Hybrid membranes based on ionic-liquid-functionalized poly(vinyl benzene chloride) beads for CO₂ capture

Efficient hybrid composite membranes for CO₂ capture were prepared using poly(vinyl benzene chloride) (PVBC) beads functionalized with an ionic liquid, butylimidazole bis(trifluoromethane)sulfonimide (BITFSI). The PVBC-BITFSI beads were synthesized by a mass-producible method involving self-crosslinking polymerization, atom transfer radical polymerization, and ion exchange. The structure and interactions of the materials were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, wide-angle X-ray scattering, and scanning electron microscopy. The beads interact well with the ionic liquid (which has high CO₂ affinity) and form an interconnecting pathway for selective CO₂ transport. Hybrid membranes i.e., PVBC-BITFSI beads complexed with 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide showed significantly enhanced selectivity (37.1 and 77.4 for CO₂/N₂ and CO₂/CO, respectively) with a CO₂ permeance of 25.4 GPU, which surpassed the performance of other prepared and reported membranes. In particular, the CO₂/CO separation performance represented one of the highest values obtained for membranes. The improved performance is due to the capability of the beads to control the diffusivity and solubility, based on less permeable crosslinked structure with functionalized CO₂-philic ionicliquid. This work suggests an effective approach to improve the selectivity of CO₂ capture membranes and has great potential to be applied in other areas based on other functional modifications of the beads.