Photocatalytic Acceptorless Dehydrogenation of Amines for Hydrogen and Imine Production Using Hollow MoS ₂ ‐ZnIn ₂ S ₄ /CeO ₂ Featuring Spatially Separated Redox Active Sites

Photocatalytic acceptorless dehydrogenation (PAD) of amines represents an innovative method for the production of hydrogen (H₂) 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, MoS₂-ZnIn₂S₄/CeO₂ (M-ZIS/C), is designed and developed with spatially separated redox active sites to mitigate these challenges. The optimized M_3%-ZIS/C_45% catalyst demonstrates remarkable performance, achieving a 27.5-fold increase in the production rate of H₂ and an 18.7-fold in increase in the yield of N-benzylidenebenzylamine (N-BBA) during the benzylamine PAD reaction compared to pure ZnIn₂S₄. Notably, the selectivity for N-BBA improved significantly from 15.6 to 97.4% upon the modification with MoS₂. Isotopic tracing experiments further confirmed that H₂ 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 H₂ production and imine synthesis.