Preparation method and application of core-shell MOF@COF heterojunction material

Abstract

This invention provides a method for preparing and applying a core-shell MOF@COF heterojunction material, relating to the field of photocatalyst materials technology. The method includes: adding a metal ion source and an organic ligand to a first solvent, obtaining a reaction product through a hydrothermal reaction, washing and drying the reaction product to obtain a MOF material; adding an amino monomer, an aldehyde monomer, and the MOF material to a second solvent, mixing them, and then subjecting the mixture to a cooling bath to obtain a solid; subjecting the solid to a heat bath in a vacuum environment, then washing and drying the product to obtain the core-shell MOF@COF heterojunction material. The core-shell MOF@COF heterojunction material prepared by this invention can effectively absorb visible light and effectively separate photogenerated carriers, promoting the generation of a sufficient number of active species, and can be widely applied in the green remediation of real-world water bodies.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst materials technology, and in particular to a method for preparing and applying a core-shell MOF@COF heterojunction material. Background Technology

[0002] In recent years, with the deterioration of the environment and the shortage of fossil energy, photocatalysis has received increasing attention. Currently, photocatalysis is mainly applied in two areas: environmental remediation and energy production, including photocatalytic degradation of organic pollutants, photocatalytic sterilization, photocatalytic hydrogen production, and carbon dioxide reduction.

[0003] Covalent organic frameworks (COFs), as a novel type of photocatalyst, possess tunable pore size, large specific surface area, high adsorption capacity, suitable band gap, and good physicochemical stability. These are the foundations for utilizing COFs as advantageous photocatalyst components in design. However, the practical application of COFs in environmental photoremediation is limited by the low mobility and high recombination rate of photogenerated carriers, resulting in technical problems such as poor visible light response and low photogenerated carrier separation efficiency. Therefore, developing a photocatalyst that can effectively absorb visible light and effectively separate photogenerated carriers is an urgent problem to be solved. Summary of the Invention

[0004] The present invention aims to provide a method for preparing and applying a core-shell MOF@COF heterojunction material, in order to at least partially solve at least one of the above-mentioned technical problems.

[0005] To address the aforementioned technical problems, the first aspect of this invention provides a method for preparing a core-shell MOF@COF heterojunction material, comprising:

[0006] Metal ion source and organic ligand are added to the first solvent, and the reaction product is obtained by hydrothermal reaction. The reaction product is washed and dried to obtain MOF material.

[0007] After adding amino monomers, aldehyde monomers and the MOF material to the second solvent and mixing them, the mixture is cooled in a bath to obtain a solidified product.

[0008] After subjecting the solidified material to a heat bath in a vacuum environment, the product is washed and dried to obtain a core-shell MOF@COF heterojunction material.

[0009] According to a preferred embodiment of the present invention, the step of adding a metal ion source and an organic ligand to a first solvent, obtaining a reaction product through a hydrothermal reaction, and then washing and drying the reaction product to obtain a MOF material includes:

[0010] The metal ion source and organic ligand were dissolved in a first solvent by stirring and then subjected to ultrasonic treatment to obtain a mixture;

[0011] The mixture is heated at a first reaction temperature for a first reaction time to carry out a hydrothermal reaction to obtain the reaction product;

[0012] The reaction product was cooled and then washed multiple times with a first detergent to obtain a washed product.

[0013] The washed material was dried at a first drying temperature for a first drying time, cooled, and then ground to obtain MOF material.

[0014] According to a preferred embodiment of the present invention, the metal ion source is titanium isopropoxide, the organic ligand is 2-aminoterephthalic acid, the first solvent is a mixture of N,N-dimethylformamide and methanol, and the volume ratio of N,N-dimethylformamide to methanol is 4:1.

[0015] According to a preferred embodiment of the present invention, the first reaction time is 48-72 h and the first reaction temperature is 110 °C.

[0016] The reaction product was cooled and then washed repeatedly by centrifugation with a first detergent; wherein the first detergent was N,N-dimethylformamide and methanol.

