Selective Reduction of NO into N₂ Catalyzed by Rh₁-Doped Cluster Anions RhCe₂O_3-5

Catalytic conversion of toxic nitrogen oxide (NO) and carbon monoxide (CO) into nitrogen (N₂) and carbon dioxide (CO₂) is imperative under the weight of the increasingly stringent emission regulations, while a fundamental understanding of the nature of the active site to selectively drive N₂ generation is elusive. Herein, in combination with state-of-the-art mass-spectrometric experiments and quantum-chemical calculations, we demonstrated that the rhodium-cerium oxide clusters RhCe₂O_3-5^- can catalytically drive NO reduction by CO and give rise to N₂ and CO₂. This finding represents a sharp improvement in cluster science where N₂O is commonly produced in the rarely established examples of catalytic NO reduction mediated with gas-phase clusters. We demonstrated the importance of the unique chemical environment in the RhCe₂O₃^- cluster to guide the substantially improved N₂ selectivity: a triatomic Lewis "acid-base-acid" Ce^δ+-Rh^δ--Ce^δ+ site is proposed to strongly adsorb two NO molecules as well as the N₂O intermediate that is attached on the Rh atom and can facilely dissociate to form N₂ assisted by both Ce atoms.