Direct charge transfer mediated by asymmetrically coordinated Zn–N2O2 sites in graphitic carbon nitride toward water purification with hydrogen peroxide photosynthesis

The development of highly efficient photocatalysts for the simultaneous degradation of emerging contaminants (ECs) and clean energy production represents an ideal approach for addressing the dual challenges of environmental pollution and the energy crisis. Herein, a zinc (Zn) single-atom catalyst with asymmetrically coordinated Zn–N 2 O 2 sites in graphitic carbon nitride (Zn SA -CN) is reported for the simultaneous photocatalytic degradation of ECs and production of hydrogen peroxide (H 2 O 2 ) via oxygen (O 2 ) reduction. Experimental and characterization results showed that the asymmetric Zn–N 2 O 2 coordination induced charge polarization at the surface of graphitic carbon nitride (g-C 3 N 4 ). The non-uniform charge distribution of Zn single atoms on g-C 3 N 4 improved the adsorption of pollutants and expanded the light absorption range. Moreover, the adsorbed pollutants further amplified charge polarization and light absorption via molecular modification. The synergistic interaction between the modified pollutants and visible light accelerated the direct electron transfer from ciprofloxacin (CIP) to O 2 for H 2 O 2 production, mitigating the overall energy demand of the water treatment process. This study elucidates the synergistic effect between the molecular modification of pollutants and light energy absorption induced by asymmetric coordination structures, offering new insights into energy conversion coupled to wastewater recycling.