Interaction of ionic liquids with the surface of silica gel using nanocluster approach: a combined density functional theory and experimental study

摘要

Silica gel-confined ionic liquid (IL) is a class of heterogeneous catalysts with broad catalytic applications. Leaching of the IL from the surface of the support is the major drawback of these catalysts, which reduce the catalyst efficiency during the chemical reactions. To investigate the effect of the hydrogen bonding on the leaching phenomena, the interaction between the 1-ethyl-3-methylimidazolium-based IL with various anions (Cl~-, Br~-, HSO_4~-, NO_3~-, BF_4~-, and PF_6~-) and the surface of the silica gel were studied using density functional theory. Hence, a hydroxylated cage-like cluster of silica gel, Si_4O_6(OH), was selected to mimic the surface. The values of ΔE_(interaction) show that ILs with halogen counter ions have stronger interactions than that of the IL with BF_4~- and PF_6~- counter ions. We also carried out stirring–filtration method for some prepared samples of IL@silica to experimentally explore the leaching phenomena. The results show good agreement with computational achievements.