A bismuth oxybromide-based bi-interface electric field heterojunction photocatalyst, a preparation method and application thereof

Abstract

This invention provides a bismuth oxybromine-based dual-interface electric field heterojunction photocatalyst, its preparation method, and its application. The preparation method includes: uniformly mixing MIL-68(In), a sulfur source, and a first solvent, and carrying out a first solvothermal reaction at 120℃~180℃ to obtain an In2S3 / MIL-68(In) composite material; then uniformly mixing the In2S3 / MIL-68(In) composite material with a bismuth source, a bromine source, a polyol, an anionic surfactant, and a second solvent, and carrying out a second solvothermal reaction at 100~160℃ to obtain the bismuth oxybromine-based dual-interface electric field heterojunction photocatalyst. This invention constructs a heterojunction structure with dual-interface electric fields (In-S bonds and Bi-S bonds), forming a synergistically enhanced built-in electric field, effectively driving the spatial separation and directional migration of photogenerated electrons and holes, significantly improving the carrier separation efficiency and intrinsic photocatalytic activity of the material.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, specifically to a bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] With rapid industrialization, large quantities of recalcitrant organic pollutants such as dyes, antibiotics, and phenols are being discharged into aquatic environments, posing a persistent threat to ecosystems and human health. Semiconductor photocatalysis, a green advanced oxidation technology that utilizes solar energy to drive pollutant decomposition, has become a research hotspot and core technology in the field of environmental governance due to its high efficiency, low energy consumption, and lack of secondary pollution.

[0003] Bismuth oxybromide (BiOBr) materials have shown promise in visible light photocatalysis due to their unique layered crystal structure, moderate band gap (approximately 2.7 eV), and good chemical stability. However, single BiOBr materials suffer from inherent drawbacks such as rapid photo-electron-hole recombination rates and limited visible light absorption range, making it difficult to meet practical application requirements in terms of quantum efficiency and catalytic performance. To address this, researchers have developed bismuth-rich Bi5O7Br as a promising alternative material. Compared to traditional BiOBr, Bi5O7B has a narrower band gap (approximately 2.3-2.5 eV), meaning it has a wider absorption range and higher utilization rate for visible light. More importantly, Bi5O7B crystals possess a stronger internal polarization electric field, stemming from its unique asymmetric structure of alternating [Bi5O7] and Br layers. This electric field can more effectively drive the separation and migration of photogenerated charges, thus providing a new approach to solving the charge recombination problem.

[0004] To further enhance photocatalytic performance, constructing heterojunctions is one of the most effective strategies. Traditional binary heterojunctions (such as CdS / BiOBr, Angew. Chem. Int. Ed. 2025, 64, e202505456; g-C3N4 / BiOBr, Chin. J. Catal. 2025, 72, 118-129) can promote charge separation to some extent by forming a single built-in electric field at the interface of the two semiconductors. However, the charge separation path of such structures is relatively simple, the range of electric field is limited, and photogenerated carriers may recombine in the bulk phase or at a single interface, resulting in a bottleneck in performance improvement. In contrast, ternary heterojunction systems exhibit significant advantages. By carefully selecting a third material with a matching band structure for recombination, synergistic charge transfer channels with two or even multiple interfaces can be constructed (such as BiOBr / Fe3O4 / Ti3C2). In this structure, a directionally synergistic built-in electric field can be formed at the two heterojunctions, providing a high-speed S-shaped transport path for photogenerated electrons and holes, thereby achieving more thorough and faster charge space separation. Simultaneously, the components can achieve functional complementarity in terms of light absorption, adsorption capacity, and active sites, producing a synergistic catalytic effect. Although the theoretical advantages of ternary heterojunctions are obvious, research on constructing heterojunction photocatalysts with a clear synergistic effect of dual-interface electric fields using high-performance Bi5O7Br as the core component is still insufficient. Existing preparation methods are often cumbersome and lack controllability, making it difficult to precisely control the heterojunction interface structure, while interface quality is precisely the key to determining the built-in electric field strength and charge transport efficiency. Therefore, developing a simple, mild, and structurally controllable method for preparing Bi5O7Br-based dual-interface electric field heterojunctions is of great value for promoting the practical application of highly efficient visible light photocatalysts. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst, its preparation method and application, aiming to solve the technical problems of existing photocatalysts such as narrow visible light response, rapid carrier recombination, insufficient degradation efficiency and stability, and complex preparation process.

