A nano-herbicide based on β-ketoenamine covalent organic framework materials, its preparation method and application

Abstract

The present invention provides a nano-herbicide based on β-ketoenamine covalent organic framework materials, its preparation method and application, belonging to the technical field of pesticide formulations. The nano-herbicide provided by the present invention comprises β-ketoenamine covalent organic framework materials and dicamba loaded on the surface and internal pores of the β-ketoenamine covalent organic framework materials. By utilizing the hydrogen bond action of the carboxyl group of dicamba, a series of β-ketoenamine covalent organic framework materials with large surface areas and abundant β-ketoamine groups are introduced, and the nano-herbicide is constructed by the hydrogen bond action between the ketone carbonyl or enol of the β-ketoenamine covalent organic framework materials and the carboxyl hydrogen of dicamba. The nano-herbicide of the present invention has a high dicamba loading amount. Compared with commercially available dicamba, the evaporation rate of dicamba is significantly reduced, thereby reducing the leaching potential. At the same time, it can maintain a weed control effect similar to that of the commercially available dicamba commercial formulation and improve the safety to non-target organisms.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide formulations, and particularly relates to a nano-herbicide based on β-ketoenamine covalent organic framework materials, a preparation method thereof, and an application thereof. Background Art

[0002] Applying pesticides is one of the most effective ways to control pests and weeds. Herbicides are an important class of chemical pesticides for controlling unwanted plants. Among them, the original drug of dicamba (3,6-dichloro-2-methoxybenzoic acid, Dicamba) is a widely used herbicide due to its selective herbicidal performance and low price.

[0003] However, dicamba has high leaching and volatility, which leads to its easy migration in the environment (soil, water, and air). Specifically, the vapor pressure of dicamba at 25 °C is 4.5×10 -3 Pa, and it has moderate volatility after application. However, due to dicamba spray drift and off-target, even at low doses, it will damage soybeans, tomatoes, or other plants that are intolerant to dicamba. In addition, due to the good water solubility of dicamba, the problem of soil leaching is still very serious. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a nano-herbicide based on β-ketoenamine covalent organic framework materials, a preparation method thereof, and an application thereof. The nano-herbicide provided by the present invention can significantly reduce the adverse effects of dicamba on the environment while maintaining good weed control efficiency.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a nano-herbicide based on β-ketoenamine covalent organic framework materials, comprising β-ketoenamine covalent organic framework materials and dicamba loaded on the surface and internal pores of the β-ketoenamine covalent organic framework materials;

[0007] The β-ketoenamine covalent organic framework materials include one or more of TpPa-COF, TpBD-COF, and TpBDMe-COF.

[0008] Preferably, the loading amount of dicamba in the nano-herbicide based on β-ketoenamine covalent organic framework materials is 10.1-28.5%.

[0009] Preferably, the pore size of the β-ketoenamine covalent organic framework materials is 2.17-3.0 nm, and the specific surface area is 1261-1767 m 2 / g.

[0010] Preferably, the particle size of the nano-herbicide based on the β-ketoenamine covalent organic framework material is 350-500 nm.

[0011] The present invention provides a preparation method of the above-mentioned nano-herbicide based on the β-ketoenamine covalent organic framework material, comprising the following steps:

[0012] Disperse the β-ketoenamine covalent organic framework material in an aqueous dicamba solution, stir and centrifuge, wash and dry the obtained solid to obtain the nano-herbicide based on the β-ketoenamine covalent organic framework material.

[0013] Preferably, the concentration of the aqueous dicamba solution is 6 mg / mL; the centrifugation rate is 10000-12000 rpm, and the time is 9-12 min.

[0014] Preferably, the preparation method of the β-ketoenamine covalent organic framework material comprises the following steps:

[0015] Mix 1,3,5-triformylphloroglucinol, an aniline ligand, pyridine and an organic solvent, and carry out a solvothermal reaction to obtain the β-ketoenamine covalent organic framework material;

[0016] The aniline ligand is p-phenylenediamine, benzidine or 4,4'-diamino-3,3'-dimethylbiphenyl.

[0017] Preferably, the molar ratio of 1,3,5-triformylphloroglucinol to the aniline ligand is 1:1.5;

[0018] The temperature of the solvothermal reaction is 115-125 °C, and the time is 70-80 h.

[0019] The present invention provides the application of the above-mentioned nano-herbicide based on the β-ketoenamine covalent organic framework material in weeding of gramineous plants.

[0020] Preferably, the application amount of the nano-herbicide based on the β-ketoenamine covalent organic framework material is 28-50 g / mu.

[0021] The present invention provides a nano-herbicide based on β-ketoenamine covalent organic framework materials (denoted as Dicamba@COF), which comprises β-ketoenamine covalent organic framework materials and dicamba loaded on the surfaces and internal pores of the β-ketoenamine covalent organic framework materials; the β-ketoenamine covalent organic framework materials include one or more of TpPa-COF, TpBD-COF and TpBDMe-COF. By utilizing the hydrogen bond interaction of the carboxyl group of dicamba, a series of β-ketoenamine covalent organic framework materials with large surface areas and abundant β-ketoamine groups are introduced, and a nano-herbicide is constructed by means of the hydrogen bond interaction between the keto carbonyl or enol of the β-ketoenamine covalent organic framework materials and the carboxyl hydrogen of dicamba. The nano-herbicide dicamba based on β-ketoenamine covalent organic framework materials provided by the present invention has a high dicamba loading amount. Compared with commercially available dicamba, the volatilization rate of dicamba is significantly reduced, thereby reducing the leaching potential. At the same time, it can maintain a weed control effect similar to that of the commercially available dicamba commercial preparation, and improve the safety to non-target organisms.

