Aerobic Oxidation of Alcohols on Au Nanocatalyst: Insight to the Roles of the Ni-Al Layered Double Hydroxides Support.

Au nanoparticles (NPs) supported on Ni-Al layered double hydroxides (LDHs) were shown to be efficient heterogeneous catalysts for the highly selective oxidation of alcohols to the corresponding aldehydes or ketones under base-free or even solvent-free conditions with O₂ as the sole oxidant. The Au NPs can be uniformly distributed on Ni-Al LDHs support, which is beneficial to the catalytic activity. In addition, the weak Brønsted basic property of the support enables the aerobic oxidation of alcohols under base-free conditions. More importantly, unlike Al₂O₃, which is inert, Ni-Al-LDHs are redox-actively involved in prompting the electron transfer to O₂ via the Au nanocatalyst because of the presence of Ni^II. Both of the basic and the redox properties of Ni-Al-LDHs can be tuned by adjusting the ratio of Ni:Al to achieve the best synergistic effects between Au NPs and the supports. The activity of the obtained Au catalysts was found to be structurally associated with the arrangements of NiO₆ and AlO₆ octahedra in the surface hydroxide layers which were different from the bulk Ni:Al ratio. [ABSTRACT FROM AUTHOR]