comprises the following steps:

(1) Mix and swell the original silkworm excrement with ZnCl ₂ solution and then freeze-dry; activate the pore expansion reaction in N ₂ , Ar gas and other protective gases after freeze-drying silkworm excrement, and then rinse with dilute hydrochloric acid and deionized water , and dried to obtain the silkworm excrement-based hierarchical porous carbon material.

(2) The silkworm excrement-based hierarchical porous carbon material and the metal salt solution (the cation is Cr ³⁺ , Fe ²⁺ or Cu ²⁺ ) were oscillated and mixed, then centrifugally dried, then put into the plasma reactor, and the input voltage was controlled to 20 ~50V, pass _O2 to carry out surface modification, after modification, wash and dry to obtain highly dispersed metal oxide porous carbon MOFs composite material;

(3) Mix highly dispersed metal oxide porous carbon MOFs composite materials and polycarboxylic acid ligands according to the mass volume ratio of 1:50-100, put them into a high-pressure reactor for reaction, and then wash, centrifuge and dry to obtain Silkworm excrement porous carbon MOFs composites.

As a further preference of the scheme, in step (1), the mass-to-mass ratio of the original silkworm excrement and the ZnCl solution with a mass concentration of 0.25 to 0.30 g/mL is ₁ :100 to 200, the mixing temperature is 30 to 50°C, and the mixing time is 0.5 to 50°C. 3h. The freeze-drying process is to pre-freeze at -25°C to -20°C for 2 to 4 hours, and then cool down to -60°C to -40°C for 24 to 72 hours.

As a further preference of the technical solution, in the step (1), the temperature for the reaction between ZnCl ₂ and freeze-dried silkworm excrement to activate the pore expansion is 300-700° C., and the reaction time is 0.5-5 hours.

As a further preference of the technical solution, in the step (2), the material-to-liquid ratio of the silkworm excrement-based hierarchical porous carbon material to the metal salt is 1:50-100, and the modification time is 1-30 minutes.

As a further preferred technical solution, the cation of the metal salt solution is Cr ³⁺ , Fe ²⁺ or Cu ²⁺ , the concentration of the metal salt solution is 0.1-3.0 mol/L, the shaking mixing temperature is 30-60°C, and the mixing time is 6-24 hours ; The drying temperature after mixing with the metal salt solution is 100-200°C, and the drying time is 2-12 hours.

As a further preferred technical solution, the drying temperature after mixing with the metal salt solution in the step (2) is 100-200° C., and the drying time is 2-12 hours.

As a further preferred technical solution, the reaction temperature in the step (3) is 160-220° C., and the reaction time is 12-22 hours; the polycarboxylic acid ligand is terephthalic acid or trimellitic acid.

The silkworm excrement porous carbon MOFs composite material of the present invention has a three-dimensional pore structure, its Langmuir specific surface area is 2500-3000m ² /g, and the total pore volume is about 1.50-2.50cm ³ /g.

The silkworm excrement porous carbon MOFs composite material of the present invention can be applied in the slow and controlled release of medicines, especially in the slow and controlled release of pesticides.

The product of the present invention is applied in the field of slow and controlled release of pesticides. The material can be used to adsorb the neonicotinoid pesticide thiamethoxam, and the adsorption load can reach more than 500 mg/g, and the slow and controlled release within the effective time of 15 to 60 days can be prepared. Pesticide carrier (calculated by releasing 90% of the total amount of thiamethoxam as the end point).

The principle of the invention: due to the limited swelling effect of the special polymer structure of silkworm excrement in aqueous solution, the volume after swelling will increase by 1 to 20 times, and the swollen silkworm excrement will be freeze-dried step by step. Silkworm excrement maintains a fluffy polymer structure during swelling, and then freeze-drying ensures sufficient drying of silkworm excrement, and further consolidates its structure, which can extend the carbon skeleton of silkworm excrement and improve the specific surface area and porosity of silkworm excrement-based carbon materials after carbonization and activation. At the same time, adding ZnCl ₂ solution in the swelling process can fully mix the activator ZnCl ₂ with silkworm excrement, which is more conducive to obtaining better activating materials in the next step.

