A hollow ZnO composite catalytic material loaded with COF and a preparation method and application thereof

Abstract

The application belongs to the technical field of photocatalysts, and relates to a method for preparing hydrogen peroxide through photocatalysis, in particular to a hollow ZnO composite catalytic material loaded with COF as well as a preparation method and application thereof. The material is in a hollow nanosphere structure, and the nanosphere structure takes the ZnO hollow sphere as a framework and the TpPa-1 particles are coated on the outer surface of the ZnO. The composite catalytic material has a higher specific surface area and can promote the photocatalytic production of hydrogen peroxide. Moreover, the hollow structure provides sufficient space inside the ZnO, promotes multiple refraction and reflection of light, and thus realizes efficient light capture and utilization. The combination of TpPa-1 and zinc oxide forms a heterojunction, which not only increases the number of surface active sites, but also optimizes the reaction path by adjusting the local electronic state of TpPa-1, effectively separates photo-generated electrons and holes, and thus improves the photocatalytic activity.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, and relates to a method for photocatalytic preparation of hydrogen peroxide, specifically to a COF-supported hollow ZnO composite catalytic material, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Zinc oxide (ZnO) is a common metal oxide semiconductor with advantages such as low preparation cost, diverse morphologies, low toxicity, chemical stability, high electron mobility, and good photocatalytic activity. However, in practical applications, its catalytic activity is less than ideal due to limitations such as low specific surface area, poor visible light absorption, and severe photogenerated carrier recombination. Covalent organic framework (COF) materials, with their high specific surface area and abundant porous structure, show great potential in the field of photocatalysis, but their application is hindered by poor stability and unclear active site mechanisms. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a COF-supported hollow ZnO composite catalytic material, its preparation method, and its applications. The composite catalytic material provided by this invention is formed by combining hollow ZnO spheres with TpPa-1, exhibiting a higher specific surface area, providing more surface active sites, and promoting photocatalytic hydrogen peroxide production. Furthermore, the hollow structure provides ample space within the ZnO, promoting multiple refractions and reflections of light, thereby achieving efficient light capture and utilization. Combining TpPa-1 with zinc oxide to form a heterojunction not only increases the number of surface active sites but also optimizes the reaction pathway by adjusting the local electronic states of TpPa-1, effectively separating photogenerated electrons and holes, thereby improving photocatalytic activity.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, there is a hollow ZnO composite catalytic material loaded with COF, which is a hollow nanosphere structure. The nanosphere structure has a ZnO hollow sphere as the skeleton and TpPa-1 particles coated on the outer surface of ZnO. The TpPa-1 particles are a covalent organic skeleton formed by trialdehyde phloroglucinol and p-phenylenediamine as raw materials.

[0006] The COF-loaded hollow ZnO composite catalytic material provided by this invention, with TpPa-1 loaded on the surface of hollow ZnO spheres, not only enables ZnO and TpPa-1 to form a heterojunction with an internal electric field, effectively separating photogenerated electrons and holes, but also enhances the active sites for redox reactions by increasing the specific surface area. Moreover, TpPa-1 has a wide absorption range in the visible light range, with an absorption edge around 650 nm, greatly broadening the visible light absorption range of the material. The synergistic effect of these characteristics makes the composite material exhibit excellent photocatalytic activity.

[0007] Furthermore, if the ZnO / TpPa-1 composite material does not coat the ZnO hollow spheres with TpPa-1, and is merely a physically mixed ZnO / TpPa-1 photocatalyst, its performance will be poor due to problems such as excessively fast electron-hole recombination rates and low visible light utilization. This invention designs the composite catalytic material as a hollow sphere structure, which can effectively improve the low visible light utilization.

[0008] Experiments have shown that, compared with ordinary hollow ZnO nanosphere catalytic materials, the in-situ grown COF-supported hollow ZnO composite catalytic material provided by this invention has more significant photocatalytic hydrogen peroxide production activity.

