Engineering of Single Atomic Cu-N₃ Active Sites for Efficient Singlet Oxygen Production in Photocatalysis

Photocatalytic generation of singlet oxygen (1O2) is an attractive strategy to convert organic chemicals to high value-added products. However, the scarcity of suitable active sites in photocatalysts commonly leads to the poor adsorption and activation of oxygen molecules from a triplet state to a singlet state. Here, we report single atomic Cu-N3 sites on tubular g-C3N4 for the production of singlet oxygen. X-ray absorption fine spectroscopy, in combination with high-resolution electron microscopy techniques, determines the existence of atomically dispersed Cu sites with Cu-N3 coordination mode. The combined analysis of electron spin resonance and time-resolved optical spectra confirmed that a single atomic Cu-N3 structure facilitates a high concentration of 1O2 generation due to charge transport, electron–hole interaction, and exciton effect. Benefiting from the merits, a single atomic photocatalyst yields nearly 100% conversion and selectivity from thioanisole to sulfoxide within 2.5 h under visible light irradiation. This work deeply reveals the design and construction of catalysts with specific active sites, which are helpful to improve the activation efficiency of oxygen.