Redox-active and Brønsted basic dual sites for photocatalytic activation of benzylic C–H bonds based on pyridinium derivatives

A mild and efficient photocatalytic C–H bond activation strategy has been developed based on organic small molecules. A combination of the excellent redox-active activity of the pyridinium unit and Brønsted basic site of the N-heterocyclic unit offers a concerted pathway for H abstraction through concomitant proton and electron transfer, thus solving the key dehydrogenation process of C–H bond activation. The photocatalytic system shows high performance in selective oxidation of ethylbenzene, toluene and its homologue, and a gram-level conversion of p-xylene into terephthalic acid has been achieved at room temperature under an air atmosphere without any co-catalysts and additives.