Titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation and preparation method and application thereof

Abstract

This invention discloses a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, its preparation method, and its application, belonging to the fields of nanomaterials and photocatalysis. It comprises sodium-modified titanium dioxide and a metal-doped zeolite imidazolium ester framework material. The defects introduced into the titanium dioxide through sodium modification effectively broaden the material's light absorption range and act as electron trapping centers, significantly suppressing the recombination of photogenerated carriers and improving light energy utilization efficiency. The Z-shaped heterojunction constructed between the sodium-modified titanium dioxide and the metal-doped zeolite imidazolium ester framework material forms a highly efficient directional charge transfer channel, achieving charge spatial separation while maximizing the preservation of the system's high redox potential, providing a strong driving force for deep CO2 reduction. The metal-doped zeolite imidazolium ester framework material, with its high specific surface area, porous structure, and active metal sites, synergistically enhances the physical enrichment and chemical activation capabilities of CO2.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and photocatalysis technology, specifically relating to a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, its preparation method and application. Background Technology

[0002] With increasingly severe energy and environmental challenges, converting inexhaustible solar energy into storable chemical energy has become an ideal solution. Among these, photocatalytic reduction of carbon dioxide has attracted particular attention. It aims to use sunlight to drive a reaction that directly converts the greenhouse gas CO2 into high-value fuels such as methanol and methane, potentially achieving both carbon cycling and clean energy storage, which has profound implications.

[0003] However, the development of this technology is limited by the performance of highly efficient photocatalytic materials. Taking classic titanium dioxide as an example, its intrinsic band gap is large, it mainly absorbs ultraviolet light, and its utilization rate of visible light, which constitutes the majority of the solar spectrum, is low. In addition, the electron-hole pairs generated by photoexcitation of the material are prone to rapid recombination in bulk, resulting in a limited number of charge carriers participating in surface reactions. To improve charge separation efficiency, constructing type II heterojunctions is a common approach, but this often causes a significant decrease in the redox potential of photogenerated electrons and holes, which is not conducive to the deep reduction of CO2 processes that require strong reducing power. At the same time, most catalysts still have significant shortcomings in terms of CO2 adsorption and enrichment, molecular activation, and selective regulation of catalytic pathways. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] In a first aspect, the present invention provides a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, comprising titanium dioxide and a zeolite imidazole ester framework material; wherein a Z-shaped heterojunction charge transfer interface is formed between the titanium dioxide and the zeolite imidazole ester framework material.

[0007] Preferably, the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation includes sodium-modified titanium dioxide and zeolite imidazole ester framework material.

[0008] Preferably, the titanium dioxide composite photocatalyst based on defect engineering and heterojunction control comprises titanium dioxide and a metal-doped zeolite imidazole ester framework material; preferably, the metal-doped zeolite imidazole ester framework material is metal-doped ZIF-8; preferably, the metal is selected from at least one of cobalt, copper, nickel, iron and manganese.

[0009] Preferably, the titanium dioxide composite photocatalyst based on defect engineering and heterojunction control comprises sodium-modified titanium dioxide and metal-doped zeolite imidazole ester framework material; a Z-shaped heterojunction charge transfer interface is formed between the sodium-modified titanium dioxide and the metal-doped zeolite imidazole ester framework material.

[0010] Preferably, in the sodium-modified titanium dioxide, the molar ratio of sodium to titanium is (0.01~0.2):1.

[0011] Preferably, the sodium-modified titanium dioxide surface has a titanate structure and defects, including hydroxyl defects and oxygen vacancy defects.

[0012] Preferably, in the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, the mass ratio of sodium-modified titanium dioxide to metal-doped zeolite imidazole ester framework material is 1:(0.5~4).

[0013] Preferably, the metal-doped zeolite imidazole ester framework material is metal-doped ZIF-8.

[0014] Preferably, the metal is selected from at least one of cobalt, copper, nickel, iron and manganese, with copper being the most preferred.

[0015] Preferably, in the metal-doped ZIF-8, copper ions partially replace zinc ions in the ZIF-8 framework in an atomically dispersed form, and the mass ratio of copper to zinc is (0.5~50):100.

[0016] A second aspect of the present invention provides a method for preparing the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation as described in the first aspect, comprising: Titanium dioxide, a zinc source, and organic ligands react in a solvent to grow a zeolite imidazole ester framework material in situ on the surface of titanium dioxide, resulting in a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation.

