Extending aromatic acids on TiO2 for cooperative photocatalysis with triethylamine: Violet light-induced selective aerobic oxidation of sulfides

Designing visible light photocatalysts with a metal oxide semiconductor as the starting material could expand a new horizon for the conversion and storage of solar energy. Here, the benchmark photocatalyst TiO2 was used to pursue this goal by anchoring aromatic acids. Extending the aromatic acid was strategically deployed to design TiO2 complexes with violet light-induced selective aerobic oxidation of sulfide as the probe reaction. With benzoic acid (BA) as the initial molecule, horizontally extending one or two benzene rings furnishes 2-naphthoic acid (2-NA) and 2-anthracene acid (2-AA). Moreover, triethylamine (TEA), an electron transfer mediator, was introduced to maintain the integrity of the anchored aromatic acids. Notably, there was a direct correlation between the pi-conjugation of aromatic acid ligand and the selective aerobic oxidation of sulfides. Among the three aromatic acids, 2-AA delivered the best result over TiO2 due to the most extensive pi-conjugated system. Ultimately, violet light-induced selective aerobic oxidation of sulfides into corresponding sulfoxides was conveniently realized by cooperative photocatalysis of 2-AA-TiO2 with 10 mol% of TEA. This work affords an extending strategy for designing the next-generation ligands for semiconductors to expand visible light-induced selective reactions. (C) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

Designing visible light photocatalysts with a metal oxide semiconductor as the starting material expands the possibilities for solar energy conversion and storage. In this study, TiO2 was used as the benchmark photocatalyst and aromatic acids were anchored to it. By strategically extending the aromatic acids, TiO2 complexes were designed for violet light-induced selective aerobic oxidation of sulfide. The introduction of triethylamine maintained the integrity of the anchored aromatic acids. The pi-conjugation of the aromatic acid ligand directly correlated with the selective aerobic oxidation of sulfides, and 2-anthracene acid showed the best performance over TiO2 due to its extensive pi-conjugated system.