Highly efficient and reversible CO2 capture by imidazolate-based ether-functionalized ionic liquids with a capture transforming process

Abstract

In this work, several kinds of imidazolate-based ether-functionalized ionic liquids (ILs) were synthesized and used for CO2 capture. It is note-worthy that IL with [C6O2mim]+ as cation has much smaller molecular weight but similar mole capacity compared with those with [P66614]+, which is usually used as cation for anion-functionalized ILs in the carbon capture process. Among these task functionalized ILs, [C6O2mim][4-Br-Im] can be a potential candidate for carbon capture. Not only has [C6O2mim][4-Br-Im] an extremely high CO2 capacity (more than 1.60mol CO2 per mol IL achieved), but also shows high uptake efficiency and recovery capability. In addition, [C6O2mim][4-Br-Im] has higher thermal stability, higher water stability and lower absorption enthalpy. The mechanism of this carbon capture process was investigated by FT-IR and NMR spectroscopy. Surprisingly, in this process, CO2 first bound the cations to form zwitterions. When CO2 was continuously bubbled into ILs, the zwitterions started to dissociate and the anions combined with CO2. It is verified that this process is a carbon capture transforming process with the Cationic-drive transforming to Anionic-drive. This work offers a deep understanding of the combination process between CO2 and imidazolate-based with aprotic heterocyclic anions.