[0017] The washed items are vacuum dried at a first drying temperature for a first drying time, wherein: the first drying temperature is 100℃ and the first drying time is 12 to 24 hours.

[0018] According to a preferred embodiment of the present invention, the step of adding amino monomers, aldehyde monomers, and the MOF material to the second solvent, followed by a cooling bath to obtain a solidified product includes:

[0019] The amino monomer, aldehyde monomer, second solvent, and MOF material are sequentially added to the reactor and mixed.

[0020] The reactor was placed in a liquid nitrogen bath, and after the mixed solution in the reactor was completely frozen and solidified, a solidified product was obtained.

[0021] According to a preferred embodiment of the present invention, the step of subjecting the solidified material to a heat bath in a vacuum environment and then washing and drying the product to obtain a core-shell MOF@COF heterojunction material comprises:

[0022] The reactor was evacuated and sealed. The sealed reactor was placed in an oil bath and reacted at the oil bath temperature for a second reaction time to obtain the reactants.

[0023] The reactants were washed, dried, and ground multiple times to obtain a core-shell MOF@COF heterojunction material.

[0024] According to a preferred embodiment of the present invention, the amino monomer is melamine, the aldehyde monomer is trialdehyde phloroglucinol, and the molar ratio of melamine to trialdehyde phloroglucinol is 1:1;

[0025] The second solvent is mesitylene, 1,4-dioxane and acetic acid, and the volume ratio of mesitylene, 1,4-dioxane and acetic acid is 5:5:1.

[0026] According to a preferred embodiment of the present invention, the oil bath temperature is 120-180°C, the reactor is a quartz tube or an ampoule, and the second reaction time is 12-72 hours.

[0027] The reactants were centrifuged and washed multiple times with a second detergent, then vacuum dried and ground to obtain a core-shell MOF@COF heterojunction material. The second detergent was a mixed solution of acetone and tetrahydrofuran. The vacuum drying temperature was 100°C and the vacuum drying time was 12-24 hours.

[0028] To address the aforementioned technical problems, a second aspect of the present invention provides a photocatalyst prepared using the preparation method of the core-shell MOF@COF heterojunction material described in any one of the above-mentioned methods.

[0029] According to a preferred embodiment of the present invention, the photocatalyst is used for the degradation and detoxification of organic pollutants in environmental water bodies, wherein:

[0030] The organic pollutant is a paraben, including any one of methylparaben, ethylparaben, and propylparaben, which are widely present in water bodies.

[0031] In summary, the preparation method and application of the core-shell MOF@COF heterojunction material of the present invention involve adding a metal ion source and an organic ligand to a first solvent, obtaining a reaction product through a hydrothermal reaction, washing and drying the reaction product to obtain a MOF material; adding an amino monomer, an aldehyde monomer, and the MOF material to a second solvent, mixing them, and then subjecting the mixture to a cooling bath to obtain a solid; subjecting the solid to a heat bath in a vacuum environment, washing and drying the product to obtain the core-shell MOF@COF heterojunction material. By combining MOF and COF materials with appropriate band arrangements and similar chemical structures, photogenerated electrons and holes can be effectively distributed to different bulk phases. In this way, the core-shell MOF@COF heterojunction material fully demonstrates the advantages of heterojunction while retaining the basic morphology of each component monomer. After absorbing photons, it can not only achieve spatial charge-hole separation, but also achieve rapid charge transfer through the CN bond connecting the MOF and COF components. Thus, it can effectively absorb visible light and effectively separate photogenerated carriers, promoting the generation of a sufficient number of active species. It can be widely used in the green remediation of water bodies in the actual environment. Attached Figure Description

[0032] Figure 1 This is a schematic flowchart of a method for preparing a core-shell MOF@COF heterojunction material according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram illustrating the synthesis of the core-shell MOF@COF heterojunction material in Embodiment 1 of the present invention;

[0034] Figure 3 This is a scanning electron microscope image of the core-shell MOF@COF heterojunction material prepared in Example 1 of the present invention;

[0035] Figure 4 This is the infrared spectrum of the core-shell MOF@COF heterojunction material prepared in Embodiment 1 of the present invention;

[0036] Figure 5 This is the N2 adsorption-desorption curve of the core-shell MOF@COF heterojunction material prepared in Example 1 of the present invention. Detailed Implementation

[0037] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0039] This invention provides a method for preparing a core-shell MOF@COF heterojunction material, wherein MOF is an abbreviation for Metal Organic Framework (MOF). Figure 1 As shown, the method includes:

[0040] S1. Add the metal ion source and organic ligand to the first solvent and obtain the reaction product through hydrothermal reaction. After washing and drying the reaction product, the MOF material is obtained.