[0022] The results of the examples show that compared with free dicamba acid, Dicamba@TpBD-COF prepared by the present invention not only has a 50.62% reduction in volatilization rate, but also the leaching possibility is minimized. Moreover, compared with the commercially available dicamba preparation, the herbicidal effect of dicamba on Chenopodium Album L. is similar. In addition, both TpBD-COF and Dicamba@TpBD-COF show good biosafety to non-target wheat Triticum aestivum L., and even have a slight promoting effect on the growth and photosynthesis of wheat. The soil treated with Dicamba@TpBD-COF shows a more complex and closely related microbial community associated with nitrogen fixation, which is beneficial to plant growth. Description of the Drawings

[0023] Figure 1 is the construction mechanism of the nano-herbicide based on β-ketoenamine covalent organic framework materials;

[0024] Figure 2 is the X-ray diffraction result of the β-ketoenamine COF obtained in Examples 1 to 3;

[0025] Figure 3 is the BET specific surface area and pore size distribution of the β-ketoenamine COF obtained in Examples 1 to 3;

[0026] Figure 4 are the scanning electron microscope and transmission electron microscope pictures of the β-ketoenamine COF obtained in Examples 1 to 3;

[0027] Figure 5 is the loading amount of dicamba by different β-ketoenamine COF;

[0028] Figure 6 Zeta potential diagrams of β-ketoenamine COF and Dicamba@COF obtained from Examples 1-3;

[0029] Figure 7 Schematic diagram of the interaction between dicamba and β-ketoenamine COF;

[0030] Figure 8 XRD comparison diagrams of Dicamba@TpBD-COF and the original TpBD-COF;

[0031] Figure 9 TEM comparison diagrams of Dicamba@TpBD-COF and the original TpBD-COF;

[0032] Figure 10 Particle size distribution diagram of Dicamba@TpBD-COF;

[0033] Figure 11 Nitrogen adsorption-desorption isotherm comparison diagrams of Dicamba@TpBD-COF and the original TpBD-COF;

[0034] Figure 12 Pore size distribution comparison diagrams of Dicamba@TpBD-COF and the original TpBD-COF;

[0035] Figure 13 Fourier transform infrared spectroscopy comparison diagrams of Dicamba@TpBD-COF and the original TpBD-COF;

[0036] Figure 14 XPS spectra of dicamba and Dicamba@TpBD-COF;

[0037] Figure 15 O 1s XPS spectrum comparison diagrams of Dicamba@TpBD-COF and the original TpBD-COF;

[0038] Figure 16 Schematic diagram of the interaction between TpBD-COF and dicamba;

[0039] Figure 17 Zeta potential of TpBD-COF at different pH values;

[0040] Figure 18 Release curves of Dicamba@TpBD-COF at different pH values (1.6, 7.0, and 10.0);

[0041] Figure 19Schematic diagram of the structural evolution of β-ketoenamine covalent organic framework materials under acidic and alkaline conditions;

[0042] Figure 20 Leaching results of Dicamba@TpBD-COF and free acid dicamba in different soils;

[0043] Figure 21 Biological activities of samples with different dicamba active ingredients against target weeds;

[0044] Figure 22 Results of biosafety assessment of samples with different dicamba active ingredients against non-target plants;

[0045] Figure 23 Dilution curves of bacteria under different sample treatments;

[0046] Figure 24 Sobs index in soil after different sample treatments;

[0047] Figure 25 Results of complexity analysis of co-occurrence network on soil bacteria connections. Detailed implementation methods

[0048] The present invention provides a nano-herbicide based on β-ketoenamine covalent organic framework materials, including β-ketoenamine covalent organic framework materials and dicamba loaded on the surface and internal pores of the β-ketoenamine covalent organic framework materials. In the present invention, the β-ketoenamine covalent organic framework materials include one or several of TpPa-COF, TpBD-COF, and TpBDMe-COF.

[0049] In the present invention, the pore size of the β-ketoenamine covalent organic framework materials is preferably 2.17~3.0 nm, and the specific surface area is preferably 1261~1767 m 2 / g, specifically it can be 1261 m 2 / g, 1767 m 2 / g or 1468 m 2 / g.

[0050] In the present invention, the loading amount of dicamba in the nano-herbicide based on β-ketoenamine covalent organic framework materials is preferably 10.1~28.5%, specifically it can be 10.1%, 15.6%, or 28.5%.

[0051] In the present invention, the particle size of the nano-herbicide based on β-ketoenamine covalent organic framework materials is preferably 350~500 nm, specifically it can be 350 nm, 400 nm, 450 nm, or 500 nm.

[0052] The present invention provides a method for preparing the above-mentioned nano herbicide based on β-ketoenamine covalent organic framework material, comprising the following steps:

[0053] Disperse the β-ketoenamine covalent organic framework material in an aqueous dicamba solution, stir and centrifuge, wash and dry the obtained solid to obtain a nano herbicide based on β-ketoenamine covalent organic framework material.

[0054] In the present invention, the concentration of the aqueous dicamba solution is preferably 6 mg / mL; the mass ratio of the β-ketoenamine covalent organic framework material to dicamba is preferably 1:1.

