Trifluoromethyl-modified pyrene-based covalent organic framework materials, methods of making and applications thereof

Abstract

The application discloses a trifluoromethyl-modified pyrene-based covalent organic framework material, a preparation method and application thereof, and belongs to the field of new energy materials and photocatalysis technology. The structural characteristics of the trifluoromethyl-modified pyrene-based covalent organic framework material are that the imine bond position has a quinoline ring and a trifluoromethyl group formed by reaction, and the preparation process comprises the following steps: pyrene-based covalent organic framework material is prepared by one-step condensation reaction of an amino monomer and an aldehyde monomer; and the pyrene-based covalent organic framework material and a trifluoromethyl phenyl alkyne are connected by a Pawaroff reaction, so that a benzene ring structure is connected to the pyrene-based covalent organic framework material, and a trifluoromethyl functional group is introduced into the pore structure of the pyrene-based covalent organic framework material, thereby preparing the trifluoromethyl-modified pyrene-based covalent organic framework material. The material obtained by the application has photocatalytic activity, has the characteristics of good chemical stability, high catalytic activity, wide application range and the like, and can be applied to photocatalytic degradation of various organic pollutants, such as fluorine-containing pesticides.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials and photocatalytic degradation of pollutants, and particularly relates to a trifluoromethyl-modified pyrene covalent organic framework material, its preparation method and application. Background Technology

[0002] In recent years, with the development of agricultural technology, various fluorinated pesticides have become a new trend in the global pesticide industry due to their advantages such as high selectivity, high adaptability, high added value, and low cost. In the past decade, fluorinated pesticides account for about half of the more than 100 newly developed or recently patented chemical pesticides internationally, mainly including herbicides, insecticides, and fungicides. However, the excessive use of fluorinated pesticides has led to serious environmental pollution in water bodies, causing harm to human health and damaging ecosystems. Currently, the treatment of fluorinated pesticide wastewater mainly employs some traditional methods (such as membrane separation, ozone oxidation, or electrochemical oxidation), but these methods still have drawbacks such as incomplete degradation and high degradation costs.

[0003] Covalent organic frameworks (COFs), as a novel type of crystalline porous organic polymer, possess highly ordered pore sizes and designable tunable pore structures. Due to their significant intrinsic properties, such as excellent chemical stability, high surface area, abundant functional sites, and uniform and tunable pore sizes, COFs are finding increasingly widespread applications in semiconductors, sensing, adsorption, membrane separation, energy storage, and heterogeneous catalysis. Patent CN112608490A discloses a thioether-functionalized pyrene-based covalent organic framework material, its preparation method, and its applications. Specifically, 2,5-bis(2-(ethylthio)ethoxy)terephthalohydrazide and 1,3,6,8-tetra-(p-aldehydephenyl)-pyrene are added to a solvent system to react and prepare the thioether-functionalized pyrene-based covalent organic framework material. The pyrene-based covalent organic framework material prepared by this patented technology exhibits good response to visible light and has good potential application value in the field of photocatalytic water splitting for hydrogen production.

[0004] However, the thioether-functionalized pyrene covalent organic framework materials disclosed in the above patents are prepared by a traditional one-step condensation reaction. The low degree of conjugation results in poor chemical stability, easy decomposition and loss of photocatalytic activity, thus affecting the recycling rate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to overcome the problem that COFs prepared by existing COFs preparation methods have poor chemical stability due to low conjugation. This invention proposes a trifluoromethyl-modified pyrene covalent organic framework material with higher chemical stability, higher catalytic activity, and wider applicability, which can effectively remove fluoride-containing pesticide pollutants from water, along with its preparation method and applications.

[0006] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a trifluoromethyl-modified pyrene covalent organic framework material, the structural formula of which is shown below:

[0008]

[0009] In the formula, R1 is a functional group of H, OH or OCH3, and R2 is a trifluoromethylphenyl alkynylene.

[0010] Another aspect of the present invention provides a method for preparing a trifluoromethyl-modified pyrene covalent organic framework material, comprising: a pyrene covalent organic framework material preparation step, and a trifluoromethyl-modified pyrene covalent organic framework material preparation step; the pyrene covalent organic framework material preparation step comprises: an amino monomer and an aldehyde monomer undergoing a one-step condensation reaction to prepare a pyrene covalent organic framework material; the trifluoromethyl-modified pyrene covalent organic framework material preparation step comprises: the pyrene covalent organic framework material and a trifluoromethylphenyl alkyne undergoing a Povarov reaction to attach a benzene ring structure to the pyrene covalent organic framework material, and simultaneously introducing a trifluoromethyl functional group into the pore structure of the pyrene covalent organic framework material to prepare a trifluoromethyl-modified pyrene covalent organic framework material.