[0017] Preferably, the preparation method includes: dispersing titanium dioxide nanoparticles in an aqueous NaOH solution, carrying out a hydrothermal reaction, and then washing, drying, and calcining to obtain sodium-modified titanium dioxide; Sodium-modified titanium dioxide, a zinc source, a doped metal source, and an organic ligand are reacted in a solvent, and a metal-doped zeolite imidazole ester framework material is grown in situ on the sodium-modified titanium dioxide surface to obtain a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation.

[0018] Preferably, the concentration of the NaOH aqueous solution is 0.5~30 mol / L.

[0019] Preferably, the hydrothermal reaction is carried out at a temperature of 120~200℃ for a time of 12~48 h.

[0020] Preferably, the calcination is carried out at 400-500℃ for 1-3 hours.

[0021] Preferably, the zinc source is zinc nitrate or its hydrate.

[0022] Preferably, the doped metal source includes at least one of cobalt nitrate, cuprous chloride, copper nitrate, nickel nitrate, ferrous chloride, manganese chloride, or their hydrates.

[0023] Preferably, the solvent includes at least one of N,N-dimethylformamide, anhydrous ethanol, and methanol.

[0024] Preferably, sodium-modified titanium dioxide, a zinc source, a doped metal source, and an organic ligand are reacted in a solvent, and the reaction is carried out at room temperature for 12 to 48 hours.

[0025] A third aspect of the present invention provides an application of the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation described in the first aspect in the photocatalytic reduction of carbon dioxide to methanol.

[0026] Preferably, the photocatalytic reduction of carbon dioxide to methanol is carried out in a pure water medium without the addition of sacrificial agents.

[0027] A fourth aspect of the present invention provides a method for photocatalytic reduction of carbon dioxide to methanol, comprising: reducing carbon dioxide to methanol in a pure water medium under light irradiation and photocatalysis. The photocatalyst is the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation as described in the first aspect.

[0028] The beneficial effects of this invention are as follows: This invention provides a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, which can significantly suppress photogenerated carrier recombination and greatly enhance the adsorption and activation capacity of CO2, thereby achieving efficient and highly selective photocatalytic reduction of carbon dioxide to methanol in a sacrificial agent-free, pure water system. Specifically, firstly, the defects introduced into titanium dioxide by sodium modification effectively broaden the light absorption range of the material and act as electron trapping centers, significantly suppressing photogenerated carrier recombination and improving light energy utilization efficiency. Secondly, the Z-shaped heterojunction constructed between sodium-modified titanium dioxide and metal-doped zeolite imidazole ester framework material forms an efficient directional charge transfer channel, achieving charge spatial separation while maximizing the preservation of the system's high redox potential, providing a strong driving force for deep CO2 reduction. Thirdly, the metal-doped zeolite imidazole ester framework material, with its high specific surface area, porous structure, and active metal sites, synergistically enhances the physical enrichment and chemical activation capacity of CO2. Attached Figure Description

[0029] 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.

[0030] Figure 1 The image shows a scanning electron microscope (SEM) image of the composite photocatalyst prepared in Example 1 of this invention.

[0031] Figure 2 The X-ray diffraction patterns are those of the composite photocatalysts prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0032] Figure 3 This is a transmission electron microscope (TEM) image of the composite photocatalyst prepared in Example 1 of the present invention.

[0033] Figure 4 The images show the UV-Vis diffuse reflectance spectra of the composite photocatalysts prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0034] Figure 5 The transient fluorescence spectra of the composite photocatalysts prepared in Example 1 and Comparative Examples 1-3 of this invention are shown.

[0035] Figure 6 This is a comparison chart showing the yield and selectivity of the composite photocatalysts prepared in Examples 1-7 and Comparative Examples 1-3 under the same conditions for the photocatalytic reduction of CO2 to produce products. Detailed Implementation

[0036] This invention provides a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, its preparation method, and its application. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of this invention. The method and application of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the method and application described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0037] To address the systemic challenges in existing photocatalytic CO2 reduction technologies, such as limited light absorption of single materials (e.g., TiO2), severe carrier recombination, and the decrease in redox potential and insufficient CO2 enrichment and activation capacity of traditional heterojunctions (e.g., type II) when promoting charge separation, this invention provides a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, its preparation method, and its application. It proposes a composite catalyst design concept that synergistically regulates the process through defect engineering and Z-type heterojunctions.

[0038] Specifically, this invention first modifies TiO2 with sodium to broaden its photoresponse range and suppress carrier recombination by introducing defect states. Then, it is combined with a metal-doped zeolite imidazole ester framework material (M-ZIF-8) with high specific surface area and tunable metal sites to construct a tight Z-shaped heterojunction in situ. This structure cleverly combines the excellent CO2 adsorption and activation function of M-ZIF-8 with the unique advantages of Z-shaped heterojunctions—simultaneously achieving efficient charge transfer and maintaining a high redox potential—forming a synergistic catalytic system integrating broad-spectrum absorption, efficient charge separation and transport, strong redox capability, and high-concentration CO2 enrichment and activation. Ultimately, efficient and highly selective conversion of CO2 to methanol is achieved in a sacrificial agent-free, pure water system, providing a new strategy for designing multifunctional integrated photocatalysts.