[0055] In the present invention, the stirring rate is preferably 500-600 rpm, and the time is preferably 8-9 h. In the present invention, the centrifugation rate is preferably 10000-12000 rpm, more preferably 10000 rpm, and the time is preferably 9-12 min, more preferably 10 min.

[0056] In the present invention, the washing is preferably water washing; the number of washing times is preferably 3 times. In the present invention, the drying temperature is preferably 60 °C.

[0057] In the present invention, the method for preparing the β-ketoenamine covalent organic framework material preferably comprises the following steps:

[0058] Mix 1,3,5-triformylphloroglucinol, aniline ligand, pyridine and an organic solvent, and carry out a solvothermal reaction to obtain a β-ketoenamine covalent organic framework material.

[0059] In the present invention, the aniline ligand is p-phenylenediamine, benzidine or 4,4'-diamino-3,3'-dimethylbiphenyl. Specifically, when the β-ketoenamine covalent organic framework material is TpPa-COF, the aniline ligand is p-phenylenediamine; when the β-ketoenamine covalent organic framework material is TpBD-COF, the aniline ligand is benzidine; when the β-ketoenamine covalent organic framework material is TpBDMe-COF, the aniline ligand is 4,4'-diamino-3,3'-dimethylbiphenyl.

[0060] In the present invention, the molar ratio of 1,3,5-triformylphloroglucinol to the aniline ligand is 1:1.5.

[0061] In the present invention, the molar amount of 1,3,5-triformylphloroglucinol to the volume of pyridine is preferably 0.4 mmol: 0.1-0.5 mL.

[0062] In the present invention, when the β-ketoenamine covalent organic framework material is TpPa-COF, the organic solvent is preferably dimethylacetamide and o-dichlorobenzene, and the volume ratio of dimethylacetamide to o-dichlorobenzene is preferably 3:1; when the β-ketoenamine covalent organic framework material is TpBD-COF, the organic solvent is preferably o-dichlorobenzene and n-butanol, and the volume ratio of o-dichlorobenzene to n-butanol is preferably 9:1; when the β-ketoenamine covalent organic framework material is TpBDMe-COF, the organic solvent is preferably o-dichlorobenzene and n-butanol, and the volume ratio of o-dichlorobenzene to n-butanol is preferably 9:1.

[0063] In the present invention, the mixing method is preferably ultrasonic mixing, and the ultrasonic mixing time is preferably 10 min; in the present invention, the solvothermal reaction is preferably carried out under vacuum conditions, the temperature of the solvothermal reaction is preferably 115-125 °C, more preferably 120 °C, and the time is preferably 70-80 h, more preferably 72 h.

[0064] After the solvothermal reaction, the present invention preferably performs solid-liquid separation on the obtained solvothermal reaction product, washes and dries the obtained solid to obtain the β-ketoenamine covalent organic framework material. In the present invention, the solid-liquid separation is preferably centrifugation; the detergent used for washing is preferably tetrahydrofuran; the drying is preferably vacuum drying, and the drying temperature is preferably 60 °C.

[0065] The construction mechanism of the nano-herbicide based on the β-ketoenamine covalent organic framework material in the present invention is as Figure 1 shown.

[0066] The present invention provides the application of the above-mentioned nano-herbicide based on the β-ketoenamine covalent organic framework material in weeding gramineous plants.

[0067] In the present invention, the application concentration of the nano-herbicide based on the β-ketoenamine covalent organic framework material is preferably 28-50 g / mu, more preferably 30-40 g / mu.

[0068] The following examples will detail the nano-herbicide based on the β-ketoenamine covalent organic framework material provided by the present invention, its preparation method and application, but they should not be construed as limiting the scope of protection of the present invention.

[0069] In the following examples:

[0070] Source of raw materials:

[0071] 1,3,5-triformylphloroglucinol (Tp) was purchased from Bidepharm Comp. p-Phenylenediamine (Pa), benzidine (BD), 4,4'-diamino-3,3'-dimethylbiphenyl (BDMe), dimethylacetamide (DMAC), o-dichlorobenzene (o-DCB), and n-butanol (n-BuOH) were all purchased from Energy Chemical. Other reagents and solvents were commercially available and used without any further purification. Tetrahydrofuran (THF) was from Sigma-Aldrich (Shanghai) Trading Co., Ltd., and 0.3% sodium hypochlorite was from Beijing Bank Technology Co., Ltd.

[0072] Plant source: Wheat seeds were provided by the Institute of Plant Protection, Chinese Academy of Agricultural Sciences. Usually, 3 - 5 seeds were planted in a greenhouse after soaking in gibberellic acid for 24 hours to break dormancy. The greenhouse environmental conditions were controlled at 26 °C, with a photoperiod of 14 hours and a relative humidity of 65 - 80%. Wheat seedlings were disinfected with 0.3% sodium hypochlorite for about 10 minutes and washed 3 times with ultrapure water. 6 - 8 wheat seeds were planted in each pot and germinated in the greenhouse. The greenhouse conditions were 20 °C, with 12 hours of light and a relative humidity of 60%.

[0073] Example 1

[0074]

[0075] Preparation of TpPa-COF:

[0076] 1,3,5-triformylphloroglucinol (Tp, 0.4 mmol, 84.1 mg), p-phenylenediamine (Pa, 0.6 mmol, 64.9 mg), 0.1 mL of pyridine, 3.75 mL of dimethylacetamide (DMAC), and 1.25 mL of o-dichlorobenzene (o-DCB) were injected into an 80 mL heat-resistant tube. The mixture was sonicated for 10 minutes, degassed by three freeze-pump-thaw cycles, sealed under vacuum, and heated in an air-circulating oven at 120 °C for 72 hours. After cooling to room temperature, the precipitate was centrifuged, continuously washed with tetrahydrofuran (THF), and dried overnight in a vacuum oven at 60 °C to obtain TpPa-COF.

