A carvacol-loaded covalent organic framework composite photocatalyst and a preparation method and application thereof

Abstract

The application discloses a carvacol-loaded covalent organic framework composite photocatalyst and a preparation method and application thereof, and belongs to the technical field of photocatalysis. The catalyst is prepared by introducing carvacol into a covalent organic framework through an impregnation method. Under visible light irradiation, the composite catalyst has a hydrogen peroxide synthesis yield of up to 7681 μmol·g ‑1 ·h ‑1 in pure water, and can directly utilize in-situ generated hydrogen peroxide to achieve efficient inactivation of escherichia coli in water bodies without adding any exogenous iron ions, and can completely kill in 75 min. The carvacol is first compounded with the covalent organic framework as an electron transfer medium in the application, which significantly improves the photogenerated carrier separation efficiency and photocatalytic performance, and has the advantages of high efficiency, greenness and simple process, and provides a novel integrated solution for photocatalytic preparation of hydrogen peroxide and water body disinfection.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a carvacrol-supported covalent organic framework composite photocatalyst, its preparation method, and its application. Background Technology

[0002] Bacterial infections caused by waterborne pathogens have seriously threatened human health, making the development of efficient and environmentally friendly new water disinfection technologies crucial. Hydrogen peroxide (H2O2), as a green disinfectant, decomposes only into water, making it environmentally friendly and showing great potential in sterilization. However, current large-scale production of hydrogen peroxide mainly relies on the energy-intensive and polluting anthraquinone process. Therefore, developing green and sustainable hydrogen peroxide preparation methods has become a key research focus.

[0003] Photocatalysis, utilizing clean solar energy to drive chemical reactions, has shown great potential in environmental purification and energy conversion. Particularly in water disinfection, photocatalysis can efficiently inactivate pathogenic microorganisms by generating reactive oxygen species such as hydrogen peroxide, and is considered a green solution that can replace traditional disinfection processes such as chlorination and ozone. However, the practical application of this technology still faces several key bottlenecks.

[0004] First, traditional semiconductor photocatalysts (such as TiO2 and ZnO) generally suffer from weak visible light absorption and rapid recombination rates of photogenerated carriers, resulting in low light energy utilization efficiency and limited hydrogen peroxide yield, making it difficult to meet the requirements for efficient sterilization. In recent years, covalent organic frameworks (COFs) have become a research hotspot in the field of photocatalysis due to their designable pore structures, high specific surface area, and excellent visible light response characteristics. Through reasonable structural design, the photogenerated charge separation efficiency of COFs materials has been significantly improved, providing the possibility for optimizing basic photocatalytic performance. However, even with high-performance COFs materials, the concentration of hydrogen peroxide generated in situ during the photocatalytic process is often insufficient to achieve rapid and thorough microbial inactivation. Therefore, existing technologies typically introduce Fenton or Fenton-like reaction systems for enhancement, i.e., adding ferrous ions (Fe2+) to the system. 2+ Transition metals such as hydrogen peroxide (H₂O) react with photocatalyst-generated hydrogen peroxide to produce more potent hydroxyl radicals. While this strategy effectively increases the sterilization rate, the addition of exogenous metal ions increases the number of treatment steps and reagent costs. Secondly, residual iron ions may cause secondary pollution of water bodies, requiring subsequent removal. Finally, the presence of metal ions may also adversely affect the stability of the photocatalyst itself. Therefore, developing an integrated technology that achieves high-concentration in-situ generation of hydrogen peroxide and efficient sterilization solely through the photocatalyst itself without the need for exogenous additives has become a pressing challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing photocatalytic systems, such as low visible light utilization, rapid recombination of photogenerated carriers, and reliance on exogenous additives for efficient sterilization, this invention provides a carvacrol-supported covalent organic framework composite photocatalyst, its preparation method, and its applications. By precisely introducing carvacrol as an electron transfer medium into a covalent organic framework synthesized from specific building blocks, a novel composite photocatalytic material is constructed, achieving a solution that combines high photocatalytic activity, a green sterilization process, and excellent stability.

[0006] To achieve this objective, the following solution is provided: This invention provides a method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, wherein carvacrol is loaded onto the covalent organic framework photocatalyst by an impregnation method; the covalent organic framework photocatalyst is prepared by covalently linking benzotrithiophene-2,5,8-trialdehyde and [2,2'-bipyridine]-6,6'-diamine.

