Semiconductor cooperative photocatalysis with TEMPO

Visible light photocatalysis could potentially address a variety of challenges in environment and energy. Here, we discuss semiconductor cooperative photocatalysis with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), a redox mediator, to aid electron transfer. In a non-conductive organic solvent, electron transfer between photocatalyst and TEMPO occurs, thereby leading to the selective oxidation of organic molecules. The photocatalyst should possess both flexible and rigid properties to ensure TEMPO-mediated electron transfer. Organic dye–semiconductors, metal–organic frameworks and covalent organic frameworks have been studied to facilitate cooperative photocatalysis with TEMPO for the selective aerobic oxidation of sulfides, amines, alcohols, and alkanes. This review could help to offer new insight into mediation of electron transfer in photocatalysis and help to overcome long-standing obstacles to success.