Direct Photocatalytic Conversion of Aldehydes to Esters Using Supported Gold Nanoparticles under Visible Light Irradiation at Room Temperature

Visible light can drive esterification from aldehydes and alcohols using supported gold nanoparticles (Au/Al2O3) as photocatalysts at ambient temperatures. The gold nanoparticles (AuNPs) absorb visible light due to the localized surface plasmon resonance (LSPR) effect, and the conduction electrons of the AuNPs gain the energy of the incident light. The energetic electrons, which concentrate at the NP surface, facilitate the activation of a range of aldehyde and alcohol substrates. The photocatalytic efficiencies strongly depend on the Au loading, particle sizes of the AuNPs, irradiance, and wavelength of the light irradiation. Finally, a plausible reaction mechanism was proposed, and the Au/Al2O3 catalysts can be reused several times without significantly losing activity. The knowledge acquired in this study may inspire further studies in new efficient recyclable photocatalysts and a wide range of organic synthesis driven by sunlight.