[0009] In a second aspect, a method for preparing the composite catalytic material described in the first aspect of the present invention includes the following steps: Zinc salt, template agent, and chelating agent are mixed evenly in ethanol and subjected to a first solvothermal treatment to prepare zinc oxide precursor; The zinc oxide precursor was calcined in air to obtain ZnO hollow spheres with a hollow structure; The ZnO hollow spheres are mixed evenly with trialdehyde phloroglucinol and p-phenylenediamine in ethanol and then subjected to a second solvothermal treatment to obtain the final product.

[0010] After mixing ZnO hollow spheres with trialdehyde phloroglucinol and p-phenylenediamine, a second solvothermal treatment is performed. This not only allows the trialdehyde phloroglucinol and p-phenylenediamine to react on the surface of ZnO hollow spheres to generate TpPa-1, thereby coating the outer surface of ZnO with TpPa-1 particles to form a composite material, but also maintains the hollow structure of the ZnO hollow spheres.

[0011] Thirdly, the application of the composite catalytic material described in the first aspect of the present invention in the photocatalytic preparation of hydrogen peroxide.

[0012] The beneficial effects of this invention are as follows: The hollow ZnO / TpPa-1 composite catalytic material prepared in this invention first obtains a ZnO precursor using a simple solvothermal method. The ZnO precursor is then calcined at high temperature, converting the internal template agent into CO2, successfully yielding hollow ZnO spheres. These hollow ZnO spheres react with trialdehyde phloroglucinol and p-phenylenediamine in an organic solvent. This composite catalytic material not only possesses a hollow structure and well-defined internal voids, providing more opportunities for multiple reflections and refractions of light, thus improving light absorption and utilization efficiency; but also exhibits abundant active sites and a large specific surface area endowed by COF materials, facilitating reactant adsorption and increasing the number of active sites and specific surface area, thereby exhibiting excellent photocatalytic activity. Attached Figure Description

[0013] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0014] Figure 1 These are the X-ray diffraction (XRD) patterns of ZnO hollow spheres, granular TpPa-1 materials, and ZTP-3 materials with hollow structures prepared in Examples 1, 2, and 5 of this invention, respectively.

[0015] Figure 2 This is the solid-state nuclear magnetic resonance (NMR) carbon spectrum of the particulate TpPa-1 material prepared in Example 2 of this invention.

[0016] Figure 3 This is a scanning electron microscope (SEM) image of the hollow ZnO material prepared in Example 1 of this invention, with a scale bar of 100 nm.

[0017] Figure 4 This is a transmission electron microscope (TEM) image of the hollow ZnO material prepared in Example 1 of this invention, with a scale bar of 100 nm.

[0018] Figure 5 These are scanning electron microscope (SEM) images of ZTP-3 prepared in Example 5 of this invention.

[0019] Figure 6 This is a transmission electron microscope (TEM) image of ZTP-3 prepared in Example 5 of this invention.

[0020] Figure 7 These are the photocatalytic hydrogen peroxide production performance diagrams of hollow ZnO materials, particulate TpPa-1 materials, and COF-supported hollow ZnO composite catalyst materials prepared in Examples 1, 2, 3, 4, 5, 6, and 7 of this invention. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] To further address the problem of low efficiency in the photocatalytic generation of hydrogen peroxide from ZnO materials, this invention proposes a COF-supported hollow ZnO composite catalytic material, its preparation method, and its application.

[0024] In a typical embodiment of the present invention, a hollow ZnO composite catalytic material loaded with COF is provided, which is a hollow nanosphere structure. The nanosphere structure has a ZnO hollow sphere as the skeleton and TpPa-1 particles coated on the outer surface of ZnO. The TpPa-1 particles are a covalent organic skeleton formed by trialdehyde phloroglucinol and p-phenylenediamine as raw materials.