[0041] For example, this step may include:

[0042] S11. The metal ion source and organic ligand are stirred and dissolved in the first solvent, and then subjected to ultrasonic treatment to obtain a mixture;

[0043] In a preferred embodiment, the metal ion source is titanium isopropoxide, the organic ligand is 2-aminoterephthalic acid, and the first solvent is a mixture of N,N-dimethylformamide and methanol, wherein the volume ratio of N,N-dimethylformamide to methanol is 4:1.

[0044] S12. The mixture is heated at the first reaction temperature for the first reaction time to carry out a hydrothermal reaction to obtain the reaction product;

[0045] The first reaction time is 48–72 hours, for example, 54 hours. The first reaction temperature is 100–110°C, preferably 110°C.

[0046] S13. After cooling the reaction product, wash it multiple times with the first detergent to obtain the washed product;

[0047] Specifically, after the reaction product is naturally cooled to room temperature, it is washed multiple times by centrifugation with a first detergent; wherein: the first detergent is N,N-dimethylformamide and methanol;

[0048] S14. Dry the washed material at the first drying temperature for the first drying time, cool it, and then grind it to obtain MOF material.

[0049] Specifically, the washed material is heated to a first drying temperature and dried for a first drying time in a vacuum drying oven. After being removed and allowed to cool naturally to room temperature, it is ground to obtain an amino-modified metal-organic framework NH2-MIL-125(Ti). The first drying temperature is 100℃, and the first drying time is 12–24 h.

[0050] S2. After adding amino monomers, aldehyde monomers and the MOF material to the second solvent and mixing them, the mixture is cooled in a cooling bath to obtain a solidified product.

[0051] For example, this step may include:

[0052] S21. The amino monomer, aldehyde monomer, second solvent, and MOF material are added to the reactor sequentially and mixed.

[0053] Wherein, the amino monomer can be 1,3,5-tris(4-aminophenyl)benzene, 1,3,5-trihydroxy-2,4,6-triaminobenzene, or 4-(4-aminophenyl)-2,6-di(4-aminophenyl)pyridine, and the aldehyde monomer can be 1,3,5-tribromo-2,4,6-benzaldehyde, 2-hydroxy-1,3,5-benzenetriformaldehyde, 2,4,6-tris(4-formylphenyl)pyridine, or pyromellitic tricarboxaldehyde, etc. This invention does not impose specific limitations. The second solvent depends on the amino and aldehyde monomers used.

[0054] In a preferred embodiment, the amino monomer is melamine, the aldehyde monomer is trialdehyde phloroglucinol, and the molar ratio of melamine to trialdehyde phloroglucinol is 1:1.

[0055] The second solvent is mesitylene, 1,4-dioxane and acetic acid, and the volume ratio of mesitylene, 1,4-dioxane and acetic acid is 5:5:1.

[0056] S22. Place the reactor in a liquid nitrogen bath and wait for the mixed solution in the reactor to completely freeze and solidify to obtain the solidified product.

[0057] S3. After subjecting the solidified material to a heat bath in a vacuum environment, the product is washed and dried to obtain a core-shell MOF@COF heterojunction material.

[0058] For example, this step may include:

[0059] S31. Evacuate and seal the reactor, place the sealed reactor in an oil bath, and react for the second reaction time at the oil bath temperature to obtain the reactants;

[0060] Wherein: the oil bath temperature is 120-180℃, the reactor is a quartz tube or ampoule, and the second reaction time is 12-72 hours.

