3D hexagonal mesoporous silica and its organic functionalization for high CO2 uptake.

Highly ordered 3D-hexagonal mesoporous silica HMS-3 and its vinyl- and 3-chloropropyl-functionalized analogues HMS-4 and -5, respectively, are synthesized under strongly alkaline conditions at 277 K. Tetraethyl orthosilicate, vinyltrimethoxysilane, and 3-chloropropyltrimethoxysilane are used as silica sources, and cetyltrimethylammonium bromide as the structure-directing agent. The 3D-hexagonal pore structures of HMS-3, 4-, and -5 were confirmed by powder XRD and high-resolution TEM studies. Brunauer-Emmett-Teller surface areas of these materials are 1353, 1211, and 603 m(2) g(-1) for HMS-3, -4, and -5, respectively. Among these materials, vinyl-functionalized mesoporous material HMS-4 adsorbs the highest CO(2) (5.5 mmol g(-1) , 24.3 wt%) under 3 bar pressure at 273 K. The 3D-hexagonal pore openings, very high surface area, and cagelike mesopores as well as organic functionalization could be responsible for very high CO(2) uptakes of these materials compared to other related mesoporous silica-based materials.