[0025] In some embodiments, the mass ratio of ZnO hollow spheres to TpPa-1 particles is 100:30~85. When the mass ratio of ZnO hollow spheres to TpPa-1 particles is 100:50~55, the photocatalytic performance of the composite catalytic material is better.

[0026] Another embodiment of the present invention provides a method for preparing the above-mentioned composite catalytic material, comprising the following steps: Zinc salt, template agent, and chelating agent are mixed evenly in ethanol and subjected to a first solvothermal treatment to prepare zinc oxide precursor; The zinc oxide precursor was calcined in air to obtain ZnO hollow spheres with a hollow structure; The ZnO hollow spheres are mixed evenly with trialdehyde phloroglucinol and p-phenylenediamine in ethanol and then subjected to a second solvothermal treatment to obtain the final product.

[0027] The zinc salts described in this invention refer to compounds whose cation is zinc ion; they can be inorganic salts, such as zinc chloride, zinc sulfate, and zinc nitrate; or they can be organic salts, such as zinc acetate. Studies have shown that zinc acetate is more effective.

[0028] In some embodiments, the template agent is polyvinylpyrrolidone (PVP). The template agent described in this invention is polyvinylpyrrolidone (PVP); it can be PVP with different average molecular weights (MW), such as 10,000, 40,000, 58,000, 130,000, etc. Studies have shown that using polyvinylpyrrolidone with an average molecular weight (MW) of 40,000 yields better results.

[0029] The chelating agent described in this invention is a compound capable of forming a stable chelate with metallic zinc ions. It can be an inorganic chelating agent, such as sodium hexametaphosphate, sodium tripolyphosphate, or boric acid; or an organic chelating agent, such as salicylic acid. In some embodiments, the chelating agent is salicylic acid. Studies have shown that salicylic acid is more effective.

[0030] The solvothermal method described in this invention refers to a method that uses organic solvents or non-aqueous solvents as solvents to carry out a reaction in a closed system (such as an autoclave), and creates a high-temperature and high-pressure environment by heating and pressurizing, thereby performing the treatment.

[0031] In some embodiments, the zinc salt, template agent, and chelating agent are calculated as zinc acetate dihydrate, PVP, and salicylic acid, respectively, and the mass ratio of zinc salt, template agent, and chelating agent is 0.4~0.6:1~1.2:0.3~0.5.

[0032] In some embodiments, the temperature of the first solvothermal treatment is 160~180 °C, and the time is 12~14 h.

[0033] In some embodiments, the calcination temperature is 500–600 °C, and the calcination time is 3.5–4.5 h. Specifically, the heating rate during calcination is 1–2 °C·min. -1 .

[0034] In some embodiments, the temperature of the second solvothermal treatment is 180~200 °C, and the time is 36~48 h.

[0035] In some embodiments, the mass ratio of the ZnO hollow spheres to trialdehyde phloroglucinol and p-phenylenediamine is 1:0.2~0.6:0.15~0.45. Studies have shown that the composite catalytic material with a hollow structure is related to the amount of trialdehyde phloroglucinol and p-phenylenediamine added. When the mass ratio of ZnO hollow spheres, trialdehyde phloroglucinol, and p-phenylenediamine is 1:0.3~0.4:0.2~0.3, the photocatalytic hydrogen peroxide production of the prepared composite catalytic material is better.

[0036] A third embodiment of the present invention provides an application of the above-mentioned composite catalytic material in the photocatalytic preparation of hydrogen peroxide.

[0037] Specifically, the composite catalytic material is added to a solution containing ethanol, mixed evenly, and then irradiated with light.

