Synthesis method and application of efficient Fenton-like catalyst

Abstract

The invention discloses a synthesis method and application of a high-efficiency Fenton-like catalyst, cobalt hydroxide nanoparticles are effectively confined in a COF pore channel, and the stability, the recycling performance and the catalytic activity of the catalyst are remarkably improved by utilizing the synergistic effect of a nano confinement effect and a Fenton-like reaction. The COF carrier has a regular pore channel structure and good chemical stability, can effectively improve the local concentration of free radicals in pore channels, reduces the consumption of the free radicals by soluble organic matters, and optimizes the activation path of an oxidizing agent, thereby improving the degradation efficiency of pollutants.

Description

Technical Field

[0001] The present invention relates to a synthesis method and application of an efficient Fenton-like catalyst, in particular to a synthesis method and application of an efficient Fenton-like catalyst based on a Co(OH)₂-confined catalyst with a COF support, belonging to the field of nanocomposites. Background Art

[0002] Water pollution has become an increasingly severe environmental problem globally, posing a serious threat to human health and the ecosystem. Industrial wastewater, agricultural runoff, and domestic sewage contain a large number of refractory pollutants such as organic pollutants, heavy metal ions, and antibiotics. After these pollutants enter the water body, they not only affect water quality but may also accumulate through the food chain, endangering biodiversity and human health. For water pollution treatment, the Fenton-like oxidation technology has been widely studied and applied due to its efficient free radical (such as hydroxyl radical, •OH) oxidation ability. However, the traditional Fenton-like system mainly relies on homogeneous catalysts (such as the Fe²⁺ / H₂O₂ system), suffering from problems such as easy catalyst loss, narrow pH application range (usually requiring pH < 4), complex by-products, and iron sludge precipitation. These defects greatly limit its application in actual water treatment. In contrast, heterogeneous Fenton-like catalysts (such as metal oxides, metal-carbon composites) have become a research hotspot in recent years due to their higher recyclability and stability. However, heterogeneous Fenton-like catalysts generally suffer from mass transfer limitations, and short-lived free radicals (10⁻ 6 −10⁻ 9 s) are difficult to effectively diffuse around pollutants, resulting in a decrease in catalytic efficiency. In addition, the non-selective reaction of free radicals in water is easily interfered by coexisting substances (such as dissolved organic matter, anions, etc.), thus reducing the degradation efficiency of target pollutants. Therefore, how to improve the free radical utilization rate of heterogeneous Fenton-like catalysts and enhance their applicability in complex water environments remains an urgent challenge to be solved.

[0003] Nano-confined technology is expected to overcome the mass transfer limitation problem of traditional heterogeneous Fenton-like reactions by confining catalytic reactions in nano-scale spaces. Research shows that confining short-lived free radicals and pollutants in nano-confined structures can significantly improve the utilization rate of free radicals, thereby enhancing the catalytic efficiency. For example, when certain metal oxide nanosheets or nanoparticles are loaded into two-dimensional layered membranes, metal-organic frameworks, or hollow nanospheres, they exhibit higher oxidation activity and a wider applicable pH range. In addition, the nano-confined environment can change the diffusion behavior of free radicals, increase the reaction probability between target pollutants and reactive oxygen species, and reduce the possibility of free radicals being consumed by dissolved organic matter. This confinement effect may also affect the activation path of oxidants (such as H2O2 or peroxymonosulfate (PMS)), change the reaction selectivity, and thus optimize the catalytic process. Therefore, the design of heterogeneous Fenton-like catalysts based on the nano-confined effect provides a new strategy for the efficient removal of water pollutants. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a synthesis method and application of an efficient Fenton-like catalyst, a Co(OH)2-confined catalyst based on a COF carrier, which enhances the reaction probability between free radicals and pollutants and significantly improves the catalytic degradation efficiency.

