Atomically dispersed manganese catalysts with electron-deficient Mn–N2O2 sites to enhance the selective oxidation of benzyl alcohol to benzaldehyde via PMS-based non-radical oxidation pathway

The selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) is one of the effective methods for synthesizing chlorine-free benzaldehyde, but developing an efficient catalytic system remains a challenge. The peroxymonosulfate (PMS) is an inexpensive and soluble solid oxidant that has been widely used in oxidation reactions in aqueous media, however, there are still difficulties in activating PMS using atomically dispersed metal catalysts based on non-free radical pathways. Herein, an atomically dispersed manganese catalyst (Mn 1 /NLC), featuring electron-deficient Mn–N 2 O 2 sites anchored on a nitrogen and oxygen co-doped carbon support, is synthesized through a combined process of ball milling and high-temperature pyrolysis. The Mn 1 /NLC catalyst exhibits outstanding performance in the selective oxidation of BzOH to BzH by efficiently activating PMS, achieving 98.5% BzOH conversion and 99.2% BzH selectivity with a high turnover frequency of 1470.6 h −1 within 3 h at a PMS dosage of 10 mg and 45 °C, which surpasses the majority of the reported catalysts. Electron paramagnetic resonance, radical quenching experiments, and electrochemical analysis collectively reveal that the Mn–N 2 O 2 reaction sites lead to the formation of a high-valent Mn species, which enhances the adsorption of C H bonds and activation of PMS to significantly promote the occurrence of non-radical oxidation pathway, including singlet oxygen ( 1 O 2 ) generation and electron transfer processes (ETP). The synergistic effect of 1 O 2 and ETP enables Mn 1 /NLC to perform efficient and selective C H oxidation of various aromatic alcohols under mild conditions, while also demonstrating excellent cycling stability. This study provides a novel strategy for the design of high-performance atomically dispersed metal catalysts for the selective oxidation of aromatic alcohols.