Immobilization of Ionic Liquids with a New Cellulose Ester Containing Imidazolium Cation for High‐Performance CO2 Separation Membranes

Abstract CO 2 gas separation is of significant importance to protect the environment and utilize the carbon resource. In this work, two kinds of new cellulose esters containing imidazolium cation, cellulose acetate (CA) 1‐butyl‐3‐methylimidazolium chloride and CA 1‐butyl‐3‐methylimidazolium bis(trifluoromethane sulfonyl)imide (CA‐BmimTf 2 N), are designed and synthesized. The resultant cationized cellulose esters effectively lock various ionic liquids (ILs) via electrostatic interactions. Due to the strong attraction interactions, the obtained cellulose ester/ILs composite membranes are uniform, smooth, and highly transparent. Moreover, the added ILs with a long alkyl chain in the cation and a bis(trifluoromethane sulfonyl)imide anion remarkably improve the CO 2 permeability of the cellulose ester/ILs membranes, because of the dramatic increase of the CO 2 diffusion rate. The CA‐BmimTf 2 N/C 10 mimTf 2 N membranes exhibit the highest CO 2 permeability, which is 3800% higher than that of CA membrane and 1700% higher than that of CA‐BmimTf 2 N membrane. More importantly, the CA‐BmimTf 2 N/C 10 mimTf 2 N membranes have good mechanical properties and thermal stability. Such high‐performance CO 2 separation membranes with high CO 2 permeability, high transparency, and good mechanical property have a huge potential in the practical utilization for gas separation.