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0039] Example 1: A method for preparing ZnO hollow sphere material includes the following steps: 1.1 g of PVP (average molecular weight 40,000, MW) was dissolved in 60 mL of ethanol solution and stirred at room temperature until dissolved. Then, 0.5 g of zinc acetate dihydrate and 0.4 g of salicylic acid were added, and the mixture was magnetically stirred for 3 h at room temperature. The clear solution was transferred to a 100 mL polytetrafluoroethylene-lined reactor and solvothermal treated in an oven at 160 °C for 12 h. After natural cooling to room temperature, the resulting precipitate was centrifuged, washed, dried, and ground. The resulting pale yellow powder was placed in a tube furnace and heated at 1 °C for 1 min. -1 The ZnO hollow sphere material is obtained by heating to 550 ℃ and calcining for 4 h, followed by natural cooling and grinding.

[0040] Example 2: A method for preparing particulate TpPa-1 material includes the following steps: 21 mg of trialdehyde phloroglucinol and 16.2 mg of p-phenylenediamine were added to 30 mL of ethanol, sonicated for 20 min, and then stirred continuously at room temperature for 30 min to form a homogeneous suspension. The resulting suspension was transferred to a 50 mL polytetrafluoroethylene-lined reactor and solvothermal treated in an oven at 180 °C for 48 h. After natural cooling to room temperature, the resulting precipitate was centrifuged, washed, dried, and ground to obtain the granular TpPa-1 material.

[0041] The reaction formula for preparing TpPa-1 in this embodiment is shown below: .

[0042] Example 3: A method for preparing a COF-supported hollow ZnO composite catalytic material (i.e., a ZnO / TpPa-1 composite material with a hollow structure) includes the following steps: 0.1 g of the hollow-structured ZnO prepared in Example 1 was added to 30 mL of ethanol and sonicated for 20 min. Then, 21 mg of trialdehyde phloroglucinol and 16.2 mg of p-phenylenediamine were added, and the mixture was stirred at room temperature to form a homogeneous suspension. The resulting suspension was transferred to a 50 mL polytetrafluoroethylene-lined reactor and solvothermal treated in an oven at 180 °C for 48 h. After natural cooling to room temperature, the resulting precipitate was centrifuged, washed, dried, and ground to obtain the hollow-structured ZnO / TpPa-1 composite material, denoted as ZTP-1.

[0043] Example 4: A method for preparing a COF-supported hollow ZnO composite catalytic material (i.e., a ZnO / TpPa-1 composite material with a hollow structure) includes the following steps: 0.1 g of the hollow-structured ZnO prepared in Example 1 was added to 30 mL of ethanol and sonicated for 20 min. Then, 28 mg of trialdehyde phloroglucinol and 21.6 mg of p-phenylenediamine were added, and the mixture was stirred at room temperature to form a homogeneous suspension. The resulting suspension was transferred to a 50 mL polytetrafluoroethylene-lined reactor and solvothermal treated in an oven at 180 °C for 48 h. After natural cooling to room temperature, the resulting precipitate was centrifuged, washed, dried, and ground to obtain the hollow-structured ZnO / TpPa-1 composite material, denoted as ZTP-2.

[0044] Example 5: A method for preparing a COF-supported hollow ZnO composite catalytic material (i.e., a ZnO / TpPa-1 composite material with a hollow structure) includes the following steps: 0.1 g of the hollow-structured ZnO prepared in Example 1 was added to 30 mL of ethanol. After ultrasonic treatment for 20 min, 35.6 mg of trialdehyde phloroglucinol and 27.5 mg of p-phenylenediamine were added, and stirring was continued at room temperature to form a homogeneous suspension. The resulting suspension was transferred to a 50 mL polytetrafluoroethylene-lined reactor and solvothermal treated in an oven at 180 °C for 48 h. After natural cooling to room temperature, the resulting precipitate was centrifuged, washed, dried, and ground to obtain the hollow-structured ZnO / TpPa-1 composite material, denoted as ZTP-3.

