Nano herbicide based on beta-ketoenamine covalent organic framework material as well as preparation method and application of nano herbicide

Abstract

The invention provides a nano herbicide based on a beta-ketoenamine covalent organic framework material as well as a preparation method and application of the nano herbicide, and belongs to the technical field of pesticide preparations. The nano herbicide provided by the invention comprises a beta-keto-enamine covalent organic framework material and dicamba loaded on the surface and internal pores of the beta-keto-enamine covalent organic framework material. A series of beta-keto-enamine covalent organic framework materials with large surface area and rich beta-keto-amine groups are introduced by utilizing the hydrogen-bond interaction of dicamba carboxyl, and the nano herbicide is constructed by utilizing the hydrogen-bond interaction between keto-carbonyl or enol of the beta-keto-enamine covalent organic framework materials and carboxyl hydrogen of dicamba. The load capacity of the nano herbicide dicamba is high, and compared with commercially available dicamba, the volatilization rate of the dicamba is remarkably reduced, so that the leaching potential is reduced, meanwhile, the weed control effect similar to that of a commercial dicamba preparation purchased in the market can be kept, and the safety to non-target organisms is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide preparations, and in particular to a nano herbicide based on a beta-ketoenamine covalent organic skeleton material, and a preparation method and 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 undesirable plants, among which Dicamba (3,6-dichloro-2-methoxybenzoic acid, Dicamba) is a widely used herbicide due to its selective weed control performance and low price.

[0003] However, dicamba has high leaching and volatility, which makes it easy to migrate in the environment (soil, water and air). Specifically, the vapor pressure of dicamba at 25°C is 4.5×10 -3 Pa, which is moderately volatile after application, can damage soybeans, tomatoes or other plants that are not tolerant to dicamba even at low doses due to dicamba spray drift and off-target effects. In addition, soil leaching is still a very serious problem due to the good water solubility of dicamba. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a nano-herbicide based on β-ketoenamine covalent organic framework material and its preparation method and application. 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 object of the invention, the present invention provides the following technical solutions: The present invention provides a nano herbicide based on a β-ketoenamine covalent organic framework material, comprising 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 includes one or more of TpPa-COF, TpBD-COF and TpBDMe-COF.

[0006] Preferably, the loading amount of dicamba in the nano-herbicide based on β-ketoenamine covalent organic framework material is 10.1-28.5%.

[0007] Preferably, the β-ketoenamine covalent organic framework material has a pore size of 2.17-3.0 nm and a specific surface area of ​​1261-1767 m 2 / g.

[0008] Preferably, the particle size of the nano-herbicide based on β-ketoenamine covalent organic framework material is 350-500 nm.

[0009] 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: 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.

[0010] Preferably, 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.

[0011] Preferably, the method for preparing 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 p-phenylenediamine, benzidine or 4,4'-diamino-3,3'-dimethylbiphenyl.

[0012] Preferably, 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.

[0013] The present invention provides application of the nano herbicide based on beta-ketoenamine covalent organic framework material in weeding of gramineous plants.

[0014] Preferably, the application amount of the nano herbicide based on β-ketoenamine covalent organic framework material is 28-50 g / mu.

[0015] The present invention provides a nano-herbicide based on a β-ketoenamine covalent organic framework material (denoted as Dicamba@COF), comprising 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 comprises one or more of TpPa-COF, TpBD-COF and TpBDMe-COF. The present invention utilizes the hydrogen bonding effect of the carboxyl group of dicamba to introduce a series of β-ketoenamine covalent organic framework materials with large surface areas and abundant β-ketoamine groups, and utilizes the hydrogen bonding effect between the ketocarbonyl or enol of the β-ketoenamine covalent organic framework material and the carboxyl hydrogen of dicamba to construct the nano-herbicide. The nano-herbicide dicamba based on the β-ketoenamine covalent organic framework material provided by the present invention has a high loading amount of dicamba, and compared with commercially available dicamba, the volatilization rate of dicamba is significantly reduced, thereby reducing the leaching potential, while being able to maintain a weed control effect similar to that of commercial dicamba preparations purchased on the market, and improving the safety to non-target organisms.

