Journal of the American Chemical Society, Vol.139, No.1, 269-276, 2017
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 O-2. This unique phenomenon is based on the surface complexation of benzyl alcohol (BnOH) with the Bronsted 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 O-2 with Al2O3 also activates the adsorbed O-2 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.