Tandem reaction of olefins and CO2 to cyclic carbonates over polyetheretherketone fiber-supported ionic liquids via relay catalysis in a spinning basket reactor

Abstract

The chemical fixation of CO₂ into cyclic carbonates from low-toxicity and inexpensive olefins is one of the most promising routes for the industrial application of CO₂. Herein, a commercially available polyetheretherketone fiber (PEEK) was directionally functionalized by post-grafting procedures to immobilize imidazolium hydrogen carbonate ionic liquids into its surface layer, and the as-obtained fiber-supported ionic liquids (PEEK-MIMHCO₃), capable of acting as bifunctional catalysts for the direct conversion of olefins and CO₂ to cyclic carbonates via relay catalysis in one pot, are reported. The resulting fibers during the course of utilization were analyzed and characterized using diverse techniques in term of morphology, mechanical properties, X-ray diffraction, elemental analysis, FTIR spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis to assure the reliability of this strategy. Moreover, the ionic liquid functionalized fiber was very beneficial for the enrichment of CO₂ in the surface layer of the PEEK fiber backbone, and PEEK-MIMHCO₃ could provide HCO₃⁻ to accelerate olefin epoxidation, as well as generating a carbene-CO₂ adduct for facilitation of CO₂ cycloaddition, which successively promoted the reaction, which proceeded smoothly via relay catalysis to obtain cyclic carbonates with yields and turnover frequency (TOF) value superior to the majority of previous reports. Furthermore, the fiber catalyst in the spinning basket reactor could be simply recycled for at least 10 runs with good active stability at gram-scale under metal-free and additional solvent-free conditions, affording a cleaner method for the direct conversion of CO₂ with the potential for industrial application.