[0039] A first typical embodiment of the present invention provides a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, comprising titanium dioxide and a zeolite imidazole ester framework material; a Z-shaped heterojunction charge transfer interface is formed between the titanium dioxide and the zeolite imidazole ester framework material.

[0040] In this invention, the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation includes sodium-modified titanium dioxide and zeolite imidazole ester framework material.

[0041] In this invention, the titanium dioxide composite photocatalyst based on defect engineering and heterojunction control comprises titanium dioxide and a metal-doped zeolite imidazole ester framework material; preferably, the metal-doped zeolite imidazole ester framework material is metal-doped ZIF-8; preferably, the metal is selected from at least one of cobalt, copper, nickel, iron and manganese.

[0042] In this invention, the titanium dioxide composite photocatalyst based on defect engineering and heterojunction control comprises sodium-modified titanium dioxide and metal-doped zeolite imidazole ester framework material; a Z-shaped heterojunction charge transfer interface is formed between the sodium-modified titanium dioxide and the metal-doped zeolite imidazole ester framework material.

[0043] In this invention, the mass ratio of sodium to titanium dioxide is (0.01~0.2):1. Within this mass ratio range, Na ion doping can improve the electronic structure of TiO2 and promote the separation of photogenerated carriers; however, excessive Na ion doping will damage its crystallinity, reduce its specific surface area, and ultimately lead to a sharp decrease in the catalytic efficiency of the composite photocatalyst.

[0044] In this invention, the sodium-modified titanium dioxide surface has a titanate structure and defects, including hydroxyl defects and oxygen vacancy defects.

[0045] In this invention, the mass ratio of sodium-modified titanium dioxide to metal-doped zeolite imidazole ester framework material in the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation is 1:(0.5~4). The main function of sodium-modified titanium dioxide is light absorption, while the metal-doped zeolite imidazole ester framework material serves as a CO2 enrichment center and catalytic active site. The composite of the two forms a heterojunction that promotes the separation of photogenerated electrons and holes. Excessive sodium modification of titanium dioxide leads to excessive electron recombination and insufficient active sites, while excessive metal-doped zeolite imidazole ester framework material reduces light absorption and affects photocatalytic performance.

[0046] In this invention, the metal-doped zeolite imidazolium ester framework material is metal-doped ZIF-8. ZIF-8 plays a role in enhancing the adsorption and capture of CO2 in this composite photocatalyst. Furthermore, Zn, as the central atom, forms a Cu-Zn bimetallic active site with Cu to stabilize CO*, and forms a heterojunction with sodium-modified titanium dioxide, promoting the separation of photogenerated electrons and holes. Other types of zeolite imidazolium ester framework materials, with different central atoms, produce different photocatalytic effects.

[0047] In this invention, the metal is selected from at least one of cobalt, copper, nickel, iron and manganese.

[0048] In this invention, the metal is copper; In metal-doped ZIF-8, copper ions partially replace zinc ions in the ZIF-8 framework in an atomically dispersed manner, with a copper to zinc mass ratio of (0.5~50):100.

[0049] In the ZIF-8 framework, copper primarily substitutes for zinc sites to form isolated Cu. 2+ For single-atom sites, the optimal doping amount is 10 wt%. In metal-doped ZIF-8, the amount of copper doping is affected by the stability of the ZIF-8 framework. Excessive copper ion doping will reduce the stability of the ZIF-8 framework, and excessive copper will form agglomerates on the ZIF-8 surface, resulting in uneven active sites.

[0050] In this invention, the titanate structure and abundant defects and hydroxyl groups induced in situ on the TiO2 surface by sodium not only broaden the light absorption range of the material but also serve as highly efficient electron-capturing centers, significantly delaying the recombination of photogenerated electron-hole pairs. Furthermore, the relationship between sodium-modified titanium dioxide (Na-TiO2) and the metal-doped zeolite imidazole ester framework material (M-ZIF-8) is not a simple physical composite but rather a tight Z-shaped heterojunction interface constructed in situ between Na-TiO2 and M-ZIF-8. This structure drives photogenerated electrons to migrate from the conduction band of M-ZIF-8 to the valence band of Na-TiO2 and recombine with holes, thus retaining strong reducing electrons in the conduction band of Na-TiO2 and strong oxidizing holes in the valence band of M-ZIF-8. This charge migration path achieves spatial separation while maximizing the preservation of the system's high redox potential, which is beneficial for the deep reduction of CO2 to methanol. Furthermore, the M-ZIF-8 component performs a dual function: its inherent ultra-high specific surface area and hierarchical porous structure enable highly efficient physical enrichment of CO2 molecules; while the atomically dispersed M active sites can chemically adsorb and activate CO2 molecules, lowering the reaction energy barrier. The combination of these two aspects ensures a high local CO2 concentration and high reactivity on the catalyst surface.