[0007] Furthermore, the specific steps include: S1. A mixture of benzotrithiophene-2,5,8-trialdehyde, [2,2'-bipyridine]-6,6'-diamine, o-dichlorobenzene, n-butanol, and acetic acid solution was ultrasonically treated and then rapidly frozen. This process was repeated three times, involving freezing, vacuuming, and thawing. The mixture was then heated to react, cooled to room temperature, and the resulting solid was washed and vacuum dried to obtain a covalent organic framework photocatalyst. S2. The covalent organic framework photocatalyst is mixed with anhydrous ethanol and carvacrol solution, sonicated and stirred evenly, and heated to react. After the reaction is completed, it is cooled to room temperature, and the resulting solid is washed and vacuum dried to obtain the carvacrol-supported covalent organic framework composite photocatalyst.

[0008] Further, in step S1, the molar ratio of benzotrithiophene-2,5,8-trialdehyde to [2,2'-bipyridine]-6,6'-diamine is 0.250 : 0.303.

[0009] Furthermore, in step S1, the volume ratio of o-dichlorobenzene, n-butanol, and acetic acid solution is 3:3:1, and the concentration of acetic acid solution is 6 M.

[0010] Furthermore, in step S1, the temperature of the heating reaction is 140-200℃, and the reaction time is 70-80 h.

[0011] Furthermore, in step S2, the concentration of the carvacrol solution is 5-30 μL / mL.

[0012] Furthermore, in step S2, the temperature of the heating reaction is 50-70 °C, and the reaction time is 10-14 h.

[0013] This invention provides a carvacrol-supported covalent organic framework composite photocatalyst.

[0014] This invention provides the application of carvacrol-supported covalent organic framework composite photocatalyst in the synthesis of hydrogen peroxide.

[0015] The present invention also provides a method for inactivating Escherichia coli in water, which uses a covalent organic framework composite photocatalyst supported on carvacrol to synthesize hydrogen peroxide, and uses the synthesized hydrogen peroxide to inactivate Escherichia coli in water without adding exogenous iron ions.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes carvacrol as an excellent electron transfer medium. When introduced into the COF framework, it serves as a highly efficient electron capture and transport channel. This significantly suppresses the rapid recombination problem of photogenerated carriers commonly found in COF materials after photoexcitation, prolongs the lifetime of photogenerated carriers, and provides more active charges for photocatalytic reactions. Simultaneously, due to the improved electron separation efficiency, the composite material's ability to utilize visible light to drive oxygen reduction or water oxidation to generate hydrogen peroxide is greatly enhanced. Results show that the optimal loading of the composite photocatalyst achieves a H2O2 yield of up to 7681 μmol·g in pure water. - ¹·h - ¹ Compared to the unloaded parent COF, it achieves a leap in performance; finally, carvacrol itself has certain antibacterial activity, and its loading not only improves the photocatalytic performance, but also gives the catalyst itself a dual bactericidal mechanism. The two work synergistically, so that the composite material can achieve efficient sterilization without the addition of iron sources or other co-catalysts.

[0017] 2. This invention utilizes a mixed solvent system of o-dichlorobenzene, n-butanol, and 6 M acetic acid in a specific volume ratio (3:3:1) to provide a suitable microenvironment for the condensation reaction between benzotrithiophene trialdehyde and bipyridine diamine, which is conducive to the formation of a highly ordered and well-crystallized COF framework. This ensures that the COF, as a support, has a high specific surface area and abundant pores, providing sufficient space and sites for the effective loading of carvacrol. High-quality COF synthesis is a prerequisite for subsequent modification to achieve high performance. The COF parent material synthesized by this method possesses strong visible light absorption and inherent photocatalytic activity, laying a solid foundation for constructing high-performance composite materials.

[0018] 3. Traditional Fenton or Fenton-like sterilization technologies require the continuous addition of soluble iron salts, leading to residual iron ions in the water, which may cause secondary pollution, colored precipitation, or impact on the aquatic environment. This invention completely eliminates the need for iron source addition, resulting in a greener sterilization process and cleaner water. This demonstrates that the H2O2 generated by the photocatalysis of the composite material can efficiently inactivate bacteria through different pathways, broadening our understanding of the mechanism of photocatalytic sterilization. Since precise addition and monitoring of iron salt concentration are unnecessary, the operational complexity and cost in practical water treatment applications are reduced, making the system easier to maintain and automate.

