Selective Reduction of NO into N Catalyzed by the RhMO Clusters (M = Ta, V, and Al): Importance of the Triatomic Lewis Acid-Base-Acid M-Rh-M Site.

Catalytic NO reduction by CO into N and CO is imperative owing to the increasingly rigorous emission regulation. Identifying the nature of active sites that govern the reactivity and selectivity of NO reduction is pivotal to tailor catalysts, while it is extremely challenging because of the complexity of real-life systems. Guided by our newly discovered triatomic Lewis acid-base-acid (LABA, Ce-Rh-Ce) site that accounts for the selective reduction of NO into N catalyzed by the RhCeO cluster in gas-phase experiments, the reactivity of the RhMO (M = Ta, V, and Al) clusters in catalytic NO reduction by CO was explored. We determined theoretically that the LABA site still prevails to reduce NO to N mediated by RhTaO and RhVO, and the strong M-oxygen affinity was emphasized to construct the LABA site. An overall assessment highlights that RhVO functions as a more promising catalyst because the well-fitting V-O bonding strength facilitates both elementary reactions of NO reduction and CO oxidation.