[0016] The results of the examples show that the Dicamba@TpBD-COF prepared by the present invention not only has a 50.62% lower volatility and a minimum leaching possibility compared to the free acid of dicamba, but also has a similar weed control effect on the weed Chenopodium Album L. compared to the dicamba preparations purchased on the market. In addition, both TpBD-COF and Dicamba@TpBD-COF showed good biosafety against the non-target wheat Triticum aestivum L., and even had a slight promoting effect on the growth and photosynthesis of wheat. The soil treated with Dicamba@TpBD-COF showed that the microbial community related to nitrogen fixation was more complex and more closely connected, which was conducive to plant growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The construction mechanism of nanoherbicides based on β-ketoenamine covalent organic framework materials; Figure 2 The X-ray diffraction results of the β-ketoenamine COF obtained in Examples 1 to 3; Figure 3 The BET specific surface area and pore size distribution of the β-ketoenamine COF obtained in Examples 1 to 3; Figure 4 The scanning electron microscope and transmission electron microscope images of the β-ketoenamine COF obtained in Examples 1 to 3; Figure 5 is the loading amount of dicamba on different β-ketoenamine COFs; Figure 6Zeta potential diagrams of β-ketoenamine COF and Dicamba@COF obtained in Examples 1 to 3; Figure 7 Schematic diagram of the interaction between dicamba and β-ketoenamine COF; Figure 8 XRD comparison diagram of Dicamba@TpBD-COF and original TpBD-COF; Fig. 9 TEM comparison of Dicamba@TpBD-COF and original TpBD-COF; Fig.10 is the particle size distribution diagram of Dicamba@TpBD-COF; Fig.11 Comparison of nitrogen adsorption-desorption isotherms of Dicamba@TpBD-COF and pristine TpBD-COF; Fig.12 Comparison of pore size distribution between Dicamba@TpBD-COF and original TpBD-COF; Fig.13 Comparison of Fourier transform infrared spectra of Dicamba@TpBD-COF and original TpBD-COF; Fig.14 XPS spectra of Dicamba and Dicamba@TpBD-COF; Fig.15 Comparison of O 1s XPS spectra of Dicamba@TpBD-COF and pristine TpBD-COF; Fig.16 Schematic diagram of the interaction between TpBD-COF and dicamba; Fig.17 is the Zeta potential of TpBD-COF at different pH values; Fig.18 The release curves of Dicamba@TpBD-COF at different pH values ​​(1.6, 7.0, and 10.0); Fig.19 Illustration of the structural evolution of β-ketoenamine covalent organic framework materials under acidic and alkaline conditions; Fig. 20 The leaching results of Dicamba@TpBD-COF and free acid dicamba in different soils; Fig.21 The biological activities of samples of different dicamba active ingredients against target weeds; Fig. 22 The biosafety assessment results of samples of different dicamba active ingredients on non-target plants; Fig.23Dilution curves of bacteria under different sample treatments; Fig.24 Sobs index in soil after different sample treatments; Fig.25 The results of complexity analysis of soil bacterial connections in co-occurrence networks. DETAILED DESCRIPTION

[0018] The present invention provides a nano herbicide based on a β-ketoenamine covalent organic framework material, comprising a β-ketoenamine covalent organic framework material and dicamba loaded on the surface and internal pores of the β-ketoenamine covalent organic framework material. In the present invention, the β-ketoenamine covalent organic framework material comprises one or more of TpPa-COF, TpBD-COF and TpBDMe-COF.

[0019] In the present invention, the pore size of the β-ketoenamine covalent organic framework material is preferably 2.17-3.0 nm, and the specific surface area is preferably 1261-1767 m 2 / g, specifically 1261m 2 / g, 1767 m 2 / g or 1468m 2 / g.

[0020] In the present invention, the loading amount of dicamba in the nano herbicide based on β-ketoenamine covalent organic framework material is preferably 10.1-28.5%, specifically 10.1%, 15.6% or 28.5%.

[0021] In the present invention, the particle size of the nano herbicide based on the β-ketoenamine covalent organic framework material is preferably 350-500 nm, specifically 350 nm, 400 nm, 450 nm or 500 nm.

[0022] 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: 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.

