Recyclable Cu@C3N4-Catalyzed Hydroxylation of Aryl Boronic Acids in Water under Visible Light: Synthesis of Phenols under Ambient Conditions and Room Temperature

A heterogeneous photocatalyst based on copper-doped g-C3N4 was developed for the oxidative hydroxylation of aryl boronic acids into phenols at room temperature under the irradiation of blue light (460 nm). The reaction proceeded efficiently in water as a green solvent and air as a green oxidant, giving various phenols as products with high yields in a short reaction time. Importantly, this heterogeneous catalyst can be used at least 5 times with the reactivities maintained.