Highly selective production of singlet oxygen by manipulating the spin state of single-atom Co–N moieties and electron localization

Singlet oxygen (1O2) is a reactive species with oxidation selectivity that is preferred in advanced oxidation processes. However, the underlying mechanism of 1O2 selective production remain ambiguous. In this study, we demonstrated that electron localization and high spin state of metal active sites favored peroxymonosulfate (PMS) co-adsorption and dissociation, which promoted selective production of 1O2. Under theoretical guidance, single Co atoms anchored on uneven graphite carbon nitride nanosheet (Co-SA/CMN) was fabricated and exhibited the highest 1O2 production selectivity so far with 87.8% of the PMS consumed was converted to 1O2. The Co-SA/CMN/PMS system exhibited remarkable degradation efficiency to multiple organic pollutants, show strong resistance to environmental interference and robust stability at the device level. Co-SA/CMN/PMS oxidation was assessed as a safe and detoxifying technology, the estrogenic activity and toxicity originating from 17β-estradiol (E2) or its degradation by-products were sufficiently removed. These findings deepen the mechanistic understanding of the origins of high 1O2 production selectivity and provide a rational strategy for precisely controlling 1O2 generation in PMS activation.