Cyano-group-rich carbon nitride supported interlayer single-atomic Fe–N4 sites for photo-Fenton degradation of emerging organic pollutants

• Interlayer single atomic Fe–N 4 sites on D C -CN are designed via an i n-situ strategy. • Fe/D C -CN exhibits photo-Fenton deep oxidation capability and robust reusability. • Fe/D C -CN film achieves long-term degradation of pharmaceutical wastewater. • Accelerated charge separation dynamics and ≡Fe(III)/≡Fe(II) redox facilitate H 2 O 2 activity. • Plentiful ROSs contribute to the deep oxidation of organic micropollutants. A cyano-group-rich g-C 3 N 4 -supported single-atom iron catalyst with interlayer Fe–N 4 sites (Fe/D C -CN) is fabricated via a simple and in-situ pretreatment combined with a thermal polymerization method. The Fe/D C -CN demonstrates exceptional photo-Fenton catalytic degradation activity towards the single or mixed recalcitrant organic pollutants in simulation or pharmaceutical wastewater. In the degradation of methylparaben (MPB), the apparent first-order rate constants for the Fe/D C -CN photo-Fenton systems were 31.2 and 18.7 times higher than those of the Fenton and photocatalytic systems, respectively, and the TOC removal efficiency reached 100% after 12 h of reaction. Subsequently, in the custom-made quartz slide-supported Fe/D C -CN film continuous-flow photo-Fenton reactor, long-term efficient degradation of organic pollutants in actual pharmaceutical wastewater is realized. The superior photo-Fenton catalytic oxidation capability of Fe/D C -CN is primarily ascribed to the synergistic effect between the interlayer electronic channel constructed by single-atom Fe–N 4 coordination and the internal electric field induced by cyano groups, which effectively promotes the photogenerated charge separation and migration. This further accelerates the H 2 O 2 activation efficiency and facilitates the photocatalysis process, resulting in a significant generation of reactive oxygen species that enables the deep oxidation of target organic pollutants while essentially eliminating ecological toxicity associated with intermediate products.