[0051] A second typical embodiment of the present invention provides a method for preparing the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, comprising: Titanium dioxide, a zinc source, and organic ligands react in a solvent to grow a zeolite imidazole ester framework material in situ on the surface of titanium dioxide, resulting in a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation.

[0052] The preparation process of this titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation is simple, mild, and easy to follow. The preparation methods used are all conventional in the field, requiring no complex equipment or harsh conditions. The raw materials are readily available, and it has good reproducibility and potential for large-scale application.

[0053] In this invention, the preparation method includes: Titanium dioxide nanoparticles were dispersed in NaOH aqueous solution and subjected to a hydrothermal reaction. After washing, drying and calcination, sodium-modified titanium dioxide was obtained. Sodium-modified titanium dioxide, a zinc source, a doped metal source, and an organic ligand are reacted in a solvent, and a metal-doped zeolite imidazole ester framework material is grown in situ on the sodium-modified titanium dioxide surface to obtain a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation.

[0054] In the preparation of sodium-modified titanium dioxide, the product obtained after hydrothermal treatment with NaOH is an amorphous product, which is then calcined to obtain anatase phase product.

[0055] In this invention, the concentration of the NaOH aqueous solution is 0.5~30 mol / L.

[0056] In this invention, the hydrothermal reaction temperature is 120~200℃ and the time is 12~48 h.

[0057] In this invention, the calcination is carried out at 400-500℃ for 1-3 hours.

[0058] In this invention, the zinc source is zinc nitrate or its hydrate.

[0059] In this invention, the doped metal source includes, but is not limited to, at least one of cobalt nitrate, cuprous chloride, copper nitrate, nickel nitrate, ferrous chloride, manganese chloride, or their hydrates.

[0060] In this invention, the solvent includes, but is not limited to, at least one of N,N-dimethylformamide (DMF), anhydrous ethanol, and methanol.

[0061] In this invention, sodium-modified titanium dioxide, a zinc source, a doped metal source, and an organic ligand are reacted in a solvent. The reaction is carried out at room temperature for 12 to 48 hours.

[0062] In the preparation process, the porous structure formed by the doped metal and ZIF-8 is key to the photocatalytic reduction of carbon dioxide to methanol. The active sites of Cu stabilize CO radicals and inhibit CO radical desorption to generate CO; the porous structure of ZIF-8 enhances CO2 adsorption. Excess Cu in the preparation of Cu-ZIF-8 will lead to a decrease in the stability of the ZIF-8 framework and uneven distribution of active sites.

[0063] The third typical embodiment of the present invention provides an application of the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation in the photocatalytic reduction of carbon dioxide to methanol.

[0064] In this invention, the photocatalytic reduction of carbon dioxide to methanol is carried out in a pure water medium without the addition of sacrificial agents.

[0065] A fourth typical embodiment of the present invention provides a method for photocatalytic reduction of carbon dioxide to methanol, comprising: reducing carbon dioxide to methanol in a pure water medium under light irradiation and photocatalysis. The photocatalyst is the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation.

[0066] This invention provides a titanium dioxide composite photocatalyst based on defect engineering and heterojunction modulation. It is formed by in-situ growth of Na-TiO2, consisting of titanate and defect-rich Na-TiO2 formed by NaOH heat treatment, and a metal-doped MOF, creating a Z-shaped heterojunction between the two. This composite photocatalyst can effectively modulate the energy band and promote charge separation, enhancing CO2 enrichment and activation capabilities. The Z-shaped heterojunction enables the directional migration and spatial separation of photogenerated carriers, maximizing the preservation of the system's strong reducing power. Under mild conditions of pure water and no sacrificial agents, this catalyst exhibits excellent photocatalytic CO2 reduction to methanol production. The preparation method of this invention is simple, providing a new approach for the design and development of efficient and highly selective CO2 photoreduction catalysts.

[0067] 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.

[0068] Unless otherwise specified, all reagents and materials used in the following examples and comparative examples are commercially available.