[0005] To solve the above technical problems, the technical solution of the present invention is: a synthesis method of an efficient Fenton-like catalyst, and its innovation lies in: the synthesis method of the efficient Fenton-like catalyst is used to synthesize and prepare a Co(OH)2-confined catalyst based on a COF carrier, including the following steps: Step S1: Synthesis of COF Add 120 mg of trimesic aldehyde and 372 mg of 2,5-dibutoxyterephthalohydrazide to a mixed solvent of 10 mL of mesitylene and 1,4-dioxane, then add 1.5 mL of acetic acid thereto. Heat the above mixed solution in a stainless steel autoclave in an oven at 110 °C - 130 °C for 65 h - 75 h, then filter, wash, vacuum dry at 55 °C - 65 °C, and grind the product to obtain COF powder; Step S2: Synthesis of Co(OH)2 / COF Dissolve 20 mg of cobalt chloride hexahydrate in 200 μL of absolute ethanol; take 20 mg of the COF powder obtained in step S1, impregnate it with the alcoholic solution of cobalt chloride, and then vacuum dry at 55 °C - 65 °C for 0.8 h - 1.2 h; add the obtained mixture to 20 mL of ammonia water, stir for 1 h, then centrifuge at 5000 rpm to obtain a precipitate. After washing the precipitate, vacuum dry at 60 °C for 6 h to obtain Co(OH)2 / COF.

[0006] Preferably, in the step S1, the volume ratio of mesitylene to 1,4-dioxane in the mixed solvent of mesitylene and 1,4-dioxane is 2-4:1.

[0007] Preferably, in the step S1, the volume ratio of mesitylene to 1,4-dioxane in the mixed solvent of mesitylene and 1,4-dioxane is 3:1.

[0008] Preferably, in the step S1, the above mixed solution is heated in a stainless steel reactor in a 120 °C oven for 72 h, and then the product is filtered, washed, vacuum dried at 60 °C, and ground to obtain COF powder.

[0009] Preferably, in the step S2, 20 mg of cobalt chloride hexahydrate is added to 200 μL of absolute ethanol and completely dissolved by heating and ultrasonic treatment.

[0010] Preferably, in the step S2, 20 mg of cobalt chloride hexahydrate is added to 200 μL of absolute ethanol and completely dissolved; 20 mg of the COF powder obtained in the step S1 is impregnated with the alcoholic solution of cobalt chloride, and then vacuum dried at 60 °C for 1 h.

[0011] Preferably, in the step S2, the concentration of the ammonia water is 1.25%-14%.

[0012] Preferably, in the step S2, the concentration of the ammonia water is 8%.

[0013] Application of a highly efficient Fenton-like catalyst: A Co(OH)2-confined catalyst based on a COF support synthesized by using the synthesis method of the highly efficient Fenton-like catalyst is used for degrading water pollutants.

[0014] The advantages of the present invention are as follows: The present invention effectively confines cobalt hydroxide nanoparticles in the COF pores by using a catalyst, and significantly improves the stability, recycling performance and catalytic activity of the catalyst by the synergistic effect of the nano-confinement effect and the Fenton-like reaction. The COF support has a regular pore structure and good chemical stability, can effectively increase the local concentration of free radicals in the pores, reduce the consumption of free radicals by dissolved organic matter, and optimize the activation path of the oxidant, thereby improving the degradation efficiency of pollutants.

[0015] This application aims to solve the problems of low catalytic efficiency and low free radical utilization rate in traditional Fenton-like technologies. It is a synthesis method and application of a Co(OH)2 / COF catalyst. The COF is synthesized by a solvothermal method, which is simple to operate and has high reproducibility. The obtained COF has a large specific surface area and good stability. Using COFs as a carrier, the catalytic efficiency of the Co(OH)2 catalyst is significantly enhanced through the nano-confinement effect. The regular pore structure of COFs not only provides an efficient microenvironment for the catalytic reaction but also restricts the diffusion of free radicals (•OH), increases their local concentration, thereby enhancing the reaction probability between free radicals and pollutants and significantly improving the catalytic degradation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0017] Figure 1 It is a scanning electron microscope image of COF in the present invention.

[0018] Figure 2 It is a transmission electron microscope image of Co(OH)2 / COF in the present invention.

[0019] Figure 3 It is a detection chart of Co(OH)2 / COF catalyzing PMS for the degradation of rhodamine 6G in water in the present invention.

