Incomplete CO ₂ Desorption Enhances O ₂ Stability of Solid Amine Carbon Capture Sorbents

Abstract Reducing carbon dioxide (CO ₂ ) emissions is a critical environmental challenge. Capturing CO ₂ by solid polyethylenimine (PEI) sorbents is proposed as a strategy to address this concern. The CO ₂ forms carbamates with the amine groups on the solid sorbent. However, solid PEI sorbents are unstable under O ₂ ‐containing flue gas streams, a property that has greatly limited their industrial importance. To combat this O ₂ ‐sensitivity, the amount of CO ₂ desorbed per cycle is reduced to protect amines by the formed carbamates. These carbamates sufficiently reduce oxidative cleavage and maintain a low k _deac of −0.00373 cycle ⁻¹ while maintaining a working capacity of 2.88 wt% (0.65 mmol g ⁻¹ ) under an O ₂ ‐containing gas mixture. Additionally, it is discovered that the degradation rate can be tuned through adjusting the sorbent working capacity; this tunability can be used to inform future process simulations. This approach offers an additive‐free pathway toward oxidatively stable PEI carbon capture sorbents.