Chain-length engineering and mechanistic insights of amino ionic liquids for enhanced CO₂ capture onto mesoporous silica

Conventional CO₂ capture methods, such as amine-based absorption, are hindered by solvent degradation, and corrosion issues, while solid adsorbents often suffer from limited adsorption capacity under flue gas conditions. To address these challenges, ionic liquids (ILs)-modified materials have emerged as promising alternatives due to their high efficiency, tunability, and environmental compatibility. Herein, using Lys as the anion, DETA, TETA, and TEPA were respectively combined to synthesize ILs with different chain lengths using one-step synthesis. These ILs were then loaded onto the mesoporous silica C803 carrier by impregnation. Characterization results indicate uniform distribution of ILs within the carrier without disruption of its mesoporous structure. At 298 K and 0.1Mpa, 66 wt% [TETA][Lys]-C803 exhibited the highest CO₂ adsorption capacity (2.51 mmol/g), representing 700% increase compared to C803, which was capacity further increased to 2.82 mmol/g at 308 K and 0.1Mpa. The material exhibited an excellent IAST-predicted CO₂/N₂ selectivity of up to 200.17 for a 15/85 CO₂/N₂ mixture, rapid adsorption kinetics (95% equilibrium in 6 min), and stable recyclability (unchanged performance after five cycles). Combined FTIR and DFT analyses revealed that lysine anions stabilize products and zwitterionic intermediates via electrostatic networks, thus enhancing CO₂ amine binding energy remarkably. The study further provides a novel strategy and theoretical basis for developing high-performance, renewable CO₂ capture materials for flue gas.