[0020] Figure 4 It is a line chart showing the change of rhodamine 6G concentration with time during the degradation process in Examples 1-3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The synthesis method of the high-efficiency Fenton-like catalyst of the present invention is used to synthesize and prepare a Co(OH)2-confined catalyst based on a COF carrier, including the following steps: Step S1: Synthesis of COF Add 120 mg of trimesic aldehyde and 372 mg of 2,5-dibutoxyterephthalohydrazide to a mixed solvent of 10 mL of mesitylene and 1,4-dioxane. Then add 1.5 mL of acetic acid to the above mixed solution. Heat the mixed solution in a stainless steel autoclave in an oven at 110 °C - 130 °C for 65 h - 75 h. Then filter, wash, vacuum dry at 55 °C - 65 °C, and grind the product to obtain COF powder; Step S2: Synthesis of Co(OH)2 / COF Dissolve 20 mg of cobalt chloride hexahydrate in 200 μL of absolute ethanol; take 20 mg of the COF powder obtained in step S1, impregnate it with the alcoholic solution of cobalt chloride, and then vacuum dry it at 55 °C - 65 °C for 0.8 h - 1.2 h; add the obtained mixture to 20 mL of ammonia water, stir for 1 h, then centrifuge at 5000 rpm to obtain a precipitate. After washing the precipitate, vacuum dry it at 60 °C for 6 h to obtain Co(OH)2 / COF.

[0022] In the mixed solvent of mesitylene and 1,4-dioxane in step S1, the volume ratio of mesitylene to 1,4-dioxane is 2 - 4:1, and the optimal ratio is 3:1. Heat the above mixed solution in a stainless steel autoclave in an oven at 120 °C for 72 h, then filter, wash, vacuum dry at 60 °C, and grind the product to obtain COF powder.

[0023] In step S2, dissolve 20 mg of cobalt chloride hexahydrate in 200 μL of absolute ethanol by heating and ultrasonic method until completely dissolved. Dissolve 20 mg of cobalt chloride hexahydrate in 200 μL of absolute ethanol; take 20 mg of the COF powder obtained in step S1, impregnate it with the alcoholic solution of cobalt chloride, and then vacuum dry it at 60 °C for 1 h. The concentration of the above ammonia water is 1.25% - 14%, and the optimal concentration is 8%.

[0024] Application of the high-efficiency Fenton-like catalyst of the present invention. The Co(OH)2-confined catalyst based on the COF carrier prepared by the synthesis method of the present application is applied to the degradation of water pollutants.

[0025] Among many nano-confined carrier materials, covalent organic frameworks (COFs) are considered ideal heterogeneous catalyst carriers due to their unique porous structure, chemical stability, and tunable functionalization characteristics. COFs have a regular pore structure, and the pore size range is usually in the nanometer level (2 - 50 nm), which can effectively limit the catalytic reaction area, enhance the local concentration of free radicals in the pores, and improve the catalytic efficiency. In addition, the organic framework formed by covalent bonds in COFs gives them excellent stability in acidic and alkaline environments, overcoming the disadvantage that some MOFs are prone to disintegration in the aqueous phase. Therefore, using COFs as the carrier of nano-confined catalysts can not only improve the stability and recyclability of the catalyst, but also optimize the structure and surface chemical properties of the catalyst, providing new ideas for the efficient design of Fenton-like catalytic systems.

[0026] This application is based on COFs as nano-confined carriers, confining cobalt hydroxide (Co(OH)2) within the pore structure of COFs to construct an efficient heterogeneous Fenton-like catalyst. Due to its unique redox properties and excellent H2O2 activation ability, cobalt hydroxide exhibits high catalytic activity in the Fenton-like reaction. However, individual cobalt hydroxide nanoparticles tend to aggregate in the aqueous phase, leading to a reduced specific surface area and the active sites being easily oxidized or passivated, thus affecting the catalytic stability. Confining Co(OH)2 nanoparticles within the COF pores can not only prevent their aggregation and improve the dispersion of catalytic active sites, but also the confinement effect of COFs can enhance the local concentration of free radicals and improve the utilization efficiency of free radicals. In addition, the organic framework of COFs may regulate the oxidation state of Co(OH)2 through electron transfer, thereby optimizing the activation path of H2O2 and improving the selectivity and degradation efficiency of the Fenton-like reaction. Therefore, through the nano-confinement effect of COFs, this application constructs an efficient and synergistic Fenton-like catalytic system, providing a new catalytic material design strategy for water pollution treatment.

[0027] This invention effectively confines cobalt hydroxide nanoparticles within the COF pores using a catalyst, and significantly improves the stability, recyclability and catalytic activity of the catalyst through the synergistic effect of the nano-confinement effect and the Fenton-like reaction. The COF carrier has a regular pore structure and good chemical stability, which can effectively increase the local concentration of free radicals within the pores, reduce the consumption of free radicals by dissolved organic matter, and optimize the activation path of the oxidant, thereby improving the degradation efficiency of pollutants.

