标题：Photoimmobilized Ni Clusters Boost Photodehydrogenative Coupling of Amines to Imines via Enhanced Hydrogen Evolution Kinetics
编辑：Yi Huang; Cuibo Liu; Mengyang Li；Huizhi Li；Yongwang Li；Ren Su* and Bin Zhang*
单位：1 Institute of Molecular Plus, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, P. R. China
2 Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, P. R. China
3 SynCat@Beijing, Synfuels China Technology Co. Ltd., Beijing 101407, P. R. China
4 Soochow Institute for Energy and Materials InnovationS (SIEMIS), Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Soochow University, Suzhou, P. R. China
摘要：Imines are important precursors for pharmaceutical, agricultural, and synthetic chemistry. The state-of-art synthesis of imines via condensation of amines with aldehydes or ketones often uses homogeneous catalysts and dehydrating agents to promote the elimination of water, which requires huge manpower input for the late-stage purification process and is usually environmentally unfriendly. Photocatalytic synthesis of imines from amines oxidation via the release of hydrogen (H2) is of great promise due to the mild reaction characteristics; however, the efficiency of such a reaction lags due to the missing designed photocatalyst owing to the ambiguous reaction mechanism. Here, we demonstrate that by constructing in situ photoimmobilized Ni clusters on the CdS photocatalyst, the generation of imines is dramatically improved with the rapid release of molecular H2 under visible light illumination. Mechanistic investigation reveals that the adsorption of photogenerated hydrogen atoms during the dehydrogenation of amines is significantly weakened on Ni clusters, thus resulting in fast C?N coupling kinetics for the generation of imines. The photocatalyst presents stable performance with high efficiency. A remarkably apparent quantum efficiency (AQE) of ～44% is realized under 420 nm irradiation for the conversion of 4-methoxybenzylamine within six consecutive runs. Furthermore, a series of primary and secondary amines bearing different functional groups (i.e., heterocyclic, aliphatic, N-heterocycles) that are synthetically challenging by the condensation process can be selectively converted to the corresponding imines, featuring its application prospect.