Granular double networks as a platform for mechanically tough facilitated transport membranes for olefin/paraffin separations

Olefin/paraffin separations, performed industrially by cryogenic distillation, are energy intensive and account for 0.3% of global energy use. Membranes offer a lower-energy separation method but suffer a trade-off between mechanical robustness and separation performance. Facilitated transport via silver salts (e.g., AgTf₂N) that selectively coordinate with olefins can enhance separation; however, common host matrices (e.g., PEGDA) are brittle and risk fracture during processing and service. Here, we introduce granular double networks (GDNs) as a material platform that overcomes this trade-off. In GDNs, highly crosslinked polymer particles are dispersed in a chemically similar, loosely crosslinked continuous matrix containing the silver salt. This hierarchical design preserves the facilitated transport mechanism while introducing energy dissipation mechanisms at particle-matrix interfaces and within the network, yielding fracture toughnesses >2000 J/m². Simultaneously, the C₂H₄/C₂H₆ separation performance reaches the upper bound with only 25% AgTf₂N, demonstrating that mechanical reinforcement need not compromise facilitated transport. These results establish GDNs as durable, high-performance membranes for olefin/paraffin separations and suggest molecular-level design guidelines for combining mechanical toughness with selective gas transport.