Layered double hydroxide supported gold nanoclusters by glutathione-capped Au nanoclusters precursor method for highly efficient aerobic oxidation of alcohols

Abstract

M₃Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 ± 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ∼0.23 wt% upon synergetic interaction between AuNCs and M₃Al-LDH. AuNCs/Mg₃Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg₃Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity or selectivity. The AuNCs/M(= Ni, Co)₃Al-LDH catalysts present even higher alcohol oxidation activity than AuNCs/Mg₃Al-LDH. Particularly, AuNCs/Ni₃Al-LDH-0.22 exhibits the highest activity (46 500 h⁻¹) for the aerobic oxidation of 1-phenylethanol under solvent-free conditions attributed to its strongest Au–support synergy. The excellent activity and stability of AuNCs/M₃Al-LDH catalysts render these materials promising candidates for green base-free selective oxidation of alcohols by molecular oxygen.