[0006] In a first aspect, the present invention provides a method for preparing a bismuth oxybromodimethyl bromide-based dual-interface electric field heterojunction photocatalyst, comprising the following steps: S1. Mix MIL-68(In), sulfur source and first solvent evenly, and carry out first solvothermal reaction at 120℃~180℃. After solid-liquid separation, washing and drying, In2S3 / MIL-68(In) composite material is obtained. S2. The In2S3 / MIL-68(In) composite material is mixed with bismuth source, bromine source, polyol, anionic surfactant and second solvent, and a second solvothermal reaction is carried out at 100~160℃. After solid-liquid separation, washing and drying, a bismuth oxybromine-based dual-interface electric field heterojunction photocatalyst is obtained.

[0007] In a second aspect, the present invention provides a bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst, which is prepared by the preparation method described in the first aspect.

[0008] Thirdly, the present invention provides an application of a bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst in the photocatalytic degradation of organic pollutants.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst provided by the present invention forms a synergistically enhanced built-in electric field by constructing a heterojunction structure with dual-interface electric fields (In-S bond and Bi-S bond), which effectively drives the spatial separation and directional migration of photogenerated electrons and holes, thereby significantly suppressing the recombination of electron-hole pairs and significantly improving the carrier separation efficiency and intrinsic photocatalytic activity of the material.

[0010] (2) The preparation methods (hydrothermal, solvothermal and in-situ growth methods) used in this invention are simple, mild and highly controllable, and can easily achieve precise control of catalyst morphology, size and component ratio. They have good repeatability and lay a solid foundation for large-scale preparation.

[0011] (3) The catalyst prepared by the present invention exhibits excellent performance in the efficient degradation of organic pollutants, thanks to the synergistic effect of the dual interface electric field and the stable heterojunction structure. Attached Figure Description

[0012] Figure 1 The image shows a scanning electron microscope (SEM) image of the Bi5O7Br / In2S3 / MIL-68(In) composite catalyst prepared in Example 1 of this invention. Figure 2 The image shows a scanning electron microscope (SEM) image of the In2S3 / MIL-68(In) composite catalyst prepared in Comparative Example 1 of this invention. Figure 3 The image shows a scanning electron microscope (SEM) image of the Bi5O7Br catalyst prepared in Comparative Example 4 of this invention. Figure 4 The results show the performance of the catalysts prepared in the various embodiments and comparative examples of this invention in the photocatalytic degradation of organic pollutants under simulated visible light. Detailed Implementation

[0013] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0014] To address the technical challenges of existing photocatalysts, such as narrow visible light response, rapid carrier recombination, insufficient degradation efficiency and stability, and complex preparation processes, this invention provides a bismuth oxybromine-based dual-interface electric field heterojunction photocatalyst, its preparation method, and its application. Specifically, by constructing a heterojunction and introducing an interfacial electric field strategy, MOF is combined with In2S3 to form a core-shell structure, which is then combined with Bi5O7Br to construct a dual-interface heterojunction. This generates a synergistic built-in electric field, further enhancing charge separation efficiency.

[0015] In a first aspect, embodiments of the present invention provide a method for preparing a bismuth oxybromodiphenyl ether-based dual-interface electric field heterojunction photocatalyst, comprising the following steps: S1. Mix MIL-68(In), sulfur source and first solvent evenly, and carry out first solvothermal reaction at 120℃~180℃. After solid-liquid separation, washing and drying, In2S3 / MIL-68(In) composite material is obtained. S2. The In2S3 / MIL-68(In) composite material is mixed with bismuth source, bromine source, polyol, anionic surfactant and second solvent, and a second solvothermal reaction is carried out at 100~160℃. After solid-liquid separation, washing and drying, a bismuth oxybromine-based dual-interface electric field heterojunction photocatalyst is obtained.

