Efficient Absorption of CO₂ by Introduction of Intramolecular Hydrogen Bonding in Chiral Amino Acid Ionic Liquids

Abstract

Developing advanced materials, such as ionic liquids (ILs), is highly desired for post-combustion capture of carbon dioxide (CO2). In this paper, we first develop a series of chiral amino acid ILs for efficient, fast, and reversible capture of CO2. Our data reveal that the dianionic form of IL is beneficial to the formation of intramolecular hydrogen bonding, which can remarkably mitigate the viscosity increase during CO2 absorption. The enhanced absorption capacity of CO2 in the IL is mainly due to the multi-site absorption from both the amino group and the negative oxygen group. The dominating absorption pathway is that the amino group reacts with CO2 via an intramolecular proton transfer from the amino group to the negative oxygen group, leading to the formation of the intramolecular hydrogen bonding between carbamate and the protonated oxygen group. As a result, the enhanced absorption performance of amino-functionalized ionic liquids (AFILs) is achieved, especially a controllable viscosity change during the uptake, providing an important foundation for building smart absorption systems based on AFILs.