[0023] In the present invention, the concentration of the dicamba aqueous solution is preferably 6 mg / mL; the mass ratio of the β-ketoenamine covalent organic framework material to dicamba is preferably 1:1.

[0024] In the present invention, the stirring rate is preferably 500-600 rpm, and the time is preferably 8-9 hours. In the present invention, the centrifugal rate is preferably 10000-12000 rpm, more preferably 10000 rpm, and the time is preferably 9-12 minutes, more preferably 10 minutes.

[0025] In the present invention, the washing is preferably water washing; the number of washing is preferably 3. In the present invention, the drying temperature is preferably 60°C.

[0026] In the present invention, the method for preparing the β-ketoenamine covalent organic framework material preferably 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.

[0027] 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.

[0028] In the present invention, the molar ratio of the 1,3,5-triformylphloroglucinol to the aniline ligand is 1:1.5.

[0029] In the present invention, the volume ratio of the molar amount of the 1,3,5-triformylphloroglucinol to pyridine is preferably 0.4 mmol: 0.1-0.5 mL.

[0030] 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.

[0031] In the present invention, the mixing method is preferably ultrasonic mixing, and the ultrasonic mixing time is preferably 10 minutes; in the present invention, the solvent thermal reaction is preferably carried out under vacuum conditions, the temperature of the solvent thermal reaction is preferably 115-125°C, more preferably 120°C, and the time is preferably 70-80 hours, more preferably 72 hours.

[0032] After the solvothermal reaction, the present invention preferably performs solid-liquid separation on the obtained solvothermal reaction product, washes and dries the obtained solid, and obtains a β-ketoenamine covalent organic framework material. In the present invention, the solid-liquid separation is preferably centrifugation; the detergent used in the washing is preferably tetrahydrofuran; the drying is preferably vacuum drying, and the drying temperature is preferably 60°C.

[0033] The construction mechanism of the nano-herbicide based on β-ketoenamine covalent organic framework material of the present invention is as follows Figure 1 shown.

[0034] The present invention provides application of the nano herbicide based on beta-ketoenamine covalent organic framework material in weeding of gramineous plants.

[0035] In the present invention, the application concentration of the nano herbicide based on β-ketoenamine covalent organic framework material is preferably 28-50 g / mu, more preferably 30-40 g / mu.

[0036] The nano-herbicide based on β-ketoenamine covalent organic framework material provided by the present invention and its preparation method and application are described in detail below in conjunction with the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0037] In the following embodiments: Source of raw materials: 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 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 Bank of Beijing Technology Co., Ltd.

[0038] Plant source: Wheat seeds were provided by the Institute of Plant Protection, Chinese Academy of Agricultural Sciences. Typically, 3 to 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, a photoperiod of 14 hours, and a relative humidity of 65 to 80%. Wheat seedlings were sterilized with 0.3% sodium hypochlorite for about 10 minutes and washed three times with ultrapure water. 6 to 8 wheat seeds were planted in each pot and germinated in a greenhouse. The greenhouse conditions were 20°C, 12 hours of light, and 60% relative humidity.

[0039] Example 1

[0040] Preparation of TpPa-COF: 1,3,5-Triformylphloroglucinol (Tp, 0.4 mmol, 84.1 mg), p-phenylenediamine (Pa, 0.6 mmol, 64.9 mg), 0.1 mL pyridine, 3.75 mL dimethylacetamide (DMAC), and 1.25 mL o-dichlorobenzene (o-DCB) were injected into an 80 mL heat-resistant tube. The mixture was sonicated for 10 min, degassed by three freeze pump-thaw cycles, sealed under vacuum, and heated in an air circulating oven at 120 °C for 72 h. After cooling to room temperature, the precipitate was centrifuged, washed continuously with tetrahydrofuran (THF), and dried in a vacuum oven at 60 °C overnight to obtain TpPa-COF.

[0041] Preparation of Dicamba@TpPa-COF: TpPa-COF (30 mg) was dispersed in 5 mL of 6 mg / mL dicamba (96.0% purity) aqueous solution. 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 drug loading (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 liquid after centrifugation, and was determined by high performance liquid chromatography (HPLC).

