Activation of peroxymonosulfate via coordination engineering of Co and carbon dots.

Nitrogen-rich carbon dots loading with transition metals have received tremendous attention during the last decade due to superior catalytic performance in toxic pollutants degradation. The cobalt-doped carbon dots (Co-CDs) with high content of pyrrolic N have been synthesized in formamide solution via one-step solvothermal method. The pyrrolic N offers binding sites for the cobalt ions, forming CoN bond which facilitates the peroxymonosulfate (PMS) adsorption. It was found that the degradation in the Co-CDs/PMS system was dominated by high-valent cobalt-oxo species (CoIV=O) through a nonradical pathway. The simulation reveals that the formation of CoIVO species is favored by cleavage of the CoN bond and electron transfer from Co atom to O atom in the PMS. This study provides a deep understanding of PMS activation by carbon dots, and inspires rational design of environmental catalysts.