In-situ Synthesis of Ionic Liquids on B-doped Mesoporous SiO₂ Catalyst for Epoxide-CO₂ Cycloaddition

A series of functionalized ionic liquids (ILs) immobilized on B-doped mesoporous SiO₂ catalysts were fabricated for effectively converting CO₂ into cyclic carbonates under metal-absent and cocatalyst-free conditions. Functionalized imidazolium ILs were in-situ synthesized by Debus-Rdziszewski imidazole reaction. Among the prepared catalysts, 5B−SiO₂−NH₂−3−I catalyst owing to the synergistic effects of nucleophile, Lewis acid-base and hydroxyl hydrogen bond donors in the catalyst, presented the better catalytic activity for propylene epoxide to the product of propylene carbonate with 99% yield and selectivity at 110 °C and 2 MPa CO₂. The catalyst also displayed moderate yield for various mono-substituent epoxides. Besides, the gradual decline in the product yield during consecutive runs could be easily refreshed by aqueous acidic solution washing.