Secondary Ligand Engineering Cu‐MOFs for Enhanced Catalytic Epoxidation of Styrenes

Tunable and efficient catalysts are crucial for epoxidation of styrenes to produce high‐value fine‐chemical intermediates. By changing coordinators of the copper‐center, a series of Cu‐BDC‐ L s (BDC and L are shorted for benzenedicarboxylic acid and the second ligand, respectively) were synthesized through secondary ligand engineering strategy via a one‐pot solvothermal method to enhance the catalytic performance of styrene epoxidation reactions. Notably, the selectivity toward styrene oxide improved from 35.3% for the Cu‐BDC catalyst to 68.1% for Cu‐BDC‐SDI (SDI refers to 1,1'‐sulfonyldiimidazole) system. Compared to the other as‐synthesized Cu‐based mixed‐ligand metal‐organic framework (Cu‐mix‐MOF) materials, Cu‐BDC‐SDI exhibited highest selectivity of styrene oxide. Solvent type, solvent dosage, temperature and time were optimized to obtain moderate to high selectivity and yield. Furthermore, the as‐synthesized Cu‐mix‐MOF catalyst demonstrated good stability and acceptable reusability. It is proposed that the coordination of SDI with Cu 2+ via its S and N atoms increases the electro‐positivity of Cu 2+ , which promotes the activation of oxidant tert‐butyl hydroperoxide (TBHP) to form Cu 2+ ‐OOR intermediates that selectively attack the C═C bond of styrene, thereby favoring the production of styrene oxide. This research provides a new strategy to fabricate highly efficient and cost‐effective catalysts for epoxidation reactions.