Additives enhancing supported amines performance in CO₂ capture from air

The utilization of supported amines as adsorbents in direct air capture (DAC) has been demonstrated to be a promising strategy for the reduction of CO₂ emissions. To improve the performance of amine-based adsorbents, the incorporation of additives has been widely adopted. In the present study, we conduct a comprehensive comparison of seven additives on tetraethylenepentamine-impregnated mesoporous silica as a representative amine-based adsorbent. The results indicate that minor molecular weight additives with hydroxyl groups show improved adsorption–desorption performance and increase oxidative stability. A proposed mechanism for these improvements is the combined physical and chemical promotion effects of hydroxyl groups. Through a comprehensive review of existing literature, it is found that the effects of additives on amine-based adsorbents are dependent on factors, such as additive type, pristine adsorbent properties, incorporation method, and testing conditions. Based on these findings, it is recommended that future DAC systems prioritize the use of hydroxyl-containing additives, whereas higher CO₂ concentration and temperature capture may benefit from the incorporation of additives without hydroxyl groups. These conclusions are expected to contribute to the design of efficient adsorbents for CO₂ capture.