[0077] Preparation of Dicamba@TpPa-COF:

[0078] TpPa-COF (30 mg) was dispersed in 5 mL of an aqueous solution of dicamba (purity 96.0%) at a concentration of 6 mg / mL. The suspension was stirred for 8 hours and then centrifuged at 10,000 rpm for 10 minutes. The collected precipitate was washed three times and dried in an oven at 60 °C to obtain Dicamba@TpPa-COF. Subsequently, the loading amount (LC) of dicamba in the β-ketoenamine covalent organic framework material was calculated based on the difference between the content of dicamba free acid in the initial suspension and the content of dicamba free acid in the supernatant and washing solution after centrifugation, and was determined by high performance liquid chromatography (HPLC).

[0079] Example 2

[0080]

[0081] Preparation of TpBD-COF:

[0082] 1,3,5-Trimethoxybenzene-2,4,6-tricarbaldehyde (Tp, 0.4 mmol, 84.1 mg), benzidine (BD, 0.6 mmol, 110.5 mg), 0.5 mL of pyridine, 4.5 mL of o-DCB, and 0.5 mL of n-butanol were placed in an 80 mL heat-resistant tube. The mixture was sonicated for 10 minutes, degassed by three freeze-pump-thaw cycles, sealed under vacuum, and heated in an air-circulating oven at 120 °C for 72 hours. After cooling to room temperature, it was centrifuged and continuously washed with THF, and then dried overnight in a vacuum oven at 60 °C to obtain TpBD-COF.

[0083] Preparation of Dicamba@TpBD-COF:

[0084] TpBD-COF (30 mg) was dispersed in 5 mL of an aqueous solution of dicamba (purity 96.0%) at a concentration of 6 mg / mL. The suspension was stirred for 8 hours and then centrifuged at 10,000 rpm for 10 minutes. The collected precipitate was washed three times and dried in an oven at 60 °C to obtain Dicamba@TpBD-COF.

[0085] Example 3

[0086]

[0087] Preparation of TpBDMe-COF:

[0088] 1,3,5-triformylphloroglucinol (Tp, 0.4 mmol, 84.1 mg), 4,4'-diamino-3,3'-dimethylbiphenyl (BDMe, 0.6 mmol, 127.4 mg), 0.5 mL of pyridine, 4.5 mL of o-DCB, and 0.5 mL of n-sodium were charged into an 80 mL heat-resistant tube. The mixture was sonicated for 10 minutes, degassed by three freeze-pump-thaw cycles, sealed under vacuum, and heated in an air-circulating oven at 120 °C for 72 hours. After cooling to room temperature, it was centrifuged, continuously washed with THF, and dried overnight in a vacuum oven at 60 °C to obtain TpBDMe-COF.

[0089] Preparation of Dicamba@TpBDMe-COF:

[0090] TpBDMe-COF (30 mg) was dispersed in 5 mL of an aqueous solution of dicamba (purity 96.0%, 6 mg / mL). The suspension was stirred for 8 hours and then centrifuged at 10,000 rpm for 10 minutes. The collected precipitate was washed three times and dried in an oven at 60 °C to obtain Dicamba@TpBDMe-COF.

[0091] Structural characterization

[0092] (1) X-ray diffraction (XRD) tests were performed on the β-ketoenamine covalent organic framework materials (β-ketoenamine COF) obtained in Examples 1 to 3, and the results are as Figure 2 shown. It can be seen that the X-ray diffraction pattern of β-ketoenamine COF is in good agreement with the simulated pattern, demonstrating the successful synthesis of β-ketoenamine COF.

[0093] (2) Nitrogen adsorption-desorption tests were performed on the β-ketoenamine COF obtained in Examples 1 to 3, and the BET specific surface area and pore size distribution of the obtained β-ketoenamine COF are as Figure 3 shown. It can be seen that all β-ketoenamine COFs have a high BET specific surface area (1261 m 2 / g for TpPa-COF, 1767 m 2 / g for TpBD-COF, 1468 m 2 / g for TpBDMe-COF), and a uniformly distributed pore size, which is beneficial for drug loading.

[0094] (3) Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) tests were performed on the β-ketoenamine COF obtained in Examples 1 to 3, and the results are as Figure 4 shown. Figure 4Among them, the left column is the scanning electron microscope image, and the right column is the transmission electron microscope image. The results show that the β-ketoenamine COFs prepared by the present invention are all hollow spherical structures, and the TpBD-COF spheres are more uniformly dispersed.

[0095] (4) Using water as a solvent, the drug loading capacity (LC) of dicamba with different ratios to TpBD-COF was studied, and the obtained results are shown in Table 1.

[0096] Table 1 Drug loading capacity of dicamba on the hollow spheres of TpBD-COF a

[0097]

[0098] In Table 1, a is TpBD-COF (30 mg), H2O (5.0 mL), room temperature. The values are the average ± SD of five replicates. The following values in the LC (%) column are statistically different by Duncan's multiple range test at P ≤ 0.05; b is the mass ratio (weight ratio) of dicamba to the hollow spheres of TpBD-COF.