[0042] Example 2

[0043] Preparation of TpBD-COF: 1,3,5-triformyltetrachlorophloroglucinol (Tp, 0.4 mmol, 84.1 mg), benzidine (BD, 0.6 mmol, 110.5 mg), 0.5 mL pyridine, 4.5 mL o-DCB, and 0.5 mL n-butanol (n-BuOH) were placed in an 80 mL heat-resistant tube. The mixture was sonicated for 10 min, degassed by three freeze pump-thaw cycles, sealed under vacuum, and heated in an air circulating oven at 120 °C for 72 h. After cooling to room temperature, centrifuged, washed continuously with THF, and dried in a vacuum oven at 60 °C overnight to obtain TpBD-COF.

[0044] Preparation of Dicamba@TpBD-COF: TpBD-COF (30 mg) was dispersed in 5 mL of 6 mg / mL dicamba (96.0% purity) aqueous solution. 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.

[0045] Example 3

[0046] Preparation of TpBDMe-COF: 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 pyridine, 4.5 mL o-DCB, and 0.5 mL 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, centrifugation was performed, the mixture was continuously washed with THF, and dried in a vacuum oven at 60°C overnight to obtain TpBDMe-COF.

[0047] Preparation of Dicamba@TpBDMe-COF: TpBDMe-COF (30 mg) was dispersed in 5 mL of 6 mg / mL Dicamba (96.0% purity) aqueous solution. 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.

[0048] Structural characterization (1) The β-ketoenamine covalent organic framework material (β-ketoenamine COF) obtained in Examples 1 to 3 was subjected to an X-ray diffraction (XRD) test, and the results obtained were as follows: Figure 2 As shown, it can be seen that the X-ray diffraction pattern of β-ketoenamine COF is in good agreement with the simulation pattern, proving the successful synthesis of β-ketoenamine COF.

[0049] (2) The β-ketoenamine COF obtained in Examples 1 to 3 was subjected to nitrogen adsorption-desorption test. The BET specific surface area and pore size distribution of the obtained β-ketoenamine COF were as follows: Figure 3 As shown in Figure 2, all β-ketoenamine COFs have a high BET specific surface area (TpPa-COF is 1261 m 2 / g, TpBD-COF is 1767 m 2 / g, TpBDMe-COF is 1468m 2 / g), and uniformly distributed pore sizes, which are beneficial for drug loading.

[0050] (3) The β-ketoenamine COF obtained in Examples 1 to 3 was tested by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results are as follows: Figure 4 shown. Figure 4 The left column is a scanning electron microscope image, and the right column is a transmission electron microscope image. The results show that the β-ketoenamine COF prepared by the present invention are all hollow spherical structures, among which the TpBD-COF spheres are more evenly dispersed.

[0051] (4) Using water as solvent, the drug loading (LC) at different ratios of dicamba to TpBD-COF was studied. The results are shown in Table 1.

[0052] Table 1 Drug loading of dicamba on TpBD-COF hollow spheres a

[0053] In Table 1, a is TpBD-COF (30 mg), H2O (5.0 mL), room temperature. The values ​​are the mean ± SD of five replicates. The following values ​​in the LC (%) column were statistically significant at P ≤ 0.05 by Duncan's multiple range test; b is the mass ratio (weight ratio) of dicamba to TpBD-COF hollow spheres.

[0054] As can be seen from Table 1, as the mass ratio of Dicamba@TpBD-COF increases, the loading content also increases until the ratio is 1:1, in which case the loading content of Dicamba 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 loading content of Dicamba in TpPa-COF and TpBDMe-COF is 10.1% and 15.6%, respectively, which are lower than TpBD-COF. 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.

[0055] (5) The Zeta potential diagrams of β-ketoenamine COF and Dicamba@COF obtained in Examples 1 to 3 are shown in Figure 6 As shown. It can be seen that the potential of β-ketoenamine-COF is negative, but the potential increases after loading dicamba (Dicamba@COF), especially Dicamba@TpBD-COF, indicating that the interaction between dicamba and β-ketoenamine COF is strong. The schematic diagram of the interaction between dicamba and β-ketoenamine COF is shown in Figure 7 shown.

