Modifying CuC2PhC2Cu with TiO2 for Visible-Light-Driven Amine Coupling under Aerobic and Anaerobic Conditions.

Imine compounds are important intermediates in organic synthesis. The efficient synthesis of imines under mild conditions remains a challenge. Here, utilizing multichannel CuC2PhC2Cu as a light antenna and a small amount of TiO2 nanoparticles as a modifier, we construct an efficient photocatalyst system for amines coupling with visible light as the only energy input. The TiO2/CuC2PhC2Cu composite catalyst achieves a high imine yield under both aerobic and anaerobic conditions. Investigations confirm that TiO2 nanoparticles are able to increase the amount of oxygen-containing groups and promote the separation of photogenerated carriers of CuC2PhC2Cu, in turn accelerating the formation of reactive oxygen species. The TiO2/CuC2PhC2Cu exhibited much better performance than other composites (ZrO2/CuC2PhC2Cu, Fe2O3/CuC2PhC2Cu, Au/P25, and TiO2/PhC2Cu). The main reactive oxygen species, intermediates, and reaction route are identified, while the reaction mechanism in the presence and absence of oxygen is proposed. The catalyst system is also applicable to other benzylamine substituents and shows good stability. This work not only explores the application of copper phenylacetylide-based photocatalysts in the organic synthesis field but also presents a strategy for designing efficient systems for the photocatalytic process under aerobic/anaerobic conditions.