[0011] Preferably, the molar ratio of the pyrene-based covalent organic framework material to the trifluoromethylphenyl acetyne is 1:1.5-3.5.

[0012] Preferably, the trifluoromethylphenylacetylene is trifluoromethylphenylacetylene; the trifluoromethylphenylacetylene is selected from at least one of 3,5-bistrifluoromethylphenylacetylene, 2-trifluoromethylphenylacetylene, 3-trifluoromethylphenylacetylene or 4-trifluoromethylphenylacetylene.

[0013] Preferably, the preparation steps of the trifluoromethyl-modified pyrene covalent organic framework material specifically include: mixing the pyrene covalent organic framework material, the trifluoromethylphenyl alkyne, an organic solvent, a catalyst, and a dehydrogenating agent, and carrying out a solvothermal reaction to obtain the trifluoromethyl-modified pyrene covalent organic framework material; the organic solvent is benzene or an alkyl-substituted benzene compound (preferably benzene, toluene, xylene, or mesitylene); the catalyst is aluminum trichloride, trifluoroacetic acid, trifluoromethanesulfonic acid, or boron trifluoride ether; and the dehydrogenating agent is isopropanol, tetrachlorobenzoquinone, or ethylbenzene.

[0014] Preferably, the solvothermal reaction is carried out at a temperature of 90-150°C for 2-7 days.

[0015] Preferably, the pyrene-based covalent organic framework material, the trifluoromethylphenyl acetyne, the organic solvent, the catalyst, and the dehydrogenating agent are mixed, and the mixed solution is sealed under an inert atmosphere to carry out a solvothermal reaction.

[0016] Preferably, the solvothermal reaction further includes: washing the reaction product with at least one of methanol, dichloromethane, saturated sodium bicarbonate aqueous solution, tetrahydrofuran, N,N-dimethylformamide and acetone, centrifuging, and then drying it under vacuum at a drying temperature of 60-100℃ for 6-12 hours.

[0017] Preferably, the amino monomer is 4,4',4”,4”'-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine, and the aldehyde monomer is selected from any one of terephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 4,4'-biphenyl dicarboxaldehyde, 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde, 3,3'-dimethoxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde, [1,1':4',1”-terphenyl]-4,4”-dicarboxaldehyde, and 2,5-dimethoxy-[1,1':4',1”-terphenyl]-4,4”-dicarboxaldehyde.

[0018] This invention also provides an application of the above-mentioned trifluoromethyl-modified pyrene covalent organic framework material in the photocatalytic degradation of fluoride-containing pesticides in water.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention provides a trifluoromethyl-modified pyrene covalent organic framework material, which not only maintains the characteristics of high crystallinity and high specific surface area, but also, due to the FF effect of trifluoromethyl and its strong hydrophobicity, can interact well with pollutants, rapidly and selectively adsorbing organic pollutants such as fluorinated pesticides and photocatalytically degrading them. It has the characteristics of strong chemical stability and high catalytic activity. In this trifluoromethyl-modified pyrene covalent organic framework material, the planar pyrene units give the pyrene covalent organic framework a certain planar structure. The fluorination of trifluoromethyl further enhances the planarity of the pyrene covalent organic framework. Better AA stacking enhances the π-π interaction force between the covalent organic framework layers, improves crystallinity, effectively promotes the migration of photogenerated carriers, and greatly improves the photocatalytic effect.

[0021] This invention provides a method for preparing trifluoromethyl-modified pyrene covalent organic framework materials. Through the Povarov reaction, a new benzene ring structure is connected to the pyrene covalent organic framework material (pyrene COFs). This enhances the cycloaddition conjugation effect of the pyrene COFs, thereby improving the chemical stability of the material. Simultaneously, while maintaining the high crystallinity and high specific surface area of ​​the pyrene COFs, the method introduces trifluoromethyl functional groups of adjustable number and position into the pore structure of the pyrene COFs. This method features simple processing conditions, convenient operation, and is conducive to large-scale production.