[0056] (6) In order to further study the interaction between Dicamba and β-ketoenamine COF, the present invention systematically characterized Dicamba@TpBD-COF and compared it with the original TpBD-COF. The XRD comparison of Dicamba@TpBD-COF and the original TpBD-COF is shown in Figure 2. Figure 8 As shown, the TEM comparison diagram is as follows Fig. 9 As shown in Figure 2, the particle size distribution of Dicamba@TpBD-COF is shown in Figure 2. Fig.10 As shown in the figure, 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 420nm remain unchanged. This shows that after loading Dicamba, the structure of TpBD-COF remains stable.

[0057] Comparison of nitrogen adsorption-desorption isotherms between Dicamba@TpBD-COF and pristine TpBD-COF Fig.11 As shown in the pore size distribution comparison diagram Fig.12 The mesostructure characteristics of Dicamba@TpBD-COF and original TpBD-COF are shown in Table 2.

[0058] Table 2 Mesoporous structures of Dicamba@TpBD-COF and TpBD-COF

[0059] It can be seen that after loading Dicamba, the BET surface area increased from 1767 m 2 / g reduced to 11.7m 2 / g, pore volume from 1.01 cm 3 / g reduced to 0.03cm 3 / g, the original mesopores of TpBD-COF (about 2.17 nm) also disappeared, indicating that the pores of TpBD-COF were filled with Dicamba (about 0.72 nm in size).

[0060] Comparison of Fourier transform infrared spectra of Dicamba@TpBD-COF and original TpBD-COF is shown in the figure below. Fig.13 As shown, the XPS spectra of Dicamba and Dicamba@TpBD-COF are as follows Fig.14 As shown in the figure, the comparison of O 1s XPS spectra is shown in Fig.15 As shown. The Fourier transform infrared (FT-IR) spectrum shows that at 61698cm -1 The tensile vibration is higher at 1722 cm -1 This may be due to the interaction between Dicamba and TpBD-COF, which destroys the intermolecular hydrogen bonds between Dicamba molecules. X-ray photoelectron spectroscopy (XPS) spectra show that the elemental composition of Dicamba@TpBD-COF (C, N, O, Cl) is a combination of Dicamba free acid (C, O and Cl) and TpBD-COF (C, N and O). More importantly, the XPS O 1s deconvolution results show that the peaks of 530.85eV and 532.35 eV, C=O and C-OH of DpBD-COF shifted to 531.13 eV and 533.48eV, indicating the formation of hydrogen bonds between the keto carbon group 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 shown in the figure. Fig.16 shown. Fig.16 In the reaction, there is a hydrogen bonding interaction between the keto carbonyl or enol group of TpBD-COF and the carboxyl hydrogen of dicamba.

[0061] (7) Zeta potential of TpBD-COF at different pH values Fig.17 As shown, it can be seen that the Zeta potential of TpBD-COF at different pH values ​​is positive under acidic conditions and negative under neutral and alkaline conditions, and it is easier to bind to dicamba under neutral and alkaline conditions.

[0062] Performance Testing (1) Thermogravimetric and volatility experiments The weight of the active ingredient of dicamba was measured and placed in a platinum pot at 60°C isothermal environment. After 24 hours, the dicamba free acid was dissolved in 10 mL of methanol. Dicamba@TpBD-COF was dispersed in 10 mL of methanol and ultrasonicated for 3 hours. The concentration of dicamba in the methanol solution was determined by high performance liquid chromatography. The volatilization 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.

[0063] The release curves of Dicamba@TpBD-COF at different pH values ​​(1.6, 7.0 and 10.0) are shown in Figure 2. Fig.18 shown. Fig.18 In the figure, 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 volatilization 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 both acidic and alkaline conditions. Among them, the structural evolution diagram of β-ketoenamine covalent organic framework materials under acidic and alkaline conditions is shown in the figure. Fig.19 As shown, Fig.19 The characteristics of β-ketoenamine covalent organic framework materials as amphoteric substances are shown.

[0064] In addition, the present invention also uses four kinetic models, namely zero-order, first-order, Higuchi and Ritger-Peppas, to fit the release data, thereby exploring the release kinetics. The results are shown in Table 3.