This patent uses the impregnation method to form highly dispersed metal salt adsorption on the surface of silkworm excrement-based hierarchical porous carbon material, and then forms highly dispersed metal oxide modification on the surface of the material under the condition of oxygen-enriched atmosphere by means of plasma modification. Then the metal oxide MOFs material was used to grow the precursor, and the silkworm excrement porous carbon MOFs composite material was prepared. Since the polycarboxylic acid in the raw material contains a large number of carboxylic acid groups, carboxylic acid groups can be formed on the surface of the composite material. Most of the conventional pesticide molecules contain polar groups (carboxyl, carbonyl, sulfur-containing and chlorine-containing groups, etc.), and this part of the polar group is also the main active part of the pesticide. These polar groups can interact with silkworm excrement Carboxylic acid group binding. By controlling the impregnation of silkworm excrement metal salt solution and the growth conditions of MOFs hydration reaction, the dispersion of MOFs materials and the amount of carboxylic acid in MOFs materials can be adjusted, and then the adsorption force of pesticides and carbon materials can be adjusted to achieve slow and controlled release of pesticides. .

Plasma refers to ionized gas, which is a collection of particles such as electrons, ions, atoms, molecules or free radicals, which are extremely active reactive species. The particles in the plasma can destroy the bond energy between the molecules of the original material, and make the molecules in the material combine with the ions in the plasma to form new chemical bonds. Since its energy is much lower than that of high-energy radioactive rays, the plasma only involves the bonding of materials. The surface does not affect the bulk properties of the material, and the plasma modification has the advantages of high efficiency, environmental protection, easy control, and convenient operation.

Compared with the prior art, the advantages of the present invention are:

1. The raw material silkworm excrement used in the present invention has a natural three-dimensional wrinkled structure and contains a large amount of carboxyl, hydroxyl and amino groups and cellulose components. _The activation mechanism of ZnCl is to dissolve cellulose to remove water molecules, and use ZnCl to activate and enlarge _pores to treat silkworms. Sand can form a high specific surface microporous structure on the surface of activated silkworm excrement, and obtain a higher adsorption capacity for pesticides through the microporous structure.

2. Through the swelling effect of silkworm excrement, the volume of silkworm excrement can be increased by 1 to 20 times without changing the polymer configuration of silkworm excrement. After swelling, the internal structure of silkworm excrement can be fixed by freeze-drying, which can improve carbonization. Porosity and specific surface area of silkworm excrement-based carbon materials after activation.

_3. Adsorb ZnCl2 solution into silkworm excrement during the swelling process, and fix ZnCl2 inside and _on the surface of silkworm excrement by freeze _- drying. This method improves the dispersion of activator ZnCl2 and silkworm excrement, which is more conducive to the next activation .

4. The present invention prepares highly dispersed silkworm excrement MOFs composite material by impregnation method on the surface of silkworm excrement-based hierarchical porous carbon material to form highly dispersed metal salt adsorption. Compared with conventional MOFs preparation materials, the growth of MOFs materials can be enhanced. Higher dispersion is beneficial to increase the specific surface area and the number of carboxyl groups of the composite material.

5. The present invention modifies the silkworm excrement-based hierarchical porous carbon material impregnated with metal salts by means of plasma, and oxygen molecules are ionized into ionic oxygen atoms in an oxygen atmosphere, and react with metal salts to form metal oxides. Compared with the traditional hydration method, the MOFs prepared by the impregnation-plasma-hydration method grow more uniformly and more on the silkworm excrement-based carbon materials, and the specific surface area is higher.

6. The present invention controls the number of carboxyl carboxylic acid groups on the surface of silkworm excrement through factors such as silkworm excrement metal salt solution immersion and MOFs hydration reaction growth conditions, because carboxylic acid groups will have an important impact on the adsorption force between pesticides and materials, Therefore, the adsorption force between silkworm excrement-based hierarchical porous carbon materials and pesticide molecules can be regulated by the impregnation of silkworm excrement metal salt solution and the growth conditions of MOFs hydration reaction, so as to achieve the purpose of slow and controlled release of pesticides.

