Amine-modified ordered mesoporous silica: Effect of pore size on carbon dioxide capture

Three mesoporous silica materials with different pore sizes (33 Å for small pore size MCM-41; 38 Å for SBA-12; 71 Å for large pore size SBA-15) and pore connectivity (2D for MCM-41 and SBA-15-type materials; 3D for SBA-12 material) were prepared and functionalized with aminopropyl (AP) ligands by post-synthesis treatment. The materials were characterized by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and nitrogen adsorption/desorption experiments. The carbon dioxide sorption on modified mesoporous molecular sieves was investigated by using of microbalances at 25 °C, and the influence of pore size and pore architecture on CO2 sorption was discussed. The large pore silica, SBA-15, showed the largest carbon dioxide sorption capacity (1.5 mmol/g), relating to highest amine surface density in this material. On the other hand, three-dimensional accessibility of amine sites inside the pores of SBA-12 silica resulted in a faster response to CO2 uptake in comparison with MCM-41 and SBA-15 molecular sieves.