Imidazolium ionic liquid functionalized UiO-66-NH2 as highly efficient catalysts for chemical fixation of CO2 into cyclic carbonates

Imidazolium ionic liquids functionalized UiO-66-NH2 MOFs were synthesized by two different approach, further applied as efficient catalysts for the catalytic conversion of CO2 into cyclic carbonates. The functionalized UiO-66-NH2 were investigated using various characterization technologies including XRD, NMR, FT-IR, XPS, TG-DTG, TEM, N2-adsorption, and NH3-TPD. The octahedron structure of UiO-66-NH2 becomes rough after UiO-66-NH2 interacted with 1-(4-carboxybutyl)-3-methylimidazolium bromide via amidation, while some small grains were formed around UiO-66-NH2 species when UiO-66-NH2 was functionalized by 1-(3-sulfopropyl)-3-methylimidazolium bromide ([SPMIM]Br) via the H2N– and HSO3– interaction. Moreover, when [SPMIM]Br was grafted onto the surface of UiO-66-NH2, a higher catalytic activity was found to exhibit 98.12% conversion of epichlorohydrin (ECH) and 98.23% selectivity to chloropropene carbonate (CPC) under optimized conditions (Initial pressure 2.5 MPa, 1.2 wt% catalyst of ECH, 95 °C, reaction time 8 h). No significant deactivation of the catalyst was observed after the [SPMIM]Br functionalized UiO-66-NH2 was reused three times. Furthermore, several additional coupling reactions were investigated with other epoxides as substrates.