Enabling Specific Benzene Oxidation by Tuning the Adsorption Behavior on Au Loaded MgAl Layered Double Hydroxides

Abstract

Direct and selective oxidation of benzene to phenol is a long-term goal in industry. Although great efforts have been made in homogenous catalysis, it still remains a huge challenge to drive this reaction via heterogeneous catalysts under mild conditions. Herein, a single-atom Au loaded MgAl-layered double hydroxide (Au₁ -MgAl-LDH) with a well-defined structure, in which the Au single atoms are located on the top of Al³⁺ with Au-O₄ coordination as revealed by extended x-ray-absorption fine-structure (EXAFS)and density-functional theory (DFT)calculation is reported. The photocatalytic results prove the Au₁ -MgAl-LDH is capable of driving benzene oxidation reaction with O₂ in water, and exhibits a high selectivity of 99% for phenol. While contrast experiment shows a ≈99% selectivity for aliphatic acid with Au nanoparticle loaded MgAl-LDH (Au-NP-MgAl-LDH). Detailed characterizations confirm that the origin of the selectivity difference can be attributed to the profound adsorption behavior of substrate benzene with Au single atoms and nanoparticles. For Au₁ -MgAl-LDH, single Au-C bond is formed in benzene activation and result in the production of phenol. While for Au-NP-MgAl-LDH, multiple AuC bonds are generated in benzene activation, leading to the crack of CC bond.