Why are Ionic Liquids Attractive for CO2 Absorption? An Overview

As the climate debate is hotting up, so is the (re) search for finding powerful new materials for the efficient and cost-effective removal of CO2 from flue-gas streams from power plants and other emission sources. Ionic liquids (ILs), exhibiting higher CO2 solubility than conventional organic solvents, have received considerable interest as new CO2 absorbents. The present paper evaluates the advantages and disadvantages of ILs, and provides an overview of the recent developments of ILs for CO2 capture. In conventional ILs, CO2 is absorbed by occupying the free space between the ions through physical absorption mechanisms. As another promising strategy, task-specific ILs have been studied that, by attaching functional groups to the ions, allow the formation of chemical bonds to improve the overall absorption capacity during the CO2 capture process. Other strategies include using ILs as reaction media or as selective absorption materials.