7. The material prepared by the present invention is used to adsorb the neonicotinoid pesticide thiamethoxam, and its adsorption capacity can reach more than 500 mg/g, and the slow-release time within the range of 15 to 60 days can be prepared by adjusting the carbonization temperature. Pesticide carrier (calculated by releasing 90% of the total amount of thiamethoxam as the end point).

Description of drawings

Figure 1 is an electron microscope scanning image of the original silkworm excrement section.

Fig. 2 is an electron microscope scanning image of silkworm excrement slices after swelling and freeze-drying.

Fig. 3 is an electron microscope scanning picture of the inner surface of silkworm excrement after swelling and freeze-drying.

Fig. 4 is an electron microscope scanning image of the silkworm excrement porous carbon MOFs composite material in Example 1.

Figure 5 is the XRD pattern of silkworm excrement-based carbon material

Fig. 6 is the XED figure of embodiment 5 silkworm excrement porous carbon MOFs composite material and hydration method

Fig. 7 Loading curves of different sustained-release materials.

Fig. 8 The sustained-release release curves of different sustained-release materials.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples, but the protection scope of the present invention is not limited to the range expressed in the examples.

Example 1

A preparation method of silkworm excrement porous carbon MOFs composite material, comprising the following steps,

(1) Mix and swell the original silkworm excrement and ZnCl ₂ solution with a mass concentration of 0.25 g/mL at 30°C for 3.0 h at a mass-to-mass ratio of 1:100, then remove the silkworm excrement, and freeze-dry the silkworm excrement. Freeze and pretreat at -20°C for 4 hours, then cool down to -60°C and freeze-dry for 24 hours to obtain freeze-dried silkworm excrement.

(2) Raise the freeze-dried silkworm excrement to 300°C at a heating rate of 5°C/min in _N2 atmosphere, and keep it at 300°C for 5.0h for pore expansion reaction. Wash and dissolve ZnCl ₂ in 1mol/L HCl, then wash with deionized water to pH ≈ 7, centrifuge, dry in an oven overnight, and obtain silkworm excrement-based hierarchical porous carbon material after drying.

(3) Mix silkworm excrement-based hierarchical porous carbon material with 0.1mol/L Fe ₂ (NO ₃ ) ₃ solution according to mass-to-mass ratio 1:50, rotate at 100r/min, temperature 30°C, and mix for 6 hours, then centrifuge and dry Drying, drying temperature 100 ℃, drying time 2h.

(4) Put 1.0 g of the dried and impregnated material into the plasma reactor, feed _O2 as the modified gas, the input voltage of the plasma reactor is 20V, the modification time is 30min, and after the modification, clean it with deionized water for 3 After drying at low temperature for a second time, highly dispersed metal oxide porous carbon MOFs composites were obtained.

(5) Mix highly dispersed metal oxide porous carbon MOFs composite material and terephthalic acid according to mass-to-mass ratio of 1:50, and react in a high-pressure reactor at a reaction temperature of 160°C for a reaction time of 12 hours, and then deionized water After cleaning three times, the porous carbon MOFs composite material was obtained by drying at low temperature.

Example 2

(1) Mix and swell the original silkworm excrement and ZnCl ₂ solution with a mass concentration of 0.25 g/mL at 35°C for 2.5 hours at a mass-to-mass ratio of 1:120, then remove the silkworm excrement, and freeze-dry the silkworm excrement. Freeze and pretreat at -20°C for 3 hours, then cool down to -55°C and freeze-dry for 36 hours to obtain freeze-dried silkworm excrement.

(2) Raise the freeze-dried silkworm excrement to 350°C at a heating rate of 5°C/min in an Ar atmosphere, and keep it at 350°C for 4.0h to carry out the pore expansion reaction. After naturally cooling down to room temperature, dissolve the obtained solid Wash and dissolve ZnCl ₂ in 1 mol/L HCl, then use deionized water to wash to pH ≈ 7, then centrifuge, place in an oven to dry overnight, and obtain silkworm excrement-based hierarchical porous carbon material after drying.

