Degradation of amine-functionalized adsorbents in carbon capture and direct air capture applications: Mechanism and solutions

•The formation of urea groups in CO2 adsorbents caused by high-concentration CO2.•O2 induces the oxidation of CO2 adsorbents.•Heating induces amine loss and side reactions of CO2 adsorbents.•Acidic gases can occupy amine groups and reduce the CO2 uptake capacity of CO2 adsorbents.•Surface and structural engineering of the amines and carriers can suppress the degradation of CO2 adsorbents. Amine-functionalized CO2 adsorbents are very promising materials for carbon capture and direct air carbon capture because of their high CO2 uptake capacity and low regeneration temperature (below 120 °C). However, these adsorbents can degrade in conditions such as heating and steam treatment, or exposure to flue gas, air, vacuum, or high-concentration CO2 atmospheres. Understanding the mechanisms related to this stability is crucial for the research and application of organic amine adsorbents. In this review, the degradation mechanisms of amine-functionalized adsorbents are introduced. Including CO2 induced deactivation, oxidation reactions caused by O2, amine loss and decomposition reactions due to heating, and amine deactivation effects by acidic gases. Based on these mechanisms, approaches to inhibit this degradation process are illustrated.