Regulation of Novel Multi‐Center Ionic Liquids for Synergetically Catalyzing CO₂ Conversion into Cyclic Carbonates

Abstract

A family of novel multi-center ionic liquids (ILs) were designed for the target of efficient transformation of CO 2 into cyclic carbonates. The multi-center structures could expose more active sites than single-center ones in cycloaddition reaction. Among these ILs, with the chain-regulation strategy, the multicenter hexabutylimidazole bromobenzene (BIM-6) exhibited the performance with 95 % propylene epoxide (PO) conversion and 99 % selectivity (130°C, 2.5 MPa, ILs amount 0.15 mol%, 1 h). Moreover, the multi-center ILs showed good reusability after 5 cycles and extensive suitability for different terminal epoxides. Density functional theory (DFT) and noncovalent interactions (NCI) illustrated that hydrogen-bond formed between the multi-center ILs and epoxides, together with hindrance of side chain lengths setting bromide free, synergistically activated reactants. Thus, the possible mechanism based on hydrogen-bond induction and hindrance regulation was proposed. This study provides a new approach for development of highly efficient ILs in the green chemical process.

High Density Poly(ionic liquid)s with Spatial Structure Regulation for Efficient Carbon Dioxide Cycloaddition

“…(%) Selec. (%) Ionic density (mmol g À 1 ) TOF (h À 1 ) [b] 1 [c] Ply[DVBVIM]Br [23] 56 99 3.0 28 6 [d] PVBIMCl [24] 45.6 99 0.7 2.7 7 [e] P(DMAEMA-EtOH)Br [21] 98. [f] Ply[PhSVIM]Br 75 99 5.0 7 17 [f] PVIm-6-SCD [17] 98.5 99.7 5.0 27…”

“…so the reduction of the binding energy is favorable to the freeing of bromine, which can promote the reaction. [23]…”

“…These multicenter ILs could reach or even exceed the catalytic perform-ance of equivalent single center ILs. [11] Furthermore, hexabutylimidazolium bromomethylbenzene (BIM-6) with six active centers was screened out, with a catalytic conversion of 93 %. The amount of catalyst was significantly reduced (0.15 mol% for ILs).…”

“…developed a series of multi‐center imidazolium‐based ILs with a breakthrough from the conventional single pair of anion and cation to six pairs. These multi‐center ILs could reach or even exceed the catalytic performance of equivalent single center ILs [11] . Furthermore, hexabutylimidazolium bromomethylbenzene (BIM‐6) with six active centers was screened out, with a catalytic conversion of 93 %.…”

Sterically regulated halogen‐free bifunctional ionic liquids for catalytic conversion of CO2 into cyclic carbonates

“…[8] Therefore ILs are widely used in different chemical reactions. [9] For the chemical conversion of CO 2 , ILs are highly effective catalysts. [10] Previously we reported on the study of halogen ionic liquid catalysts, the ionic liquid catalysts exhibited excellent conversion, selectivity and good reusability, and we studied the effect of the change of ionic liquid chain length on the catalytic activity.…”