[0099] It can be seen from Table 1 that as the mass ratio of Dicamba@TpBD-COF increases, the loading content also increases until the ratio is 1:1. In this case, the dicamba loading content in TpBD-COF is as high as 28.5%. This means that the absorption of dicamba in TpBD-COF reaches saturation. Under similar conditions, the dicamba loading contents in TpPa-COF and TpBDMe-COF are 10.1% and 15.6% respectively, both lower than that of TpBD-COF, as shown in Figure 5 . This may be due to the smaller pore size of TpPa-COF and the steric hindrance of the methyl group in TpBDMe-COF.

[0100] (5) The Zeta potential diagrams of the β-ketoenamine COFs and Dicamba@COF obtained in Examples 1 to 3 are as shown in Figure 6 . It can be seen that the potentials of the β-ketoenamine-COFs are all negative, but the potentials increase after loading dicamba (Dicamba@COF), especially Dicamba@TpBD-COF, indicating a strong interaction between dicamba and the β-ketoenamine COF. The schematic diagram of the interaction between dicamba and the β-ketoenamine COF is as shown in Figure 7 .

[0101] (6) In order to study the interaction between Dicamba and the β-ketoenamine COF more deeply, the present invention characterized Dicamba@TpBD-COF systematically and compared it with the original TpBD-COF. The XRD comparison diagram of Dicamba@TpBD-COF and the original TpBD-COF is as shown inFigure 8 As shown, the TEM comparison diagram is as Figure 9 shown, the particle size distribution diagram of Dicamba@TpBD-COF is as Figure 10 shown. It can be seen that the typical XRD peaks of TpBD-COF can still be seen in the XRD pattern of Dicamba@TpBD-COF, and the hollow spherical morphology and diameter of 420 nm remain unchanged. This indicates that the structure of TpBD-COF remains stable after loading Dicamba.

[0102] The comparison diagram of the nitrogen adsorption-desorption isotherms of Dicamba@TpBD-COF and the original TpBD-COF is as Figure 11 shown, and the comparison diagram of the pore size distribution is as Figure 12 shown. The mesoporous structure characteristics of Dicamba@TpBD-COF and the original TpBD-COF are shown in Table 2.

[0103] Table 2 Mesoporous structures of Dicamba@TpBD-COF and TpBD-COF

[0104]

[0105] It can be seen that after loading Dicamba, the BET surface area decreases from 1767 m 2 / g to 11.7 m 2 / g, and the pore volume decreases from 1.01 cm 3 / g to 0.03 cm 3 / g. The original mesopores (about 2.17 nm) in TpBD-COF also disappear, indicating that the pores of TpBD-COF are filled with Dicamba (with a size of about 0.72 nm).

[0106] The comparison diagram of the Fourier transform infrared spectra of Dicamba@TpBD-COF and the original TpBD-COF is as Figure 13 shown, the XPS spectra of dicamba and Dicamba@TpBD-COF are as Figure 14 shown, and the comparison diagram of the O 1s XPS spectra is as Figure 15 shown. The Fourier transform infrared (FT-IR) spectra show that the stretching vibration at 61698 cm -1 shifts to a higher 1722 cm -1Transfer may be due to the interaction between Dicamba and TpBD-COF, which disrupts the intermolecular hydrogen bonds between Dicamba molecules. X-ray photoelectron spectroscopy (XPS) spectra indicate that the elemental composition of Dicamba@TpBD-COF (C, N, O, Cl) is that of Dicamba free acid (C, O, and Cl) and TpBD-COF (a combination of C, N, and O). More importantly, the XPS O 1s deconvolution results show that the peaks of 530.85 eV and 532.35 eV for C=O and C-OH of DpBD-COF shift to 531.13 eV and 533.48 eV, indicating the formation of hydrogen bonds between the keto carbonyl or enol of TpBD-COF and the carboxyl hydrogen of Dicamba. Among them, the schematic diagram of the interaction between TpBD-COF and dicamba is as shown in Figure 16 shown. Figure 16 Among them, the hydrogen bond interaction between the keto carbonyl or enol of TpBD-COF and the carboxyl hydrogen of dicamba.

[0107] (7)The Zeta potential of TpBD-COF at different pH values is as shown in Figure 17 shown. It can be seen that the Zeta potential of TpBD-COF is positive under acidic conditions and negative under neutral and alkaline conditions at different pH values, and it is easier to bind with dicamba under neutral and alkaline conditions.

[0108] Performance test

[0109] (1)Thermogravimetric and volatility experiments

[0110] Determine the weight of the active ingredient of dicamba, put it into a platinum crucible, and place it in an isothermal environment at 60 °C. After 24 h, the dicamba free acid is dissolved in 10 mL of methanol. Disperse Dicamba@TpBD-COF in 10 mL of methanol and sonicate for 3 hours. The concentration of dicamba in the methanol solution is determined by high performance liquid chromatography. The evaporation rate of dicamba in each sample is equal to the mass loss of dicamba under isothermal conditions divided by the initial mass of dicamba in the sample.

[0111] The release curves of Dicamba@TpBD-COF at different pH values (1.6, 7.0, and 10.0) are as shown in Figure 18 shown. Figure 18In it, a is the cumulative release behavior of dicamba from Dicamba@TpBD-COF in aqueous solutions with different pH values; b is the TG curve of TpBD-COF and Dicamba@TpBD-COF; c is the DTG curve of TpBD-COF and Dicamba@TpBD-COF; d is the volatility rate of dicamba free acid and Dicamba@TpBD-COF. It can be seen that the release trends of dicamba under acidic (pH = 1.6) and alkaline (pH = 10.0) conditions are very similar, and the release amount is slightly higher than that under neutral (pH = 7.0) conditions. This may be due to the amphoteric properties caused by the isomerism of β-ketoenamine, which ultimately leads to the effective release of dicamba under acidic and alkaline conditions. Among them, the structural evolution diagrams of β-ketoenamine covalent organic framework materials under acidic and alkaline conditions are as Figure 19 shown, Figure 19 showing the amphoteric properties of β-ketoenamine covalent organic framework materials.

