Breaking the Permeability–Selectivity Trade‐Off With Irreversible‐Knot Rubbery Organic Frameworks

ABSTRACT The permeability–selectivity trade‐off fundamentally constrains polymeric membranes, rooted in the dichotomy between chain flexibility and precise molecular sieving. The emerging concept of rubbery organic frameworks (ROFs) aims to bridge this gap, yet its reliance on reversible covalent chemistry inherently compromises structural stability. Here, we introduce an irreversible‐chemistry paradigm by programming β ‐ketoenamine “irreversible knots” into flexible polydimethylsiloxane (PDMS) networks via enol–keto tautomerization. This approach synergistically co‐programs crosslinking density and chain rigidity, yielding a stabilized and optimized microstructure. The resulting membrane transcends the classic trade‐off, delivering a record‐high flux of 5.4 kg m −2 h −1 for ethanol/water separation—three times higher than conventional PDMS—while maintaining a separation factor of 9.2. The “rigidity‐programming” strategy demonstrates remarkable versatility, achieving top‐tier performance across diverse separations spanning representative organic/water and gas‐pair systems. Beyond performance, the membranes exhibit scalable fabrication, robust anti‐swelling stability, and long‐term operational durability, highlighting their practical potential for industrial deployment. This work establishes irreversible chemistry as a general paradigm for polymer network design, providing a robust platform to overcome traditional limitations from molecular separation to flexible functional materials.