Al₂O₃ surface complexation for photocatalytic organic transformations

The use of sunlight to drive organic reactions constitutes a green and sustainable strategy for organic synthesis. Herein, we discovered that the earth-abundant aluminum oxide (Al₂O₃) though paradigmatically known to be an insulator could induce an immense increase in the selective photo-oxidation of different benzyl alcohols in the Presence of a large variety of dyes and O₂. This unique phenomenon is based on the surface complexation of benzyl alcohol (BnOH) with the Brensted base sites on Al₂O₃, which reduces its oxidation potential and causes an upshift in its HOMO for electron abstraction by the dye. The surface complexation of O₂ with Al₂O₃ also activates the adsorbed O₂ for receiving electrons from the photoexcited dyes. This discovery brings forth a new understanding on utilizing surface complexation mechanisms between the reactants and earth abundant materials to effectively achieve a wider range of photoredox reactions. © 2016 American Chemical Society