Mesoporous silica SBA-15 samples with and without controlled framework microporosity were prepared and used directly or impregnated with polymer amine as adsorbent for CO2. These samples were evaluated for their ability to adsorb CO2 by obtaining their equilibrium adsorption isotherms using volumetric adsorption at three different temperatures of 273 K, 278 K and 283 K. The data obtained were analyzed using Freundlich adsorption isotherm model while the isosteric heats of adsorption were estimated by the Clausius-Clapeyron equation. Under comparable conditions, the adsorption performance of silica SBA-15 was found to be strongly dependent upon the framework microporosity. However, the microporosity contribution to CO2 adsorption in amine-modified SBA-15 was not obvious as amine blocked micropores and dominated CO2 adsorption. The SBA-15 sample with higher microporosity displayed higher CO2 uptake and the CO2 uptake by amine-modified SBA-15 samples correlated with their total surface areas, as expected. These findings revealed the importance of surface area in designing an adsorbent for CO2. (C) 2012 Elsevier Inc. All rights reserved.