[0112] In addition, the present invention also used four kinetic models of zero-order, first-order, Higuchi, and Ritger-Peppas to fit the release data, so as to explore the release kinetics, and the obtained results are shown in Table 3.

[0113] Table 3 Fitting parameters of Dicamba@TpBD-COF and four kinetic models at different pH values

[0114]

[0115] It can be seen that the release behavior of Dicamba@TpBD-COF is relatively consistent with the Ritger-Peppas model. At pH values of 1.6, 7.0, and 10.0, the correlation coefficients are 0.9176, 0.9493, and 0.9184, respectively. Under the three pH conditions, the fitting diffusion constant (n) is less than 0.43, indicating that the diffusion mechanism of dicamba is Fick diffusion, that is, the release of dicamba is mainly controlled by the concentration gradient.

[0116] The TG, DTG and volatility experiments of Dicamba@TpBD-COF were compared with dicamba free acid. The experimental results showed that dicamba free acid had almost 100% weight loss at temperatures of 131 - 258 °C. In contrast, the weight loss rate of Dicamba@TpBD-COF was 45%, and the starting temperature was higher, at 201 - 514 °C. Combining the TG and DTG results of Dicamba@TpBD-COF, it can be inferred that the approximately 36% weight loss between 201 - 273 °C was mainly caused by the loading of dicamba in TpBD-COF, while the approximately 14% weight loss above 372 °C should be due to the decomposition of TpBD-COF. In addition, the volatility rate of Dicamba@TpBD-COF (37.5%) was much lower than that of dicamba free acid (88.1%). These results indicate that the TpBD-COF loading method can significantly reduce the volatility rate of dicamba. The reduction of the dicamba volatility rate is beneficial to reducing its pollution and phytotoxicity to non-target areas and the environment.

[0117] (2) Soil leaching experiment

[0118] In addition to the volatility problem, the leaching and migration of dicamba in soil is another environmental risk. To evaluate the mobility of Dicamba@TpBD-COF in soil, the leaching amounts and cumulative leaching rates of Dicamba@TpBD-COF and dicamba-free acid were detected in the soils of Beijing and Sichuan provinces, respectively. The specific methods are as follows.

[0119] The soils with a surface depth of 0 - 20 cm collected in Beijing and Sichuan provinces were air-dried and sieved to a particle size of less than 2 mm at 25 °C. The treated soil was filled into plastic columns with a height of 11.4 cm and a diameter of 2.8 cm, with untreated cotton at the bottom. The top of the soil column was covered with quartz sand. After pre-wetting the column with deionized water for 30 minutes, 5 mg of dicamba free acid or Dicamba@TpBD-COF with 5 mg of dicamba active ingredient was added to the top of the column. Subsequently, the samples were eluted with deionized water and the eluate was collected. The leaching amount of dicamba was determined by high performance liquid chromatography. The cumulative leaching amount of dicamba was calculated according to the formula: E = / m ×100%, where E is the cumulative leaching amount of dicamba (%), m i is the mass of dicamba in the eluate at sampling time i, and m is the total amount of dicamba free acid applied. Each experiment was repeated three times.

[0120] Note: The soils in these two regions are silty loam and clay loam respectively, and the physical and chemical properties of the two soils are shown in Table 4.

[0121] Table 4 Physical and chemical parameters of soils in Beijing and Sichuan

[0122]

[0123] The leaching results of Dicamba@TpBD-COF and free acid dicamba in different soils are as Figure 20 shown. It can be seen that for the Beijing soil, the maximum leaching amount decreased significantly from 1.59 mg (free acid dicamba) to 0.75 mg (Dicamba@TpBD-COF), and the cumulative leaching amount of dicamba (eluted with 30 mL of water) decreased from 97.30% (free acid dicamba) to 59.98% (Dicamba@TpBD-COF). For the Sichuan soil, the trend was similar, with the maximum leaching amount decreasing from 0.81 mg to 0.55 mg, and the cumulative dicamba leaching rate decreasing from 76.60% to 54.02%. In addition, the leaching behaviors of Dicamba@TpBD-COF and free acid dicamba in the Beijing soil and Sichuan soil were also different: under the same test conditions, the movement rate of dicamba in the Sichuan soil was slower than that in the Beijing soil, which may be due to the silt and clay properties of the Sichuan soil. In summary, Dicamba@TpBD-COF can delay the movement of dicamba in the soil and reduce the leaching potential, thereby protecting groundwater from dicamba pollution.

