Photocatalytic activation of peroxymonosulfate by surface-tailored carbon quantum dots.

•Carbon quantum dots (CQDs) were synthesized by a low-cost and scalable approach.•CQDs were creatively applied as photocatalyst for activation of peroxymonosulfate.•Fine-tuning the oxygen groups can suppress the recombination of charge carriers.•Superoxide radicals and oxidative holes were identified as the primary reactive species.