  Global warming is seen as a drastic environmental problem nowadays. Carbon
dioxide (CO 2 ) concentration in the Earth's atmosphere is linked to the
average temperature on the surface of the planet. Carbon capture and storage is
an important technological endeavor aiming to improve the ecology. The present
work investigates reaction paths that are responsible for CO 2 chemisorption by
the ammonium- and phosphonium-based ionic liquids containing an aprotic
heterocyclic anion 2-cyanopyrrolidine. We show that two moles of CO 2 per one
mole of the gas scavenger can be theoretically fixed by such ionic liquids.
Both the cation and anion participate in the chemisorption. The corresponding
standard enthalpies are moderately negative. The barriers of all reactions
involving the phosphonium-based cation are relatively small and favor practical
applications of the considered sorbents. The performance of the ammonium-based
cation is less favorable due to the inherent instability of the
tetraalkylammonium ylide. The role is phosphonium ylide in the mechanism of the
reaction is carefully characterized. The reported results foster a fundamental
understanding of the outstanding CO 2 sorption performance of the quaternary
ammonium and phosphonium-based 2-cyanopyrrolidines.
