Thermally cross-linked alkynyl-based polyimide membranes for efficient helium separation and physical aging control

Membrane separation technology plays a critical role in the utilization of helium (He) resources. Yet, the performance of current polymer membranes is hindered by a trade-off between permeability and selectivity, as well as by physical aging. Solving these problems is vitally crucial for the industrial application of He separation. This study reported controllable thermal crosslinking of alkynyl-based polyimide membrane (EBPA-TB-TC) to improve He permeability and anti-aging performance. The resulting covalently crosslinked structures conferred thermal and chemical stability to the membranes, as well as increased microporosity. It led to a notable 'anti-trade-off' effect and improved anti-aging characteristics. An optimized EBPA-TB-TC membrane exhibited a superior combination with a He permeability of 61.14 Barrer and an He/N2 selectivity of 72.78. Crucially, mixed-gas He/N2 (1:1, 50/50) separation results over 50 days revealed minimal reductions in He permeability (1.34 %) and He/N2 selectivity (2.95 %), indicating fantastic anti-aging performance. These findings demonstrated the significant potential of thermally cross-linked EBPA-TB-TC membrane in long-term stable helium separation.