Promoting the regeneration of polyethylenimine-impregnated sorbents through in situ vapor purge for direct air capture

Abstract

Amine-impregnated sorbents (AIS) have been extensively investigated for direct air capture (DAC) due to their high adsorption capacity and selectivity toward atmospheric CO₂. However, there has been limited attention given to efficiently recovering the adsorbed CO₂ from AIS, leading to the regeneration remaining energy-intensive in DAC systems. Here, we employ a double-layered adsorption configuration, in situ producing vapors using water synergistically harvested from the air to effectively regenerate polyethylenimine-impregnated sorbents. This vapor-promoted regeneration provided a substantial driving force for CO₂ desorption at ambient pressure and 105°C, producing water and 99% purity CO₂ with a high working capacity of 1.61 mmol/g. Only 8.9 MJ/${\mathrm{kg}}_{C{O}_2}$ thermal energy was consumed for sorbent regeneration without the use of vacuum conditions and external purge. This in situ vapor purge enables the recovery of over 95% of the CO₂ adsorbed on AIS, paving the way for the practical application of low-cost chemisorbents in DAC.