Atomically dispersed cobalt on carbon nitride for peroxymonosulfate activation: Switchable catalysis enabled by light irradiation

Herein, we present atomically dispersed cobalt anchored carbon nitride (Co-CN) as a highly efficient peroxymonosulfate (PMS)-activation catalyst. Different from the traditional catalytic pathways, in which hydroxyl radical, sulfate radical, singlet oxygen, or surface-bound PMS engaged as primary oxidants, high-valent cobalt-oxo [Co(IV)] species generated from a unique two-electron transfer pathway are confirmed as primary oxidants. Hydroxyl radical triggered by Co(IV) serves as secondary intermediate oxidant. In addition, it is interesting to find that such Co(IV)-based nonradical pathway can be switched to a radical-dominated pathway under light irradiation, suggesting the Co-CN can not only act as a PMS activator but also as a photoswitch to regulate the PMS oxidation pathways. On the basis of experiment and DFT calculations, the switchable catalysis can be attributed to the formation of photoinduced hole-trapping sites on the single Co atoms, which result in the primary PMS activation sites convert from single Co atoms to melem units. More importantly, considering the distinctive oxidation feature of Co(IV) and radical species, our finding provides a novel strategy to expand the application possibilities of Co-based Fenton-like process in dealing with different environmental issues by flexibly controlling the PMS catalytic pathways.