Liquid Water Membranes for Carbon Dioxide Removal and Humidity Condensation in Spaceflight Systems

We report the development of an innovative liquid water membrane designed for both high-performance CO2 removal and humidity condensate capture in spaceflight systems. The membrane utilizes a sub-micron thick water layer stabilized by capillary forces within a hydrophilic-coated nanoporous structure. A transmembrane pressure gradient drives selective CO2 transport through the membrane, leveraging the high solubility of CO₂ in water for selectivities of 50:1 and 24:1 for CO2:N2 and CO2:O2, respectively. Current state-of-the-art CO₂ removal systems, such as amine sorption technologies, rely on thermal regeneration of the amine solvent, which is energy-intensive and requires heavy infrastructure unsuitable for space applications. Additionally, many competing membrane systems utilize toxic or hazardous materials, raising safety concerns for terrestrial and space environments, and perform poorly in high-humidity conditions. Our technology overcomes these limitations with a non-toxic, aqueous separation layer and a lightweight membrane module. The membrane is more efficient than traditional amine-based systems, eliminating the need for thermal regeneration by using a passive, pressure-driven mechanism. Moreover, the membranes capture water vapor as it condenses on the curved water interfaces within the membrane pores, supplementing water recovery systems like the condensing heat exchanger. This dual functionality—CO2 removal and humidity condensate capture—is not present in any competing technology and directly supports NASA's goals for reducing the weight, volume, and power requirements of life support systems. By combining high CO2 removal efficiency, water recovery capabilities, and a lightweight, non-toxic design, these membranes represent a step forward in both space and Earth-based carbon capture and water recycling technologies.