[0016] In the technical solution of this invention embodiment, the metal-organic framework material MIL-68(In) is used as the indium source and carrier. MIL-68(In) and the sulfur source undergo a solvothermal reaction in an organic solvent system, and the thiourea decomposes to provide sulfur. 2- In situ growth of In2S3 on the surface of MIL-68(In) was achieved, forming an In2S3 / MIL-68(In) composite structure. In the presence of this composite, bismuth and bromine sources were subjected to a solvothermal reaction in a solvent system, inducing the formation of bismuth oxybromine (Bi5O7Br) on the In2S3 / MIL-68(In) surface. Through the interfacial coupling effect between In-S bonds and Bi-S bonds, a tight heterojunction structure was formed with In2S3. The construction of this dual-interface electric field effectively controlled the separation and migration pathways of photogenerated electrons and holes, significantly suppressing carrier recombination, thereby endowing the material with excellent photocatalytic performance. Finally, a Bi5O7Br-based dual-interface heterojunction photocatalyst with high specific surface area, broad spectral response, and high charge separation efficiency was obtained, suitable for photocatalytic degradation of pollutants and photocatalytic synthesis.

[0017] Furthermore, in some embodiments, the reaction time of the first solvothermal reaction is 2-6 hours; the reaction time of the second solvothermal reaction is 8-20 hours.

[0018] Furthermore, in some embodiments, in step S1, the sulfur source includes at least one of thiourea, thiols, thioethers, and thiophenols.

[0019] Furthermore, in some embodiments, in step S1, the mass ratio of MIL-68(In) to the sulfur source is 1:(2~3).

[0020] Furthermore, in some embodiments, in step S1, the first solvent includes ethanol; the mass-to-volume ratio of MIL-68(In) to the first solvent is (12~20) mg: 1 mL.

[0021] Furthermore, in some embodiments, in step S2, the bismuth source includes at least one of bismuth nitrate and bismuth chloride; the bromine source includes at least one of hexadecyltrimethylammonium bromide and dodecyltrimethylammonium bromide; the polyol includes at least one of mannitol, sorbitol, polyethylene glycol, and ethylene glycol; and the anionic surfactant includes at least one of sodium oleate and sodium dodecyl sulfate.

[0022] In the technical solution of this invention, polyols, acting as morphology modifiers, effectively regulate the nucleation and growth kinetics of Bi5O7Br crystals through coordination with bismuth ions via their abundant hydroxyl functional groups. This induces the formation of nanosheet structures with specific exposed crystal faces, increasing the specific surface area and providing more active sites. The introduction of anionic surfactants further regulates the dispersibility and interfacial contact state of the product through electrostatic adsorption and steric hindrance effects, ensuring a tight interfacial bond between Bi5O7Br and In2S3 / MIL-68(In), laying the structural foundation for the efficient construction of a dual-interfacial electric field.

[0023] Furthermore, in some embodiments, in step S2, the mass ratio of the In2S3 / MIL-68(In) composite material to bismuth source, polyol, anionic surfactant, and bromine source is (0.01~0.07):(0.2~0.6):(0.5~2):(0.02~0.1):(0.1~0.5).

[0024] Furthermore, in some embodiments, in step S2, the second solvent comprises a mixed solution of water and ethanol; the mass-to-volume ratio of the In2S3 / MIL-68(In) composite material to the second solvent is (0.01~0.07) g: 60 mL.

[0025] Furthermore, in some embodiments, in step S2, the drying temperature is 60~100℃ and the drying time is 12~48h.

[0026] Furthermore, in some embodiments, the preparation method of MIL-68(In) includes: dissolving indium nitrate and terephthalic acid in N,N-dimethylformamide, stirring evenly, and then carrying out a solvothermal reaction at 120°C~140°C, followed by solid-liquid separation, washing, and drying to obtain MIL-68(In).

[0027] Secondly, embodiments of the present invention provide a bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst, which is prepared by the preparation method described in the first aspect.

[0028] Thirdly, embodiments of the present invention provide an application of a bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst in the photocatalytic degradation of organic pollutants.

