The Study On CO₂Capture By Functionalized Ionic Liquids

The development of more efficient, reversible, and economical processes for capturing CO2from the burning of fossil fuels is critical for the reduction of the emission of greenhouse gas implicated in global warming. Ionic liquids (ILs) are promising in this regard because of their negligible vapor pressures, wide liquid range, high thermal stabilities, and virtually limitless chemical tunabilities.Firstly, a novel strategy to improve CO2capture by hydroxypyridine-based ionic liquids making use of the cooperative interactions of multiple sites in the anion is reported. An extremely high capacity of CO2and excellent reversibility were achieved via introducing a nitrogen-based interacting site in the phenolate anion. Quantum mechanical calculations and spectroscopic investigations demonstrate the significance of the cooperative interactions between the electronegative nitrogen and oxygen atoms in the anion due to the π-electron delocalization. These hydroxypyridine-based ionic liquids with multiple cooperative interacting sites open a door to develop highly efficient and excellently reversible carbon capture process, and thus have great potential in acid gas separations.Secondly, a series of novel alkanolamine-based ionic liquids show a highly efficient and excellent reversible capture of CO2through multi-dentate cation coordination between alkanolamine and Li ion in a quasi-aza-crown ether fashion. These ILs reacted with CO2to form a liquid carbamate salt, achieving a high absorption capacity of CO2due to chelation. Furthermore, the captured CO2was readily released by heating or bubbling N2through the IL by tuning the chelation between thealkanolamine and Li+, leading to excellent reversibility. We believe that this highly efficient and excellently reversible process by these ILs can potentially provide an attractive alternative for CO2capture. As a new kind of ILs containing Li and quasi-aza crown ether, they can also be used in other fields such as batteries and separation.Through changing the combination of cation and anion of ILs, we provided some excellent strategies on how to improve CO2capture performance by designing the structures of the ILs.