[0061] S32. The reactants were washed, dried, and ground multiple times to obtain a core-shell MOF@COF heterojunction material.

[0062] Specifically, the reactants are centrifuged and washed multiple times with a second detergent, then vacuum dried and ground to obtain a core-shell MOF@COF heterojunction material. The second detergent is a mixed solution of acetone and tetrahydrofuran, and the vacuum drying temperature is 100°C for 12–24 hours.

[0063] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0064] Example 1

[0065] refer to Figure 2 Embodiment 1 of the present invention provides a method for preparing a core-shell MOF@COF heterojunction material, wherein: the MOF is specifically NH2-MIL-125(Ti) (Titanium Metal Organic Framework), and the core-shell MOF@COF heterojunction material is specifically TPTi.

[0066] Step 1: Synthesis of NH2-MIL-125(Ti)

[0067] Weigh 2.86 g of 2-aminoterephthalic acid and 2.86 mL of titanium isopropoxide, and dissolve them in a mixture of 40 mL of N,N-dimethylformamide and 10 mL of methanol. Sonicate the mixture to ensure thorough dispersion, then transfer it to a polytetrafluoroethylene-lined reactor and heat at 110 °C for 72 hours. After the reaction, allow it to cool naturally to room temperature, centrifuge to separate the precipitate, and wash it repeatedly with N,N-dimethylformamide and methanol. Dry the washed product in a vacuum oven at 100 °C for 12 hours, then allow it to cool naturally to room temperature and grind it to obtain NH2-MIL-125(Ti).

[0068] Step 2: Synthesis of TPTi

[0069] 0.5 mmol of trialdehyde-based phloroglucinol and 0.5 mmol of melamine were added to a quartz tube, followed by 5 mL of mesitylene, 5 mL of 1,4-dioxane, and 1 mL of 3M acetic acid. Then, 0.025–0.425 g of NH₂-MIL-125(Ti) prepared in step 1 was added to the quartz tube, and the mixture was sonicated for 15 minutes to ensure homogeneity. The quartz tube was placed in a liquid nitrogen bath, and after the solution was completely frozen, a vacuum was applied, and the quartz tube was then sealed with a flame. The quartz tube was then placed in an oil bath and reacted at 120 °C for 72 hours. After the reaction was complete, the quartz tube was allowed to cool naturally to room temperature. The tube was then opened, the precipitate was separated by centrifugation, and washed repeatedly with acetone and tetrahydrofuran. The resulting washings were then dried in a vacuum oven at 100 °C for 12 hours, allowed to cool naturally to room temperature, and then ground to obtain TPTi.

[0070] The structure of the prepared product TPTi is characterized below:

[0071] Figure 3 The image shows a scanning electron microscope (SEM) image of the TPTi obtained in this embodiment. As can be clearly seen from the image, the TPTi structure exhibits a rough cubic morphology, which includes a smooth cubic NH2-MIL-125(Ti) on the inner surface and a thin, short rod-shaped TpMA layer on the outer surface. The tight connection between the two components exhibits a core-shell structure.

[0072] Figure 4 The infrared spectrum of TPTi obtained in this embodiment is obtained from... Figure 4 As can be seen, TPTi exhibits significant bands at 1264 cm⁻¹, 1530 cm⁻¹, and 1616 cm⁻¹, which can be attributed to CN, C=C, and C=O bonds. The appearance of these peaks indicates both the successful synthesis of TPTi and the fact that, during the synthesis process, TpMA generated via the Schiff base reaction underwent enol-ketone isomerization, producing TpMA with a ketone structure.

[0073] Figure 5 The N2 adsorption-desorption curves of TPTi obtained in this embodiment are obtained from... Figure 5 As can be seen, TPTi exhibits a typical Type IV isotherm, and the adsorption-desorption curve shows significant adsorption in the range of 0.7-1.0, along with an H3 type hysteresis loop, indicating that the main component of the pore structure of TPTi is mesopores. This observation is consistent with the average pore size shown in the pore size distribution diagram.