[0029] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0030] Example 1 A method for preparing a bismuth oxybromodimethyl bromide-based dual-interface electric field heterojunction photocatalyst, the specific steps of which are as follows: (1) Dissolve 400 mg of indium nitrate tetrahydrate and 400 mg of terephthalic acid in 100 mL of DMF and stir at room temperature for 30 min. Transfer the resulting solution to a high-pressure reactor lined with polytetrafluoroethylene, seal it and place it in a 120 ℃ electric thermostatic drying oven for 2 h. After the reaction system cools naturally to room temperature, centrifuge it and wash the solid product with DMF and ethanol in sequence. After drying, MIL-68(In) is obtained.

[0031] (2) Disperse 250 mg of the above MIL-68(In) in 15 mL of ethanol, add dropwise 15 mL of ethanol solution containing 500 mg of thiourea, sonicate and stir for 30 minutes, then transfer the mixture to a polytetrafluoroethylene-lined autoclave and react at 160 °C for 2 h. After the reaction is completed, cool naturally to room temperature, centrifuge, wash the product with water and ethanol in sequence, and dry to obtain In2S3 / MIL-68(In) composite material.

[0032] (3) Take 10 mg of In2S3 / MIL-68(In) composite material and disperse it in 60 mL of a mixed solvent consisting of 30 mL of ethylene glycol and 30 mL of deionized water. Sonicate for 1 h. Then add 0.4 g of bismuth nitrate pentahydrate, 1.5 g of mannitol, 0.05 g of sodium oleate and 0.3 g of hexadecyltrimethylammonium bromide (CTAB) to the dispersion in sequence and continue to sonicate for 60 min to fully dissolve and disperse it. Transfer the mixture to a high-pressure reactor and hydrothermally react at 140 ℃ for 14 h. After the reaction is completed, cool naturally, centrifuge to collect the precipitate, and wash it several times with water and ethanol in sequence. Finally, place the product in a vacuum drying oven at 100 ℃ and dry for 24 h. After grinding, obtain Bi5O7Br / In2S3 / MIL-68(In) composite catalyst, namely bismuth oxybromine Bi5O7Br-based dual-interface electric field heterojunction photocatalyst.

[0033] Figure 1 This image shows a scanning electron microscope (SEM) image of the Bi5O7Br / In2S3 / MIL-68(In) composite catalyst prepared in this embodiment. As can be seen from the image, the composite catalyst exhibits a nanosphere morphology with a diameter ranging from approximately 300 to 500 nm, and a relatively rough surface, which may be formed by interface defects between the plate-like Bi5O7Br and the In2S3 / MIL-68(In) structure. This morphological characteristic indicates that Bi5O7Br was formed in situ and uniformly grown on the In2S3 / MIL-68(In) substrate.

[0034] Example 2 A method for preparing a bismuth oxybromodimethyl bromide-based dual-interface electric field heterojunction photocatalyst, the specific steps of which are as follows: (1) Same as in Example 1, MIL-68(In) was obtained; (2) Same as in Example 1, In2S3 / MIL-68(In) composite material was obtained; (3) Take 40 mg of In2S3 / MIL-68(In) composite material and disperse it in 60 mL of a mixed solvent consisting of 30 mL of ethylene glycol and 30 mL of deionized water. Sonicate for 1 h. Then add 0.4 g of bismuth nitrate pentahydrate, 1.5 g of mannitol, 0.05 g of sodium oleate and 0.3 g of hexadecyltrimethylammonium bromide (CTAB) to the dispersion in sequence and continue to sonicate for 60 min to fully dissolve and disperse it. Transfer the mixture to a high-pressure reactor and hydrothermally react at 140 ℃ for 14 h. After the reaction is completed, cool naturally, collect the precipitate by centrifugation, and wash it several times with water and ethanol in sequence. Finally, place the product in a vacuum drying oven at 100 ℃ and dry for 24 h. After grinding, obtain Bi5O7Br / In2S3 / MIL-68(In) composite catalyst, namely bismuth oxybromine Bi5O7Br-based dual-interface electric field heterojunction photocatalyst.

