Abstract
Repurposing the existing natural gas infrastructure by blending hydrogen with methane (i.e., Hythane) is one feasible option to develop a low-carbon hydrogen supply chain, although this process requires extraction of the hydrogen from Hythane after distribution. Membrane technology is a potential solution to tackle this application given its many advantages over other separation methods. However, industrial use of developed membrane materials has been challenging due to several practical concerns; for example, insufficient separation abilities and accelerated physical aging of thin membranes in high-free-volume glassy polymers. Herein, we propose an integrated strategy to develop highly H2-selective thin-film composite (TFC) membranes by tuning the aging behavior of polymers of intrinsic microporosity (PIM) thin films. Detailed gas permeation and two-dimensional (2D) grazing incidence wide-angle x-ray scattering (GIWAXS) studies reveal that triptycene-based PIM TFC membranes can exploit beneficial aging effects resulting from aging-induced enhancement in submicroporosity. To directly deploy TFC membranes, a simple post-treatment step was introduced to increase the aging rate, termed “hyperaging.” The hyperaged TFC membranes exhibited high H2/CH4 mixed-gas selectivity (>100), moderate H2 permeance (∼100 GPU), and good long-term stability when tested using a binary mixture with dilute H2 concentration (20 mol%), demonstrating promise for downstream hydrogen extraction toward green hydrogen supply.
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•The aging behavior of PIM-based TFC membranes was investigated.•Triptycene-based TFC membranes showed a beneficial aging effect.•This behavior was explained by the intensification of submicroporosity (<4 Å).•The aging rate of the as-prepared TFC membrane was hastened by a hyperaging step.•The hyperaged TFC membranes showed excellent H2/CH4 mixture separation abilities.