[0065] Table 3 Fitting parameters of Dicamba@TpBD-COF and four kinetic models at different pH values

[0066] It can be seen that the release behavior of Dicamba@TpBD-COF is consistent with the Ritger-Peppas model, with correlation coefficients of 0.9176, 0.9493 and 0.9184 at pH values ​​of 1.6, 7.0 and 10.0, respectively. Under the three pH conditions, the fitted diffusion constant (n) is less than 0.43, indicating that the diffusion mechanism of dicamba is Fickian diffusion, that is, the release of dicamba is mainly controlled by the concentration gradient.

[0067] The present invention compares the TG, DTG and volatility experiments of Dicamba@TpBD-COF with those of dicamba free acid. The experimental results show that dicamba free acid loses almost 100% weight at a temperature of 131~258°C. In contrast, the weight loss rate of Dicamba@TpBD-COF is 45%, and the starting temperature is relatively high, at 201~514°C. Combined with the TG and DTG results of Dicamba@TpBD-COF, it can be inferred that the weight loss of about 36% between 201~273°C is mainly caused by the loading of dicamba in TpBD-COF, while the weight loss of about 14% above 372°C should be caused by the decomposition of TpBD-COF. In addition, the volatility of Dicamba@TpBD-COF (37.5%) is much lower than that of dicamba free acid (88.1%). These results show that the TpBD-COF loading method can significantly reduce the volatility of dicamba. The reduction in the volatilization rate of dicamba is conducive to reducing its pollution and phytotoxicity to non-target areas and the environment.

[0068] (2) Soil leaching experiment In addition to the volatilization problem, the leaching and migration of dicamba in soil is another environmental risk. In order to evaluate the mobility of Dicamba@TpBD-COF in soil, the leaching amount and cumulative leaching rate of Dicamba@TpBD-COF and dicamba-free acid were tested in soils in Beijing and Sichuan Province, respectively. The specific methods are as follows.

[0069] Soil collected from Beijing and Sichuan provinces with a surface depth of 0-20 cm was air-dried and sieved to a particle size of less than 2 mm at 25°C. The treated soil was loaded into a plastic column 11.4 cm high and 2.8 cm in diameter 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. The sample was then eluted with deionized water and the eluate was collected. The dicamba leaching amount was determined by high performance liquid chromatography. The cumulative dicamba leaching amount 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 leachate at sampling time i, and m is the total amount of dicamba free acid applied. Each experiment was repeated three times.

[0070] Note: The soils in these two areas are silt loam and clay loam respectively. The physical and chemical properties of the two soils are shown in Table 4.

[0071] Table 4 Physical and chemical parameters of soils in Beijing and Sichuan

[0072] The leaching results of Dicamba@TpBD-COF and free acid Dicamba in different soils are shown in Figure 2. Fig. 20 As 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 dicamba leaching amount (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 dicamba free acid in Beijing soil and Sichuan soil were also different: under the same experimental conditions, dicamba moved slower in Sichuan soil than in Beijing soil, which may be caused by the silt and clay nature of Sichuan soil. In conclusion, Dicamba@TpBD-COF can retard the movement of dicamba in soil and reduce the leaching potential, thus protecting groundwater from dicamba contamination.

[0073] (3) Biological activity against target weeds The bioactivity experiment was conducted on the target weed Chenopodium album L. in a greenhouse. Fig.21 Photos are shown of dicamba seedlings treated with pure water (control sample), commercially available dicamba formulations, TpBD-COF, and Dicamba@TpBD-COF aqueous solutions three days after treatment, with the dicamba concentration being the same as the field application rate (480 mg / L). Fig.21 In the figure, a is a photo of the target weeds (14-day-old seedlings) after 3 days of treatment with samples of different dicamba active ingredients at 480 mg / L, and b is the reduction in fresh weight of weed seedlings after 7 days of treatment with Dicamba@TpBD-COF or commercially available dicamba preparations at different dicamba concentrations. Compared with the control group, the resveratrol sprayed with Dicamba@TpBD-COF and commercially available dicamba preparations showed deformation and warping. In addition, when the dicamba concentration was 240 mg / L, the fresh weight of weeds decreased by about 70% after 7 days of treatment with Dicamba@TpBD-COF, which was basically the same as the fresh weight reduction rate of weeds treated with commercially available dicamba preparations; when the dicamba concentration increased to 960 mg / L, the fresh weight reduction rate of weeds treated with Dicamba@TpBD-COF and the fresh weight reduction rate of weeds treated with commercially available dicamba preparations increased to about 80%. These results indicate that there is little difference in herbicidal efficacy between Dicamba@TpBD-COF and commercially available dicamba preparations.