[0022] This invention also provides the application of trifluoromethyl-modified pyrene covalent organic framework material in the photocatalytic degradation of fluoride-containing pesticides in water. It has the advantages of good degradation effect, convenient operation, low cost, recyclability, and no secondary pollution. It is a widely applicable method that can efficiently remove fluoride-containing pesticide pollutants from water, and has high application and commercial value. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the reaction process for preparing the trifluoromethyl-modified pyrene covalent organic framework material CF3-COF-1 obtained in Example 1 of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of CF3-COF-1 obtained in Example 1 of the present invention;

[0025] Figure 3 The X-ray powder diffraction pattern of CF3-COF-1 obtained in Example 1 of this invention;

[0026] Figure 4 The Fourier transform infrared spectrum of CF3-COF-1 obtained in Example 1 of this invention;

[0027] Figure 5 The image shows the solid-state ultraviolet absorption spectrum of CF3-COF-1 obtained in Example 1 of this invention.

[0028] Figure 6 Thermogravimetric analysis of CF3-COF-1 obtained in Example 1 of this invention;

[0029] Figure 7 This is a schematic diagram illustrating the degradation efficiency of CF3-COF-1 obtained in Example 1 of the present invention on fipronil after four repeated uses. Detailed Implementation

[0030] The technical solutions in specific embodiments of the present invention will now be described in detail and completely with reference to the accompanying drawings. Obviously, the described embodiments are merely some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0031] This invention provides a trifluoromethyl-modified pyrene covalent organic framework material, the structural formula of which is shown below:

[0032]

[0033] In the formula, R1 is a H, OH, or OCH3 functional group, and R2 is a trifluoromethylphenylacetylene. This trifluoromethyl-modified pyrene-based covalent organic framework material not only maintains high crystallinity and high specific surface area, but also, due to the FF effect of trifluoromethyl groups and their strong hydrophobicity, it can interact well with pollutants, rapidly and selectively adsorbing and photocatalytically degrading organic pollutants such as fluorinated pesticides. It exhibits strong chemical stability and high catalytic activity. In this trifluoromethyl-modified pyrene-based covalent organic framework material, the planar pyrene units give the pyrene-based covalent organic framework a certain planar structure. The fluorination of trifluoromethyl groups further enhances the planarity of the pyrene-based covalent organic framework. Better AA stacking strengthens the interlayer π-π interaction force of the covalent organic framework, improves crystallinity, effectively promotes the migration of photogenerated carriers, and greatly enhances the photocatalytic effect.

[0034] Another aspect of this invention provides a method for preparing a trifluoromethyl-modified pyrene covalent organic framework material, comprising: a pyrene covalent organic framework material preparation step, and a trifluoromethyl-modified pyrene covalent organic framework material preparation step; the pyrene covalent organic framework material preparation step includes: an amino monomer and an aldehyde monomer undergoing a one-step condensation reaction to prepare a pyrene covalent organic framework material; the trifluoromethyl-modified pyrene covalent organic framework material preparation step includes: the pyrene covalent organic framework material and a trifluoromethylphenyl alkyne undergoing a Povarov reaction to attach a benzene ring structure to the pyrene covalent organic framework material, while simultaneously introducing a trifluoromethyl functional group into the pore structure of the pyrene covalent organic framework material, thereby preparing a trifluoromethyl-modified pyrene covalent organic framework material. This method differs from existing one-step condensation reaction-prepared COFs, instead first using a one-step condensation reaction to prepare pyrene COFs, and then using the pyrene COFs as reactants, such as... Figure 1As shown, a new benzene ring structure is connected to a pyrene-based covalent organic framework (pyrene COFs) using the Povarov reaction. This enhances the cycloaddition conjugation effect of the pyrene COFs, thereby improving the chemical stability of the material. Simultaneously, while maintaining the high crystallinity and high specific surface area of ​​the pyrene COFs, trifluoromethyl functional groups of adjustable number and position are introduced into the pore structure of the pyrene COFs. Specifically, the selection of the R group in the trifluoromethyl-modified pyrene-based covalent organic framework prepared in this invention is as follows:

[0035]

[0036] Compared with conventional solvothermal synthesis methods carried out in Pyrex tubes, the above-mentioned preparation method of the present invention can be used for large-scale preparation in flasks, while avoiding the harsh vacuum conditions in conventional synthesis methods. It can be synthesized under any inert atmosphere, and has the characteristics of simple process conditions, convenient operation, and advantages for large-scale production.