[0045] Example 6: A method for preparing a COF-supported hollow ZnO composite catalytic material (i.e., a ZnO / TpPa-1 composite material with a hollow structure) includes the following steps: 0.1 g of the hollow-structured ZnO prepared in Example 1 was added to 30 mL of ethanol. After ultrasonic treatment for 20 min, 43.8 mg of trialdehyde phloroglucinol and 33.8 mg of p-phenylenediamine were added, and stirring was continued at room temperature to form a homogeneous suspension. The resulting suspension was transferred to a 50 mL polytetrafluoroethylene-lined reactor and solvothermal treated in an oven at 180 °C for 48 h. After natural cooling to room temperature, the resulting precipitate was centrifuged, washed, dried, and ground to obtain the hollow-structured ZnO / TpPa-1 composite material, denoted as ZTP-4.

[0046] Example 7: A method for preparing a COF-supported hollow ZnO composite catalytic material (i.e., a ZnO / TpPa-1 composite material with a hollow structure) includes the following steps: 0.1 g of the hollow-structured ZnO prepared in Example 1 was added to 30 mL of ethanol and sonicated for 20 min. Then, 53.8 mg of trialdehyde phloroglucinol and 41.5 mg of p-phenylenediamine were added, and stirring continued at room temperature to form a homogeneous suspension. The resulting suspension was transferred to a 50 mL polytetrafluoroethylene-lined reactor and solvothermal treated in an oven at 180 °C for 48 h. After natural cooling to room temperature, the resulting precipitate was centrifuged, washed, dried, and ground to obtain the hollow-structured ZnO / TpPa-1 composite material, denoted as ZTP-5.

[0047] The XRD patterns of ZnO prepared in Example 1, TpPa-1 prepared in Example 2, and the hollow ZnO / TpPa-1 composite material prepared in Example 5 are shown. The characteristic peaks of ZnO are displayed, proving the successful preparation of ZnO. Simultaneously, the characteristic peaks of TpPa-1 are also displayed, proving the successful preparation of TpPa-1. The XRD patterns of the ZnO / TpPa-1 composite material show characteristic peaks attributable to both ZnO and TpPa-1. The peak intensity of ZnO gradually decreases with increasing TpPa-1 content, while the peak intensity of TpPa-1 gradually increases with increasing TpPa-1 content. This also indicates that the hollow ZnO / TpPa-1 composite material was successfully prepared.

[0048] Example 2: Solid-state nuclear magnetic resonance (NMR) carbon spectrum of particulate TpPa-1 material prepared as shown in Figure 2. Figure 2As shown, the peaks in the 180-186 ppm range are attributed to carbonyl carbons (C=O, a), while the peak at 147 ppm is attributed to amine carbons (CN, b). The peak at 135 ppm is a carbon on a benzene ring linked to an amine group (NC=C, c), and the peak at 106 ppm is a carbon on a six-membered ring linked to a double bond (-C=C-, d). Furthermore, no characteristic enol carbon (C-OH) or imine carbon (C=N) peaks were detected at 190 ppm and 165 ppm, thus confirming the presence of keto-enol tautomerism in TpPa-1.

[0049] Depend on Figure 3 The SEM images show that the ZnO material prepared in Example 1 has a spherical morphology. Meanwhile, from... Figure 4 The TEM image shows that the ZnO material prepared in Example 1 has a hollow structure.

[0050] SEM image of ZTP-3 prepared in Example 5 is shown below. Figure 5 As shown, this indicates that ZTP-3 has a spherical morphology. At the same time, ZTP-3 retains its hollow spherical structure, as... Figure 6 As shown, the ZnO / TpPa-1 composite material prepared by coating with TpPa-1 does not destroy the original hollow structure.

[0051] The obtained COF-supported hollow ZnO composite catalyst was applied to the photocatalytic production of hydrogen peroxide, and the experimental procedure is as follows: 10 mg of the photocatalysts prepared in Examples 2, 3, 4, 5, 6, 7, and 8 of this invention were added to 36 mL of deionized water and 4 mL of anhydrous ethanol and ultrasonically dispersed. The suspension was transferred to a reactor, and pure oxygen was bubbled into the solution for 30 min to reach oxygen saturation. The reactor was irradiated with a 300 W xenon lamp with an AM1.5 filter as simulated sunlight. Every 30 min, 1 mL aliquots were collected using a syringe and discharged into sample tubes through a 0.5 μm Millipore filter. The concentration and efficiency of hydrogen peroxide generation by the photocatalyst were further calculated using iodometric titration and a pre-plotted standard curve.

