Abstract
Helium is a finite but essential resource with important applications in medicine, research, and aerospace. Conventional He-upgrading from natural methane gas (CH4) is done by cryogenic distillation. This study presents energy-efficient He-upgrading by membrane separation using the “dense” metal-organic framework (MOF) MIL-116(Ga), which enables high precision molecular sieving of non-adsorptive gases. MIL-116(Ga) membranes were synthesized on alumina disks after developing a method to homogeneously intergrow the MOF into a polycrystalline film. Single gas permeation experiments reveal exceptional ideal selectivity of αideal(H2/CH4) = 122 and αideal(He/CH4) = 87. In mixed gas permeation, the separation selectivity surpasses αideal(He/CH4) = 207 GPU. Mixed-gas tests at realistic 4:96 He/CH4 feed gas composition reached a selectivity of α(He/CH4) = 31.9 and permeance for He of P(He) = 227 GPU despite the low chemical potential. Electron microscopy uncovered a complex, grain-boundary microstructure, which limits perfect molecular sieving but still enables superior separation performance. This work demonstrates that dense MOFs, at the example of MIL-116(Ga) enables high performance He-upgrading, setting a new benchmark amongst reported MOF-based membranes. We highlight the potential of dense MOFs for the separations of small, non-adsorptive gases and the need to address grain boundary diffusion in polycrystalline MOF membranes.
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The data supporting this article have been included as part of the ESI.
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Acknowledgements
A.Ko., L.C-R., T.H., R.W., F.H.S., and A.K. acknowledge support by the Free State of Thuringia and the European Social Fund Plus within the 2022 FGR 0039 and 0040. A.K. thanks the Carl Zeiss Foundation for funding within “Breakthroughs 2020”. The authors acknowledge the use of the TESCAN MIRA SEM, funded by the project SEM@CEEC, co-financed by the Free State of Thuringia and the European Union under the EFRE program “Europe strengthens Thuringia” (2021–2027).
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A.K conceived the idea and managed the project. A.K., R.W., and F.H.S provided funding and resources. A.Ko. and E.G. prepared the materials, A.Kn. and A.Ko. carried out the permeation experiments. L.C.-R., R.S., and F.S. performed SEM measurements. F.S. conducted EDXS mapping. T.H. and R.W. did TGA-DSC, elemental analysis, and collected water vapor adsorption isotherms. A.Ko. performed XRD analysis. A.K. and A.Ko, R.W. interpreted the results. A.K. and A.Ko. wrote the original draft. A.K., A.Ko., L.C.-R., and R.W. revised the paper. All the authors read and participated in the revision process.
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Communications Materials thanks Bradley P. Ladewig and the other anonymous reviewer(s) for their contribution to the peer review of this work. A peer review file is available.
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Komal, A., Calderón Rodríguez, L., Scheffler, F. et al. Synthesis and helium separation performance of polycrystalline membranes of the high precision molecular sieve MIL-116(Ga). Commun Mater (2026). https://doi.org/10.1038/s43246-026-01156-3
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DOI: https://doi.org/10.1038/s43246-026-01156-3