[0019] 4. The composite photocatalyst successfully prepared in this invention possesses both extremely high hydrogen peroxide photosynthesis efficiency and strong in-situ bactericidal ability under visible light. The stable covalent backbone of the COF material and the robust loading of carvacrol ensure that the composite material's structure is not easily damaged during use, exhibiting good recycling potential and reducing long-term application costs. Furthermore, the impregnation method followed by modification is simple and operates under mild conditions, facilitating the transition from laboratory to large-scale production. This provides a highly efficient, safe, and sustainable novel solution for addressing pathogenic microbial pollution in water bodies. Attached Figure Description

[0020] Figure 1 X-ray powder diffraction patterns of the covalent organic framework photocatalyst and the carvacrol-supported covalent organic framework composite photocatalyst in Examples 1-6; Figure 2 Fourier transform infrared spectra of the covalent organic framework photocatalyst and the carvacrol-supported covalent organic framework composite photocatalyst in Examples 1-6; Figure 3 This is a comparison chart of the yields of hydrogen peroxide photocatalyzed by carvacrol, covalent organic framework photocatalyst and carvacrol-supported covalent organic framework composite photocatalyst in Example 7. Figure 4 This is a graph showing the time-varying effect of carvacrol, covalent organic framework photocatalyst and carvacrol-supported covalent organic framework composite photocatalyst on Escherichia coli in water in Example 8. Detailed Implementation

[0021] The present invention will be further described below with reference to preferred embodiments. The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values. These ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0022] Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0023] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0024] Example 1 This embodiment provides a method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, comprising the following steps: S1. 66.1 mg benzotrithiophene-2,5,8-trialdehyde, 55.9 mg [2,2'-bipyridine]-6,6'-diamine, 1.5 mL o-dichlorobenzene, 1.5 mL n-butanol, and 0.5 mL 6 M acetic acid solution were added to a 25 mL thick-walled solvent storage bottle and mixed. The mixture was sonicated for 1 h and then rapidly frozen in a liquid nitrogen bath. Three cycles of freezing-vacuuming-thawing were required during this process. The storage bottle was then placed in an oven at 180 °C and heated for 72 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting solid was washed several times with organic solvents such as tetrahydrofuran and methanol. Finally, the washed solid powder was dried in a vacuum drying oven at 80 °C for 12 h to obtain a covalent organic framework photocatalyst, denoted as BB-COF. S2. Weigh 50 mg of covalent organic framework photocatalyst into a 50 mL screw-top glass bottle, add 50 mL of anhydrous ethanol, sonicate for 10 min, then add 250 μL of carvacrol (CA), sonicate and stir for 10 min until the solution is homogeneous. Place the sealed screw-top glass bottle in an oil bath at 60 ℃ and heat for 12 h. After the reaction is complete, cool to room temperature, wash the obtained solid several times with deionized water, and finally dry the sample in a vacuum oven at 40 ℃ for 12 h to obtain the carvacrol-supported covalent organic framework composite photocatalyst, denoted as 5-CA / BB.

[0025] Example 2 This embodiment provides a method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, comprising the following steps: S1. 66.1 mg benzotrithiophene-2,5,8-trialdehyde, 55.9 mg [2,2'-bipyridine]-6,6'-diamine, 1.5 mL o-dichlorobenzene, 1.5 mL n-butanol, and 0.5 mL 6 M acetic acid solution were added to a 25 mL thick-walled solvent storage bottle and mixed. The mixture was sonicated for 1 h and then rapidly frozen in a liquid nitrogen bath. Three cycles of freezing-vacuuming-thawing were required during this process. The storage bottle was then placed in an oven at 150 °C and heated for 80 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting solid was washed several times with organic solvents such as tetrahydrofuran and methanol. Finally, the washed solid powder was dried in a vacuum drying oven at 40 °C for 10 h to obtain a covalent organic framework photocatalyst, denoted as BB-COF. S2. Weigh 50 mg of covalent organic framework photocatalyst into a 50 mL screw-top glass bottle, add 50 mL of anhydrous ethanol, sonicate for 10 min, then add 500 μL of carvacrol (CA), sonicate and stir for 10 min until the solution is homogeneous. Place the sealed screw-top glass bottle in an oil bath at 50 ℃ and heat for 14 h. After the reaction is complete, cool to room temperature, wash the obtained solid several times with deionized water, and finally dry the sample in a vacuum oven at 50 ℃ for 16 h to obtain the carvacrol-supported covalent organic framework composite photocatalyst, denoted as 10-CA / BB.

