High capacity CO2 sorbents based on zinc-functionalized ionic liquid confined in morphologically diverse porous matrices†
We investigated the facile production of novel high capacity CO2 sorbents based on a zinc-functionalized ionic liquid (EZT3) impregnated into several morphologically diverse porous supports: microporous alumino-silicate, non-porous nano-silica, and non-ordered mesoporous silica. These supported ionic liquid phase (SILP) hybrid sorbents with EZT3 loadings of 10 and 25 wt% were prepared via a solution intrusion-solvent evaporation method affording the deposition of a thin layer of IL on the surface of the supports. Textural, structural and thermal signatures of strong IL confinement on the surface were observed in 10 wt%-loaded sorbents, and multi-layers mimicking the bulk phase in 25 wt%-loaded sorbents. Adsorption of up to 3.4 mmol g−1 was obtained at 313 K, a remarkable uptake capacity for low IL loading sorbents, significantly surpassing previously published details of similarly loaded materials. These new sorbents exhibit dramatic performance enhancement by factors of 1.6–16.0 (cf. bare support) and 3.6–5.3 (cf. bulk EZT3) highlighting the synergy between the available contact surface and pore network of the support, and the high affinity for CO2 by the IL. Contrary to expectation, the materials based on non-porous nano-silica exhibited the highest uptake, rationalized by their unique core–shell configuration. In addition, the sorption kinetics were promoted by the external surface adsorption and facilitated diffusion into the pore network. The low IL loading and the relatively common support materials in these hybrid sorbents could potentially translate to cheaper and more sustainable CO2 capture media.