Ionic liquids (ILs) are a promising platform for developing CO2-selective sorbents. Previous calculations and experiments have shown that ILs containing azolide (aprotic, heterocyclic) anions and a charge-compensating tetraalkyl phosphonium cations react reversibly and in one-to-one proportion with CO2. In this work we use ab initio calculations to explore the energetics and mechanism of the IL-CO2 chemistry. In a set of benchmark CCSD(T) calculations, we compare the direct binding of CO2 to all isomers of the parent azolides (HxCxN5�x�,  x = 1, 2, 3, 4). CO2 binds at N centers to form planar carbamates and prefers N centers that minimize alpha N interactions. CO2 binding enthalpies correlate with measures of aromaticity, electron delocalization, proton affinity, and the Nazolide-CO2- bond rotation barriers. Binding energies systematically decrease with increasing x. GGA functionals recover binding energies nearly quantitatively while hybrid methods consistently overbind CO2? 

CO<sub>2</sub> capture chemistry of azolide-based ionic liquids

246th National Meeting (2013)

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CO2 capture chemistry of azolide-based ionic liquids

CO₂ capture chemistry of azolide-based ionic liquids