Atomically integration of O-bridged Co-Fe hetero-pairs as tandem photocatalyst towards highly efficient hydroxyl radicals production

Photocatalytic Fenton-coupled oxygen reduction reaction (ORR) is a promising strategy generated by •OH. Single-atom catalysts (SACs), featuring high atom utilization, exhibit superior catalytic activity. However, effectively catalyzing the two steps on the activity site remains a challenge. Herein, a novel Co-Fe hetero-atom pair tandem photocatalyst was precisely constructed by pre-designing the structure of covalent organic frameworks (COFs) and the introduction strategies of active sites. Thanks to the synergism of adjacent Co-Fe atoms, Co-Fe-COF presents highly efficient hydroxyl radicals production following the process of O2+H2O→H2O2→•OH. Additionally, immobilization of atom pairs on the pore walls of COF can boost the enrichment for contaminants, thus increasing the •OH utilization rates. Theoretical simulations reveal proximity electronic effect of O-bridged Co-Fe not only thermodynamically promotes the formation of OOH*, but also dynamically activates the self-healing cycle of Fe(II)/Fe(III). This work provides a novel program for designing high-performance tandem catalysts.