(3) Mix silkworm excrement-based hierarchical porous carbon material with 1.0mol/L Fe ₂ (NO ₃ ) ₃ solution according to mass-to-mass ratio 1:80, rotate at 120r/min, temperature 40°C, and dry for 8 hours, then centrifuge and dry , drying temperature 120 ℃, drying time 4h.

(4) Put 1.0 g of the material after drying and impregnating into the plasma reactor, feed _O2 as the modified gas, the input voltage of the plasma reactor is 30V, the modification time is 5min, and after the modification, clean it with deionized water for 3 After drying at low temperature for a second time, highly dispersed metal oxide porous carbon MOFs composites were obtained.

(5) Mix the highly dispersed metal oxide porous carbon MOFs composite material and terephthalic acid according to the mass-to-mass ratio of 1:60, and react in a high-pressure reactor with a reaction temperature of 170°C and a reaction time of 14 hours, and then deionized water After cleaning three times, the porous carbon MOFs composite material was obtained by drying at low temperature.

Example 3

(1) Mix and swell the original silkworm excrement and ZnCl ₂ solution with a mass concentration of 0.30 g/mL at 40°C for 2.0 h at a mass-to-mass ratio of 1:140, then remove the silkworm excrement, and freeze-dry the silkworm excrement. Freeze and pretreat at -25°C for 2 hours, then cool down to -50°C and freeze-dry for 48 hours to obtain freeze-dried silkworm excrement.

(2) Raise the freeze-dried silkworm excrement to 400°C at a heating rate of 5°C/min in _N2 atmosphere, and keep it at 400°C for 3.0h to carry out the pore expansion reaction. Wash and dissolve ZnCl ₂ in 1mol/L HCl, then wash with deionized water to pH ≈ 7, centrifuge, dry in an oven overnight, and obtain silkworm excrement-based hierarchical porous carbon material after drying.

(3) The silkworm excrement-based hierarchical porous carbon material and 1.5mol/L Cu(NO ₃ ) ₂ solution were oscillated and mixed according to the mass-to-mass ratio of 1:100, the rotation speed was 140r/min, the temperature was 40°C, and the time was 12h, and then centrifugally dried. The drying temperature is 150°C, and the drying time is 6 hours.

(4) Put 1.0 g of the dried and impregnated material into the plasma reactor, feed _O2 as the modified gas, the input voltage of the plasma reactor is 35V, and the modification time is 20min. After the modification, clean it with deionized water for 3 After drying at low temperature for a second time, highly dispersed metal oxide porous carbon MOFs composites were obtained.

(5) Mix the highly dispersed metal oxide porous carbon MOFs composite material and terephthalic acid according to the mass-to-mass ratio of 1:70, and react in a high-pressure reactor at a reaction temperature of 185°C for a reaction time of 16 hours, and then deionized water After cleaning three times, the porous carbon MOFs composite material was obtained by drying at low temperature.

Example 4

( ₁ ) Mix and swell the original silkworm excrement and the ZnCl solution with a mass concentration of 0.25g/mL at 40°C for 1.5h at a mass-to-mass ratio of 1:160, then remove the silkworm excrement, and freeze-dry the silkworm excrement. Freeze and pretreat at -25°C for 2.5 hours, then cool down to -40°C and freeze-dry for 72 hours to obtain freeze-dried silkworm excrement.

(2) Raise the freeze-dried silkworm excrement to 450°C at a heating rate of 5°C/min in _N2 atmosphere, and keep it at 450°C for 2.0h to carry out the pore expansion reaction. Wash and dissolve ZnCl ₂ in 1mol/L HCl, then wash with deionized water to pH ≈ 7, centrifuge, dry in an oven overnight, and obtain silkworm excrement-based hierarchical porous carbon material after drying.

(3) The silkworm excrement-based hierarchical porous carbon material and 2.0mol/L Cu(NO ₃ ) ₂ solution were oscillated and mixed according to the mass-to-mass ratio of 1:100, the speed was 160r/min, the temperature was 50°C, and the time was 16h, and then centrifugally dried. The drying temperature is 200°C, and the drying time is 8 hours.

(4) Put 1.0 g of the dried and impregnated material into the plasma reactor, feed _O2 as the modified gas, the input voltage of the plasma reactor is 40V, and the modification time is 15min. After the modification, clean it with deionized water for 3 After drying at low temperature for a second time, highly dispersed metal oxide porous carbon MOFs composites were obtained.

