(343j) Polymeric Membranes for Moisture-Driven Reversible CO2 Capture from Ambient Air

To address the greenhouse gas problem, novel efficient and inexpensive carbon capture technologies are needed to be utilized for direct air capture (DAC). Moisture-swing CO₂ sorption is a novel process in which the capture and release of CO₂ is triggered by the changes in the atmospheric humidity, and the CO₂ adsorption/desorption cycle is driven by the evaporation energy consumption of water. Therefore, due to its low energy requirements compared to thermally driven sorption technologies, moisture-swing CO₂ sorption can be a new approach for economical and large-scale DAC. The sorbents that are usually used for this purpose have a fixed positive side of quaternary ammonium groups that hold the mobile anion counterions on their molecular chain. CO₂ reacts with the anionic counterions (hydroxide or carbonate) and produces bicarbonates. Subsequently, carbon capture is realized through the transformation of carbonate and bicarbonate ions and is eliminated from air. Accordingly, the aim of the current research is to investigate the performance of a new polymeric sorbent in the moisture-swing CO₂ sorption process with quaternary ammonium side groups on the polymeric backbone, and anion counterions. For this purpose, we synthesized a series of ammonium-functionalized poly(arylene ether sulfone) sorbents with hydroxide and carbonate counter-ions. Next, we fabricated dense membranes using these sorbents, and evaluated their performance in consecutive humidity-driven CO₂ adsorption/desorption cycles. The obtained results confirm the capability and effectiveness of the prepared novel sorbents in capturing CO₂ from air via moisture swing cycles and can be regarded as a new promising choice for economical large-scale DAC processes.