Fixed-bed thermodynamic CO₂ adsorption tests were performed in model flue-gas onto Filtrasorb 400 and Nuchar RGC30 activated carbons (AC) functionalized with [Hmim][BF₄] and [Emim][Gly] ionic liquids (IL). A comparative analysis of the CO₂ capture results and N₂ porosity characterization data evidenced that the use of [Hmim][BF₄], a physical solvent for carbon dioxide, ended up into a worsening of the parent AC capture performance, due to a dominating pore blocking effect at all the operating temperatures. Conversely, the less sterically-hindered and amino acid-based [Emim][Gly] IL was effective in increasing the AC capture capacity at 353 K under milder impregnation conditions, the beneficial effect being attributed to both its chemical affinity towards CO₂ and low pore volume reduction. The findings derived in this work outline interesting perspectives for the application of amino acid-based IL supported onto activated carbons for CO₂ separation under post-combustion conditions, and future research efforts should be focused on the search for AC characterized by optimal pore size distribution and surface properties for IL functionalization.