Functional group effects on a metal-organic framework catalyst for CO₂ cycloaddition

A variety of metal-organic frameworks (MOFs) have been reported as efficient catalysts for CO₂ fixation reactions, such as cycloaddition to cyclic carbonates. The permanent porosity of the frameworks and the Lewis acidity of the MOF metal sites have been considered as the major contributors to the catalytic activity in the cycloaddition of CO₂. In this study, we have, instead, focused on the effects of the organic functional groups for effective catalytic ability. A total of eight different functionalized Zr-based MOFs were tested. It was revealed that the non-functionalized pristine UiO-66 MOF (UiO = University of Oslo) showed the best conversion at low temperature (77% at 50 °C), whereas the hydroxy-functionalized UiO-66-OH MOF displayed the best conversion at high temperature (91% at 140 °C). The Zr-MOF could be recycled up to four times without a significant decrease in the reactivity.