(5) Mix the highly dispersed metal oxide porous carbon MOFs composite material and trimesic acid according to the mass-to-mass ratio of 1:80, and react in a high-pressure reactor at a reaction temperature of 200°C for a reaction time of 18 hours, and then deionized water After cleaning three times, the porous carbon MOFs composite material was obtained by drying at low temperature.

Example 5

(1) Mix and swell the original silkworm excrement and ZnCl ₂ solution with a mass concentration of 0.30 g/mL at 45°C according to the plastid-to-body ratio of 1:180 for 1.0 h, then remove the silkworm excrement, and freeze-dry the silkworm excrement. Freeze and pretreat at -20°C for 4 hours, then cool down to -45°C and freeze-dry for 60 hours to obtain freeze-dried silkworm excrement.

(2) Raise the freeze-dried silkworm excrement to 550°C at a heating rate of 5°C/min in _N2 atmosphere, and keep it at 550°C for 1.0h to carry out the pore expansion reaction. Wash and dissolve ZnCl ₂ in 1mol/L HCl, then wash with deionized water to pH ≈ 7, centrifuge, dry in an oven overnight, and obtain silkworm excrement-based hierarchical porous carbon material after drying.

(3) The silkworm excrement-based hierarchical porous carbon material and 2.5mol/L Cr(NO ₃ ) ₃ solution were oscillated and mixed according to the mass-to-mass ratio of 1:100, the speed was 180r/min, the temperature was 60°C, and the time was 20h, and then centrifugally dried. The drying temperature is 120°C, and the drying time is 8 hours.

(4) Put 1.0g of the dried and impregnated material into the plasma reactor, feed _O2 as the modified gas, the input voltage of the plasma reactor is 50V, and the modification time is 1-2min. After cleaning three times and drying at low temperature, highly dispersed metal oxide porous carbon MOFs composites were obtained.

(5) Mix the highly dispersed metal oxide porous carbon MOFs composite material and trimesic acid according to the mass-to-mass ratio of 1:90, react in a high-pressure reactor, the reaction temperature is 210 ° C, the reaction time is 20h, and then deionized water After cleaning three times, the porous carbon MOFs composite material was obtained by drying at low temperature.

Example 6

( ₁ ) Mix and swell the original silkworm excrement with a ZnCl solution with a mass concentration of 0.25g/mL at 50°C at a plastid-to-body ratio of 1:200 for 0.5h, then remove the silkworm excrement, and freeze-dry the silkworm excrement. Freeze and pretreat at -20°C for 4 hours, then cool down to -40°C and freeze-dry for 72 hours to obtain freeze-dried silkworm excrement.

(2) Raise the freeze-dried silkworm excrement to 700°C at a heating rate of 5°C/min in _N2 atmosphere, and keep it at 700°C for 0.5h to carry out the pore expansion reaction. Wash and dissolve ZnCl ₂ in 1mol/L HCl, then wash with deionized water to pH ≈ 7, centrifuge, dry in an oven overnight, and obtain silkworm excrement-based hierarchical porous carbon material after drying.

(3) The silkworm excrement-based hierarchical porous carbon material and 3.0mol/L Cr(NO ₃ ) ₃ solution were shaken and mixed according to the mass-to-mass ratio of 1:100, the speed was 200r/min, the temperature was 60°C, and the time was 24h, and then centrifugally dried. The drying temperature is 180°C, and the drying time is 12 hours.

(4) Put 1.0 g of the dried and impregnated material into the plasma reactor, feed _O2 as the modified gas, the input voltage of the plasma reactor is 35V, and the modification time is 15 minutes. After the modification, clean it with deionized water for 3 After drying at low temperature for a second time, highly dispersed metal oxide porous carbon MOFs composites were obtained.

(5) Mix the highly dispersed metal oxide porous carbon MOFs composite material and trimesic acid according to the mass-to-mass ratio of 1:100, and react in a high-pressure reactor at a reaction temperature of 220°C for a reaction time of 22 hours, and then deionized water After cleaning three times, the porous carbon MOFs composite material was obtained by drying at low temperature.