[0037] In a preferred embodiment, the molar ratio of the pyrene-based covalent organic framework material to the trifluoromethylphenylacetylene is 1:1.5-3.5. This embodiment specifically limits the molar ratio of the pyrene-based covalent organic framework material to the trifluoromethylphenylacetylene because too little trifluoromethylphenylacetylene leads to incomplete trifluoromethyl grafting in the COF pore structure, affecting the catalytic effect; while excessive trifluoromethylphenylacetylene affects the solvent components in the reaction process, leading to a decrease in the crystallinity of the COF. It is understood that this molar ratio can also be any value within the range of 1:2.0, 1:2.5, 1:3.0, etc. Preferably, the molar ratio is 1:2.5.

[0038] In a preferred embodiment, the trifluoromethylphenylacetylene is trifluoromethylphenylacetylene; the trifluoromethylphenylacetylene is selected from at least one of 3,5-bistrifluoromethylphenylacetylene, 2-trifluoromethylphenylacetylene, 3-trifluoromethylphenylacetylene, or 4-trifluoromethylphenylacetylene. This embodiment specifically defines the trifluoromethylphenylacetylene as trifluoromethylphenylacetylene because its high electron-rich structure is beneficial for promoting the reaction.

[0039] In a preferred embodiment, the preparation steps of the trifluoromethyl-modified pyrene covalent organic framework material specifically include: mixing the pyrene covalent organic framework material, the trifluoromethylphenyl alkyne, an organic solvent, a catalyst, and a dehydrogenating agent, and performing a solvothermal reaction to obtain the trifluoromethyl-modified pyrene covalent organic framework; the organic solvent is benzene or an alkyl-substituted benzene compound (preferably benzene, followed by toluene, xylene, or mesitylene); the catalyst is aluminum trichloride, trifluoroacetic acid, trifluoromethanesulfonic acid, or boron trifluoride ether; and the dehydrogenating agent is isopropanol, tetrachlorobenzoquinone, or ethylbenzene. In this solvothermal reaction, by limiting the types of organic solvent, catalyst, and dehydrogenating agent, the pyrene covalent organic framework material and the trifluoromethylphenyl alkyne undergo a Povarov reaction, which is a cycloaddition reaction between the aryl imine in the COF structure and the electron-rich alkyne. Based on pyrene-based covalent organic framework materials (pyrene-based COFs), new benzene ring structures are connected to enhance the chemical stability of the material by strengthening the cycloaddition conjugation effect of pyrene-based COFs. At the same time, while maintaining the high crystallinity and high specific surface area of ​​pyrene-based COFs, trifluoromethyl functional groups with adjustable number and position are introduced into the pore structure of pyrene-based COFs.

[0040] In a preferred embodiment, the solvothermal reaction is carried out at a temperature of 90-150°C for 2-7 days. More preferably, the solvothermal reaction is carried out at a temperature of 100-120°C for 3-5 days.

[0041] In a preferred embodiment, the pyrene-based covalent organic framework material, the trifluoromethylphenylacetylene, an organic solvent, a catalyst, and a dehydrogenating agent are mixed, and the mixed solution is sealed under an inert atmosphere to carry out a solvothermal reaction. This embodiment specifically limits the solvothermal reaction to be carried out under inert gas protection, rather than under harsh vacuum conditions, because the Povarov reaction can be carried out without a vacuum environment.

[0042] In a preferred embodiment, the solvothermal reaction further includes washing the reaction product with at least one of methanol, dichloromethane, saturated sodium bicarbonate aqueous solution, tetrahydrofuran, N,N-dimethylformamide and acetone, centrifuging, and then drying it under vacuum at a drying temperature of 60-100°C for 6-12 hours.

