Highly selective hollow fiber membranes for carbon capture via in-situ layer-by-layer surface functionalization

Multilayer films of poly(ethylene oxide) (PEO) and poly(methyl acrylic acid) (PMAA) deposited on a Torlon© poly(amide imide) (PAI) hollow fiber substrate using layer-by-layer (LbL) method yield highly CO₂-selective membranes. These all-polymer membranes were deposited in-situ on low-cost, high permeability, and low selectivity Torlon© hollow fibers for post-combustion carbon capture. Surface functionalization of hollow fibers using poly(ethylene imine) (PEI) in isopropanol increased hydrophilicity, aiding LbL deposition. Coatings of [PEO₂/PMAA₂] polymeric pair were successfully deposited on both untreated hollow fiber (10, 15, and 20 bilayers) and PEI-functionalized hollow fiber substrates (2, 5, and 10 bilayers) achieving one of the highest reported selectivity for CO₂:N₂ (240:1) at 1018 Barrer CO₂ permeability (101 GPU permeance); exceeding the 2008 Robeson upper bound for homogenous polymer films. These results suggest membranes deposited via in situ LbL methodology on industrially applicable hollow fibers pave a way for carbon capture from flue gases at power plants.