Catalytic NO Reduction by Single Au-Doped Aluminum Oxide Cluster Anions: Structural Role of Au

Supported gold (Au) catalysts have attracted sustained interest, owing to their remarkable reactivity in a wide range of catalytic reactions, where Au is generally regarded as the active site or an electron buffer. Herein, through a combination of state-of-the-art mass-spectrometric experiments and quantum-chemical calculations, we demonstrate that single Au-doped aluminum oxide cluster anions AuAl₃O_4,5^- can catalyze NO reduction by CO. The catalytic cycle proceeds via a single-electron mechanism driven exclusively by the electron-rich Al site, while the Au atom remains redox-inactive and acts as a spectator throughout the reaction pathway. Detailed analyses reveal that Al actively participates in the electron-transfer processes, whereas Au forms persistent Au-Al bonds that stabilize the cluster framework and maintain a favorable energetic landscape for catalysis. These results uncover an unconventional catalytic scenario in which Au functions primarily as a structural stabilizer rather than an active center, offering molecular-level insight into metal-support interactions and deepening the mechanistic understanding of CO-mediated NO reduction in Au-based catalytic systems.