Selective Reduction of NO into N₂ Catalyzed by the RhM₂O₃^– Clusters (M = Ta, V, and Al): Importance of the Triatomic Lewis Acid–Base–Acid M^δ+–Rh^δ––M^δ+ Site

Catalytic NO reduction by CO into N₂ and CO₂ 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^δ+-Rh^δ--Ce^δ+) site that accounts for the selective reduction of NO into N₂ catalyzed by the RhCe₂O₃^- cluster in gas-phase experiments, the reactivity of the RhM₂O₃^- (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 N₂ mediated by RhTa₂O₃^- and RhV₂O₃^-, and the strong M-oxygen affinity was emphasized to construct the LABA site. An overall assessment highlights that RhV₂O₃^- functions as a more promising catalyst because the well-fitting V-O bonding strength facilitates both elementary reactions of NO reduction and CO oxidation.