Coexistence of Fe Nanoclusters Boosting Fe Single\nAtoms to Generate Singlet Oxygen for Efficient Aerobic Oxidation of\nPrimary Amines to Imines

Tuning\nthe geometric and electronic structure of the single-metal-atom\ncatalysts via simultaneous presence of metal nanoparticles or nanoclusters\n(NCs) offers an alternative avenue to improving their catalytic performance.\nHerein, we demonstrate that the coexistence of Fe NCs in proximity\nto Fe single atoms on N-doped porous carbon can significantly improve\nthe catalytic performance in aerobic oxidation of primary amines to\nimines using air as the oxidant. A broad spectrum of primary aromatic,\nheterocyclic, and aliphatic amines was efficiently and selectively\noxidized into their corresponding imines in good to high yields. Experimental\nmeasurements and theoretical calculations reveal that the proximity\nof Fe NCs interacts with Fe single atoms, which not only benefits\nthe adsorption of molecular O₂ and amine substrates but\nalso promotes the activation of O₂ to selectively generate\nsinglet oxygen (¹O₂) and then facilitates the\nkey intermediate imine formation via H-atom abstraction with a lower\nenergy barrier, thereby significantly boosting the reaction activity.