Disclosed herein are methods for C.sub.2 capture that use phase change ionic liquids (PCILs) to remove the C0.sub.2 from flue gas or other gas streams containing C0.sub.2. PCILs have high C0.sub.2 uptake and form a liquid PCIL- C0.sub.2 complex when they react with C( ).sub.2. When the liquid PCIL- C0.sub.2 complex is heated to regenerate the solid PCIL material by removing the carbon dioxide, part of the heat needed to release the C0.sub.2 can be supplied by the heat of fusion of the PCIL as it solidifies. Utilization of the heat of fusion of the PCIL to assist in its own regeneration can substantially reduce the parasitic energy loss associated with post-combustion C0.sub.2 capture.
STATEMENT REGARDING FEDERALLY SPONSORED R&D
 This invention was made with government support under Award No. DE-AR0000094 and Award No. DE-FG36-07NT43091 awarded by the Department of Energy. The government has certain rights in the invention.