Nitroarenes as the Visible-Light-Responsive Photocatalysts for the Multimode Aerobic Oxidation

Developing easy-to-prepare and versatile photocatalysts opens venues for low-cost and environmentally benign photocatalytic processes. In this work, various commercial nitroarenes, the organic cage with a nitroarene motif, and nitrated polystyrene were exploited as visible-light-responsive photocatalysts for the aerobic oxidation of benzylic amines. Two catalytic modes of the nitroarenes were revealed. In the first mode, the formation of the electron donor–acceptor complex between nitroarenes and benzylic amines through π–NH₂ interaction triggered the activation of dioxygen and the following oxidation of benzylic amines under visible-light irradiation. Among the nitroarenes, the organic cage molecule bearing six nitro groups showed the highest molecular TON, up to 886.9. The second catalytic mode involved the formation of amino-substituted nitroarenes between fluorinated nitroarenes with benzylic amines and the direct activation of dioxygen by the excited amino-substituted nitroarenes, which were verified through absorption, fluorescence, cyclic voltammetry, electron spin resonance, and controlled experiments. Furthermore, the nitrated polystyrene plastic samples could also be used as photocatalysts to catalyze aerobic oxidation, which expanded the ways of high-value utilization of plastic.