[0028] In this invention, COF is prepared by the solvothermal method, which is simple to operate and has high reproducibility. The obtained COF has a large specific surface area and good stability. Using COFs as the carrier, the catalytic efficiency of the Co(OH)2 catalyst is significantly enhanced through the nano-confinement effect. The regular pore structure of COFs not only provides an efficient microenvironment for the catalytic reaction, but also can restrict the diffusion of free radicals (•OH), increase their local concentration, thereby enhancing the reaction probability between free radicals and pollutants and significantly improving the catalytic degradation efficiency.

[0029] As Figure 3 shown, the degradation experiment: the process of Co(OH)2 / COF catalyzing the degradation of Rhodamine 6G by PMS: Disperse 4 mg of the composite material (Co(OH)2 confined catalyst based on the COF carrier) of this application in the R6G solution, add 7 mg of PMS to this solution, take samples every 2 minutes, and the reaction time lasts for 10 minutes. During the reaction process, use a spectrophotometer to measure the absorption spectrum of R6G to monitor the degradation process. Example 1:

[0030] Material synthesis: Add 7.5 mL of mesitylene and 2.5 mL of 1,4-dioxane into a Teflon liner. Then add 120 mg of benzene-1,3,5-tricarbaldehyde and 372 mg of 2,5-dibutoxyterephthalohydrazide into it, and further add 1.5 mL of acetic acid (1.5 M). Place the liner into a stainless-steel autoclave and heat it in an oven at 120 °C for 72 h. After natural cooling, take it out, separate the product by suction filtration, wash it with mesitylene and 1,4-dioxane, dry it in vacuum at 60 °C, and then grind it repeatedly with an agate mortar to obtain COF powder. Add 20 mg of cobalt(II) chloride hexahydrate into 200 μL of absolute ethanol, heat and ultrasonicate until it is completely dissolved. Take 20 mg of COF powder, impregnate it with the alcoholic solution of cobalt chloride, and then dry it in vacuum at 60 °C for 1 h. Add the mixture into 20 mL of ammonia water (1.25% - 14%), stir for 1 h, then centrifuge at 5000 rpm with a high-speed centrifuge to remove the supernatant, and obtain a precipitate. Wash the precipitate and dry it in vacuum at 60 °C for 6 h to obtain Co(OH)2 / COF.

[0031] Degradation experiment: Take 4 mg of the composite material and disperse it in the R6G solution. Add 7 mg of PMS into the solution, take samples every 2 min, and the reaction time lasts for 10 min. During the reaction process, use a spectrophotometer to measure the absorption spectrum of R6G to monitor the degradation process. Example 2:

[0032] Preparation: The raw materials, operation process, and the dosage of COF used in this example are the same as those in Example 1, except that the dosage of cobalt(II) chloride hexahydrate for loading Co(OH)2 is 15 mg. Therefore, it will not be elaborated here.

[0033] Degradation experiment: Take the Co(OH)2 / COF catalyst prepared in this example for the degradation experiment. The operation process and the dosage of materials in the experiment are the same as those in Example 1. Example 3:

[0034] Preparation: The raw materials, operation process, and the dosage of COF used in this example are the same as those in Example 1, except that the dosage of cobalt(II) chloride hexahydrate for loading Co(OH)2 is 25 mg. Therefore, it will not be elaborated here.

[0035] Degradation experiment: Take the Co(OH)2 / COF catalyst prepared in this example for the degradation experiment. The operation process and the dosage of materials in the experiment are the same as those in Example 1.

[0036] Perform the following tests on the final product Co(OH)2 / COF catalyst prepared in Example 1, as shown respectively in Figures 1 - 3 as follows.

[0037] Figure 1It is the scanning electron microscope image of COF. It can be seen from the figure that spherical COFs with sizes ranging from several hundred nanometers to micrometers are synthesized. Figure 2 It is the transmission electron microscope image of Co(OH)2 / COF. It is shown that there are tiny nanoparticles inside the spherical COF, and Co(OH)2 is successfully loaded inside the spherical COF. Figure 3 It is the detection graph of Co(OH)2 / COF catalyst activating PMS for degrading rhodamine 6G in water, and the efficient removal of rhodamine 6G is achieved within 10 minutes.

