Modulating the coordination environment of Co single-atom catalysts through sulphur doping to efficiently enhance peroxymonosulfate activation for degradation of carbamazepine

Heteroatom S was one-step doped into the zeolitic imidazolate framework (ZIF) of Co-based single-atom catalysts (Co-SACs) to modulate the coordination environment of the Co center, which then significantly enhanced peroxymonosulfate (PMS) activation. The structures of Co-SACs and S doped Co-SACs (Co-SNC) were confirmed by a series of physciochemical characterizations. The optimized Co-SNC catalyst could degrade over 99.9% of 5 mg/L carbamazepine (CBZ) in 5 min via activating PMS, with the degradation rate constant of more than 4.17 times higher than that of non-doping sample. The Co-SNC/PMS system could maintain an excellent performance in a large pH range of 3 to 9, and about 96.8% of CBZ could still be degraded after 5 cycles use. 1O2 and SO4•− were found to be the primary reactive oxygen species (ROS) in Co-SNC/PMS system by radical quenching tests and electron paramagnetic resonance analysis. Several pathways of ROS generation were analyzed by density functional theory (DFT) calculations. In addition, the doped S remarkably enhanced the electron density around the center of Co atoms and electron transfer ability, thereby reducing the activation energy for the generation of ROS. This study offers a new strategy for enhancing PMS activation by Co-SACs in the application of degrading organic pollutants.