Incorporation of a carboxyl-functionalized imidazolium-based ionic liquid into a UiO-66 type MOF for chemical fixation of CO2 into carbonates

Abstract

Incorporation of ionic liquids into metal–organic frameworks (MOFs) offers a new platform to construct heterogeneous bifunctional catalytic systems for the chemical capture and conversion of CO₂ with epoxides. Herein, an imidazolium-based ionic liquid decorated UiO-66 type MOF (P₃[BCMIm]Br@UiO-66) was successfully constructed via solvothermal assembly of the carboxyl-functionalized imidazolium ionic liquid ligand, terephthalic acid ligand and Zr(IV) ions. It exhibits the highest catalytic activity upon the cycloaddition of CO₂ (98.2% conversion of propylene oxide and 99% selectivity to propylene carbonate) under optimized conditions (2.2 Mpa CO₂, 1.0 wt%, 110 °C, reaction time 2 h). Notably, P₃[BCMIm]Br@UiO-66 outperformed the original UiO-66 materials and [BCMIm]Br. P₃[BCMIm]Br@UiO-66 retained its good catalytic performance for up to five recycling runs with only a little loss in catalytic activity. Furthermore, several additional coupling reactions were investigated with other epoxides as substrates.