Capsules with polyurea shells and ionic liquid cores for CO₂ capture

Many ionic liquids (ILs) have good solubilities of CO₂ but the high viscosity of ILs makes them cumbersome and kinetically limits gas uptake. Encapsulation of ILs is an effective approach to overcoming these limitations. In capsules with a core of IL, the chemical composition of the shell impacts performance. Here, we report the preparation of capsules with a core of the IL [Bmim][PF₆] and polymer composite shell, then evaluate how the identity of the polymer impacts CO₂ uptake. IL-in-oil Pickering emulsions stabilized by nanosheets are used, with capsules formed by interfacial polymerization between different diamines and diisocyanates (e.g., shells are polyurea and nanosheets). The capsules contain 60–80 wt% IL and the composition was verified using Fourier transform infrared spectroscopy. Optical microscopy, scanning electron microscopy, and particle sizing data showed spherical, discrete capsules with 50–125 μm in diameter. All capsules are stable up to 250°C. Brunauer–Emmett–Teller analysis of CO₂ gas uptake data showed that different polymer compositions led to different CO₂ uptake properties, with capacity ranging from 0.065 to 0.025 moles of CO₂/kg sorbent at 760 torr and 20°C. This work demonstrates that the polymer identity of the shell impacts gas uptake properties and supports that shell composition can tailor performance.