Anion-Dependent CO₂ Uptake in Ionic-Liquid-Modified Multilayer Graphene

Ionic-liquid-assisted modification of graphene offers a promising strategy for tailoring adsorption environments for CO₂ capture. Here, we experimentally investigate the influence of ionic liquid anions on CO₂ uptake behavior in multilayer graphene processed under identical conditions. FTIR measurements reveal distinct CO₂ absorption signatures for graphene treated with different ionic liquids, with PF₆ ^--treated graphene exhibiting the strongest response, while pristine graphite and the ionic liquids themselves do not exhibit detectable CO₂ absorption. Time-dependent FTIR measurements show a progressive evolution of the CO₂ absorption signal toward saturation upon continuous exposure. Raman spectroscopy indicates that ionic-liquid treatment induces structural and electronic modifications of multilayer graphene that depend on the anion employed. The observed experimental trends are qualitatively consistent with previous theoretical predictions regarding anion-dependent modifications in graphene/ionic liquid systems and highlight the potential of ionic-liquid-assisted graphene modification for engineering graphene-based materials for CO₂ capture applications.