Highly selective generation of singlet oxygen from dioxygen with atomically dispersed catalysts.

Singlet oxygen (O) as an excited electronic state of O plays a significant role in ubiquitous oxidative processes from enzymatic oxidative metabolism to industrial catalytic oxidation. Generally, O can be produced through thermal reactions or the photosensitization process; however, highly selective generation of O from O without photosensitization has never been reported. Here, we find that single-atom catalysts (SACs) with atomically dispersed MN sites on hollow N-doped carbon (M/HNC SACs, M = Fe, Co, Cu, Ni) can selectively activate O into O without photosensitization, of which the Fe/HNC SAC shows an ultrahigh single-site kinetic value of 3.30 × 10 min mol, representing top-level catalytic activity among known catalysts. Theoretical calculations suggest that different charge transfer from MN sites to chemisorbed O leads to the spin-flip process and spin reduction of O with different degrees. The superior capacity for highly selective O generation enables the Fe/HNC SAC as an efficient non-radiative therapeutic agent for inhibition of tumor cell proliferation.