[0035] Example 3 A method for preparing a bismuth oxybromodimethyl bromide-based dual-interface electric field heterojunction photocatalyst, the specific steps of which are as follows: (1) Same as in Example 1, MIL-68(In) was obtained; (2) Same as in Example 1, In2S3 / MIL-68(In) composite material was obtained; (3) Take 70 mg of In2S3 / MIL-68(In) composite material and disperse it in 60 mL of a mixed solvent consisting of 30 mL of ethylene glycol and 30 mL of deionized water. Sonicate for 1 h. Then add 0.4 g of bismuth nitrate pentahydrate, 1.5 g of mannitol, 0.05 g of sodium oleate and 0.3 g of cetyltrimethylammonium bromide (CTAB) to the dispersion in sequence and continue to sonicate for 60 min to fully dissolve and disperse it. Transfer the mixture to a high-pressure reactor and hydrothermally react at 140 ℃ for 14 h. After the reaction is completed, cool naturally, collect the precipitate by centrifugation, and wash it several times with water and ethanol in sequence. Finally, place the product in a vacuum drying oven at 100 ℃ and dry for 24 h. After grinding, obtain Bi5O7Br / In2S3 / MIL-68(In) composite catalyst, namely bismuth oxybromine Bi5O7Br-based dual-interface electric field heterojunction photocatalyst.

[0036] Example 4 A method for preparing a bismuth oxybromodimethyl bromide-based dual-interface electric field heterojunction photocatalyst, the specific steps of which are as follows: (1) Same as in Example 1, MIL-68(In) was obtained; (2) Same as in Example 1, In2S3 / MIL-68(In) composite material was obtained; (3) Take 10 mg of In2S3 / MIL-68(In) composite material and disperse it in 60 mL of a mixed solvent consisting of 30 mL of ethylene glycol and 30 mL of deionized water. Sonicate for 1 h. Then add 0.4 g of bismuth nitrate pentahydrate, 1.2 g of mannitol, 0.05 g of sodium oleate and 0.3 g of hexadecyltrimethylammonium bromide (CTAB) to the dispersion in sequence and continue to sonicate for 60 min to fully dissolve and disperse it. Transfer the mixture to a high-pressure reactor and hydrothermally react at 130 ℃ for 18 h. After the reaction is completed, cool naturally, centrifuge to collect the precipitate, and wash it several times with water and ethanol in sequence. Finally, place the product in a vacuum drying oven at 100 ℃ and dry for 24 h. After grinding, obtain Bi5O7Br / In2S3 / MIL-68(In) composite catalyst, namely bismuth oxybromine Bi5O7Br-based dual-interface electric field heterojunction photocatalyst.

[0037] Example 5 A method for preparing a bismuth oxybromodimethyl bromide-based dual-interface electric field heterojunction photocatalyst, the specific steps of which are as follows: (1) Same as in Example 1, MIL-68(In) was obtained; (2) Same as in Example 1, In2S3 / MIL-68(In) composite material was obtained; (3) Take 10 mg of In2S3 / MIL-68(In) composite material and disperse it in 60 mL of a mixed solvent consisting of 30 mL of ethylene glycol and 30 mL of deionized water. Sonicate for 1 h. Then add 0.4 g of bismuth nitrate pentahydrate, 1.4 g of mannitol, 0.06 g of sodium oleate and 0.4 g of hexadecyltrimethylammonium bromide (CTAB) to the dispersion in sequence and continue to sonicate for 60 min to fully dissolve and disperse it. Transfer the mixture to a high-pressure reactor and hydrothermally react at 160 ℃ for 18 h. After the reaction is completed, cool naturally, collect the precipitate by centrifugation, and wash it several times with water and ethanol in sequence. Finally, place the product in a vacuum drying oven at 100 ℃ and dry for 24 h. After grinding, obtain Bi5O7Br / In2S3 / MIL-68(In) composite catalyst, namely bismuth oxybromine Bi5O7Br-based dual-interface electric field heterojunction photocatalyst.

