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.