Synthesis of PEI Grafted Poly (Ionic Liquid)s: Optimization and Kinetics Modeling of Effective CO 2 Fixation Reactions

Abstract Fixing the greenhouse gas CO 2 through epoxide helps to mitigate worldwide ecological troubles. The applications of metal‐free and solvent‐free catalysts remain a challenge for CO 2 catalytic conversion. In this work, an array of quaternary ammonium salts derived from polyethyleneimine with hydroxyl groups ([PEI‐GDMAB‐C n ]Br) were constructed by the reaction of branched PEI with a molecular weight of 10000 and glycidyl alkyl dimethylammonium bromide. A range of experiments were designed to demonstrate that [PEI‐GDMAB‐C n ]Br can be considered as a valid metal‐free and solvent‐free homogeneous catalyst for the CO 2 ‐epoxide cycloaddition reaction. Among of [PEI‐GDMAB‐C n ]Br, [PEI‐GDMAB‐C 18 ]Br catalyzed the model reaction of CO 2 and epichlorohydrin under optimized reaction conditions (T=80 °C, 1.0 atm CO 2 , catalyst 1 mol%, ECH 15 mmol, 16 h) and the conversion achieved at 97.5 %. Moreover, the catalyst exhibited stable reusability and broad substrate applicability, which was used in the following cycle succinctly, because of self‐separated properties by temperature control. The [PEI‐GDMAB‐C 18 ]Br catalyzed reaction process was detected as a pseudo‐first‐order reaction after kinetic studies and an E a was calculated to be 50.65 kJ/mol. A combinatorial catalytic mechanism of hydrogen bonding and bromide ions is suggested to explain the remarkable catalytic performance of this bifunctional catalyst.