Nanosheet array-like NixMg3-xAl-LDH/rGO hybrids loaded atomically precise Aun nanoclusters for the solvent-free oxidation of benzyl alcohol

A series of hierarchically structured hybrids Ni x Mg 3-x Al-LDH/rGO (LDH: layered double hydroxides, x  = 1, 1.5 and 2, rGO: reduced graphene oxide) supported atomically precise Au n ( n  = 25, 38 and 127) nanoclusters (NCs) catalysts Au n /Ni x Mg 3-x Al-280 were firstly prepared via a double pH-controlled electrostatic adsorption method using captopril-capped Au n NCs as precursors followed proper calcination . Detailed characterizations show that the as-obtained hierarchically structured Au n NCs catalysts possess the nanosheet array-like structure formed by the LDHs nanosheets (∼55–70 × 10 nm) interdigitated vertically grown on the both sides of rGO layers, and Au n NCs with size of 1.0–1.9 nm are mainly dispersed on the edge and cross-linking sites of LDH/rGO hybrid. All the hierarchically structured Au n NCs catalysts exhibit excellent catalytic activity for the solvent-free oxidation of benzyl alcohol without additional base, and the activities show a volcanic trend with increasing Ni/Mg ratios and gradually decrease with the increased Au atomicities in Au n clusters. The highest TOF value of 5118 h −1 for the Au 25 /Ni 1.5 Mg 1.5 Al-280 can be ascribed to the smallest Au 25 NCs containing the Au 0 /Au δ+ -Ni 2+ /Mg 2+ –OH interface with the highest Au δ+ /(Au 0  + Au δ+ ) ratio, and the strongest Au 25 −LDH/rGO synergistic interaction along with hierarchical nanosheet array-like structure facilitating the transmission and diffusion of the reactants. The present work provides a new idea for preparing the hierarchically structured LDH/rGO hybrid supported metal nanoclusters catalysts with high-performance for various catalytic applications.