It is imperative to develop efficient, reversible and economic technologies for separating CO2 which mainly comes from flue gas, natural gas and syngas. Membranes based on functionalized ionic liquids (ILs) have attracted much attention from researchers in recent years, and have been considered as a very promising technology. This feature article focuses on the research progress in CO2 separation using functionalized IL membranes. The recent advances in the preparation, separation performance, and separation mechanism of supported IL membranes (SILMs), pure poly(ionic liquid) (PIL) membranes, PIL-copolymer membranes, PIL-IL composite membranes and polymer-IL composite membranes for CO2 separation have been reviewed. In addition, the future directions and prospects for CO2 separation using functionalized IL membranes are given.