Helium (He) recovery via conventional cryogenic distillation is highly energy-intensive and costly. Membrane separation features modularity and efficiency, but mixed-matrix membranes (MMMs) often suffer from discontinuous channels and poor filler–polymer compatibility, which impair separation performance. Here, we report an MMM platform by embedding a continuous 3D nanoporous ZIF-67-NH2 gel within a polyimide matrix. The gel functions as a dual-functional crosslinker, forming covalent amide linkages and hydrogen bonds with the polymer to eliminate interfacial voids, while creating interconnected, selective nanochannels through its intrinsic nanoporosity. This yields He/CH4 performance: 549 Barrer He permeability and 110.3 selectivity, surpassing the benchmark membranes. The membrane retains over 95% performance in mixed-gas tests over 180 h. Process simulations show that a hybrid membrane–cryogenic system achieves >93% He recovery and 74% energy savings. This work provides an energy-efficient platform for critical gas separations. Addressing the permeability-selectivity trade-off in helium recovery, the authors engineered MOF gel-crosslinked membranes. Covalent interfacial bonding enables defect-free, ultra-high MOF loadings, yielding exceptional separation performance that pushes beyond conventional upper bounds.
Zhang et al. (2026) studied this question.