Prediction of CO2 with amine functionalized ionic liquids interaction using density functional theory

Abstract

The current increase in Carbon dioxide (CO2) emissions has the potential to exacerbate the climate impact. As a result, technologies that reduce CO2 emissions, such as Carbon Capture and Storage (CCS), must be developed, such as ionic liquids (ILs)-based technology. Due to their outstanding properties and capability to capture CO2, ILs have been considered a green solvent to replace volatile organic solvents currently used in the separation and purification of natural gas. Among them, amine-functionalized ILs have enhanced capability to capture CO2. Nevertheless, the interaction between amine-functionalized with CO2 still is lagging. Therefore, this research aimed to provide an understanding of the interaction between amine-functionalized ILs and CO2 by examining the bonding energy of the IL, its cation and anion, and the complexation energy with CO2 using the Density Functional Theory (DFT) method on the molecular simulation software Gaussian 09W and GaussView 5.0. Gaussian 09W is used to optimize the bond and determine the complexation energy, while GaussView 5.0 is used for the geometry visualization. The bonding energies of [2-aemim]+, [BF4]-, [PF6]-, [DCA]-, [TfO]-, [Tf2N]-, CO2, and each of the five IL combinations were calculated using DFT. The complexation energy of each of the IL-CO2 combinations can then be calculated using the bonding energy data obtained from the simulation. The obtained complexation energy for IL-CO2 containing anion [BF4]-, [PF6]-, [DCA]-, [TfO]-, [Tf2N]-, are -499.32, -277.95, -750.25, -305.97, and -174.48 MJ/mole respectively. The DFT calculation revealed that the CO2 interaction with amine-functionalized ILs could be increased by weakening the cation-anion interaction strength. Interestingly, the rank of anion interaction strength with the cation follows a similar trend with the anion molecular size. From this findings, further researchers are able to initially and easily predict novel IL before doing further lab experiments, and following the identification of ILs with high CO2 solubility, the suitability of amine-functionalized ILs can be further investigated, leading to the development of compatible and highly functional solvents to improve CO2 separation performance.