[0074] (4) Biosafety assessment of non-target plants Dicamba is commonly used to control weeds in wheat fields. Therefore, wheat was selected as a non-target plant (Triticum aestivum L) for the biosafety assessment of Dicamba@TpBD-COF. The root length (RL), shoot height (SH), and fresh weight (FW) of the non-target plant seedlings were measured 14 days after the samples were treated with 480 mg / L of the active ingredient of dicamba. Fig. 22 As shown in a in .

[0075] 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 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.

[0076] In order to study the mechanism of this difference, the present invention uses chlorophyll fluorescence (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 technology, is widely used to study the photosynthetic physiological functions of different plants, and can directly reflect the interference factors that affect the photosynthetic apparatus and photosystem II (PS II) metabolism of plants. Specifically, Fv / Fm represents the photosynthetic performance under exogenous substances, which is the maximum quantum efficiency of PSII photochemistry measured under dark adaptation. The specific method is as follows: The dynamics of CF were measured using the MINI version of the Imaging PAM (Walz, Effeltrich, Germany). The modulation of the measuring light was performed using a blue LED to provide continuous light and saturation pulses. The Mini-Imaging PAM was covered with black paper to illuminate the leaves evenly. Illumination was either natural light or 204 µmol m -2 s -1 During the measurement, the fresh leaf area of ​​intact seedlings reached 2.4 × 3.2 cm. Seedlings were adapted to dark conditions for 30 min before measuring CF parameters. Five wheat seedlings were randomly selected for each treatment. CF parameters were calculated using Image-win software (Walz, Effeltrich, Germany).

[0077] Effects of different samples on photosynthesis of wheat seedlings Fig. 22As shown in b. The Fv / Fm values ​​based on different samples were all around 0.80, which is consistent with the previous research results on different plants without stress, indicating the reliability of this method in evaluating wheat photosynthesis. Y(PSII) is considered to record the actual quantum yield of photochemical energy conversion (ATP and NADPH) in PS II. The increase in Y(PSII) values ​​in seedlings treated with TpBD-COF and Dicamba@TpBD-COF may be related to the increase in stomatal conductance, which usually leads to an increase in the electron transfer efficiency and ATP / NADPH consumption of photosynthetic metabolism. In addition, the qP value representing the photochemical quenching coefficient of PSII also showed the same trend compared with Y(PSII). Therefore, the root length, shoot height and fresh weight of wheat seedlings treated with TpBD-COF / Dicamba@TpBD-COF were better than those treated with commercially available dicamba preparations, which may be due to the introduction of TpBD-COF to enhance plant photosynthesis. This means that the addition of dicamba to TpBD-COF can improve the biosafety of dicamba against non-target plants.

[0078] (5) Impact on soil microorganisms The application of herbicides may affect the health and function of soil, which can usually be detected through soil microbial communities. Therefore, the effects of TpBD-COF and Dicamba@TpBD-COF on the species and abundance of soil bacterial microorganisms were systematically investigated compared with commercially available dicamba preparations and pure water (control samples). The dilution curves of bacteria under different sample treatments are shown in Figure 2. Fig.23 As shown, it can be seen that the rarefaction curve of soil sequencing shows a rapid increase at the beginning and then plateaus as the sequencing amount increases, indicating that the sequencing depth meets the requirements.

[0079] The Sobs index represents the species richness within the sample community. The Sobs index was determined according to Illumina MiSeq sequencing, specifically: the purified amplicons were pooled in equimolar amounts and paired-end sequenced on the Illumina MiSeqPE300 platform / NovaSeqPE250 platform (Illumina, San Diego, USA) according to the standard protocol of Malliobio Biopharmaceutical Technology Co., Ltd. (Shanghai, China). The Sobs index in soil after different sample treatments was as follows: Fig.24 The community species richness of soils treated with TpBD-COF and Dicamba@TpBD-COF was higher than that of soils treated with commercially available dicamba formulations and pure water.

