Metal chlorides-catalyzed selective oxidation of cyclohexane by molecular oxygen under visible light irradiation

► Metal chlorides of easily changeable valence are active to cyclohexane photo-oxidation. ► Metal chlorides absorb visible light due to its weak coordination with solvent. ► Acetone is slightly superior to acetonitrile in the improved oxidative selectivity. ► Adding concentrated HCl can significantly promote the CuCl2-photocatalyzed cycling. ► A mechanism of light-driven redox cycling of CuCl2 for the photoreaction is proposed.