Material performance testing:

(1) SEM image of the material

Using a Japanese Hitachi S-3400N low-magnification scanning electron microscope, the original silkworm excrement slices, the silkworm excrement slices after swelling and freeze-drying, the inner surface of the silkworm excrement after swelling and freeze-drying, and the silkworm excrement porous carbon MOFs prepared in Example 1 of the present invention were composited. The material is characterized by the surface morphology of the material, as shown in Figure 1, Figure 2, Figure 3, and Figure 4.

Comparing Figure 1 and Figure 2, it can be seen that the volume of silkworm excrement becomes larger after swelling and a large number of pore structures are produced in the inner layer. Fig. 3 is an electron microscope scanning image of the inner surface of silkworm excrement after swelling, reflecting the three-dimensional network structure of silkworm excrement. Figure 4 is a scanning electron microscope image of the silkworm excrement porous carbon MOFs composite material. It can be seen that the composite material can form a porous structure.

(2) Specific surface area analysis

The 3-Flex specific surface pore size distribution instrument produced by U.S. Micro Company is used to prepare silkworm excrement porous carbon material (according to embodiment 1 activation conditions) with unswelled silkworm excrement and swelling treated silkworm excrement as raw material (activation conditions according to embodiment 1), embodiment 1 of the present invention, 3, 5 and the specific surface area values of silkworm excrement porous carbon MOFs composites by direct hydration under the same conditions were compared, and the results are shown in Table 1.

Table 1 Analysis of specific surface area of different materials

According to the data listed in Table 1, the Langmuir specific surface area of silkworm excrement porous carbon MOFs composite material prepared in the example is 2500-3000m ² /g, the porosity is 0.75-0.85cm ³ /g, and the direct swelling of silkworm without MOFs composite The specific surface area and porosity of sand-based porous carbon materials are only about 50% of those after compounding, and the specific surface area and porosity of silkworm sand-based porous carbon materials without swelling and without MOFs are only about 30% after compounding. The compounding of MOFS materials can greatly increase the specific surface area and porosity of the material. At the same time, compared with the unswelled material, the specific surface area and porosity of the unswollen silkworm sand-based carbon material are only 60% of the swollen silkworm sand-based carbon material. This shows that the silkworm excrement after swelling can increase the specific surface area and porosity of the silkworm excrement-based porous carbon material. At the same time, the composite material prepared by the embodiment is compared with the composite material prepared by the hydration method, and it is found that the specific surface area of the hydration method material is about 80% of the material of the embodiment example under the same conditions, indicating that the dipping-plasma-hydration method can improve silkworm Yield of MOFs on sand-based hierarchical porous carbon materials.

(3) XRD analysis of different silkworm sand-based carbon materials

Adopt the X-ray diffractometer of Japan Rigaku D/MAX to carry out XRD test to the silkworm excrement base porous carbon material prepared by the present invention, the composite material prepared in Example 5 and the hydrated material in Example 5, the test conditions are: Cu Kα target, The scanning speed is 0.2°/min, 30kV, and the test results are shown in Figures 5 and 6. From the comparison of Figure 5 and Figure 6, it can be seen that the composite silkworm sand porous carbon MOFs material has a typical MOFs crystal structure diagram, and the peak of the composite material prepared in Example 5 in Figure 6 is wider and more dispersed than that of the hydrated material in Example 5 , showing that the composite material prepared in Example 5 has a lower crystallinity, and at the same time, it can be seen from Table 1 that the composite material prepared in Example 5 has a better specific surface area than the hydrated material in Example 5, thereby illustrating that the composite material prepared in Example 5 has a better specific surface area than the hydrated material prepared in Example 5. The Example 5 hydrated material has better crystal dispersion.