[0080] To further explore the effects of these samples on soil bacterial communities, the complexity of soil bacterial connections was analyzed using co-occurrence networks. Specifically, the soil microbial flora was analyzed using bioinformatics using the Majorbio Cloud Platform (https: / / cloud.majorbio.com). The results are shown in Fig.25 . Fig.25 In the figure, a is pure water, b is dicamba preparation purchased on the market, 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 indicates the bacterial phylum. Table 5 extracts the corresponding soil bacterial network graph topological index.

[0081] Table 5 Topological index of soil bacterial network graph under different treatment conditions

[0082] The results showed that compared with the control group, the average degree, average clustering coefficient and positive edge percentage of the commercially purchased dicamba preparation treatment decreased, and the average path distance and negative edge percentage increased. On the contrary, compared with the control group, the total number of chains, average degree, average clustering coefficient and positive edge percentage of the network treated with TpBD-COF and Dicamba@TpBD-COF increased, and the average path distance and negative edge percentage decreased. These results all indicate that there may be extensive interactions between bacteria in response to TpBD-COF and Dicamba@TpBD-COF, which may induce soil bacteria to form highly interconnected communities. In addition, Fig.25 As shown in the figure, the bacterial community network clustered into different proteobacteria groups, among which the proteobacteria group in the soil treated with Dicamba@TpBD-COF was the most correlated. Generally, proteobacteria are found in different environments, including tea gardens, forests, and farmlands, and they are closely related to soil nitrogen cycle, especially soil nitrogen fixation ability. This may be related to the high nitrogen content of TpBD-COF. In short, the addition of dicamba to TpBD-COF can alleviate the adverse effects of dicamba and even benefit soil bacterial microorganisms.

[0083] In summary, the present invention utilizes the hydrogen bonding effect of the carboxyl group of dicamba, introduces a series of β-ketoenamine covalent organic framework materials with large surface area and rich β-ketoamine groups, and utilizes the hydrogen bonding effect between the ketocarbonyl or enol of the β-ketoenamine covalent organic framework material and the carboxyl hydrogen of dicamba to construct a nanoherbicide. Compared with dicamba free acid, the Dicamba@TpBD-COF prepared by the present invention not only reduces the volatility by 50.62%, and the leaching possibility is also minimized, but also has a similar weed control effect on the weed Chenopodium Album L. compared with the dicamba preparation purchased on the market. In addition, both TpBD-COF and Dicamba@TpBD-COF show good biosafety to non-target wheat Triticum aestivum L., and even have some promoting effect on the growth and photosynthesis of wheat. The soil treated with Dicamba@TpBD-COF shows that the microbial community related to nitrogen fixation is more complex and more closely connected, which is conducive to plant growth. In conclusion, the addition of the herbicide dicamba to TpBD-COF greatly reduced the adverse effects on the environment while maintaining a high herbicidal efficiency and even improving the safety to non-target organisms. This work provides new ideas for the application of nano-COF in pesticide loading.

[0084] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection 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 includes one or more of TpPa-COF, TpBD-COF and TpBDMe-COF.

2. The nano-herbicide based on β-ketoenamine covalent organic framework material according to claim 1, characterized in that: The loading amount of dicamba in the nano herbicide based on the β-ketoenamine covalent organic framework material is 10.1-28.5%.

3. The nano-herbicide based on β-ketoenamine covalent organic framework material according to claim 1, characterized in that: The β-ketoenamine covalent organic framework material has a pore size of 2.17-3.0 nm and a specific surface area of ​​1261-1767 m 2 / g.

4. 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.

5. The method for preparing the nano-herbicide based on β-ketoenamine covalent organic framework material according to any one of claims 1 to 4, 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.

6. The preparation method according to claim 5, 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.

7. The preparation method according to claim 5, 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 p-phenylenediamine, benzidine or 4,4'-diamino-3,3'-dimethylbiphenyl.

8. The preparation method according to claim 7, 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.

9. Use of the nano-herbicide based on β-ketoenamine covalent organic skeleton material according to any one of claims 1 to 4 or the nano-herbicide based on β-ketoenamine covalent organic skeleton material prepared by the preparation method according to any one of claims 5 to 8 in weeding Gramineae plants.

10. The use according to claim 9, 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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