The Accelerated NHPI‐PINO Cycling Mediated by Surface Co‐Superoxo for Efficient Aerobic Oxidation of Alcohols to Acids

ABSTRACT

Oxidation of alcohols to acids is a key transformation in the chemical industry; however, one‐pot oxidation to acids via the environment‐friendly and cost‐effective method remains challenging. In this study, a series of ZIF‐67‐derived CoO _x catalysts were synthesized, and ZIF‐CoO _x ‐2 exhibits a high conversion of 95.2% 2‐methyl‐1‐butanol and selectivity of 99% toward 2‐methyl‐1‐butanic acid by O ₂ in the presence of NHPI. In addition, this protocol is also efficient in the one‐pot oxidation of a variety of alcohols to acids. The gram‐scaled reaction can also be conducted using O ₂ or even air as the oxidant. EPR analysis indicates that the NHPI‐PINO cycle plays an important role in this process. Quenching experiments and Raman analysis indicate that Co‐superoxo on the surface of ZIF‐CoO _x ‐2 is an important oxidizing species facilitating the NHPI‐PINO cycle. DFT calculations further reveal that the NHPI‐PINO cycle facilitates H‐abstraction from alcohols by PINO, as well as H‐abstraction from NHPI by ROO•, thus apparently enhancing the conversion and selectivity. This study offers a sustainable method to directly oxidize alcohols to acids with high conversion and selectivity, enriching our understanding on the importance of synergistic interactions between the surface superoxo species and the NHPI‐PINO cycle in the selective oxidation of organic substrates.