Highly Selective Photooxidation of Benzyl Alcohol to Benzaldehyde by Bi–Mo/g-C₃N₄ in Aqueous Solution

Although photooxidation of benzyl alcohol to benzaldehyde in aqueous solution is an important chemical process, its selectivity cannot be readily controlled due to the overoxidation of benzaldehyde. In this study, a series of Bi–Mo/CN photocatalysts are synthesized, and their reactivity in photooxidation of benzyl alcohol under visible light is compared. Bi–Mo/CN-2 exhibits high photocatalytic reactivity in the conversion of benzyl alcohol (51%) with a high selectivity toward benzaldehyde of 99.9%. In this process, the formed ≡Bi–OO• and ≡Bi–OOH selectively oxidize benzyl alcohol to benzaldehyde via the H-abstraction pathway after O2 is photoreduced on Bi–Mo/CN, accompanied by the formation of H2O2. Meanwhile, the doped Mo utilizes the produced H2O2 or ≡Bi–OOH to produce ≡Mo–O2 peroxo, which not only contributes to the selective oxidation of benzyl alcohol to benzaldehyde but also effectively prevents overoxidation of benzaldehyde. This work provides new insight into designing novel photocatalysts for selective oxidation of organic substrates.