[0026] Example 3 This embodiment provides a method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, comprising the following steps: S1. 66.1 mg benzotrithiophene-2,5,8-trialdehyde, 55.9 mg [2,2'-bipyridine]-6,6'-diamine, 1.5 mL o-dichlorobenzene, 1.5 mL n-butanol, and 0.5 mL 6 M acetic acid solution were added to a 25 mL thick-walled solvent storage bottle and mixed. The mixture was sonicated for 1 h and then rapidly frozen in a liquid nitrogen bath. Three cycles of freezing-vacuuming-thawing were required during this process. The storage bottle was then placed in an oven at 200 °C and heated for 70 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting solid was washed several times with organic solvents such as tetrahydrofuran and methanol. Finally, the washed solid powder was dried in a vacuum drying oven at 60 °C for 14 h to obtain a covalent organic framework photocatalyst, denoted as BB-COF. S2. Weigh 50 mg of covalent organic framework photocatalyst into a 50 mL screw-top glass bottle, add 50 mL of anhydrous ethanol, sonicate for 10 min, then add 750 μL of carvacrol (CA), sonicate and stir for 10 min until the solution is homogeneous. Place the sealed screw-top glass bottle in an oil bath at 70 ℃ and heat for 10 h. After the reaction is complete, cool to room temperature, wash the obtained solid several times with deionized water, and finally dry the sample in a vacuum oven at 60 ℃ for 10 h to obtain the carvacrol-supported covalent organic framework composite photocatalyst, denoted as 15-CA / BB.

[0027] Example 4 This embodiment provides a method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, comprising the following steps: S1. 66.1 mg benzotrithiophene-2,5,8-trialdehyde, 55.9 mg [2,2'-bipyridine]-6,6'-diamine, 1.5 mL o-dichlorobenzene, 1.5 mL n-butanol, and 0.5 mL 6 M acetic acid solution were added to a 25 mL thick-walled solvent storage bottle and mixed. The mixture was sonicated for 1 h and then rapidly frozen in a liquid nitrogen bath. Three cycles of freezing-vacuuming-thawing were required during this process. The storage bottle was then placed in an oven at 180 °C and heated for 72 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting solid was washed several times with organic solvents such as tetrahydrofuran and methanol. Finally, the washed solid powder was dried in a vacuum drying oven at 80 °C for 12 h to obtain a covalent organic framework photocatalyst, denoted as BB-COF. S2. Weigh 50 mg of covalent organic framework photocatalyst into a 50 mL screw-top glass bottle, add 50 mL of anhydrous ethanol, sonicate for 10 min, then add 1000 μL of carvacrol (CA), sonicate and stir for 10 min until the solution is homogeneous. Place the sealed screw-top glass bottle in an oil bath at 60 ℃ and heat for 12 h. After the reaction is complete, cool to room temperature, wash the obtained solid several times with deionized water, and finally dry the sample in a vacuum oven at 40 ℃ for 12 h to obtain the carvacrol-supported covalent organic framework composite photocatalyst, denoted as 20-CA / BB.

[0028] Example 5 This embodiment provides a method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, comprising the following steps: S1. 66.1 mg benzotrithiophene-2,5,8-trialdehyde, 55.9 mg [2,2'-bipyridine]-6,6'-diamine, 1.5 mL o-dichlorobenzene, 1.5 mL n-butanol, and 0.5 mL 6 M acetic acid solution were added to a 25 mL thick-walled solvent storage bottle and mixed. The mixture was sonicated for 1 h and then rapidly frozen in a liquid nitrogen bath. Three cycles of freezing-vacuuming-thawing were required during this process. The storage bottle was then placed in an oven at 180 °C and heated for 72 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting solid was washed several times with organic solvents such as tetrahydrofuran and methanol. Finally, the washed solid powder was dried in a vacuum drying oven at 80 °C for 12 h to obtain a covalent organic framework photocatalyst, denoted as BB-COF. S2. Weigh 50 mg of covalent organic framework photocatalyst into a 50 mL screw-top glass bottle, add 50 mL of anhydrous ethanol, sonicate for 10 min, then add 1250 μL of carvacrol (CA), sonicate and stir for 10 min until the solution is homogeneous. Place the sealed screw-top glass bottle in an oil bath at 60 ℃ and heat for 12 h. After the reaction is complete, cool to room temperature, wash the obtained solid several times with deionized water, and finally dry the sample in a vacuum oven at 40 ℃ for 12 h to obtain the carvacrol-supported covalent organic framework composite photocatalyst, denoted as 25-CA / BB.

