Tailoring the catalytic activity of metal organic frameworks by tuning the metal center and basic functional sites

Abstract

In this study, zirconium, zinc, and copper-based metal organic framework catalysts were synthesized. In order to tune the catalytic activity, the coordinative unsaturated metal–organic frameworks were functionalized with different amines by an economical and simple post-synthetic modification strategy. In this study, systematic investigation is made by the functionalization of metal organic frameworks with primary, secondary, and tertiary amines by the post-synthesis method. Furthermore, the metal organic frameworks were also functionalized with one basic ionic liquid. The materials were characterized by powder X-ray diffraction, nitrogen adsorption, scanning electron microscopy, thermo gravimetric analysis, Fourier transform infrared, X-ray photoelectron spectroscopy, and temperature programmed desorption techniques. The applications of these bi-functional catalysts were investigated in the best suited model reaction, Knoevenagel condensation. The applicability of these catalysts was extended in the synthesis of jasminaldehyde (aldol condensation of 1-heptanal and benzaldehyde) and cyclic carbonate (cycloaddition of CO₂ to epoxide). The catalysts can be easily recovered and reused with negligible loss in the catalytic activity even after five cycles.