[0038] Example 6 A method for preparing a bismuth oxybromodimethyl bromide-based dual-interface electric field heterojunction photocatalyst, the specific steps of which are as follows: (1) Same as in Example 1, MIL-68(In) was obtained; (2) Same as in Example 1, In2S3 / MIL-68(In) composite material was obtained; (3) Take 10 mg of In2S3 / MIL-68(In) composite material and disperse it in 60 mL of a mixed solvent consisting of 30 mL of ethylene glycol and 30 mL of deionized water. Sonicate for 1 h. Then add 0.4 g of bismuth nitrate pentahydrate, 1.5 g of mannitol, 0.05 g of sodium oleate and 0.4 g of hexadecyltrimethylammonium bromide (CTAB) to the dispersion in sequence and continue to sonicate for 60 min to fully dissolve and disperse it. Transfer the mixture to a high-pressure reactor and hydrothermally react at 120 ℃ for 18 h. After the reaction is completed, cool naturally, centrifuge to collect the precipitate, and wash it several times with water and ethanol in sequence. Finally, place the product in a vacuum drying oven at 100 ℃ and dry for 24 h. After grinding, obtain Bi5O7Br / In2S3 / MIL-68(In) composite catalyst, namely bismuth oxybromine Bi5O7Br-based dual-interface electric field heterojunction photocatalyst.

[0039] Comparative Example 1 This comparative example is the In2S3 / MIL-68(In) composite material prepared according to steps (1) to (2) in Example 1.

[0040] Figure 2 The image shows a scanning electron microscope (SEM) image of the In2S3 / MIL-68(In) composite catalyst prepared in this embodiment. As can be seen from the image, MIL-68(In) has a micron rod-like structure, and after sulfidation treatment, In2S3 nanosheets are grown in situ on its surface.

[0041] Comparative Example 2 The preparation method of Bi5O7Br / MIL-68(In) interfacial electric field heterojunction photocatalyst is as follows: (1) Dissolve 400 mg indium nitrate tetrahydrate and 400 mg terephthalic acid in 100 mL DMF and stir at room temperature for 30 min. Transfer the resulting solution to a high-pressure reactor lined with polytetrafluoroethylene, seal it and place it in a 120 ℃ electric thermostatic drying oven for 2 h. After the reaction system cools naturally to room temperature, centrifuge it and wash the solid product with DMF and ethanol in sequence. After drying, MIL-68(In) is obtained. (2) Take 10 mg of MIL-68(In) composite material and disperse it in 60 mL of a mixed solvent consisting of 30 mL of ethylene glycol and 30 mL of deionized water. Sonicate for 1 h. Then, add 0.4 g of bismuth nitrate pentahydrate, 1.5 g of mannitol, 0.05 g of sodium oleate and 0.3 g of hexadecyltrimethylammonium bromide (CTAB) to the dispersion in sequence, and continue to sonicate for 60 min to fully dissolve and disperse it. Transfer the mixture to a high-pressure reactor and hydrothermally react at 140 ℃ for 14 h. After the reaction is completed, cool naturally, collect the precipitate by centrifugation, and wash it several times with water and ethanol in sequence. Finally, dry the product in a vacuum drying oven at 100 ℃ for 24 h, and grind it to obtain the Bi5O7Br / MIL-68(In) interfacial electric field heterojunction photocatalyst.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that the In2S3 / MIL-68(In) composite material and the Bi5O7Br photocatalyst were synthesized separately, and then the two were physically mixed. The specific steps are as follows: (1) Same as in Example 1, MIL-68(In) was obtained; (2) Same as in Example 1, In2S3 / MIL-68(In) composite material was obtained; (3) A 60 mL mixed solvent consisting of 30 mL ethylene glycol and 30 mL deionized water was used. Then, 0.4 g bismuth nitrate pentahydrate, 1.5 g mannitol, 0.05 g sodium oleate and 0.3 g cetyltrimethylammonium bromide (CTAB) were added to the mixture in sequence. The mixture was sonicated for 60 min to fully dissolve and disperse it. The mixture was then transferred to a high-pressure reactor and hydrothermally reacted at 140 °C for 14 h. After the reaction was completed, the mixture was naturally cooled, and the precipitate was collected by centrifugation. The precipitate was washed several times with water and ethanol in sequence. Finally, the product was dried in a vacuum drying oven at 100 °C for 24 h and then ground to obtain the Bi5O7Br photocatalyst.

[0043] (4) Disperse 0.1 g Bi5O7Br and 0.02 g In2S3 / MIL-68(In) in 50 mL of ethanol and stir vigorously for 1 h; stir the mixture for 14 h, collect by centrifugation, wash with water and ethanol several times, and finally place the product in a vacuum drying oven at 100 ℃ to dry for 24 h. After grinding, a photocatalyst physically mixed with Bi5O7Br and In2S3 / MIL-68(In) is obtained, which is denoted as Bi5O7Br / In2S3 / MIL-68(In)-mixture.

