Quantitative investigation on the physical and chemical interactions between CO2 and amine-functionalized ionic liquid [aEMMIM][BF4] by NMR

There are both physical and chemical interactions between amine-functionalized ionic liquids (ILs) and CO2. A method to estimate the ratio between physical and chemical interactions based on NMR spectra was proposed. Results showed that 21% of [aEMMIM][BF4] interacted with CO2 chemically at 1:1 (CO2/IL) stoichiometry, leading to a 94% contribution to the solubility, whereas 79% of [aEMMIM][BF4] interacted with CO2 physically at 0.017:1 stoichiometry, leading to a 6% contribution. This method can be extended to other similar systems. Tethering high sterically substitute group at IL helps to obtain an equimolar CO2 absorption.