Efficient conversion of CO2 into cyclic carbonates under atmospheric by halogen and metal-free poly(ionic liquid)s

Abstract

A novel series of halogen free, hydroxyl group containing poly(ionic liquid)s (PILs) was first synthesized from glycerol dimethyl acrylate (GDA) and 1-vinyl imidazole (1-VIM) through free radical polymerization, follow by an alkylation step and an ion-exchange procedure to form the final imidazolium hydrogen carbonate heterogenous catalyst poly(HCO3-OH-n). The chemical and physical properties were investigated by varying the monomer ratio between GDA and 1-VIM. Among them, poly (HCO3-OH-2) exhibited the highest catalytic activity for CO2 cycloaddition, with the yield of chloropropene carbonate 90% under mild conditions (80 °C, 0.1 MPa, 12 h, 0.15 g catalyst for 32 mmol epichlorohydrin) in the absence of any cocatalyst, metal or solvent. A range of substrates with good to excellent yields under atmosphere was obtained. The poly(HCO3-OH-n) catalyst is collectable and still remains acceptable catalytic activity after six runs. Finally, a preliminary kinetic is calculated on the basis of poly(HCO3-OH-2) with the activation energy value of 79.5 kJ·mol−1. This study highlights that the poly(HCO3-OH-n) enable to reach efficient CO2 conversion under mild conditions.