Computational comparison of the reactions of substituted amines with CO(2).

Substituted amines are a popular choice as molecules to selectively react with and separate CO(2) from gas mixtures. Such separations are of particular interest, for example, for CO(2) separations for carbon capture and sequestration. It is desirable to tune amine-CO(2) reaction energies to suit a particular separation.

Equimolar CO(2) absorption by anion-functionalized ionic liquids.

Amino acid ionic liquid trihexyl(tetradecyl)phosphonium methioninate [P(66614)][Met] and prolinate [P(66614)][Pro] absorb CO(2) in nearly 1:1 stoichiometry, surpassing by up to a factor of 2 the CO(2) capture efficiency of previously reported ionic liquid and aqueous amine absorbants for CO(2). Room temperature isotherms are obtained by barometric measurements in an accurately calibrated stirred cell, and the product identity is confirmed using in situ IR. Density functional theory (DFT) calculations support the 1:1 reaction stoichiometry and predict reaction enthalpies in good agreement with calorimetric measurements and isotherms.