Steering H2O2 activation pathways with synergistic Cu single-atom and cluster sites on carbon nitride nanospindle

Rational steering of catalytic reaction pathway demands atomic-level control over active-site. Conventional catalysts, however, often comprise heterogeneous mixtures of metal species, which obscures their distinct functions and synergistic potential. Here, we employed a carbon nitride nanospindle to independently install copper as single atoms, clusters, or an integrated architecture, thereby probing their interplay. We discover that copper sites fundamentally alter the reaction pathway. While the metal-free support activates O 2 to generate singlet oxygen ( 1 O 2 ), copper sites switch to the H 2 O 2 activation. Furthermore, isolated single-atom sites drive H 2 O 2 homolysis to form hydroxyl radicals (•OH) through terminal Cu−OH species, whereas clusters direct the reaction toward superoxide radicals (•O 2 − ) via bridging Cu−O(H)−Cu motifs. Integrating both sites creates a cooperative catalytic environment, boosting •O 2 − production to nearly double that of either single-site system while concurrently generating •OH. This synergy enables superior removal of refractory antibiotics, with a high kinetic constant, more than twice that of the individual systems. Operando spectroscopy reveals that the geometry of each site dictates the adsorption configuration of key intermediates (−OH/−OOH), which governs the activation barrier and selects between the •OH and •O 2 − pathways. This work helps to establish a design principle for rational design of functionally integrated active centres at the atomic level.