[0043] In a preferred embodiment, the amino monomer is 4,4',4”,4”'-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine, and the aldehyde monomer is selected from any one of terephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 4,4'-biphenyl dicarboxaldehyde, 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde, 3,3'-dimethoxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde, [1,1':4',1”-terphenyl]-4,4”-dicarboxaldehyde, and 2,5-dimethoxy-[1,1':4',1”-terphenyl]-4,4”-dicarboxaldehyde. In the preparation of pyrene-based covalent organic framework materials, the amino monomer 4,4',4”,4”'-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine (PyTTA), the aldehyde monomer 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTA), an organic solvent, and an acid catalyst are mixed and subjected to a solvothermal reaction to obtain the pyrene-based covalent organic framework material. Preferably, the molar ratio of the two monomers, 4,4',4”,4”'-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine (PyTTA) and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTA), is 1:(1.5-2.5), and more preferably 1:(1.9-2.1). Preferably, the organic solvent is a mixed solvent of o-dichlorobenzene and n-butanol, or a mixed solvent of 1,4-dioxane and mesitylene, or one of the above solvents; the catalyst is acetic acid or trifluoroacetic acid; more preferably, the organic solvent is a mixed solvent of o-dichlorobenzene and n-butanol, the acid catalyst is acetic acid, and the volume ratio of o-dichlorobenzene to n-butanol to acetic acid is 5:5:1. Preferably, the solvothermal reaction temperature is 100-150℃, and the reaction time is 3-7 days; more preferably, the solvothermal reaction temperature is 110-130℃, and the reaction time is 3-5 days. Preferably, the mixing process further includes the following treatment: the mixed solution is subjected to a freeze-pump-thaw cycle for degassing, repeated three times, and then vacuum sealed. Preferably, the solvothermal reaction further includes the following treatment: the reaction product is washed and dried; the washing is performed by centrifugation with acetone and tetrahydrofuran 3-5 times respectively; the drying is carried out under vacuum conditions; the drying temperature is 60-100℃; and the drying time is 8-12 hours.

[0044] This invention also provides an application of the above-mentioned trifluoromethyl-modified pyrene covalent organic framework material in the photocatalytic degradation of fluoride-containing pesticides in water. It should be noted that the main reasons limiting the application of existing COFs in the photocatalytic degradation of fluoride-containing pesticide pollutants in water are: 1) The chemical stability of COFs is a major factor restricting their application. Specifically, for most imine COFs, the reversible imine bonds are unstable in practical applications and may decompose in extreme environments such as strong acids, strong alkalis, and strong oxidants during photocatalytic degradation, resulting in low reusability; 2) Fluoride-containing pesticide pollutants often have high thermal stability and high chemical stability, and can exist stably in water for a long time, requiring high catalytic activity from the photocatalyst. This invention improves the preparation method of COFs to prepare a trifluoromethyl-modified pyrene covalent organic framework with strong chemical stability and high catalytic activity. When applied to the photocatalytic degradation of fluoride-containing pesticides in water, it has the advantages of good degradation effect, convenient operation, low cost, recyclability, and no secondary pollution. It is a widely applicable method that can efficiently remove fluoride-containing pesticide pollutants from water, and has high application and commercial value.

[0045] The application of the above-mentioned trifluoromethyl-modified pyrene covalent organic framework material in the photocatalytic degradation of fluoride-containing pesticides in water specifically includes the following steps: mixing the trifluoromethyl-modified pyrene covalent organic framework as a photocatalyst with fluoride-containing pesticide wastewater, stirring, and carrying out a photocatalytic reaction under light conditions to complete the degradation of fluoride-containing pesticides in the water. Preferably, the ratio of the trifluoromethyl-modified pyrene covalent organic framework to the fluoride-containing pesticide wastewater is (0.1-0.2) g: 1 L; the fluoride-containing pesticide wastewater is prepared with anhydrous methanol and deionized water at a volume ratio of 1:9. Preferably, the initial concentration of fluoride-containing pesticides in the fluoride-containing pesticide wastewater is 10-20 mg / L; the initial pH value of the fluoride-containing pesticide wastewater is 3-11; and the fluoride-containing pesticide pollutant in the fluoride-containing pesticide wastewater is at least one of trifluralin, fipronil, fluazinam, pyrifluquinazon, and bromuconazole. Preferably, the stirring is carried out in a dark room environment, the stirring time is 0.5-3 hours, and the photocatalytic reaction time is ≥1 hour.

