Boosting Catalytic Efficiency of Metal-Organic Frameworks with Electron-Withdrawing Effect for Lewis-Acid Catalysis

摘要

Metal Organic Frameworks (MOFs) have the characterization of high specific surface area, abundant metal active sites and tunable pores, making them become emerging heterogeneous catalysts. Furthermore, the clear structure of MOFs provides an excellent opportunity to explore the internal relationship between catalytic activity and structure. In addition, precise synthesis of controllable catalytic sites from the molecular level can achieve efficient catalytic preparation of high value-added chemicals. Here, we synthesize a series of MOFs (MIL-101(Fe)-X; X=H, NO2, Br, Cl) with different substituents on the tereph- thalate linker. Then the catalytic activity of MIL-101(Fe)-X was evaluated for Knoevenagel reaction with different substrates. The order of reactivity of MIL-101(Fe)-X is closely related to the ability of the electron withdrawing effect. The MIL-101(Fe)-NO2 showed the best conversion at low temperature (99.9% at 25°C). While the activity of pristine MIL-101 only can reach 80.78% of under same condition. This work illustrates the versatility of electronic effect on catalytic activity and brings possibility to tune the activity of MOFs through introducing organic ligands with different functional groups.