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

Abstract

Imidazolium ionic liquids functionalized UiO-66-NH 2 MOFs were synthesized by two different approach, further applied as efficient catalysts for the catalytic conversion of CO 2 into cyclic carbonates. The functionalized UiO-66-NH 2 were investigated using various characterization technologies including XRD, NMR, FT-IR, XPS, TG-DTG, TEM, N 2 -adsorption, and NH 3 -TPD. The octahedron structure of UiO-66-NH 2 becomes rough after UiO-66-NH 2 interacted with 1-(4-carboxybutyl)-3-methylimidazolium bromide via amidation, while some small grains were formed around UiO-66-NH 2 species when UiO-66-NH 2 was functionalized by 1-(3-sulfopropyl)-3-methylimidazolium bromide ([SPMIM]Br) via the H 2 N– and HSO 3 – interaction. Moreover, when [SPMIM]Br was grafted onto the surface of UiO-66-NH 2 , 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-NH 2 was reused three times. Furthermore, several additional coupling reactions were investigated with other epoxides as substrates. Chemical fixation of CO 2 into cyclic carbonates over ionic liquid functionalized UiO-66-NH 2 . • Two different approach was applied for the synthesis of functionalized UiO-66-NH 2 . • CO 2 can be efficiently converted into various cyclic carbonates over functionalized UiO-66-NH 2 . • 98.12% conversion of epichlorohydrin and 98.23% selectivity to chloropropene carbonate was obtained. • The difference of imidazolium ionic liquids was also studied by DFT calculations.