Tailoring the coordination environment of cobalt in a single-atom catalyst through phosphorus doping for enhanced activation of peroxymonosulfate and thus efficient degradation of sulfadiazine

The catalytic activity of single-atom catalysts (SACs) can be enhanced by engineering the coordination environment of metal centres. Herein, zeolitic imidazolate framework (ZIF) was used as a precursor to introduce P atoms into a Co-based SAC. With the P doping, the resultant ZIF-CoN3P-C could efficiently degrade 98.4% of sulfadiazine (10 mg L-1) within 5 min by activating peroxymonosulfate (PMS) with an elevated degradation rate constant 2.5 times that of ZIF-CoN4-C. Density functional theory (DFT) calculations indicate that the electron density and electron delocalisation were further concentrated around the Co centres by the P doping, which facilitated electron transfer from Co to PMS molecules and enhanced the generation of singlet oxygen (O-1(2)). The ZIF-CoN4P-C exhibited its universality and stability for the PMS-based oxidation process. Overall, these findings clarify the role of P atoms in tuning the electronic structure and reactivity of Co in ZIF-CoN3P-C for enhanced PMS activation and organic degradation.