[0074] The core-shell MOF@COF heterojunction material prepared by this invention can be used as a photocatalyst. Therefore, based on the above-described preparation method of the core-shell MOF@COF heterojunction material, this invention also provides a photocatalyst, prepared using the preparation method of the core-shell MOF@COF heterojunction material described in any one of the above-described methods. The photocatalyst is used for the degradation and detoxification of organic pollutants in environmental water bodies, wherein:

[0075] The organic pollutant is a paraben, including any one of methylparaben, ethylparaben, and propylparaben, which are widely present in water bodies.

[0076] Using the TPTi prepared in Example 1 as a photocatalyst, three commonly detected parabens (methylparaben, ethylparaben, and propylparaben) in real-world water bodies were selected as representatives to test the photocatalytic degradation performance of TPTi on organic pollutants. The test steps are as follows:

[0077] 1. Simulate visible light irradiation using a 350-watt xenon lamp with a 400 nm filter. Prepare 50 mL of 10 mg / L aqueous solutions of methylparaben, ethylparaben, and propylparaben in 100 mL beakers.

[0078] 2. Add 5 mg of the TPTi photocatalyst prepared in Example 1 to a beaker and stir magnetically for 30 minutes in the dark to reach adsorption-desorption equilibrium. Turn on the xenon lamp to carry out the photocatalytic reaction. During the reaction, at regular intervals, draw 0.5 mL of the suspension with a needle and remove impurities using a 0.22 μm microporous hydrophilic polytetrafluoroethylene needle filter.

[0079] Throughout the test, the magnetic stirring speed was maintained at 800 rpm, and the residual concentration of the target compound was determined by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry. The results showed that:

[0080] (1) After reaching adsorption-desorption equilibrium, the adsorption removal rates of methylparaben, ethylparaben and propylparaben by TPTi photocatalyst were 7.83%, 8.43% and 26.10%, respectively.

[0081] (2) Within 120 minutes, the total removal rates of methylparaben, ethylparaben, and propylparaben by TPTi were 86%, 92%, and 99%, respectively. The degradation kinetics of all reactions conformed to the pseudo-first-order reaction kinetic equation.

[0082] (3)TPTi maintains excellent degradation performance over a wide pH range and in various real water matrices.

[0083] The above results demonstrate that the core-shell MOF@COF heterojunction material TPTi exhibits excellent photocatalytic efficiency in the photocatalytic degradation of organic pollutants, and also has good potential for practical application, making it suitable for large-scale production.

[0084] Example 2

[0085] Embodiment 2 of the present invention provides a method for preparing a core-shell MOF@COF heterojunction material, comprising:

[0086] 1. Synthesis of NH2-MIL-125(Ti)

[0087] Weigh 4.35 g of 2-aminoterephthalic acid and 3.35 mL of titanium isopropoxide, and dissolve them in a mixture of 60 mL of N,N-dimethylformamide and 20 mL of methanol. Sonicate the mixture to ensure thorough dispersion, then transfer it to a polytetrafluoroethylene-lined reactor and heat at 108 °C for 60 hours. After the reaction, allow it to cool naturally to room temperature, centrifuge to separate the precipitate, and wash it repeatedly with N,N-dimethylformamide and methanol. Dry the washed product in a vacuum oven at 80 °C for 24 hours, then allow it to cool naturally to room temperature and grind it to obtain NH2-MIL-125(Ti).

[0088] 2. Synthesis of TPTi

[0089] 0.7 mmol of trialdehyde phloroglucinol and 0.7 mmol of melamine were added to a quartz tube, followed by 6 mL of mesitylene, 6 mL of 1,4-dioxane, and 1.5 mL of 3M acetic acid. Then, 0.025 g of NH₂-MIL-125(Ti) prepared in step 1 was added to the quartz tube, and the mixture was sonicated for 20 minutes to ensure homogeneity. The quartz tube was placed in a liquid nitrogen bath, and after the solution was completely frozen, a vacuum was applied, and the quartz tube was then sealed with a flame. The quartz tube was then placed in an oil bath and reacted at 120 °C for 72 hours. After the reaction, the quartz tube was allowed to cool naturally to room temperature. The tube was then opened, the precipitate was separated by centrifugation, and washed repeatedly with acetone and tetrahydrofuran. The resulting washes were then dried in a vacuum oven at 100 °C for 15 hours, allowed to cool naturally to room temperature, and then ground to obtain TPTi.