[0029] Example 6 This embodiment provides a method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, comprising the following steps: S1. 66.1 mg benzotrithiophene-2,5,8-trialdehyde, 55.9 mg [2,2'-bipyridine]-6,6'-diamine, 1.5 mL o-dichlorobenzene, 1.5 mL n-butanol, and 0.5 mL 6 M acetic acid solution were added to a 25 mL thick-walled solvent storage bottle and mixed. The mixture was sonicated for 1 h and then rapidly frozen in a liquid nitrogen bath. Three cycles of freezing-vacuuming-thawing were required during this process. The storage bottle was then placed in an oven at 180 °C and heated for 72 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting solid was washed several times with organic solvents such as tetrahydrofuran and methanol. Finally, the washed solid powder was dried in a vacuum drying oven at 80 °C for 12 h to obtain a covalent organic framework photocatalyst, denoted as BB-COF. S2. Weigh 50 mg of covalent organic framework photocatalyst into a 50 mL screw-top glass bottle, add 50 mL of anhydrous ethanol, sonicate for 10 min, then add 1500 μL of carvacrol (CA), sonicate and stir for 10 min until the solution is homogeneous. Place the sealed screw-top glass bottle in an oil bath at 60 ℃ and heat for 12 h. After the reaction is complete, cool to room temperature, wash the obtained solid several times with deionized water, and finally dry the sample in a vacuum oven at 40 ℃ for 12 h to obtain the carvacrol-supported covalent organic framework composite photocatalyst, denoted as 30-CA / BB.

[0030] The performance of the covalent organic framework photocatalyst and the carvacrol-supported covalent organic framework composite photocatalyst prepared in Examples 1-6 were tested. The results are as follows: Figure 1 As shown in the X-ray powder diffraction patterns, the carvacrol-supported covalent organic framework composite photocatalysts obtained in Examples 1-6 all exhibited diffraction peaks typical of covalent organic framework photocatalysts, indicating that the introduction of carvacrol did not alter the material structure of the parent covalent organic framework. Figure 2 As shown in the Fourier transform infrared spectra, the carvacrol-supported covalent organic framework composite photocatalysts obtained in Examples 1-6 exhibit characteristic absorption peaks belonging to carvacrol and characteristic absorption peaks consistent with those of the covalent organic framework parent material. This indicates that carvacrol was successfully introduced and the main structure of the covalent organic framework parent material was preserved. Furthermore, the carvacrol-supported covalent organic framework composite photocatalysts obtained in Examples 4-6 exhibited characteristic absorption peaks of carvacrol of the same intensity, indicating that the loading of carvacrol reached its upper limit.

[0031] Example 7 This embodiment provides the application of a carvacrol-supported covalent organic framework composite photocatalyst in the synthesis of hydrogen peroxide.

[0032] The hydrogen peroxide yield of the covalent organic framework photocatalyst and the carvacrol-supported covalent organic framework composite photocatalyst prepared in Examples 1-6 was tested under pure water conditions. The test conditions were: 300W xenon lamp as light source, λ ≥ 420nm, catalyst amount of 5mg, carvacrol amount of 200μL for comparison, and 50mL deionized water in the reaction system. The results are as follows Figure 3 As shown, compared to carvacrol and covalent organic framework photocatalysts, the carvacrol-supported covalent organic framework composite photocatalysts obtained in Examples 1-6 all exhibited improved photocatalytic performance for hydrogen peroxide production under visible light conditions. Among them, the covalent organic framework composite photocatalysts (20-CA / BB, 25-CA / BB, and 30-CA / BB) obtained in Examples 4-6 showed the same degree of improvement, with a performance reaching 7681 μmol·g. -1 ·h-1 .

[0033] Example 8 This embodiment provides an application of hydrogen peroxide synthesized via a covalent organic framework composite photocatalyst supported on carvacrol in the inactivation of Escherichia coli in water.

