The complete optimization of ionic liquid-functionalized porous amorphous silica under one-pot synthesis conditions

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 n-RIm+X− (alkylimidazolium halides) groups showed a surface area between 477 and 672 m2/g with pore sizes from 3.2 to 7.8 nm. The materials synthesized under various TEOS hydrolysis time from 180 to 420 min (pre-hydrolysis) had larger surface areas, pore volumes, and average pore diameters than those synthesized without pre-hydrolysis. FT-IR 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 conditions over different IFMSs.