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.