Low-coordinated Fe–N3 sites in carbon nitride for efficient photo-Fenton wastewater treatment

Single-atom coordinated host catalyst offers a promising strategy for photo-Fenton induced wastewater treatment due to the tunable photophysical/chemical properties. However, designing efficient atomically dispersed single-atom catalysts with highly reactive unsaturated coordination remains a challenge. Herein, we designed the low-coordinated Fe–N3 site in carbon nitride (FeCN), which showed excellent degradation efficiency for 4-CP declined to 90.1 % in Tap water and 88.2 % in Dalian Lake within 1h. X-ray absorption near-edge spectroscopy (XANES) demonstrated the monoatomic Fe was anchored to CN via the low-coordinated Fe–N3 structure. Density Functional Theory (DFT) and photoelectric characterizations demonstrated that the Fe–N3 site could facilitate the photo-generated charge migration to the Fe–N3 site due to the asymmetric electron distribution of Fe–N3 site and the Fe_d orbitals occupying the conduction band positions. Besides, project density of states (PDOS) illustrated the strong electronic interaction between the Fe–N3 site and OH*, which confirmed the Fe–N3 site facilitated the activation of H2O2 and further accelerated the performance of photo-Fenton wastewater treatment. This study can provide insights into the design of highly active low-coordination single-atom catalysts and the Fenton-like mechanisms.