Computational Design of Reactive Ionic Liquids for CO2 Capture

The physical characteristics and wide chemical tunability of ionic liquids make them an attractive alternative to aqueous amines for energy-related CO₂ separations. Most efforts to date to modify the solubility of CO₂ in ionic liquids have involved adding reactive amine functionalities to the anion or cation, with mixed success.  Here we describe our recent work to use first-principles simulations to design a novel class of ionic liquids, aprotic heterocyclc anions, or "AHAs," that react selectively, reversibly, and controllably with CO₂.  We examine trends in reactivity with AHA composition, and consider the electronics of AHA-CO2 binding that lead to the very wide range of accessible absorption energies and potentially interesting kinetic behavior.  We consider the potential interferring effects of H₂O on CO₂ binding.  Finally, we compare the CO2 chemistry of the anionic AHAs with isoelectronic, neutral carbenes, potentially suitable as absorbents in non-ionic-liquid applications.  We demonstrate the feasibility of these heterocycles as a platform for a wide range of CO₂ separations applications.