[0038] Compare the degradation experiments of Examples 1-3, as Figure 4 shown.

[0039] Figure 4 It is the line graph of the concentration of rhodamine 6G changing with time during the degradation process in Examples 1-3. It is found by comparison that the material obtained from the synthesis ratio in Example 1 has the best degradation performance.

[0040] It should be understood that the above description is for illustrative purposes and not for limitation. By reading the above description, many embodiments and many applications other than the provided examples will be obvious to those skilled in the art. Therefore, the scope of the present invention should not be determined with reference to the above description, but should be determined with reference to the appended claims and the full scope of the equivalents of these claims. For the sake of completeness, all articles and references including patent applications and publications of announcements are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to abandon such subject matter, nor should the inventor be regarded as not considering such subject matter as part of the disclosed inventive subject matter.

Claims

1. A synthesis method of an efficient Fenton-like catalyst, characterized in that: The synthesis method of the efficient Fenton-like catalyst is used to synthesize and prepare a Co(OH)₂-confined catalyst based on a COF support, including the following steps: Step S1: Synthesis of COF Add 120 mg of trimesic aldehyde and 372 mg of 2,5-dibutoxyterephthalohydrazide into a 10 mL mixed solvent of mesitylene and 1,4-dioxane. Then add 1.5 mL of acetic acid thereto. Heat the above mixed solution in a stainless steel autoclave in an oven at 110 °C - 130 °C for 65 h - 75 h. Then filter, wash, vacuum dry at 55 °C - 65 °C, and grind the product to obtain COF powder; Step S2: Synthesis of Co(OH)₂ / COF Dissolve 20 mg of cobalt chloride hexahydrate in 200 μL of absolute ethanol completely; take 20 mg of the COF powder obtained in Step S1, impregnate it with the alcoholic solution of cobalt chloride, and then vacuum dry at 55 °C - 65 °C for 0.8 h - 1.2 h; add the obtained mixture into 20 mL of ammonia water, stir for 1 h, then centrifuge at 5000 rpm to obtain a precipitate. After washing the precipitate, vacuum dry at 60 °C for 6 h to obtain Co(OH)₂ / COF.

2. The synthesis method of an efficient Fenton-like catalyst according to claim 1, characterized in that: In Step S1, the volume ratio of mesitylene to 1,4-dioxane in the mixed solvent of mesitylene and 1,4-dioxane is 2 - 4:

1.

3. The synthesis method of an efficient Fenton-like catalyst according to claim 2, characterized in that: In Step S1, the volume ratio of mesitylene to 1,4-dioxane in the mixed solvent of mesitylene and 1,4-dioxane is 3:

1.

4. The synthesis method of an efficient Fenton-like catalyst according to claim 1, characterized in that: In Step S1, heat the above mixed solution in a stainless steel autoclave in an oven at 120 °C for 72 h, then filter, wash, vacuum dry at 60 °C, and grind the product to obtain COF powder.

5. The synthesis method of an efficient Fenton-like catalyst according to claim 1, characterized in that: In Step S2, dissolve 20 mg of cobalt chloride hexahydrate in 200 μL of absolute ethanol by heating and ultrasonic method until completely dissolved.

6. The synthesis method of an efficient Fenton-like catalyst according to claim 1, characterized in that: In Step S2, dissolve 20 mg of cobalt chloride hexahydrate in 200 μL of absolute ethanol completely; take 20 mg of the COF powder obtained in Step S1, impregnate it with the alcoholic solution of cobalt chloride, and then vacuum dry at 60 °C for 1 h.

7. The synthesis method of an efficient Fenton-like catalyst according to claim 1, characterized in that: In Step S2, the concentration of the ammonia water is 1.25% - 14%.

8. The synthesis method of an efficient Fenton-like catalyst according to claim 7, characterized in that: In Step S2, the concentration of the ammonia water is 8%.

9. Application of an efficient Fenton-like catalyst, a Co(OH)₂-confined catalyst based on a COF support prepared by the synthesis method of an efficient Fenton-like catalyst described in any one of claims 1 to 8, characterized in that: Apply the Co(OH)₂-confined catalyst based on the COF support prepared by the above synthesis method to the degradation of water pollutants.

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