A pore expanded MCM-41 mesostructured silica (PE-MCM-41) was modified by double-functionalization with molecules containing amino groups in order to obtain CO2 adsorbents for industrial post-combustion applications. PE-MCM-41 was modified by grafting with aminopropyl (AP), ethylenediamino (ED) and diethylenetriamino (DT) organosilanes, by impregnation with polyethyleneimine (PEI), pentaethylenehexamine (PEHA) and tetraethylenepentamine (TEPA), and by double functionalization, impregnating PEI, PEHA and TEPA over samples previously grafted with AP and DT. CO2 adsorption properties of these materials were found to depend on the kind, amount and viscosity of the organic compound loaded. Grafted samples showed amine efficiencies in CO2 capture up to 0.38mol CO2/mol N, leading to CO2 uptakes ranging from 38.2 to 76.9mg CO2/g ads (pure CO2, 45°C, 1bar). Impregnation yielded adsorbents with higher organic content but lower efficiency (between 0.20 and 0.25mol CO2/mol N), and with a net CO2 adsorption capacity up to 96.9mg CO2/g ads. By using the double-functionalization technique, the nitrogen content was increased while maintaining high amine efficiency (0.37mol CO2/mol N) and consequently exhibiting higher CO2 adsorption capacity, up to 104mg CO2/g ads. Thus, this functionalization route was proven successful. However, at high organic loading a sharp drop in the amine efficiency was observed, being ascribed to the blocking of the MCM-41 pores by amines.