Ionic Liquids Confinement in Metal Organic Frameworks for an Effective Sorption of Toluene Vapor

The unique properties that characterize Ionic Liquids (ILs), such as excellent affinity and sorption capabilities towards Volatile Organic Compounds (VOCs), negligible vapor pressure and chemical and thermal stabilities, make them promising candidates for targeting VOCs in contaminated air. However, their relatively high viscosity (slow kinetics) and low air partition coefficients limit their direct application. Confining ILs into Metal Organic Frameworks (MOFs) structures can overcome these drawbacks and presents an innovative alternative for supporting ionic liquids to efficiently capture VOCs from the air.

Here we synthesize a novel composite material by effectively cladding [BMIM][FeCl₄] ionic liquid into MIL101(Cr) pore structure following a post-impregnation method. Material’s characterisations showed that the ionic liquid was successfully confined in the internal structure of MIL101(Cr), and textural properties were optimized for a favourable toluene capture without damaging framework structure. The selected composite improved toluene sorption capacities of commercial activated carbons (AC) and AC fibers by 40-90%, Y-Zeolite by 4 times and pristine MOFs by 3 times, especially at lower toluene concentrations (P/P₀ < 0.1 at 20 °C). Kinetics of toluene capture were also improved by the presence of the ionic liquid in the final material, exhibiting 3.5 times higher sorption rates and toluene diffusion coefficients compared to pristine MIL101 (Cr) structure, demonstrating the excellent ability of this IL/MOF composite material for toluene-polluted air treatment.