Agile CO2 Catchers

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Science  17 Dec 2010:
Vol. 330, Issue 6011, pp. 1588
DOI: 10.1126/science.330.6011.1588-b
CREDIT: GURKAN ET AL., J. PHYS. CHEM. LETT. 1, 3494 (2010)

There is vigorous ongoing research to develop sorbents that efficiently capture CO2 generated through coal combustion and thereby keep it out of the atmosphere, where its infrared absorption would contribute to global warming. It's critical to bind the gas rapidly and selectively, but not too tightly, as release for concentrated sequestration should also be facile. Aqueous amines are promising compounds for this purpose, though ionic liquids (ILs), with their low volatility and high stability, might offer even better prospects. Unfortunately, in preliminary studies, introduction of CO2 has led to an impractical rise in IL viscosity, attributed to the formation of salt bridge networks. To skirt this drawback, Gurkan et al. performed simulations on a distinct IL class comprising pyrrolide anions (charge balanced by tetraalkyl phosphonium) that could covalently capture CO2 without involving network-forming protons. They then went on to synthesize a 2-cyanopyrrolide IL, and as predicted, the medium absorbed superstoichiometric quantities of CO2 with minimal viscosity increase and even tolerated the presence of water. A variant based on a pyrazolide, rather than pyrrolide, framework confirmed the tunability of the approach.

J. Phys. Chem. Lett. 1, 3494 (2010).

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