Functionalized HKUST-1 via distal microenvironmental modification of coordination unsaturated sites as highly efficient catalysts for the cyclohexanone Baeyer-Villiger oxidation

• Functionalized X-HKUST-1 was synthesized by hydrothermal method and PSM. • Electronegative group introduction induces electron delocalization in H 3 BTC. • Ligand charge redistribution adjusts the electron density around metal center. • Br-HKUST-1 shows promising catalytic activity and recyclability in Cy=O B-V oxidation. Polycaprolactone emerges as a significant alternative to non-degradable plastics as the enhancing substantial environmental stress from the plastic products consumption. ε-Caprolactone (ε-CL), as its monomer, has attracted enormous attention. The Baeyer-Villiger (B-V) oxidation serves as an efficient method to produce lactones and esters from carbonyl compounds. In this study, an efficient functionalized metal–organic frameworks (HKUST-1) is applied to the B-V oxidation of cyclohexanone (Cy=O) to produce ε-caprolactone (ε-CL) under atmospheric pressure, utilizing molecular oxygen as the oxidant and benzaldehyde as the co-oxidant. The HKUST-1 featuring unsaturated metal centers, achieved via the removal of labile ligand solvent molecules, offer promising platforms for catalysis. And the electronegative groups are introduced to fine-tune the electronic states of the HKUST-1 through the distal microenvironment modification around coordinatively unsaturated sites (CUS). The experimental results indicated that Br-HKUST-1 achieves a 78.26 % conversion rate of Cy=O and a 94.83 % selectivity towards ε-CL. Furthermore, the yield of ε-CL remains stable at 70 % after five catalytic cycles. These findings provide a new strategy for designing catalysts suitable for the B-V oxidation of Cy=O and expound the influence of location-specific distal microenvironment modification on the catalysis.