(4) Material slow release performance analysis

The adsorption loading capacity and sustained release curve of the pesticide thiamethoxam were analyzed for the silkworm excrement porous carbon MOFs composite materials prepared in Cases 1, 3, and 5. The adsorption condition of the carbon material was that 25 mg of the slow-release material was put into 50 mL of 0.8 g/L thiamethoxam. Oscillating adsorption in the pyrethrin solution, water bath temperature 30°C, oscillation speed 200 rpm; the slow-release condition of the carbon material is to put 25mg of the slow-release material into 120mL deionized water after adsorption, change the water 100mL every day, water bath temperature 30°C, shake The rotational speed is 200 rpm, and the experimental results are shown in Figure 7 and Figure 8 respectively. It can be seen from Figure 7 that the loading capacity of the three sustained-release materials reached 500-560 mg/g after 48 hours of adsorption of thiamethoxam, and there was no significant difference among the three materials, indicating that these materials have Different slow-release effects can maintain similar adsorption effects at the same time. As can be seen from Figure 8, the release process was completed in about 15 days, 30 days and 60 days (calculated with the release of 90% of the total amount of thiamethoxam as the end point), which can meet the requirements of pesticide slow release in different periods.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those skilled in the art, on the basis of the above description, other changes or changes in different forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (8)

1. a preparation method of silkworm excrement porous carbon MOFs composite material, is characterized in that: comprise the steps, (1) Mix and swell the original silkworm excrement and ZnCl2 solution, then freeze _- dry, then activate the pore expansion reaction in the protective gas after freeze-drying silkworm excrement, then wash, centrifuge and dry to obtain the silkworm excrement-based porous carbon material; The freeze-drying process in the step (1) is to pre-freeze at -25 ºC ~ -20 ºC for 2 ~ 4 hours, and then cool down to -60 ºC ~ -40 ºC for 24 ~ 72 hours; (2) The silkworm excrement-based porous carbon material was oscillated and mixed with the metal salt solution, then centrifuged and dried, and then put into the plasma reactor, the input voltage was controlled at 20-50 V, and _O2 was introduced for surface modification, and the modification time was 1 ~30 min, wash after modification, and dry to obtain highly dispersed metal oxide silkworm excrement porous carbon MOFs composite material; (3) Mix the highly dispersed metal oxide silkworm excrement porous carbon MOFs composite material and the polycarboxylic acid ligand according to the mass volume ratio of 1: 50~100, put them into a high-pressure reactor for reaction, and then wash, centrifuge and dry Finally, silkworm excrement porous carbon MOFs composite material was obtained. 2. the preparation method of silkworm excrement porous carbon MOFs composite material according to claim 1, is characterized in that: in described step (1), the ZnCl of mass concentration 0.25 ~ 0.30 _g /mL solution mass-to-mass ratio The ratio is 1:100~200, the mixing temperature is 30~50 ºC, and the mixing time is 0.5~3 h. 3. the preparation method of silkworm excrement porous carbon MOFs composite material according to claim 1, is characterized in that: in described step (2), silkworm excrement base hierarchical porous carbon material and metal salt material-liquid ratio are 1: 50～ 100; the cation of the metal salt solution is Cr ³⁺ , Fe ²⁺ or Cu ²⁺ ; the concentration of the metal salt solution is 0.1~3.0 mol/L, the shaking mixing temperature is 30~60 ºC, and the mixing time is 6~24 h; After the solution is mixed, the drying temperature is 100-200 ºC, and the drying time is 2-12 h. 4. The preparation method of silkworm excrement porous carbon MOFs composite material according to claim 1, characterized in that: in the step (3), the reaction temperature is 160-220 ºC, and the reaction time is 12-22 h. 5. The preparation method of silkworm excrement porous carbon MOFs composite material according to claim 1, characterized in that: the polycarboxylic acid ligand is terephthalic acid or trimellitic acid. 6. the preparation method of silkworm excrement porous carbon MOFs composite material according to claim 1 is characterized in that: in described step (1), silkworm excrement activation pore expansion reaction temperature is 300～700 ºC after freeze-drying, and the reaction time is 0.5~5 hours. 7. The material obtained by the preparation method of silkworm excrement porous carbon MOFs composite material as described in any one of claims 1 to 6, characterized in that: the material is a three-dimensional pore structure, and its Langmuir specific surface area is 2500 to 3000 m ² /g . 8. The application of silkworm excrement porous carbon MOFs composite material as claimed in claim 7, characterized in that it is used in slow and controlled release of pesticides.