A Single Copper–Vanadium Oxide Cluster Cu₃VO₃^–Reduces Four NO Molecules with the Accomplishment of a Catalytic Cycle by CO

Catalytic removal of NO and CO from exhaust is imperative due to their detrimental effects on the environment and human health, while the nature of active sites driving efficient NO reduction remains elusive. Herein, in combination with state-of-the-art mass spectrometry and quantum-chemical calculations, we demonstrate that copper–vanadium oxide clusters Cu₃VO_3–5^– can catalytically reduce four NO molecules into N₂O by CO. This finding represents a significant improvement in cluster science in which two NO molecules are commonly involved in the catalysis. The key to driving this substantially improved NO reduction efficiency by Cu₃VO₃^– lies in the unique structure of intermediate product Cu₃VO₄^–, which electronically resembles Cu₃VO₃^– with a single unpaired electron localized in the V 3d orbital. This electronic configuration is vital to selectively reducing NO into N₂O. Cu₃VO₃^– can be regenerated through CO oxidation by product Cu₃VO₅^– to complete the catalysis. The fundamental reasons behind this intriguing NO reduction behavior were further rationalized by theoretical calculations.