Photocatalytic Acceptorless Dehydrogenation of Amines for Hydrogen and Imine Production Using Hollow MoS-ZnInS/CeO Featuring Spatially Separated Redox Active Sites.

Photocatalytic acceptorless dehydrogenation (PAD) of amines represents an innovative method for the production of hydrogen (H) and imines. Nonetheless, the efficiency of this reaction is often compromised by the formation of undesirable by-products, such as dibenzylamine resulting from imine hydrogenation and 1,2-diphenyl ethylenediamine due to C─C coupling. In this study, a novel hollow core/shell photocatalyst, MoS-ZnInS/CeO (M-ZIS/C), is designed and developed with spatially separated redox active sites to mitigate these challenges. The optimized M-ZIS/C catalyst demonstrates remarkable performance, achieving a 27.5-fold increase in the production rate of H and an 18.7-fold in increase in the yield of N-benzylidenebenzylamine (N-BBA) during the benzylamine PAD reaction compared to pure ZnInS. Notably, the selectivity for N-BBA improved significantly from 15.6 to 97.4% upon the modification with MoS. Isotopic tracing experiments further confirmed that H is generated from amines, with trace amounts of water acting as a proton-transfer mediator to accelerate the reaction kinetics. Additionally, in situ infrared spectroscopy revealed the reaction pathway of N─H bond cleavage to generate aldehyde imine intermediates, which subsequently undergo condensation with amines to yield imine products. This approach represents a significant advancement in energy-chemical coupled photocatalytic systems for improving efficiency and versatility in H production and imine synthesis.