Manganese assisted efficient construction of Cu+ sites and oxygen vacancies in composite hydroxides for solvent-free aerobic oxidation of alkylarenes

Abstract

Aerobic oxidation of alkylarenes is an effective approach for producing carbonyl compounds, with oxygen serving as the oxidant and solvent-free conditions being the preferred choices. Based on the tunable metal ions of layered double hydroxides (LDHs), a series of CuZnM-LDHs (M = Al, Co, Fe and Mn) containing Cu⁺ sites have been fabricated through in situ electron transfer between Cu²⁺ and doping metals. Characterization results revealed that the synergistic effect between Cu and Mn endowed CuZnMn-LDH with abundant Cu⁺ sites and oxygen vacancies. Structure–activity relationship studies indicated that Cu⁺ serves as the key catalytically active site, and oxygen vacancies promote the activation of molecular oxygen, resulting in the formation of active O₂˙⁻ species, thereby accelerating the generation of reactive PINO (N-oxylphthalimide) from NHPI (N-hydroxyphthalimide) through a HAT (hydrogen atom transfer) process. Therefore, an efficient catalytic system based on CuZnMn-LDH has been developed for the aerobic oxidation of alkylarenes under solvent-free conditions. The CuZnMn-LDH catalytic system also displayed advantages in catalytic stability, recyclability, and broad substrate tolerance.