Ultramicropore-Matched Molecular Transport in Low-Loading Mixed-Matrix Membranes via Trace-Oxygen-Mediated Thermal Reorganization.

The complementary structural tunability of polymers of intrinsic microporosity (PIMs) and metal-organic frameworks (MOFs) redefines the design space for engineering precise transport channels in mixed-matrix membranes (MMMs). Herein, we present that trace-oxygen-mediated thermal reorganization (TOTR) of PIM-1 micropores enables MOF-dominated gas transport in MMMs without requiring high filler loading. Spectroscopic analyses and molecular simulations reveal trace-oxygen-mediated radical processes that induce the PIM-1 backbone rearrangement, together with triazine crosslinking and partial π-conjugation extension, resulting in a contracted and homogenized ultramicropore distribution. Meanwhile, the dual-interface design establishes a covalently coupled MOF-polymer interface, where the interfacial carboxylated PIM-1 (cPIM-1) layer co-reorganizes with the polymer matrix to form an integrated microporous environment with suppressed defects and enhanced mechanical robustness. This coupled pore-and-interface regulation integrates PIM-1 ultramicropores and MOF micropores into pore-matched transport channels, enabling effective expression of MOF sieving capability at an ultralow filler loading of 2 wt.%. The resulting MMMs deliver approximately threefold enhancement in CO2/CH4 and CO2/N2 selectivity compared with PIM-1 membranes, while maintaining high CO2 permeability and improved resistance to physical aging and plasticization. This study may broaden the design concepts for advanced MMMs toward challenging molecular separations.