A permselective membrane for size-sieving based H₂/CO₂ separation

Titelangaben

Federer, Lukas ; Pietsch, Ingmar ; Uhlig, Felix ; Stevenson, Max ; Friedrich, Daniel ; Breu, Josef:
A permselective membrane for size-sieving based H₂/CO₂ separation.
In: Applied Clay Science. Bd. 287 (2026) . - 108191.
ISSN 0169-1317
DOI: https://doi.org/10.1016/j.clay.2026.108191

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Abstract

Continuous H2/CO2 separation via permselective membranes is highly sought after as pure H2 plays a key role in H2 economy. Aqueous nematic suspensions obtained by 1D dissolution of affordable sodium fluorohectorite allow for simple membrane fabrication by spray coating. The monolayer nanosheets have a uniform thickness of 1 nm and appreciable aspect ratio, thus self-assemble into defect-free membranes when applied onto porous mixed cellulose ester substrates. The perfectly textured restacking of individual nanosheets yields monodomain Bragg stacks with uniform interlayer space. By cation exchange with guanidinium cations, a uniform interlayer height tailored to 2.9 Å was obtained while micropores are formed between the loosely packed interlayer cations. As the interlayer height matches the kinetic diameter of H2 and is significantly smaller compared to other relevant gas species, e. g. CO2, CH4, CO or N2, perfectly selective H2 sieving may be obtained. In a Wicke-Kallenbach cell, a near-perfect separation of H2 and CO2 (4:1 ratio) at ambient conditions was obtained. The tortuous path created by the impermeable, large aspect ratio nanosheets reduces the permeance to disappointing 3 GPU (gas permeation units; 1 GPU = 10−6 cm3 cm−2 s−1 cmHg−1). While the separation mechanism playing on tortuous path has not been fully explored in this preliminary study, the permeance may be improved substantially in future studies by optimizing the roughness of the substrate, the aspect ratio of the nanosheets and the thickness of the membrane.