Cycloaddition of carbon dioxide for commercially-imperative cyclic carbonates using ionic liquid-functionalized porous amorphous silica

Ionic liquid functionalized mesoporous silicas (IFMSs) were prepared from the coupling of 1-(triethoxysilylpropyl)-3-n-alkylimidazolium halides with tetraethyl orthosilicate (TEOS) through template-free condensation under strong acidic conditions. Optimal synthesis conditions and maximum incorporation of the active sites were achieved through varying the parameters of the co-condensation method. The obtained amorphous silica having 0.20-0.93 mmol of RIm(+)X(-) groups showed a surface area between 477 and 672 m(2)/g with pore sizes from 3.2 to 7.8 nm. The materials synthesized under various TEOS pre-hydrolysis had larger surface areas, pore volumes, and average pore diameters than those synthesized without pre-hydrolysis. FT-IR, TG/DTG (thermogravimetry/differential thermogravimetry), and solid-state NMR showed that all the immobilized ionic liquid (IIL) groups were incorporated without affecting the organic moieties. Chemical fixation of carbon dioxide was studied at various carbon dioxide pressures by correlating reactivity with various parameters such as surface area, pore volume, pore size, percentage of active sites, type of counter ion, and length of the organic moiety extending from the alkyl halide. (C) 2009 Elsevier B.V. All rights reserved.