Abstract
Efficient gas separation membranes are essential for carbon capture, biogas upgrading, and hydrogen purification. Inspired by how plants absorb CO2 through water, we present a membrane platform that uses liquid water as the selective layer. Hydrophilic sub-100-nm pores stabilize water through strong capillary forces, enabling operation at feed pressures above 72 bar under dry and humid conditions. Selectivity is governed by gas solubility in water, while permeance is tuned by adjusting the water layer thickness. Reducing this thickness below 200 nm yields CO2 permeances up to 11,600 gas permeation units with CO2:N2, CO2:CH4, and CO2:H2 selectivities of 40, 26, and 31, respectively, surpassing the performance of state-of-the-art membranes. Operation is sustained for over a week without water loss, and performance scales using commercially available porous polymer supports under mixed-gas crossflow conditions. Water’s dissolution-based transport avoids saturation and reaction-rate limits, enabling a robust, high-performance, and environmentally benign gas separation platform.
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Source data are provided with this paper. Additional data supporting the findings of this study are available in the Supplementary Information and from the corresponding author upon request. Source data are provided with this paper.
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Acknowledgements
K.P.L. appreciates support from the National Aeronautics and Space Administration (NASA) via the NASA Space Technology Graduate Research Opportunity (NSTGRO) fellowship. A.P.S. gratefully acknowledges support from the U.S. National Science Foundation under CAREER Award No. CBET-2442780. We thank Dragan Mejic at the University of Colorado Boulder Chemical Engineering Instrument Shop for his assistance in manufacturing components of the high-pressure gas permeation cell. We also thank Praveen Kumar at Colorado School of Mines for assistance with transmission electron microscopy. This work was authored in part by the National Laboratory of the Rockies (NLR), operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. This work was supported by the Transformational Laboratory Directed Research and Development (TLDRD) Program at NLR. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains, and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.
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K.P.L. designed and conducted membrane fabrication, characterization, and permeation experiments and analyzed the results. A.P.S. conceived the project and provided scientific supervision throughout the study. M.A., Y.T., and P.O.S. performed permeation experiments and contributed to the analysis and interpretation of the transport data with supervision from M.P., A.R., and A.P.S. M.S.M. fabricated membranes, conducted fabrication-related characterization and analyses, and contributed to manuscript writing. J.N.S. performed XPS measurements and analysis. S.R.N. conducted SEM imaging and analysis. K.P.L., M.S.M., M.A., Y.T., J.N.S., S.R.N., P.O.S., M.P., A.R., and A.P.S. discussed the results. K.P.L., M.S.M., and A.P.S. wrote the manuscript; all authors revised and approved the final version.
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M.S.M., M.A., J.N.S., S.R.N., Y.T., P.O.S., M.P., and A.R. declare no competing financial interests. K.P.L and A.P.S are cofounders, board members, and officers of Osmopure Technologies Inc., and they hold equity in the materials covered in this work.
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Lopez, K.P., Saffer-Meng, M., Allouzi, M. et al. Water as a gas separation membrane. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70630-w
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DOI: https://doi.org/10.1038/s41467-026-70630-w
