In-situ Fe–O co-doped carbon nitride heterogenous catalyst for enhanced photo-Fenton oxidation performance towards recalcitrant organic pollutants

• In-situ thermal polymerization strategy is designed to prepare Fe/OCN. • Fe/OCN possesses ideal Fe–N and Fe–O coordination structure. • Fe/OCN exhibits excellent photo-Fenton catalytic capability and reusability. • Rapid charge separation and Fe sites’ electron accumulation promote H 2 O 2 activation. • Yielding abundant ROSs dominate deep oxidation of organic pollutants. One-step and in-situ FeCl 3 -participated molten urea thermal polymerization strategy is designed to prepare Fe–O co-doped carbon nitride photo-Fenton catalyst (Fe/OCN). Fe/OCN exhibits remarkable photo-Fenton catalytic oxidation capacity towards recalcitrant organic pollutants, in which 0.31 wt% Fe/OCN with optimal Fe-doping level exhibits significantly 60 and 6.3 times higher pseudo-first-order kinetic constant than single photocatalysis and Fenton system in the degradation of methyl orange. The enhancement of photo-Fenton catalytic performance is mainly ascribed to the realization of ideal Fe–O and Fe–N coordination structure in the framework of polymeric carbon nitride, which can not only serve as prime sites for the adsorption of target pollutants molecules and transfer channels for directed migration of photogenerated charges, but also well-modulate electronic structure and band structure of Fe/OCN. Accordingly, the resulting boosted charge carriers separation and transfer dynamics and increased electron density around Fe active centers facilitate ≡Fe(II) regeneration and H 2 O 2 activation, leading to the significant production of plentiful reactive species responsible for degradation and mineralization of organic pollutants. The present work provides new insight into the optimized design and precise regulation of carbon nitride-based photo-Fenton system for advanced wastewater treatment.