[0124] (3) Biological activity against target weeds

[0125] Biological activity experiments were conducted on the target weed Chenopodium album L. in the greenhouse. Figure 21 Pictures of Chenopodium album L. seedlings treated with pure water (control sample), commercially available dicamba formulation, TpBD-COF, and Dicamba@TpBD-COF aqueous solution for 3 days are shown. The concentration of dicamba was the same as the field application rate (480 mg / L). Figure 21In (a), it is a photo of target weeds (14-day-old seedlings) after 3 days of treatment with a sample containing 480 mg / L of different dicamba active ingredients. In (b), it shows the reduction in fresh weight of weed seedlings after 7 days of treatment with Dicamba@TpBD-COF at different dicamba concentrations or commercially available dicamba formulations. Compared with the control group, the leaves of both Dicamba@TpBD-COF and commercially available dicamba formulations showed deformation and warping. In addition, when the dicamba concentration was 240 mg / L, the fresh weight of weeds treated with Dicamba@TpBD-COF decreased by approximately 70% after 7 days, which was basically the same as the reduction rate of fresh weight of weeds treated with commercially available dicamba formulations. When the dicamba concentration increased to 960 mg / L, the reduction rates of fresh weight of weeds treated with Dicamba@TpBD-COF and commercially available dicamba formulations both increased to approximately 80%. These results indicate that there is little difference in herbicidal efficacy between Dicamba@TpBD-COF and commercially available dicamba formulations.

[0126] (4) Biosafety assessment of non-target plants

[0127] Dicamba is commonly used to control weeds in wheat fields. Therefore, wheat (Triticum aestivum L) was selected as the non-target plant for the biosafety assessment of Dicamba@TpBD-COF. After 14 days of treatment with different samples containing 480 mg / L of the dicamba active ingredient, the root length (RL), shoot height (SH), and fresh weight (FW) of non-target plant seedlings are shown in (a) as follows. Figure 22 as shown in (a).

[0128] It can be seen that the root length (RL), shoot height (SH), and fresh weight (FW) of wheat seedlings treated with commercially available dicamba formulations were all lower than those of the control group (seedlings treated with pure water). In contrast, the growth of wheat seedlings treated with TpBD-COF and Dicamba@TpBD-COF was better than that of the control group.

[0129] To study the mechanism of this difference, the present invention used chlorophyll fluorescence method (CF) to study the effects of different samples on the photosynthesis of wheat seedlings. Generally, chlorophyll fluorescence technology, as a rapid, sensitive, and non-destructive technique, is widely used to study the photosynthetic physiological functions of different plants and can directly reflect the interfering factors affecting the photosynthetic apparatus and photosystem II (PS II) metabolism of plants. Specifically, Fv / Fm represents the photosynthetic performance under exogenous substance conditions and is the maximum quantum efficiency of PSII photochemistry measured under dark adaptation. The specific method is as follows:

[0130] The kinetics of CF were measured using the MINI version of Imaging PAM (Walz, Effeltrich, Germany). The modulation of the measuring light was carried out using a blue LED to provide continuous light and saturating pulses. The Mini-Imaging PAM was covered with black paper and the leaves were uniformly irradiated. The light was natural light or 204 µmol m -2 s -1 . During the measurement, the fresh leaf area of the intact seedlings could reach 2.4 × 3.2 cm. Before measuring the CF parameters, the seedlings were adapted to the dark condition for 30 minutes. Five wheat seedlings were randomly selected for each treatment for determination. The CF parameters were calculated using Image-win software (Walz, Effeltrich, Germany).

[0131] The effects of different samples on the photosynthesis of wheat seedlings are shown in Figure 22 b. The Fv / Fm values based on different samples were all around 0.80, which was consistent with the previous research results on different unstressed plants, indicating the reliability of this method in evaluating wheat photosynthesis. Y(PSII) was considered to record the actual quantum yield of photochemical energy conversion (ATP and NADPH) in PS II. The increase in the Y(PSII) values of the seedlings treated with TpBD-COF and Dicamba@TpBD-COF might be related to the increase in stomatal conductance, which usually leads to an increase in the electron transfer efficiency of photosynthetic metabolism and the consumption of ATP / NADPH. In addition, the qP value representing the photochemical quenching coefficient of PSII also showed the same trend as Y(PSII). Therefore, the root length, shoot height, and fresh weight of the wheat seedlings treated with TpBD-COF / Dicamba@TpBD-COF were better than those treated with the commercially available dicamba formulation, which might be due to the enhancement of plant photosynthesis by introducing TpBD-COF. This means that adding dicamba to TpBD-COF can improve the biosafety of dicamba to non-target plants.

[0132] (5) Effects on soil microorganisms

[0133] Applying herbicides may affect the health and function of the soil, which can usually be detected through the soil microbial community. Therefore, compared with the commercially available dicamba formulation and pure water (control sample), the effects of TpBD-COF and Dicamba@TpBD-COF on the species and abundance of soil bacterial microorganisms were systematically studied in this invention. The dilution curves of bacteria under different sample treatments are shown in Figure 23 . It can be seen that the dilution curves of soil sequencing showed a rapid increase at the beginning and then plateaued with the increase in the sequencing amount, indicating that the sequencing depths all met the requirements.

[0134] The Sobs index represents the species richness within the sample community. The Sobs index was determined by Illumina MiSeq sequencing as follows: purified amplicons were pooled in equimolar amounts and paired-end sequenced on the Illumina SeqPE300 platform / NovaSeqPE250 platform (Illumina, San Diego, USA) according to the standard protocol of Majorbio Biotechnology Co., Ltd. (Shanghai, China). The Sobs indices in the soil after different sample treatments are shown as Figure 24 follows. The community species richness of the soil treated with TpBD-COF and Dicamba@TpBD-COF was higher than that of the soil treated with the commercially available dicamba formulation and pure water.