[0044] Comparative Example 4 The preparation method of Bi5O7Br catalyst, with specific steps as follows: Take a 60 mL mixed solvent consisting of 30 mL ethylene glycol and 30 mL deionized water, and then add 0.4 g bismuth nitrate pentahydrate, 1.5 g mannitol, 0.05 g sodium oleate and 0.3 g cetyltrimethylammonium bromide (CTAB) to the mixture in sequence. Continue sonication for 60 min to ensure complete dissolution and dispersion. Transfer the mixture to a high-pressure reactor and hydrothermally react at 140 ℃ for 14 h. After the reaction is completed, allow it to cool naturally, collect the precipitate by centrifugation, and wash it several times with water and ethanol in sequence. Finally, place the product in a vacuum drying oven at 100 ℃ and dry it for 24 h. After grinding, obtain the Bi5O7Br photocatalyst.

[0045] Figure 3 This is a scanning electron microscope (SEM) image of the Bi5O7Br catalyst prepared in this embodiment. As can be seen from the image, Bi5O7Br exhibits a plate-like structure with uniform morphology.

[0046] Comparative Example 5 Preparation of MIL-68(In): 400 mg of indium nitrate tetrahydrate and 400 mg of terephthalic acid were dissolved in 100 mL of DMF and stirred at room temperature for 30 min. The resulting solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene, sealed, and placed in a 120 ℃ electric thermostatic drying oven for 2 h. After the reaction system cooled naturally to room temperature, it was centrifuged, and the solid product was washed with DMF and ethanol in sequence. After drying, MIL-68(In) was obtained.

[0047] Performance testing The catalysts obtained in each embodiment and comparative example were subjected to performance tests for photocatalytic degradation of organic pollutants (tetracycline) under simulated visible light (initial tetracycline concentration 10 mg / L, catalyst dosage 0.2 g / L). The test results are as follows: Figure 4 As shown.

[0048] Figure 4 The results showed that the catalysts prepared in Examples 1-6 exhibited significantly higher rates of tetracycline degradation under visible light conditions compared to the comparative examples. For the single Bi5O7Br photocatalyst, the degradation performance was significantly lower than that of the Bi5O7Br-based dual-interface electric field heterojunction photocatalyst, and the photocatalytic activity of the In2S3 / MIL-68(In) photocatalyst was also limited. The physically mixed Bi5O7Br / In2S3 / MIL-68(In)-mixed catalyst performed worse than the in-situ grown Bi5O7Br composite material, further validating that the dual interface improves carrier separation efficiency and enhances photocatalytic degradation performance.

[0049] The principle of the technical solution in this invention is as follows: In2S3 has a narrow band gap, which can effectively absorb visible light. When combined with Bi5O7Br, it further optimizes the overall light absorption performance of the material and improves the utilization rate of visible light. In the preparation process, MIL-68(In) and thiourea undergo a hydrothermal reaction in an ethanol system. The decomposition of thiourea provides sulfur. 2- This process allows In2S3 to grow in situ on the surface of MIL-68(In), forming an In2S3 / MIL-68(In) composite structure. In the presence of this composite, bismuth nitrate pentahydrate and hexadecyltrimethylammonium bromide (CTAB) are reacted in an ethylene glycol-water mixed solution. CTAB provides Br... - Bismuth oxybromide (Bi5O7Br) was induced to form on the In2S3 / MIL-68(In) surface under hydrothermal conditions, and formed a tight heterojunction structure with In2S3 through the interfacial coupling effect between In-S bonds and Bi-S bonds. The construction of this dual-interfacial electric field effectively modulates the separation and migration path of photogenerated electrons and holes, significantly suppresses carrier recombination, and thus endows the material with excellent photocatalytic performance.

[0050] In-situ growth of In2S3 nanosheets on the surface of MIL-68(In) microrods forms a conductive network, providing a rapid migration path for photogenerated charges. Simultaneously, the close contact between Bi5O7Br sheets and In2S3 nanosheets further reduces the interfacial charge transfer resistance. The synergistic effect among Bi5O7Br, In2S3, and MIL-68(In) not only optimizes the band structure but also promotes the directional migration of charge carriers through the dual-interfacial electric field, thereby significantly improving the degradation performance of tetracycline organic pollutants.