[0069] Example 1 A method for preparing a titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation includes the following steps: Preparation of S1 and Na-TiO2: Take 20 mL of tetrabutyl titanate, disperse it in 80 mL of anhydrous ethanol, add 4 mL of deionized water while stirring vigorously, and hydrolyze at room temperature for 2 hours to obtain a transparent sol. Disperse the sol in 150 mL of 10 mol·L⁻¹ solution. -1 A homogeneous suspension was formed by magnetic stirring in a NaOH aqueous solution for 30 minutes. The suspension was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE) and subjected to hydrothermal reaction at 180 °C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting precipitate was then diluted with deionized water and 0.5 mol·L⁻¹ -1The HCl solution was repeatedly centrifuged and washed until the filtrate was neutral (pH≈7), then dried in a vacuum drying oven at 80℃ for 12 hours, and calcined in a muffle furnace at 450℃ for 2 hours to obtain Na-TiO2 powder. The Na / Ti mass ratio was determined to be approximately 0.0166 by ICP-OES.

[0070] Construction of S2 and Z-type heterojunction composite photocatalysts: Accurately weigh 50.0 mg of Na-TiO2 powder prepared in step S1 and place it in a 250 mL three-necked flask. Add 20 mL of DMF and sonicate for 30 minutes to form a homogeneous and stable suspension. Add 82 mg of Zn(NO3)2·6H2O and 4.8 mg of CuCl2·2H2O to the suspension sequentially. Stir magnetically at room temperature for 30 minutes until the metal salt is completely dissolved, forming a homogeneous mixed dispersion (named Solution A). In another container, dissolve 180 mg of 2-methylimidazole in 10 mL of methanol to form a clear solution (named Solution B). Quickly pour Solution B into Solution A under vigorous stirring. Continue stirring the mixture at room temperature for 24 hours. After the reaction is complete, centrifuge the resulting solid product and wash it at least three times with deionized water and DMF to remove unreacted raw materials and solvents. Finally, the product was dried in a vacuum drying oven at 60°C for 12 hours to obtain the titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation.

[0071] In the Na-TiO2 / Cu-ZIF-8 obtained in this embodiment, the mass ratio of Na-TiO2 to Cu-ZIF-8 is 1:1.

[0072] Example 2 A method for preparing a titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation includes the following steps: Preparation of S1 and Na-TiO2: Same as Example 1.

[0073] Construction of S2 and Z-type heterojunction composite photocatalysts: Accurately weigh 50.0 mg of Na-TiO2 powder prepared in step S1 and place it in a 250 mL three-necked flask. Add 20 mL of DMF and sonicate for 30 minutes to form a homogeneous and stable suspension. Add 41 mg of Zn(NO3)2·6H2O and 2.4 mg of CuCl2·2H2O to the suspension sequentially. Stir magnetically at room temperature for 30 minutes until the metal salt is completely dissolved, forming a homogeneous mixed dispersion (named Solution A). In another container, dissolve 90 mg of 2-methylimidazole in 10 mL of DMF to form a clear solution (named Solution B). Quickly pour Solution B into Solution A under vigorous stirring. Continue stirring the mixture at room temperature for 24 hours. After the reaction is complete, centrifuge the resulting solid product and wash it at least three times with deionized water and DMF to remove unreacted raw materials and solvents. Finally, the product was dried in a vacuum drying oven at 60°C for 12 hours to obtain the titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation.

[0074] In the Na-TiO2 / Cu-ZIF-8 obtained in this embodiment, the mass ratio of Na-TiO2 to Cu-ZIF-8 is 1:0.5.

[0075] Example 3 A method for preparing a titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation includes the following steps: Preparation of S1 and Na-TiO2: Same as Example 1.

[0076] Construction of S2 and Z-type heterojunction composite photocatalysts: Accurately weigh 50.0 mg of the Na-TiO2 powder prepared in step S1 and place it in a 250 mL three-necked flask. Add 20 mL of DMF and sonicate for 30 minutes to form a homogeneous and stable suspension. Add 164 mg of Zn(NO3)2·6H2O and 9.6 mg of CuCl2·2H2O to the suspension sequentially. Stir magnetically at room temperature for 30 minutes until the metal salt is completely dissolved, forming a homogeneous mixed dispersion (named Solution A). In another container, dissolve 360 ​​mg of 2-methylimidazole in 20 mL of DMF to form a clear solution (named Solution B). Quickly pour Solution B into Solution A under vigorous stirring. Continue stirring the mixture at room temperature for 24 hours. After the reaction is complete, centrifuge the resulting solid product and wash it at least three times with deionized water and DMF to remove unreacted raw materials and solvents. Finally, the product was dried in a vacuum drying oven at 60°C for 12 hours to obtain the titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation.