[0046] To more clearly and in detail introduce the trifluoromethyl-modified pyrene covalent organic framework material, its preparation method and application provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0047] Example 1

[0048] A trifluoromethyl-modified pyrene covalent organic framework material, the preparation method of which is as follows: Figure 1 As shown, it is prepared by the following method:

[0049] Preparation steps of unmodified COF-1:

[0050] 4,4',4”,4”'-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine (67.8 mg, 0.12 mmol) and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (46.4 mg, 0.24 mmol) were added to a 6.6 mL mixture of o-dichlorobenzene, n-butanol, and 6M acetic acid in a volume ratio of 5:5:1. The mixture was then placed in a 30 mL vacuum thick-walled glass tube and sonicated for 5 min to ensure homogeneity. The vacuum thick-walled glass tube was subjected to three cycles of liquid nitrogen freezing-pumping-thawing and then vacuum-sealed. The tube was then placed in an oil bath at 120 °C for 3 days. After the reaction, the resulting sample was centrifuged three times with acetone and tetrahydrofuran, and dried in a vacuum oven at 80 °C for 12 h to obtain red powder COF-1 in 91% yield.

[0051] CF 3- COF-1 post-modification steps:

[0052] COF-1 (100 mg), tetrachlorobenzoquinone (200 mg, 0.75 mmol), 3,5-bis(trifluoromethylphenylacetylene) (220 μL, 1.25 mmol), and boron trifluoride ether (100 μL, 0.75 mmol) were added to toluene (25 mL) and placed in a 50 mL flask. The mixture was sonicated for 5 min to ensure homogeneity. The 50 mL flask was sealed under an inert atmosphere and reacted in an oil bath at 110 °C for 3 days. After the reaction was complete, the resulting sample was centrifuged three times with saturated sodium bicarbonate aqueous solution and tetrahydrofuran, respectively, and dried in a vacuum oven at 80 °C for 12 h to obtain red powder CF in 94% yield. 3- COF-1.

[0053] Structural characterization and performance test results:

[0054] like Figure 2 As shown, the prepared CF 3- COF-1 exhibits bulk crystals composed of layered and sheet-like structures with a wavelength of approximately 40 nm to 100 nm. The COF-1 prepared in Example 1... 3- COF-1 was subjected to X-ray powder diffraction testing, and the results are as follows: Figure 3 As shown, CF 3- The X-ray powder diffraction pattern of COF-1 showed good peak shapes at 3.8°, 5.8°, 9.4°, 15.3°, and 23.3°, corresponding to the (110), (200), (220), (330), and (001) crystal planes, respectively. This peak shape matches the most stable AA packing mode in the structural simulation. The COF-1 prepared in Example 1... 3- Fourier transform infrared spectroscopy was performed on COF-1, and the results are as follows: Figure 4 As shown, CF 3-Fourier transform infrared spectroscopy of COF-1 shows that at 1624 cm⁻¹... -1 The stretching vibration of the C=N bond at 1300 cm⁻¹ indicates the formation of an imine functional group. -1 The presence of stretching vibrations of the CF bond indicates successful post-modification of the CF3 functional group. The CF3 prepared in Example 1 was then used... 3- COF-1 was subjected to solid-state ultraviolet absorption spectroscopy testing, and the test results are as follows: Figure 5 As shown, CF 3- The solid-state UV absorption spectrum of COF-1 shows that it has a wide visible light absorption range, exhibiting strong visible light utilization and photocatalytic activity. The COF-1 prepared in Example 1... 3- COF-1 underwent thermogravimetric analysis, and the test results are as follows: Figure 6 As shown, CF 3- COF-1 has a thermal decomposition temperature of approximately 440℃, demonstrating extremely high stability.

[0055] Example 2

[0056] Preparation steps of unmodified COF-2:

[0057] 4,4',4”,4”'-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine (67.8 mg, 0.12 mmol) and terephthalaldehyde (32.2 mg, 0.24 mmol) were added to a 6.6 mL mixture of o-dichlorobenzene, n-butanol, and 6M acetic acid in a volume ratio of 5:5:1. The mixture was then placed in a 30 mL vacuum thick-walled glass tube and sonicated for 5 min to ensure homogeneity. The vacuum thick-walled glass tube was subjected to three cycles of liquid nitrogen freezing-pumping-thawing and then vacuum-sealed. The tube was then placed in a 120 °C oil bath for 3 days. After the reaction, the resulting sample was centrifuged three times with acetone and tetrahydrofuran, and dried in a vacuum oven at 80 °C for 12 h to obtain a yellow powder COF-2 in 92% yield.

