Effects of doping metal on the catalytic performance of manganese-based layered double hydroxides in the aerobic oxidation of alcohols

The selective aerobic oxidation of alcohols to produce corresponding aldehydes is a highly significant protocol in organic synthesis. In this study, a series of metal-doped MgMn layered double hydroxides (LDHs) have been fabricated (MMgMn-LDHs, M = Cu, Co or Ni), characterized, and explored for their performance in the aerobic oxidation of alcohols. The findings reveal that doping with metals can regulate the electronic properties of manganese and the distribution of surface oxygen species. Among them, Cu doping in CuMgMn-LDH results in the generation of stable low-state Mn species (Mn²⁺ and Mn³⁺ species) and oxygen vacancies, which exhibits the lowest activation energy, as well as the best performances toward benzyl alcohol oxidation. Kinetic studies indicate that the aerobic oxidation of benzyl alcohol follows pseudo-first-order kinetics. Mechanism investigations reveal that Mn²⁺ and Mn³⁺ species can accelerate the aerobic oxidation of alcohols through HAT (hydrogen atom transfer) and PCET (proton coupled electron transfer) processes, respectively, with the former being the dominant pathway. Moreover, the CuMgMn-LDH catalytic system demonstrates broad substrate tolerance, good catalytic stability, and recyclability, highlighting its convenience and practicality as a catalytic process for aldehyde production.