Hyperaging-induced H2-selective thin-film composite membranes with enhanced submicroporosity toward green hydrogen supply

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.

Automated summary

Blending hydrogen with methane using existing natural gas infrastructure to develop a low-carbon hydrogen supply chain is a viable option, although extracting hydrogen from the mixed gas after distribution poses a challenge. Membrane technology, specifically thin-film composite membranes made from polymers of intrinsic microporosity (PIM), shows potential for addressing this challenge due to their aging-induced enhancement in submicroporosity. By introducing a hyperaging post-treatment step, PIM membranes demonstrated high selectivity and stability for downstream hydrogen extraction.