[0058] CF 3- COF-2 post-modification steps:

[0059] COF-2 (100 mg), tetrachlorobenzoquinone (200 mg, 0.75 mmol), 3,5-bis(trifluoromethyl)phenylacetylene (220 μL, 1.25 mmol), and boron trifluoride ether (100 μL, 0.75 mmol) were added to toluene (25 mL) and placed in a 50 mL flask. The mixture was sonicated for 5 min to ensure homogeneity. The 50 mL flask was sealed under an inert atmosphere and reacted in an oil bath at 110 °C for 3 days. After the reaction was complete, the resulting sample was centrifuged three times with saturated sodium bicarbonate aqueous solution and tetrahydrofuran, respectively, and dried in a vacuum oven at 80 °C for 12 h to obtain a reddish-brown powder CF in 91% yield. 3-COF-2.

[0060] Structural characterization and performance test results:

[0061] The prepared CF 3- COF-2 exhibits similar morphological characteristics to Example 1, as well as high crystallinity, wide visible light absorption capacity, and high stability.

[0062] Example 3

[0063] Preparation steps of unmodified COF-3:

[0064] 4,4',4”,4”'-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine (67.8 mg, 0.12 mmol) and 2,5-dimethoxy-[1,1':4',1”-terphenyl]-4,4”-dicarboxaldehyde (83.1 mg, 0.24 mmol) were added to a 6.6 mL mixture of o-dichlorobenzene, n-butanol, and 6M acetic acid in a volume ratio of 5:5:1. The mixture was then placed in a 30 mL vacuum thick-walled glass tube and sonicated for 5 min to ensure homogeneity. The vacuum thick-walled glass tube was subjected to three cycles of liquid nitrogen freezing-pumping-thawing and then vacuum-sealed. The tube was then placed in a 120 °C oil bath for 3 days. After the reaction, the resulting sample was centrifuged three times with acetone and tetrahydrofuran, and dried in a vacuum oven at 80 °C for 12 h to obtain a deep yellow powder COF-3 in 85% yield.

[0065] CF 3- COF-3 post-modification steps:

[0066] COF-3 (100 mg), tetrachlorobenzoquinone (200 mg, 0.75 mmol), 3,5-bis(trifluoromethyl)phenylacetylene (220 μL, 1.25 mmol), and boron trifluoride ether (100 μL, 0.75 mmol) were added to toluene (25 mL) and placed in a 50 mL flask. The mixture was sonicated for 5 min to ensure homogeneity. The 50 mL flask was sealed under an inert atmosphere and reacted in an oil bath at 110 °C for 3 days. After the reaction was complete, the resulting sample was centrifuged three times with saturated sodium bicarbonate aqueous solution and tetrahydrofuran, respectively, and dried in a vacuum oven at 80 °C for 12 h to obtain a reddish-brown powder CF in 87% yield. 3- COF-3.

[0067] Structural characterization and performance test results:

[0068] The prepared CF 3- COF-3 exhibits similar morphological characteristics to Example 1, as well as high crystallinity, wide visible light absorption capacity, and high stability.

[0069] Comparative Example 1

[0070] The preparation steps for unmodified COF-1 are the same as in Example 1.

[0071] Structural characterization and performance test results:

[0072] The prepared COF-1 exhibits a bulk crystal structure consisting of layered and sheet-like deposits with a wavelength of approximately 40 nm to 100 nm. The X-ray powder diffraction pattern of COF-1 shows good peak shapes at 3.8°, 5.9°, 7.8°, 9.6°, and 23.3°, corresponding to the (110), (200), (220), (330), and (001) crystal planes, respectively. This peak shape matches the most stable AA packing mode simulated in the structure simulation. The Fourier transform infrared spectrum of COF-1 shows a peak shape at 1624 cm⁻¹. -1 The presence of C=N bond stretching vibrations indicates the formation of an imine functional group. The solid-state UV absorption spectrum of COF-1 shows a wide visible light absorption range, demonstrating strong visible light utilization and photocatalytic activity. COF-1 has a thermal decomposition temperature of approximately 400℃.

[0073] Performance testing

[0074] The CF prepared in Example 1 3- COF-1 is used in the photocatalytic degradation of fluoride-containing pesticides in water, as detailed below.

