Functionalization of Ordered Mesoporous Silica (MCM-48) with Task-Specific Ionic Liquid for Enhanced Carbon Capture

This work presents new composites of AAILs@MCM-48 obtained by functionalizing ordered mesoporous silica MCM-48 with two amino acid-based ionic liquids (AAILs) ([Emim][Gly] and [Emim][Ala]) to improve carbon capture and the selectivity of CO₂ over nitrogen. Thermogravimetric and XRD analyses of the composites showed that the MCM-48 support's thermal and structural integrity was preserved after the AAILs were encapsulated. An N₂ adsorption-desorption study at 77 K confirmed AAIL encapsulation in the porous support. Under post-combustion flue gas conditions, both [Emim][Gly]@MCM-48 and [Emim][Ala]@MCM-48 demonstrated improved CO₂ adsorption in comparison to the unmodified MCM-48, with a CO₂ partial pressure of around 0.15 bar. Regarding the maximal CO₂ uptake, the 40 wt.%-[Emim][Gly] composite outperformed the others at 303 K, with values of 0.74 and 0.82 mmol g^-1, respectively, at 0.1 and 0.2 bar. These numbers show a 10× and 5× increase, respectively, compared to the pure MCM-48 under identical conditions. In addition, the selectivity of the composites was improved significantly at 0.1 bar: the selectivity of composites containing 40 wt.% [Emim][Ala] increased to 17, compared to 2 for pristine MCM-48. These composites outperform other silica-based studies reported in the literature, even those using amines as solvents. The presented composites offer therefore promising prospects for advancing carbon capture technology.