Graphene-doped membranes for direct air capture (m-DAC) of CO2

• New materials for Membrane Direct Air Capture (m-DAC) demonstrated • Performance evaluated in dry and humid conditions in realistic CO 2 settings • Performance overcome expected Robeson upper bound • Process modelling to showcase financial viability potential Rising atmospheric CO 2 levels drive the urgent need for efficient capture technologies. Conventional methods such as amine-based absorption and solid desiccants are energy-intensive and costly. Membrane gas separation offers a promising alternative due to its process simplicity and potential cost reduction, though its application in Direct Air Capture (DAC) remains underexplored. Unlike cyclic sorbent-based DAC systems, membrane-based separation enables continuous CO2 capture without chemical regeneration steps. This approach offers a scalable, modular pathway for low-maintenance DAC operation. This study presents highly CO 2 -selective and permeable polymeric membranes able to strip CO 2 from synthetic ambient air. The performance of the membranes was enhanced by incorporating amine-functionalized graphene oxide (GO) into micron-thin block-copolymer membranes, supporting interfacial engineering to increase CO 2 affinity and enhance flux via interstitial diffusion. The membranes achieved CO 2 /N₂ selectivities of 68±2 and permeabilities of 21.27±0.5 GPU under DAC conditions (0.04% v/v CO 2 in N₂). The stability of the performance in humid conditions up to 45 RH% was also tested and the selectivities found to remain on par with dry air testing, supporting the development of m-DAC as a viable route to support atmospheric CO 2 capture. A multi-stage membrane process simulation was also conducted to evaluate the scalability of the process, demonstrating its feasibility and cost for large-scale CO 2 capture.