Surface‐like NOx Reduction at an Atomically‐Precise Tricopper Cluster

Abstract The combustion of nitrogen‐containing fuels and increasing use of nitrogen‐rich fertilizers is accumulating NO x pollutants in the environment. Copper is an attractive catalyst material for reductive NO x remediation, yet ambiguity persists regarding the elementary bond‐making and bond‐breaking steps occurring at the catalyst interface. Starting from a molecular tricuprous μ 3 ‐oxo complex ( 1 ), an unusually reduced and highly reactive surface‐like cluster ( 2 ) has been prepared. Characterization data and electronic structure calculations are consistent with 2 featuring σ‐aromaticity that primes the tricopper core for two‐electron chemistry. Cluster 2 mediates catalytic reductive coupling of NO to N 2 , proceeding through N 2 O, via sequential oxygen atom transfer steps. Stoichiometric reduction of NO 3 − and NO 2 − is also disclosed, mapping the complete denitrification cycle at an atomically‐precise molecular cluster.