[0135] To further explore the effects of these samples on the soil bacterial community, the complexity of soil bacterial connections was analyzed using a co-occurrence network. Specifically, bioinformatics analysis of the soil microbiota was performed using the Majorbio Cloud Platform (https: / / cloud.majorbio.com), and the results are shown in Figure 25 . Figure 25 In, a is pure water, b is the commercially available dicamba formulation, c is TpBD-COF, and d is Dicamba@TpBD-COF. Note: The number of connections (degree) is proportional to the size of each node; red edges indicate positive interactions between two bacterial nodes, and green edges indicate negative interactions; the color of each node represents the bacterial phylum. Table 5 extracts the corresponding topological indices of the soil bacterial network diagram.

[0136] Table 5 Topological indices of the soil bacterial network diagram under different treatment conditions

[0137]

[0138] The results showed that compared with the control group, the average degree, average clustering coefficient, and positive edge percentage decreased, while the average path distance and negative edge percentage increased in the soil treated with the commercially available dicamba formulation. In contrast, compared with the control group, the total number of network links, average degree, average clustering coefficient, and positive edge percentage increased, while the average path distance and negative edge percentage decreased in the soil treated with TpBD-COF and Dicamba@TpBD-COF. These results all indicate that there may be extensive interaction relationships between bacteria in the response to TpBD-COF and Dicamba@TpBD-COF, which may induce soil bacteria to form highly interconnected communities. In addition, as Figure 25As shown, the bacterial community network aggregates into different Proteobacteria groups, among which the Proteobacteria group in the soil treated with Dicamba@TpBD-COF has the strongest correlation. Generally, Proteobacteria exist in different environments, including tea gardens, forests, and farmlands, etc., and they are closely related to the soil nitrogen cycle, especially the soil nitrogen fixation ability. This may be related to the high nitrogen content of TpBD-COF. In short, adding dicamba to TpBD-COF can mitigate the adverse effects of dicamba and even be beneficial to soil bacterial microorganisms.

[0139] In summary, the present invention utilizes the hydrogen bond action of the carboxyl group of dicamba to introduce a series of β-ketoenamine covalent organic framework materials with a large surface area and rich β-ketoamine groups, and constructs a nano-herbicide by using the hydrogen bond action between the keto carbonyl or enol of the β-ketoenamine covalent organic framework material and the carboxyl hydrogen of dicamba. Compared with dicamba free acid, the Dicamba@TpBD-COF prepared in the present invention not only has a 50.62% reduction in the volatilization rate, but also the leaching possibility is minimized. Moreover, compared with the commercially available dicamba formulation, the herbicidal effect of dicamba on the weed Chenopodium Album L. is similar. In addition, both TpBD-COF and Dicamba@TpBD-COF show good biosafety to the non-target wheat Triticum aestivum L., and even have a slight promoting effect on the growth and photosynthesis of wheat. The soil treated with Dicamba@TpBD-COF shows a more complex and closely related microbial community related to nitrogen fixation, which is beneficial to plant growth. In short, adding the herbicide dicamba to TpBD-COF greatly reduces the adverse effects on the environment, while maintaining a high herbicidal efficiency and even improving the safety to non-target organisms. This work provides a new idea for the application of nano-COF in pesticide loading.

[0140] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A nano-herbicide based on β-ketoenamine covalent organic framework material, characterized in that: It includes a β-ketoenamine covalent organic framework material and dicamba loaded on the surface and internal pores of the β-ketoenamine covalent organic framework material; The β-ketoenamine covalent organic framework material is TpBD-COF; The loading amount of dicamba in the nano-herbicide based on β-ketoenamine covalent organic framework material is 15.6% to 28.5%; The β-ketoenamine covalent organic framework material has a hollow sphere structure; the pore size of the β-ketoenamine covalent organic framework material is 2.17-3.0 nm, and the specific surface area is 1261-1767 m 2 / g.

2. The nano-herbicide based on β-ketoenamine covalent organic framework material according to claim 1, characterized in that: The particle size of the nano herbicide based on the β-ketoenamine covalent organic framework material is 350-500 nm.

3. The method for preparing a nano-herbicide based on a β-ketoenamine covalent organic framework material according to any one of claims 1 to 2, characterized in that: The following steps are involved: The beta-ketoenamine covalent organic framework material is dispersed in a dicamba aqueous solution, stirred and centrifuged, and the obtained solid is washed and dried to obtain a nano herbicide based on the beta-ketoenamine covalent organic framework material.

4. The preparation method according to claim 3, characterized in that: The concentration of the dicamba aqueous solution is 6 mg / mL; The centrifugal speed is 10000-12000 rpm, and the time is 9-12 min.

5. The preparation method according to claim 3, characterized in that: The preparation method of the β-ketoenamine covalent organic framework material comprises the following steps: 1,3,5-triformylphloroglucinol, aniline ligands, pyridine and an organic solvent are mixed and subjected to a solvothermal reaction to obtain a β-ketoenamine covalent organic framework material; The aniline ligand is benzidine.

6. The preparation method according to claim 5, characterized in that: The molar ratio of the 1,3,5-triformylphloroglucinol to the aniline ligand is 1:1.5; The temperature of the solvent thermal reaction is 115-125° C. and the time is 70-80 hours.

7. Use of the nano-herbicide based on β-ketoenamine covalent organic skeleton material according to any one of claims 1 to 2 or the nano-herbicide based on β-ketoenamine covalent organic skeleton material prepared by the preparation method according to any one of claims 3 to 6 in weeding Gramineae plants.

8. The use according to claim 7, characterized in that: The application amount of the nano herbicide based on β-ketoenamine covalent organic framework material is 28-50 g / mu.

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