Surface-Engineered Asymmetric Hollow Fiber Membranes with Facilitated Transport Interfaces for CO 2 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 report a surface engineering strategy to fabricate high-performance asymmetric hollow fiber membranes with an amine-functionalized surface monolayer. We utilized a brominated 6FDA-DAM polyimide precursor to fabricate asymmetric hollow fiber membranes via spinning, where bromine groups adjust the fractional free volume and serve as reactive sites for nucleophilic substitution. By grafting diamines onto the membrane surface, we successfully established a facilitated transport layer via surface reactions on the monolayer of asymmetric hollow fiber membranes. 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. The CO2 permeance of amine-grafted membrane can reach 1362GPU and the CO2/N2 selectivity can reach 65 at 0.2 MPa, which are 1.33 times and 1.38 times of the CO2 permeance and the CO2/N2 selectivity of the PI-Br-70% membrane, respectively. This demonstrated 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 220 hours of continuous operation. This study presents a reliable method for developing scalable membranes with high flux and durability for energy-efficient carbon capture.