Controllable Synthesis Of Bismuth-Based Semiconductor Materials And Its Application In Photocatalytic Organic Synthesis

With the development of semiconductor micro-nano functional materials and the improvement of organic synthesis process, the emergence and application of photocatalytic organic synthesis has greatly satisfied people’s energy and environmental requirements. Compared with traditional organic synthesis, photocatalytic organic reaction system has many advantages including mild reaction conditions, without using strong oxidants or strong reducing agents, cheap catalyst materials, and many more. The design and optimization of the photocatalyst can achieve a high conversion rate for a certain reaction or a good selectivity to the target product. Considering the above facts, this dissertation focuses on the design and optimization of bismuth-based photocatalysts and their applications in photocatalytic coupling reaction of phenolic compounds and the oxidation of amine compounds. The main contents include the following aspects:（1） The photocatalytic oxidative coupling reactions of 2,6-disubstituted phenols were achieved on Pt/BiVO₄. BiVO₄ was synthesized by a facile solvothermal route and Pt/BiVO₄ composites were prepared through a photoreduction deposition method. Taking the photocatalytic oxidative coupling reaction of 2,6-dimethylphenol as a model, the optimal synthetic conditions for obtaining Pt/BiVO₄ with the best photocatalytic activity were screened. In addition, the reaction mechanism was proposed on the basis of experimental results. The photocatalytic oxidative coupling reaction was further extended to the other substrates. As a result, the conversion rate of 2,6-dimethyl phenol to 3,3’,5,5’-tetramethyl-4,4-bisphenol on Pt/BiVO₄ could reach 92%, and the selectivity of the target product is 81 %. Significantly, the oxidative coupling reaction of 2,4-di-tert-butylphenol, which was difficult to complete by the traditional thermal catalysis, has been successfully achieved with high conversion and selectivity through the present photocatalytic route. This work firstly report the photocatalytic coupling reaction of 2,6-disubstituted phenols, which provides a green pathway for the coupling of carbon and carbon bonds between benzene rings in organic synthesis.（2） The photocatalytic activity of Bi₂WO₆ was enhanced through a new defect engineering strategy. Bi₂WO₆ nanoplates with oxygen vacancies were prepared by a solvothermal route. The influence of the concentration of oxygen vacancies on the photocatalytic activity of Bi₂WO₆ nanoplates was systematically studied. The experimental results showed that the photocatalytic activity of Bi₂WO₆ for converting secondary amine to imine could be greatly enhanced by only controlling the concentration of oxygen vacancies in the material, without the use of any co-catalyst or doping. The present study provides a useful reference for the design of cheap and efficient photocatalysts for photocatalytic organic reaction synthesis.