Supported Ionic Liquid Membranes with Dual-Site Interaction Mechanism for Efficient Separation of CO2

Selective separation of CO2 from flue gas conforms to the criterion of sustainable society. Herein, a series of imidazolium-based phenolate ionic liquids (ILs) that have dual-site interaction centers to isolate CO2 from N2 by supported ionic liquid membranes (SILMs) is designed and prepared. Density, viscosity, and CO2 solubility in these ILs were measured. The effects of the electron-withdrawing or electron-donating ability of the substituents on the anion, the operation temperature and partial pressure on the permeability of CO2, and the ideal selectivity of CO2/N2 were investigated systematically. High permeability (up to 2540 barrers) and selectivity of CO2/N2 (up to 127) are achieved in 1-butyl-3-methylimidazolium phenolate ([bmim][PhO]) containing 15 wt % H2O under humidified condition. A novel facilitated transport mechanism, transfer of CO2 from carbene to phenolated anion, is proposed based on NMR, FT-IR, and theoretical calculation results. The new pathway is believed to offer an alternative opp...