Simulation Study of CO2-Reactive Aprotic Heterocyclic Anion Ionic Liquids: Water Interactions, Liquid Structure, and CO2 Solubility

The focus of this dissertation is to explore how classical molecular dynamics (CMD) simulations and ab initio calculations can be used to further the current understanding of AHA IL systems. The dissertation starts with a review of the development of CO2-reactive ILs and the role that simulations played in advancing their design. CMD simulations are used to examine the liquid structure and dynamics of both pure ILs and IL-water mixtures. The water solubility and the observed changes in dynamics from the addition of water are explained through structural analysis of hydrogen bonds formed between water and the anions. The liquid structure is examined through comparison of measured and computed structure functions for a series of ILs with different combinations of cations and anions. The fact that the liquid structure functions do not change appreciably upon reaction with CO2 is used to explain why viscosities of AHA ILs do not change much upon reaction with CO2. A method is presented for calculating CO2 solubilities in AHA ILs using the Gibbs free energy of reaction. The method is able to predict isotherms with the characteristic shapes of experimental isotherms, but the predicted isotherms are highly sensitive to the calculated model parameters. The methods used in this dissertation provide a means to compare different ILs within the same family, and to select ILs with promising properties prior to synthesis.