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

Abstract

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.

Continuous gas phase catalytic transformation of levulinic acid to γ‐valerolactone over supported Au catalysts

“…Catalyst physico‐chemical characteristics are given in Table . The SSA range from 52 m 2 g −1 (Au/TiO 2 ) to 166 m 2 g −1 (Au/Al 2 O 3 ) and the values obtained for each system are in agreement with those reported in the literature . The TPR profiles of laboratory synthesised Au/Al 2 O 3 (A), Au/CeO 2 (B) and Au/TiO 2 (C) are presented in Fig.…”

“…Surface acidity in the case of Al 2 O 3 , CeO 2 and TiO 2 is associated with uptake at Al 3+ , Ce 4+ or Ti 4+ Lewis acid centres, as demonstrated by XPS, temperature‐programmed reaction, NMR and FT‐IR measurements. The quantity of NH 3 chemisorbed/desorbed (Table ) on the three Au catalysts (12–28 × 10 −2 mmol g −1 ) was comparable with that reported for Al 2 O 3 , CeO 2 , and TiO 2 supported Au systems (10–38 × 10 −2 mmol g −1 ).…”

Supported Palladium Nanoparticles Catalyzed Ortho-Directed C–C Coupling Reaction via a Pd0/PdII/PdIV Catalytic Cycle

“…The PdNPs on γ-Al 2 O 3 and other supports were prepared by a modified impregnation-reduction method using the preparation of Au/γ-Al 2 O 3 for reference. 64 For example, 3 wt% Pd/γ-Al 2 O 3 catalyst was prepared by the following procedure: 0.97 g of γ-Al 2 O 3 powder was suspended in 50 mL of distilled water, followed by adding 28. Thin layer chromatography (TLC) was performed on pre-coated silica gel GF254 plates.…”

Highly efficient self-esterification of aliphatic alcohols using supported gold nanoparticles under mild conditions

“…In this study, we prepared a series of Au NP catalysts supported on zirconia (ZrO 2 ) with various Au loading (0.5 wt%, 1.5 wt%, 3.0 wt% and 5.0 wt%) by the impregnation-reduction method [32][33][34][35]. The ZrO 2 enables the uniform distribution of Au NPs on the solid support surface, and the readily recycling of the catalysts after reaction.…”