Solvent-free aerobic alcohol oxidation using Cu/Nb2O5: Green and highly selective photocatalytic system

Photooxidation of alcohols without organic solvents in the presence of O2 took place at the atmospheric pressure and room temperature over Nb2O5 and Cu/Nb2O5, avoiding the cost, toxicity, and purification problems associated with transition-metal systems. Loading of a small amount of copper on Nb2O5 significantly enhanced activity without lowering selectivity. On the other hand, loading of Pt, Ni, Rh, Ru, and Ag showed no promotion effect. The selectivities of the photooxidation of aliphatic, aromatic and heteroatom-containing alcohols over Cu/Nb2O5 were in the range of 80–99%. Cu/Nb2O5 was easily separated from the reaction mixture and was reusable without reducing the catalytic performance.

Solvent-free aerobic oxidation of alcohols proceeds selectively at room temperature and atmospheric pressure by using Nb2O5 or Cu/Nb2O5 photocatalysts. Cu/Nb2O5 shows remarkably enhanced photocatalytic activity without lowering selectivity than Nb2O5 in oxidation of various alcohols.Figure optionsDownload as PowerPoint slideHighlights
► Solvent-free aerobic oxidation of alcohols using Cu/Nb2O5 photocatalyst.
► Enhanced photocatalytic activity of Nb2O5 by the addition of Cu.
► The 1-phenylethanol is quantitatively converted to acetophenone under solvent-free and mild conditions.