CO2 Capture by Hybrid Ultramicroporous TIFSIX‐3‐Ni under Humid Conditions Using Non‐Equilibrium Cycling

Abstract Although pyrazine‐linked hybrid ultramicroporous materials (HUMs, pore size <7 Å) are benchmark physisorbents for trace carbon dioxide (CO 2 ) capture under dry conditions, their affinity for water (H 2 O) mitigates their carbon capture performance in humid conditions. Herein, we report on the co‐adsorption of H 2 O and CO 2 by TIFSIX‐3‐Ni—a high CO 2 affinity HUM—and find that slow H 2 O sorption kinetics can enable CO 2 uptake and release using shortened adsorption cycles with retention of ca. 90 % of dry CO 2 uptake. Insight into co‐adsorption is provided by in situ infrared spectroscopy and ab initio calculations. The binding sites and sorption mechanisms reveal that both CO 2 and H 2 O molecules occupy the same ultramicropore through favorable interactions between CO 2 and H 2 O at low water loading. An energetically favored water network displaces CO 2 molecules at higher loading. Our results offer bottom‐up design principles and insight into co‐adsorption of CO 2 and H 2 O that is likely to be relevant across the full spectrum of carbon capture sorbents to better understand and address the challenge posed by humidity to gas capture.