[0077] In the Na-TiO2 / Cu-ZIF-8 obtained in this embodiment, the mass ratio of Na-TiO2 to Cu-ZIF-8 is 1:2.

[0078] Example 4 A method for preparing a titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation includes the following steps: Preparation of S1 and Na-TiO2: Same as Example 1.

[0079] Preparation of S2 and Cu-ZIF-8: 1.0 g of Zn(NO3)2·6H2O and 0.059 g of CuCl2·2H2O (Cu / Zn mass ratio 10:100) were dissolved in 40 mL of DMF, denoted as solution A. 1.313 g of 2-methylimidazole was dissolved in 40 mL of DMF, denoted as solution B. Solution B was rapidly poured into solution A under vigorous stirring, and the reaction was continued at room temperature for 24 hours. After the reaction was complete, the resulting product was centrifuged, washed three times with DMF and deionized water, and dried under vacuum overnight at 60 °C to obtain Cu-ZIF-8 powder.

[0080] Construction of S3 and Z-type heterojunction composite photocatalysts: Accurately weigh 50.0 mg of Na-TiO2 powder prepared in step S1 and place it in a 250 mL three-necked flask. Weigh 50 mg of Cu-ZIF-8 powder prepared in step S2 and add it to the flask. Add 50 mL of DMF solution to disperse the powder. Stir the mixture of Na-TiO2 and Cu-ZIF-8 at room temperature for 4 hours. After the reaction is complete, centrifuge the resulting solid product and wash it at least three times with deionized water and DMF to remove unreacted raw materials and solvents. Finally, dry the product in a vacuum drying oven at 60 °C for 12 hours to obtain the final composite photocatalyst.

[0081] In the Na-TiO2 / Cu-ZIF-8 obtained in this embodiment, the mass ratio of Na-TiO2 to Cu-ZIF-8 is 1:1.

[0082] Example 5 A method for preparing a titanium dioxide composite photocatalyst Na-TiO2 / Co-ZIF-8 based on defect engineering and heterojunction regulation includes the following steps: Preparation of S1 and Na-TiO2: Same as Example 1.

[0083] Construction of S2 and Z-type heterojunction composite photocatalysts: The difference from Example 1 is that the copper salt (CuCl2·2H2O) is replaced with an equimolar amount of the cobalt salt Co(NO3)2·6H2O.

[0084] In the Na-TiO2 / Co-ZIF-8 obtained in this embodiment, the mass ratio of Na-TiO2 to Co-ZIF-8 is 1:1.

[0085] Example 6 A method for preparing a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation includes the following steps: Accurately weigh 50.0 mg of TiO2 powder and place it in a 250 mL three-necked flask. Add 20 mL of DMF and sonicate for 30 minutes to form a homogeneous and stable suspension. Add 82 mg of Zn(NO3)2·6H2O and 4.8 mg of CuCl2·2H2O sequentially to the suspension. Stir magnetically at room temperature for 30 minutes until the metal salt is completely dissolved, forming a homogeneous mixed dispersion (named Solution A). In another container, dissolve 180 mg of 2-methylimidazole in 10 mL of methanol to form a clear solution (named Solution B). Quickly pour Solution B into Solution A under vigorous stirring. Continue stirring the mixture at room temperature for 24 hours. After the reaction, centrifuge the resulting solid product and wash it at least three times with deionized water and DMF to remove unreacted raw materials and solvent. Finally, dry the product in a vacuum drying oven at 60 °C for 12 hours to obtain the TiO2 / Cu-ZIF-8 titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation.

[0086] In the TiO2 / Cu-ZIF-8 obtained in this embodiment, the mass ratio of TiO2 to Cu-ZIF-8 is 1:1.

[0087] Example 7 A method for preparing a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation includes the following steps: Preparation of S1 and Na-TiO2: Same as Example 1.

[0088] Construction of S2 and Z-type heterojunction composite photocatalysts: Accurately weigh 50.0 mg of TiO2 powder and place it in a 250 mL three-necked flask. Add 20 mL of DMF and sonicate for 30 minutes to form a homogeneous and stable suspension. Add 82 mg of Zn(NO3)2·6H2O to the suspension. Stir magnetically at room temperature for 30 minutes until the metal salt is completely dissolved, forming a homogeneous mixed dispersion (named Solution A). In another container, dissolve 180 mg of 2-methylimidazole in 10 mL of methanol to form a clear solution (named Solution B). Under vigorous stirring, quickly pour Solution B into Solution A. Continue stirring the mixture at room temperature for 24 hours. After the reaction is complete, centrifuge the obtained solid product and wash it at least three times with deionized water and DMF to remove unreacted raw materials and solvents. Finally, dry the product in a vacuum drying oven at 60 °C for 12 hours to obtain the titanium dioxide composite photocatalyst Na-TiO2 / ZIF-8 based on defect engineering and heterojunction regulation.

