Incomplete CO₂ Desorption Enhances O₂ Stability of Solid Amine Carbon Capture Sorbents

Reducing carbon dioxide (CO₂) emissions is a critical environmental challenge. Capturing CO₂ by solid polyethylenimine (PEI) sorbents is proposed as a strategy to address this concern. The CO₂ forms carbamates with the amine groups on the solid sorbent. However, solid PEI sorbents are unstable under O₂-containing flue gas streams, a property that has greatly limited their industrial importance. To combat this O₂-sensitivity, the amount of CO₂ 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 O₂-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.