Breaking The Permeance‐Selectivity Tradeoff for Post‐Combustion Carbon Capture: A Bio‐Inspired Strategy to Form Ultrathin Hollow Fiber Membranes

Abstract Thin film composite (TFC) hollow fiber membranes with ultrathin selective layer are desirable to maximize the gas permeance for practical applications. Herein, a bio‐inspired strategy is proposed to fabricate sub‐100‐nm membranes via a tree‐mimicking polymer network with amphipathic components featuring multifunctionalities. The hydrophobic polydimethylsiloxane (PDMS) brushes act as the roots that can strongly cling to the gutter layer, the PDMS crosslinkers function as the xylems to enable fast gas transport, and the hydrophilic ethylene‐oxide moieties (brushes and mobile molecules) resemble tree leaves that selectively attract CO₂ molecules. As a result, a ≈27 nm‐thick selective layer can be attached to the hollow fiber‐supported PDMS gutter layer through a simple dip‐coating method without any modification. Furthermore, a CO₂ permeance of ≈2700 GPU and a CO₂/N₂ selectivity of ≈21 that is beyond the permeance‐selectivity upper bound for hollow fiber membranes is achieved. This bio‐inspired concept can potentially open the possibility of scalable hollow fiber membranes production for commercial applications in post‐combustion carbon capture and beyond.