[0090] It should be clarified that the present invention is not limited to the specific structures and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0091] It should also be noted that the exemplary embodiments mentioned in this invention describe methods or systems based on a series of steps or apparatus. However, this invention is not limited to the order of the steps described above; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0092] The above description is merely a specific embodiment of the present invention. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A method for preparing a core-shell MOF@COF heterojunction material, characterized in that, The method includes: A metal ion source and an organic ligand are added to a first solvent, and a reaction product is obtained through a hydrothermal reaction. The reaction product is washed and dried to obtain the MOF material. The metal ion source is titanium isopropoxide, the organic ligand is 2-aminoterephthalic acid, and the first solvent is a mixture of N,N-dimethylformamide and methanol, with a volume ratio of N,N-dimethylformamide to methanol of 4:

1. An amino monomer, an aldehyde monomer, and the MOF material are added to a second solvent and mixed. The mixture is then cooled in a cooling bath to obtain a solid. The amino monomer is melamine, and the aldehyde monomer is trialdehyde phloroglucinol. The molar ratio of melamine to trialdehyde phloroglucinol is 1:

1. The reactor is evacuated and sealed. The sealed reactor is placed in an oil bath and reacted at the oil bath temperature for a second reaction time to obtain reactants. The reactants are then repeatedly centrifuged and washed with a second detergent, vacuum dried, and ground to obtain core-shell MOF@COF heterojunction material. The second detergent is a mixed solution of acetone and tetrahydrofuran. The vacuum drying temperature is 100°C and the vacuum drying time is 12-24 hours. The oil bath temperature is 120-180°C. The reactor is a quartz tube or ampoule. The second reaction time is 12-72 hours.

2. The method of claim 1, wherein, The step of adding a metal ion source and an organic ligand to a first solvent and obtaining a reaction product through a hydrothermal reaction, followed by washing and drying the reaction product to obtain a MOF material, includes: The metal ion source and organic ligand were dissolved in a first solvent by stirring and then subjected to ultrasonic treatment to obtain a mixture; The mixture is heated at a first reaction temperature for a first reaction time to carry out a hydrothermal reaction to obtain the reaction product; The reaction product was cooled and then washed multiple times with a first detergent to obtain a washed product. The washed material was dried at a first drying temperature for a first drying time, cooled, and then ground to obtain MOF material.

3. The method of claim 2, wherein, The first reaction time is 48~72h, and the first reaction temperature is 110℃; The reaction product was cooled and then washed repeatedly by centrifugation with a first detergent; wherein the first detergent was N,N-dimethylformamide and methanol. The washed items are vacuum dried at a first drying temperature for a first drying time, wherein: the first drying temperature is 100℃ and the first drying time is 12~24h.

4. The method according to claim 2, characterized in that, The process of adding amino monomers, aldehyde monomers, and the MOF material to the second solvent, followed by a cooling bath, yields a solidified product comprising: The amino monomer, aldehyde monomer, second solvent, and MOF material are sequentially added to the reactor and mixed. The reactor was placed in a liquid nitrogen bath, and after the mixed solution in the reactor was completely frozen and solidified, a solidified product was obtained.

5. The method according to claim 1 or 4, characterized in that, The second solvent is mesitylene, 1,4-dioxane and acetic acid, and the volume ratio of mesitylene, 1,4-dioxane and acetic acid is 5:5:

1.

6. A photocatalyst, characterized in that, It is prepared using the preparation method of core-shell MOF@COF heterojunction material according to any one of claims 1-5.

7. The photocatalyst according to claim 6, characterized in that, The photocatalyst is used for the degradation and detoxification of organic pollutants in environmental water bodies, wherein: The organic pollutant is a paraben, including any one of methylparaben, ethylparaben, and propylparaben, which are widely present in water bodies.

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