Novel urea derivative-based ionic liquids with dual-functions: CO2 capture and conversion under metal- and solvent-free conditions

Abstract

Several urea derivative-based ionic liquids (UDILs) with superior thermal stability were facilely synthesized, structurally analyzed, and applied to CO₂ capture and conversion under mild conditions. These UDILs reversibly capture CO₂ with double molar CO₂ absorption and exhibit outstanding catalytic activity for the conversion of CO₂ and various epoxides to cyclic carbonates under metal- and solvent-free conditions. The effects of reaction parameters on the catalytic activity for propylene carbonate (PC) synthesis from propylene oxide (PO) and CO₂ were thoroughly investigated. Because water is inevitably contained in real gases requiring treatment, the influence of water on CO₂ capture and conversion was also studied. Furthermore, reaction kinetic studies were also undertaken and a cation–anion synergistic catalytic mechanism was proposed. The single-component, metal-free, dual functional, stable, and easily recyclable ionic liquids reported herein are interesting materials, displaying a good performance for both CO₂ capture and conversion.