[0089] In the Na-TiO2 / ZIF-8 obtained in this embodiment, the mass ratio of Na-TiO2 to ZIF-8 is 1:1.

[0090] Comparative Example 1 A method for preparing a photocatalyst includes the following steps: 1.0 g of Zn(NO3)2·6H2O and 0.059 g of CuCl2·2H2O (Cu / Zn mass ratio 10:100) were dissolved in 40 mL of DMF, denoted as solution A. 1.313 g of 2-methylimidazole was dissolved in 40 mL of DMF, denoted as solution B. Solution B was rapidly poured into solution A under vigorous stirring, and the reaction was continued at room temperature for 24 hours. After the reaction was complete, the resulting product was centrifuged, washed three times with DMF and deionized water, and dried under vacuum overnight at 60 °C to obtain Cu-ZIF-8 powder.

[0091] Comparative Example 2 A method for preparing a photocatalyst includes the following steps: Take 20 mL of tetrabutyl titanate and disperse it in 80 mL of anhydrous ethanol. Add 4 mL of deionized water while stirring vigorously, and hydrolyze at room temperature for 2 hours to obtain a transparent sol. Disperse the sol in 150 mL of 10 mol·L⁻¹ ethanol. -1 A homogeneous suspension was formed by magnetic stirring in a NaOH aqueous solution for 30 minutes. The suspension was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE) and subjected to hydrothermal reaction at 180 °C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting precipitate was then diluted with deionized water and 0.5 mol·L⁻¹ -1The HCl solution was repeatedly centrifuged and washed until the filtrate was neutral (pH≈7), then dried in a vacuum drying oven at 80℃ for 12 hours, and calcined in a muffle furnace at 450℃ for 2 hours to obtain Na-TiO2 powder. The Na / Ti mass ratio was determined to be approximately 0.0166 by ICP-OES.

[0092] Comparative Example 3 Commercial P25 TiO2 powder without any treatment was used directly as a photocatalyst.

[0093] Performance testing: 1. Characterization Figure 1 The image shows the SEM spectrum of the titanium dioxide composite photocatalyst Na-TiO2 / Cu-ZIF-8 based on defect engineering and heterojunction regulation obtained in Example 1 of this invention. As can be seen from the image, the composite photocatalyst has a band-like structure and the Cu-ZIF-8 on the surface of Na-TiO2 is uniformly distributed.

[0094] Figure 2 The XRD patterns of Example 1 and Comparative Examples 1-2 of this invention show that the composite photocatalyst has good crystallinity. The positions of Cu-ZIF-8 at 7.3°, 10.4°, 12.7°, 14.7°, 16.4°, 18.0°, and 24.5° correspond to the (011), (002), (112), (022), (013), and (222) crystal planes, respectively, and the composite photocatalyst still has good crystallinity.

[0095] Figure 3 The image shows the TEM spectrum of the titanium dioxide composite photocatalyst Na-TiO2 / Co-ZIF-8 based on defect engineering and heterojunction regulation obtained in Example 1 of this invention. Combined with the SEM spectrum, it can be clearly seen that the structure of the composite photocatalyst is a band-like structure, which forms a good loading interface with the surface Cu-ZIF-8, providing a basis for the formation of Z-type heterojunction.

[0096] Figure 4 and Figure 5 The UV-Vis diffuse reflectance and transient fluorescence spectra of the examples and comparative examples are shown respectively. Compared with the comparative example, Example 1 can obtain higher light absorption and higher fluorescence lifetime.

[0097] 2. Application of photocatalysts in the photocatalytic reduction of carbon dioxide to methanol The photocatalytic reduction reaction was carried out in a quartz glass reactor. 20 mg of photocatalyst and 50 mL of deionized water were added to the reactor and thoroughly mixed using ultrasound. The reaction temperature was maintained at 298 K using a cryogenic cooling circulation system. The reactor was purged with nitrogen for 30 minutes to eliminate the influence of air, followed by a 30-minute carbon dioxide purging to ensure complete carbon dioxide injection. The photocatalytic reduction of CO2 was then carried out under 300 W xenon lamp irradiation, without the addition of any other auxiliary catalysts or sacrificial agents. All reduction experiments were repeated three times to ensure stability and reproducibility. The products of the photocatalytic reduction reaction were analyzed using gas chromatography (GC) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0098] Figure 6 The figures show the products and selectivity of the photocatalytic reduction of CO2 by the composite photocatalysts obtained in Examples 1-5 and Comparative Examples 1-5. As can be seen from the figures, Example 1 has a higher methanol product yield and selectivity, with a selectivity of 91.86%.

