Green and Efficient Oxidation of Cyclohexane to KA-Oil over Co–Ce@ZIF-8: Synergistic Effect of Co–N Enables In Situ Decomposition of CHHP

ZIF-8-based materials exhibit exceptional structural and chemical properties that render them highly promising for catalytic applications. The one-step highly selective oxidation of cyclohexane to KA-oil, a key precursor to ε-caprolactam (nylon-6 monomer) and adipic acid (nylon-66 monomer), remains a considerable challenge due to issues of low selectivity and overoxidation. In this study, bimetallic Co–Ce (1:1)@ZIF-8 synthesized via the hydrothermal method served as the catalyst, achieving 7.1% cyclohexane conversion with 87.7% KA-oil selectivity under optimal conditions. Combined experimental and characterization results reveal that an appropriate amount of Co–N facilitates the in situ directional conversion of the cyclohexyl hydroperoxide (CHHP) intermediate into KA-oil. Density functional theory (DFT) calculations and kinetic experiments further indicate that the incorporation of Ce promotes the catalyst’s electron mobility and increases electron density, thereby reducing the apparent activation energy for cyclohexane oxidation and significantly improving catalytic efficiency. In situ DRIFTS investigations corroborate the proposed reaction mechanism. This study offers valuable insights for the rational design of efficient catalysts for the selective oxidation of alkanes.