Post-Synthetic Defunctionalization of Ammonium-Functionalized Zr-Based Metal-Organic Framework MIP-202 for Knoevenagel Condensation Reaction

A new recyclable and stable catalyst based on a Zr metal-organic framework, namely MIP-202 has been constructed through a simple post‐synthetic modification strategy as an extremely efficient and applied heterogeneous catalyst for Knoevenagel condensation reaction between benzaldehyde and ethyl cyanoacetate under mild reaction conditions. The principal purpose of this study is to reduce the amount of the protonated amine functional groups (NH3+) in the pores of MIP-202 using the solvent assisted ligand exchange (SALE), in order to achieve an optimal structure to obtain higher efficiencies in Knoevenagel condensation reaction. The resultant catalyst is characterized via various techniques including PXRD, FT-IR, FE-SEM, EDX, BET, AAS, CHN, and TG analyses. The post-modified catalyst exhibited high catalytic performance with 90% efficiency, which is an enhanced activity compared to the pristine MIP-202 MOF, and also four recycling stability without a significant decrease in catalytic activity. Therefore, it was proved that the adjustment of functional groups is an effective method for the improvement of the reaction process. The catalytic mechanism has also been investigated.