An enhancement of CO2 capture in a type-III porous liquid by 2-Methylimidazole zinc salt (ZIF-8)

Porous liquids (PLs) with porosity and fluidity have shown great potential in gas separation. In this work, a type-III PLs were synthesized by mixing 2-Methylimidazole zinc salt (ZIF-8) nanoparticles as the main units and 1-Ethyl-3-methylimidazolium Bis(trifluoro-methanesulfonyl)-imide ([EMlm][NTf 2 ]) as the solvent. Molecular dynamics simulation evidenced the permanent, vacant, rigid pores of PLs. The prepared PLs were characterized, and their CO 2 uptake performances were obtained using a CO 2 static absorption system. ZIF-8 could significantly increase the CO 2 absorption capacity of the porous liquid, and when the mass fraction of ZIF-8 inside PLs was 10 wt%, the CO 2 absorption capacity increased by 143 %. Then, the CO 2 absorption characteristics of porous liquids were studied in different conditions, including temperature, pressure, and concentration of the ZIF-8. The CO 2 adsorption heat calculated by the Clausius–Clapeyron relation is −6.5 kJ/mol. The absorption rate of PLs was studied using the damping film theory. The CO 2 uptake capacity of the PLs decreased with temperature but increased with pressure and CO 2 concentration. Subsequently, the absorption-adsorption model was established to predict the CO 2 uptake capacity of PLs. The theoretical values agree with the experimental values, indicating that the developed absorption-adsorption model can predict the CO 2 uptake properties of PLs. Finally, analysis of the CO 2 cyclic performance of the PLs showed the PLs could be regenerated under negative pressure, and the CO 2 uptake capacity remained stable after five cycles, indicating the [EMIm][NTf 2 ]/ZIF-8 PLs could be applied in CO 2 capture.