Surface-engineered asymmetric hollow fiber membranes with facilitated transport interfaces for CO2 capture

Abstract

Capturing low-pressure CO₂ from industrial flue gas is challenging due to the trade-off between permeability and selectivity in polymeric membranes. To address this issue, we reported a surface engineering strategy to fabricate high-performance asymmetric hollow fiber membranes (AHFMs) with an amine-functionalized surface-localized ultra-thin functional layer. We utilized a brominated 6FDA-DAM polyimide precursor to fabricate AHMs via spinning, where bromine groups disrupt polymer chain packing to optimize bulk diffusion pathways, while simultaneously serving as reactive sites for nucleophilic substitution. By grafting polyamines onto the membrane surface, we successfully established a facilitated transport layer via surface reactions on the surface-localized ultra-thin functional layer. This design synergizes the fast permeation of the solution-diffusion bulk with the high affinity of the facilitated transport surface. In comparison with the pristine membrane, the amine-grafted membrane exhibited a simultaneous enhancement in separation performance. Under single-gas conditions at 0.2 MPa, the CO₂ permeance of the membrane can reach 1362 GPU and the ideal CO₂/N₂ selectivity can reach 65, representing 1.33 times and 1.38 times increases over the pristine PI-Br-70% membrane, respectively. This demonstrates the efficacy of the surface functionalization strategy. Furthermore, the chemically cross-linked surface provides structural rigidity that effectively suppresses CO₂-induced plasticization. The membrane also ensured stable separation performance over 1440 h of continuous operation. This study presents a reliable method for developing scalable membranes with high flux and durability for energy-efficient carbon capture.