[0034] The bactericidal effects of carvacrol, covalent organic framework photocatalyst, and the carvacrol-supported covalent organic framework composite photocatalyst (20-CA / BB) prepared in Example 4 were tested under dark and light conditions. The test conditions were as follows: a 300W xenon lamp was used as the light source, λ ≥ 420 nm, the amount of catalyst used was 15 mg, the amount of carvacrol used for comparison was 200 μL, Escherichia coli was used as the experimental bacteria, and the reaction system consisted of 0.5 mL of bacterial solution and 49.5 mL of 0.9% sterile physiological saline. At the same time interval, 1 mL of the reaction solution was taken and serially diluted, and the inactivation of bacteria was observed by plate counting method. The results are as follows Figure 4 As shown, in the pure carvacrol reaction system, the concentration of *E. coli* remained essentially unchanged; in the reaction system of the covalent organic framework photocatalyst material, *E. coli* still survived at 90 min; while in the reaction system of the carvacrol-supported covalent organic framework composite photocatalyst (20-CA / BB) prepared in Example 4, the bacteria were completely killed at 75 min, demonstrating a much better bactericidal effect than the parent material. This proves that this photocatalyst can be used without adding any exogenous Fe. 2+ Under certain conditions, it can completely inactivate E. coli in water, proving its efficient and green self-driven sterilization ability.

[0035] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a carvacrol-supported covalent organic framework composite photocatalyst, characterized in that, Carvacrol was loaded onto a covalent organic framework photocatalyst by impregnation; the covalent organic framework photocatalyst was prepared by covalently linking benzotrithiophene-2,5,8-trialdehyde and [2,2'-bipyridine]-6,6'-diamine.

2. The method for preparing a carvacrol-supported covalent organic framework composite photocatalyst according to claim 1, characterized in that, Specifically, the following steps are included: S1. A mixture of benzotrithiophene-2,5,8-trialdehyde, [2,2'-bipyridine]-6,6'-diamine, o-dichlorobenzene, n-butanol, and acetic acid solution was ultrasonically treated and then rapidly frozen. This process was repeated three times, involving freezing, vacuuming, and thawing. The mixture was then heated to react, cooled to room temperature, and the resulting solid was washed and vacuum dried to obtain a covalent organic framework photocatalyst. S2. The covalent organic framework photocatalyst is mixed with anhydrous ethanol and carvacrol solution, sonicated and stirred evenly, and heated to react. After the reaction is completed, it is cooled to room temperature, and the resulting solid is washed and vacuum dried to obtain the carvacrol-supported covalent organic framework composite photocatalyst.

3. The method for preparing a carvacrol-supported covalent organic framework composite photocatalyst according to claim 2, characterized in that, In step S1, the molar ratio of benzotrithiophene-2,5,8-trialdehyde to [2,2'-bipyridine]-6,6'-diamine is 0.250 : 0.

303.

4. The method for preparing a carvacrol-supported covalent organic framework composite photocatalyst according to claim 2, characterized in that, In step S1, the volume ratio of o-dichlorobenzene, n-butanol, and acetic acid solution is 3:3:1, and the concentration of acetic acid solution is 6 M.

5. The method for preparing a carvacrol-supported covalent organic framework composite photocatalyst according to claim 2, characterized in that, In step S1, the temperature of the heating reaction is 140-200 °C, and the reaction time is 70-80 h.

6. The method for preparing a carvacrol-supported covalent organic framework composite photocatalyst according to claim 2, characterized in that, In step S2, the concentration of the carvacrol solution is 5-30 μL / mL.

7. The method for preparing a carvacrol-supported covalent organic framework composite photocatalyst according to claim 2, characterized in that, In step S2, the temperature of the heating reaction is 50-70 °C, and the reaction time is 10-14 h.

8. The carvacrol-supported covalent organic framework composite photocatalyst prepared by any one of the preparation methods described in claims 1-7.

9. The application of the carvacrol-supported covalent organic framework composite photocatalyst according to claim 8 in the synthesis of hydrogen peroxide.

10. A method for inactivating Escherichia coli in water, characterized in that, Hydrogen peroxide was synthesized using the carvacrol-supported covalent organic framework composite photocatalyst as described in claim 8, and the synthesized hydrogen peroxide was used to inactivate Escherichia coli in water without the addition of exogenous iron ions.

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