Investigation of CO2 Capture Ability in Amino Acid Ionic Liquid-Functionalized Metal-organic Frameworks

Abstract

Due to their significant porosity and adjustable structures, metal-organic frameworks (MOFs) exhibit great promise for CO₂ sequestration. This investigation focuses on the augmentation of CO₂ capture capabilities in MOF-177 through impregnation with two amino acid-derived ionic liquids (AAILs), [BMIm]Glu and [BMIm]Asn. The AAIL@MOF-177 composites obtained were analyzed, confirming successful AAIL loading without significant disruption of the MOF structure. Remarkably, the composites demonstrated a marked enhancement in CO₂ uptake and preference for CO₂/N₂ and CO₂/CH₄ relative to the pristine MOF-177, especially under low-pressure conditions typical of post-combustion flue gas. The optimal AAIL loading was determined to be 30 wt.%. Under conditions of 0.2 bar and 25 ℃, [BMIm]Asn-30@MOF-177 achieved a CO₂ uptake of 0.48 mmol/g, a 3.5-fold increase over pristine MOF-177. Furthermore, [BMIm]Asn-30@MOF-177 demonstrated superior CO₂/N₂ and CO₂/CH₄ selectivities of 14.2 and 11.9, respectively, under 0.2 bar and 35 ℃. This enhanced performance arises from the robust chemical affinity between CO₂ and the amino groups in the AAIL anions, especially the two amino groups in [BMIm]Asn. The composites also showed excellent reusability over multiple adsorption-desorption cycles. These findings demonstrate the promising potential of AAIL-functionalized MOFs for efficient CO₂ capture.