[0052] The hydrogen peroxide production efficiency of the photocatalysts prepared in each embodiment of the present invention is shown in the figure. Figure 7 .from Figure 7 It can be seen that the photocatalytic hydrogen peroxide production efficiency of the prepared COF-supported hollow ZnO composite catalyst is higher than that of the hollow ZnO material, especially ZTP-3 prepared in Example 5, which achieves a photocatalytic hydrogen peroxide production efficiency of 5.32 mmol·g. -1 ·h -1The performance of the composite material is approximately 5.8 times that of hollow ZnO. The improved photocatalytic efficiency for hydrogen peroxide production is likely due to the presence of the hollow structure and the high specific surface area and abundant pore structure of COF, which give the composite catalytic material a larger surface area and higher light collection efficiency. The inner sphere electric field heterojunction constructed from the covalent organic framework of ZnO and TpPa-1 can significantly increase the number of reactive sites. Furthermore, by adjusting the local electronic states of TpPa-1, the reaction pathway can be optimized, promoting the efficient separation of photogenerated electrons and holes. This results in the composite catalytic material exhibiting excellent photocatalytic activity and achieving efficient hydrogen peroxide production. These results demonstrate the significant importance of constructing a hollow structure and loading TpPa-1 for enhancing the photocatalytic activity of the composite material.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hollow ZnO composite catalytic material supported on COF, characterized in that, It has a hollow nanosphere structure, with ZnO hollow spheres as the framework and TpPa-1 particles coated on the outer surface of ZnO. The TpPa-1 particles are a covalent organic framework formed by trialdehyde phloroglucinol and p-phenylenediamine as raw materials.

2. The composite catalytic material as described in claim 1, characterized in that, The mass ratio of ZnO hollow spheres to TpPa-1 particles is 100:30~85.

3. A method for preparing the composite catalytic material according to claim 1, characterized in that, Includes the following steps: Zinc salt, template agent, and chelating agent are mixed evenly in ethanol and subjected to a first solvothermal treatment to prepare zinc oxide precursor; The zinc oxide precursor was calcined in air to obtain ZnO hollow spheres with a hollow structure; The ZnO hollow spheres are mixed evenly with trialdehyde phloroglucinol and p-phenylenediamine in ethanol and then subjected to a second solvothermal treatment to obtain the final product.

4. The preparation method according to claim 3, characterized in that, The template agent is polyvinylpyrrolidone; Alternatively, the chelating agent may be salicylic acid.

5. The preparation method according to claim 3, characterized in that, The zinc salt, template agent, and chelating agent are calculated as zinc acetate dihydrate, PVP, and salicylic acid, respectively, and the mass ratio of zinc salt, template agent, and chelating agent is 0.4~0.6:1~1.2:0.3~0.

5.

6. The preparation method according to claim 3, characterized in that, The first solvothermal treatment is carried out at a temperature of 160~180 ℃ for 12~14 h.

7. The preparation method according to claim 3, characterized in that, The calcination temperature is 500~600 ℃, and the calcination time is 3.5~4.5 h.

8. The preparation method according to claim 3, characterized in that, The second solvothermal treatment is carried out at a temperature of 180~200 ℃ for a time of 48~36 h.

9. The preparation method according to claim 3, characterized in that, The mass ratio of the ZnO hollow spheres to trialdehyde phloroglucinol and p-phenylenediamine is 1:0.2~0.6:0.15~0.

45.

10. The application of the composite catalytic material according to claim 1 or 2 in the photocatalytic preparation of hydrogen peroxide.

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