[0051] In summary, this invention successfully constructed a Bi5O7Br-based heterojunction photocatalyst with a dual-interface electric field through a three-step method. This catalyst, leveraging the synergistic enhancement effect of the built-in electric fields at the Bi5O7Br / In2S3 and In2S3 / MIL-68(In) dual interfaces, significantly improved the photogenerated carrier separation efficiency and visible light absorption capacity, exhibiting high activity in the degradation of organic pollutants. Its preparation process is characterized by mild conditions, simple procedures, and low cost, making it easy to scale up production and demonstrating broad application prospects in industrial wastewater treatment and environmental remediation.

[0052] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for preparing a bismuth oxybromide-based bi-interfacial electric field heterojunction photocatalyst, characterized in that, Includes the following steps: S1. Mix MIL-68(In), sulfur source and first solvent evenly, and carry out first solvothermal reaction at 120℃~180℃. After solid-liquid separation, washing and drying, In2S3 / MIL-68(In) composite material is obtained. S2. The In2S3 / MIL-68(In) composite material is mixed with bismuth source, bromine source, polyol, anionic surfactant and second solvent, and subjected to a second solvothermal reaction at 100~160℃. After solid-liquid separation, washing and drying, a bismuth oxybromine-based dual-interface electric field heterojunction photocatalyst is obtained.

2. The method for preparing a BiOBr-based bi-interfacial electric field heterojunction photocatalyst according to claim 1, characterized in that, The reaction time for the first solvothermal reaction is 2-6 hours; And / or, the reaction time of the second solvothermal reaction is 8~20h.

3. The method for preparing a BiOBr-based bifacial electric field junction photocatalyst according to claim 1, characterized in that, In step S1, the sulfur source includes at least one of thiourea, thiol, thioether, and thiophenol. And / or, the mass ratio of the MIL-68(In) to the sulfur source is 1:(2~3).

4. The method for preparing a BiOBr-based bifacial electric field junction photocatalyst according to claim 1, characterized in that, In step S1, the first solvent includes ethanol; And / or, the mass-to-volume ratio of MIL-68(In) to the first solvent is (12~20) mg: 1 mL.

5. The method for preparing a BiOBr-based bifacial electric field junction photocatalyst according to claim 1, characterized in that, In step S2, the bismuth source includes at least one of bismuth nitrate and bismuth chloride; And / or, the bromine source includes at least one of hexadecyltrimethylammonium bromide and dodecyltrimethylammonium bromide; And / or, the polyol includes at least one of mannitol, sorbitol, polyethylene glycol, and ethylene glycol; And / or, the anionic surfactant includes at least one of sodium oleate and sodium dodecyl sulfate.

6. The method for preparing a BiOBr-based bifacial electric field junction photocatalyst according to claim 1, characterized in that, In step S2, the mass ratio of the In2S3 / MIL-68(In) composite material to bismuth source, polyol, anionic surfactant, and bromine source is (0.01~0.07):(0.2~0.6):(0.5~2):(0.02~0.1):(0.1~0.5).

7. The method according to claim 1, wherein the method is characterized by, In step S2, the second solvent comprises a mixed solution of water and ethanol; And / or, the mass-to-volume ratio of the In2S3 / MIL-68(In) composite material to the second solvent is (0.01~0.07) g: 60 mL.

8. The method according to claim 1, wherein the method is characterized by, The preparation method of MIL-68(In) includes: dissolving indium nitrate and terephthalic acid in N,N-dimethylformamide, stirring evenly, and then carrying out a solvothermal reaction at 120℃~140℃. After solid-liquid separation, washing, and drying, MIL-68(In) is obtained.

9. A BiOBr-based bi-interfacial electric field heterojunction photocatalyst, characterized in that, It is prepared by the preparation method of the bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst according to any one of claims 1 to 8.

10. The application of the bismuth bromooxybismuth-based dual-interface electric field heterojunction photocatalyst as described in claim 9 in the photocatalytic degradation of organic pollutants.

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