Ultramicroporous Ionic Liquid-Supported Aerogel Composites

Recently, low-concentration ammonia (NH₃) capture has attracted considerable attention for applications in ammonia-hydrogen fuel cells and confined spaces. The main objective of this study was to develop novel ultramicropore ionic liquid-supported aerogel composites (UILACs), designed to effectively expose the multiple hydrogen bonding sites of the ionic liquid through the constructed ultramicropore structure in order to capture and selectively separate low-concentration NH₃. UILACs achieved a maximum NH₃ capacity of 164.69 mg NH₃/g absorbent at 25 °C and 0.10 MPa, which was 3.47 times higher than that of the pure aerogel. In breakthrough experiments with low NH₃ concentrations (1000-10,000 ppm), UILACs exhibited exceptional NH₃/H₂ and NH₃/N₂ selectivity of 2460 and 10,474, respectively, at 1000 ppm NH₃, values which are 31.5 and 22.1 times higher than the pure aerogel. These values significantly exceeded those of aerogels, owing to high hydroxyl ammonium ionic liquid (HAIL) loading, interactions between HAIL and NH₃, and ultramicropores, as confirmed by density functional theory (DFT) calculations and isothermal analysis. Furthermore, UILACs maintained stable adsorption performance through ten adsorption-desorption cycles, demonstrating UILACs' potentials for efficient NH₃ capture and separation in energy applications.