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

A cyano-group-rich g-C3N4-supported single-atom iron catalyst with interlayer Fe-N4 sites (Fe/DC-CN) is fabricated via a simple and in-situ pretreatment combined with a thermal polymerization method. The Fe/DC-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/DC-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/DC-CN film continuous-flow photoFenton reactor, long-term efficient degradation of organic pollutants in actual pharmaceutical wastewater is realized. The superior photo-Fenton catalytic oxidation capability of Fe/DC-CN is primarily ascribed to the synergistic effect between the interlayer electronic channel constructed by single-atom Fe-N4 coordination and the internal electric field induced by cyano groups, which effectively promotes the photogenerated charge separation and migration. This further accelerates the H2O2 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.