Multifunctional periodic mesoporous organosilica supported dual imidazolium ionic liquids as novel and efficient catalysts for heterogeneous Knoevenagel condensation

A type of multifunctional periodic mesoporous organosilica supported dual imidazolium ionic liquids PMO-IL-anion have been designed and prepared, characterized and evaluated as heterogeneous catalysts for the Knoevenagel condensation. The as-fabricated supported ionic liquids show good catalytic performances in the Knoevenagel condensation at room temperature, especially the supported ionic liquids PMO-IL-NTf₂ and PMO-IL-PF₆, based on a synergetic effect between the Lewis-base-type sites of dual functionalized imidazolium ionic liquids and active sites of periodic mesoporous organosilica. The best catalytic performance over PMO-IL-NTf₂ was observed with excellent yields of 93～99% in a short time of 20～30 min. In addition, the heterogeneous catalyst offers simple operation for recovery and the recycling test showed that it could be reused for five times without significant loss of catalytic activity, thus making this process economical and environmental-friendly.