[0075] 5 mg of CF prepared in Example 1 3- COF-1 was used as a photocatalyst and suspended in 50 ml of an aqueous solution (prepared as ultrapure water: methanol 1:9) containing 40 mg / L fipronil. The solution was stirred for 30 min in the dark to allow COF-1 to react with the photocatalyst. 3- COF-1 was uniformly dispersed in solution and subjected to photocatalytic degradation for 1 hour under visible light (≥420 nm) irradiation. The remaining fipronil content in the solution was detected by ultraviolet absorption spectroscopy. The ultraviolet absorption spectrum showed that COF-1... 3- COF-1 exhibited a degradation rate of up to 84.8% for fipronil under visible light photocatalysis for 1 hour. The COF-1 residues were washed with anhydrous ethanol and ultrapure water after the reaction by vacuum filtration. 3- COF-1 was dried in a vacuum oven at 80℃ for 12 hours, and the above-mentioned photocatalytic degradation experiment of fluoride-containing pesticides in water was repeated four times to test its recyclability. Figure 7 As shown, CF 3- COF-1 maintained a degradation rate of over 80% for fipronil even after four repeated applications.

[0076] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of trifluoromethyl-modified pyrene covalent organic framework materials in the photocatalytic degradation of fipronil in water, characterized in that: The structural formula of the trifluoromethyl-modified pyrene covalent organic framework material is shown below: In the formula, R1 is a functional group of H, OH or OCH3, and R2 is a trifluoromethylphenyl group.

2. The application according to claim 1, characterized in that, The preparation method of trifluoromethyl-modified pyrene covalent organic framework material includes: pyrene covalent organic framework material preparation steps, and trifluoromethyl-modified pyrene covalent organic framework material preparation steps; The preparation steps of the pyrene-based covalent organic framework material include: preparing the pyrene-based covalent organic framework material by a one-step condensation reaction of an amino monomer and an aldehyde monomer; The preparation steps of the trifluoromethyl-modified pyrene covalent organic framework material include: the pyrene covalent organic framework material and trifluoromethylphenyl alkyne are subjected to a Povarov reaction to connect a benzene ring structure to the pyrene covalent organic framework material, and at the same time, trifluoromethyl functional groups are introduced into the pore structure of the pyrene covalent organic framework material to prepare the trifluoromethyl-modified pyrene covalent organic framework material.

3. The application according to claim 2, characterized in that, The molar ratio of the pyrene-based covalent organic framework material to the trifluoromethylphenyl acetyne is 1:1.5-3.

5.

4. The application according to claim 2, characterized in that, The trifluoromethylphenylacetylene is trifluoromethylphenylacetylene; the trifluoromethylphenylacetylene is selected from at least one of 3,5-bistrifluoromethylphenylacetylene, 2-trifluoromethylphenylacetylene, 3-trifluoromethylphenylacetylene or 4-trifluoromethylphenylacetylene.

5. The application according to claim 2, characterized in that, The preparation steps of the trifluoromethyl-modified pyrene covalent organic framework material specifically include: mixing the pyrene covalent organic framework material, the trifluoromethylphenyl alkyne, an organic solvent, a catalyst, and a dehydrogenating agent, and carrying out a solvothermal reaction to obtain the trifluoromethyl-modified pyrene covalent organic framework; the organic solvent is benzene or an alkyl-substituted benzene compound; the catalyst is aluminum trichloride, trifluoroacetic acid, trifluoromethanesulfonic acid, or boron trifluoride ether; and the dehydrogenating agent is isopropanol, tetrachlorobenzoquinone, or ethylbenzene.

6. The application according to claim 5, characterized in that, The solvothermal reaction is carried out at a temperature of 90-150ºC for 2-7 days.

7. The application according to claim 5, characterized in that, The pyrene-based covalent organic framework material, the trifluoromethylphenyl acetyne, the organic solvent, the catalyst, and the dehydrogenating agent are mixed, and the mixed solution is sealed under an inert atmosphere to carry out a solvothermal reaction.

8. The application according to claim 5, characterized in that, The solvothermal reaction further includes washing the reaction product with at least one of methanol, dichloromethane, saturated sodium bicarbonate aqueous solution, tetrahydrofuran, N,N-dimethylformamide and acetone, centrifuging, and then drying it under vacuum at a drying temperature of 60-100 ºC for 6-12 h.

9. The application according to claim 2, characterized in that, The amino monomer is 4,4',4'',4'''-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine, and the aldehyde monomer is selected from any one of terephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, and 2,5-dihydroxyterephthalaldehyde.

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