MOF/silica-based composite incorporating low-volatility ionic liquids for efficient CO2 adsorption

Amine scrubbing, while mature for CO 2 capture, suffers from solvent volatility. To address this, we developed a novel solid adsorbent by incorporating low-volatility ionic liquids (ILs), [TEPA][NO 3 ] and [PEHA][NO 3 ], into a hierarchical UiO-66@SBA-15 composite (US). The growth of UiO-66 within the mesochannels of SBA-15 was facilitated by interactions between Zr 4+ and surface Si–OH groups. IL loading dramatically increased the density of amine-based CO 2 adsorption sites. The optimized adsorbent, US-T60, achieved a high CO 2 capacity of 4.73 mmol g -1 at 60 °C under 15% CO 2 /85% N 2 , which is 4.15 times that of the pristine US composite. It also exhibited excellent regeneration stability, retaining 93% of its initial capacity after five cycles. Kinetic analyses indicated a mixed physisorption-chemisorption process, well-described by the Avrami model. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that CO 2 capture proceeded via two pathways: the rapid formation of ammonium carbamate ion pairs under amine-rich conditions, and the formation of hydrogen-bonded carbamic acid when proton transfer was hindered. Combined with its high capacity, good stability, and tunable adsorption mechanism, this family of IL-incorporated hierarchical composites demonstrates promising potential for application in post-combustion flue gas CO 2 capture.