[0099] 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 titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, characterized in that, It includes titanium dioxide and zeolite imidazole ester framework material; a Z-shaped heterojunction charge transfer interface is formed between the titanium dioxide and the zeolite imidazole ester framework material.

2. The titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation as described in claim 1, characterized in that, The titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation includes sodium-modified titanium dioxide and zeolite imidazole ester framework material. Alternatively, the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation comprises titanium dioxide and a metal-doped zeolite imidazole ester framework material; preferably, the metal-doped zeolite imidazole ester framework material is metal-doped ZIF-8; preferably, the metal is selected from at least one of cobalt, copper, nickel, iron and manganese.

3. The titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation as described in claim 1, characterized in that, The titanium dioxide composite photocatalyst based on defect engineering and heterojunction control includes sodium-modified titanium dioxide and metal-doped zeolite imidazole ester framework material; a Z-shaped heterojunction charge transfer interface is formed between the sodium-modified titanium dioxide and the metal-doped zeolite imidazole ester framework material. Preferably, in the sodium-modified titanium dioxide, the molar ratio of sodium to titanium is (0.01~0.2):1; Preferably, the sodium-modified titanium dioxide surface has a titanate structure and defects, including hydroxyl defects and oxygen vacancy defects; Preferably, in the titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation, the mass ratio of sodium-modified titanium dioxide to metal-doped zeolite imidazole ester framework material is 1:(0.5~4).

4. The titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation as described in claim 3, characterized in that, The metal-doped zeolite imidazole ester framework material is metal-doped ZIF-8; Preferably, the metal is selected from at least one of cobalt, copper, nickel, iron and manganese, with copper being the most preferred; Preferably, in the metal-doped ZIF-8, copper ions partially replace zinc ions in the ZIF-8 framework in an atomically dispersed form, and the mass ratio of copper to zinc is (0.5~50):

100.

5. A method for preparing a titanium dioxide composite photocatalyst based on defect engineering and heterojunction control as described in any one of claims 1-4, characterized in that, include: Titanium dioxide, a zinc source, and organic ligands react in a solvent to grow a zeolite imidazole ester framework material in situ on the surface of titanium dioxide, resulting in a titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation.

6. The preparation method according to claim 5, characterized in that, The preparation method includes: dispersing titanium dioxide nanopowder in NaOH aqueous solution, carrying out hydrothermal reaction, and then washing, drying and calcining to obtain sodium-modified titanium dioxide; Sodium-modified titanium dioxide, zinc source, doped metal source and organic ligand react in solvent, and metal-doped zeolite imidazole ester framework material is grown in situ on sodium-modified titanium dioxide surface to obtain titanium dioxide composite photocatalyst based on defect engineering and heterojunction regulation. Preferably, the concentration of the NaOH aqueous solution is 0.5~30 mol / L; Preferably, the hydrothermal reaction is carried out at a temperature of 120~200℃ for a time of 12~48 h; Preferably, the calcination is carried out at 400-500℃ for 1-3 hours.

7. The preparation method according to claim 6, characterized in that, The zinc source is zinc nitrate or its hydrate; Preferably, the doped metal source includes at least one of cobalt nitrate, cuprous chloride, copper nitrate, nickel nitrate, ferrous chloride, manganese chloride, or their hydrates.

8. The preparation method according to claim 6, characterized in that, The solvent includes at least one of N,N-dimethylformamide, anhydrous ethanol, and methanol; Preferably, sodium-modified titanium dioxide, a zinc source, a doped metal source, and an organic ligand are reacted in a solvent, and the reaction is carried out at room temperature for 12 to 48 hours.

9. The application of the titanium dioxide composite photocatalyst based on defect engineering and heterojunction control as described in any one of claims 1-4 in the photocatalytic reduction of carbon dioxide to methanol; Preferably, the photocatalytic reduction of carbon dioxide to methanol is carried out in a pure water medium without the addition of sacrificial agents.

10. A method for photocatalytic reduction of carbon dioxide to methanol, characterized in that, include: Under light conditions and with the catalytic action of a photocatalyst, carbon dioxide is reduced to methanol in a pure water medium; The photocatalyst is the titanium dioxide composite photocatalyst based on defect engineering and heterojunction control as described in any one of claims 1-4.

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