Theoretical Studies on Task-specific Ionic Liquid of 1-(4-Butylamino)-3-methyl Imidazolium Tetrafluoroborate for Capturing CO2

Abstract

Novel task-specific ionic liquids (ILs) of 1-(4-butylamino)-3-methyl imidazolium [Bamim]⁺ tetrafluoroborate [BF₄]^– and its reaction with CO₂ were systematically studied at B3LYP/6- 311++G** level. Two stable ionic liquids and two molecular complexes from the reactions of those ionic liquids and CO₂ were optimized with no imaginary frequencies. The energies including zero point energy and basis sets superimposition energy were calculated. The interactions mechanism between the ion-pairs and the reaction characteristics of ionic liquids and CO₂ were analyzed based on natural bond orbital and atom in molecular calculations. The results show that the interactions between ion-pairs are mainly displayed as hydrogen bonds (H-bonds) and they are reinforced by charge dispersion and redistribution of [Bamim]⁺ and [BF₄]^–. The interaction energies between ion-pairs are greater than -300 kJ/mol and those between ionic liquid and CO₂ are about -10 kJ/mol. The reaction of ionic liquids and CO₂ is physical absorption, the molar absorbing ratio is 1:1 and ionic liquid may have a mild regeneration condition theoretically.