High capacity CO 2 absorption and low energy regeneration in a biphasic absorbent driven by acid–base dual site synergy

Abstract This study presents a novel biphasic absorbent (DDHI) regulated by a dual‐site ionic liquid to resolve the persistent trade‐off between absorption efficiency and regeneration energy in CO 2 capture. The high performance of DDHI is attributed to a newly verified acid–base dual sites synergistic mechanism. The basic site of [N 1111 ][Glu] synergizes with the primary amine (DETA) to enhance CO 2 capture, while its acidic site provides protons to promote product decomposition, significantly lowering the regeneration energy. This dual functionality results in a high CO 2 absorption capacity of 4.6 mol/kg (a 1.3‐fold increase over the IL‐free system) and a low regeneration energy of 1.71 GJ/t CO 2 , with excellent stability over multiple cycles under mild conditions. Spectroscopic analyses and quantum calculations confirm this mechanism, elucidating the distinct roles of the dual sites. This study provides a new perspective for the development of high efficiency, low energy biphasic absorbents.