Non-solvent-induced microstructure rearrangement for significantly enhanced CO2/N2 separation performance of Pebax 2533 membranes

Abstract

The development of membranes exhibiting both high CO₂ permeability and selectivity is crucial for climate change mitigation. In this study, a simple and efficient non-solvent induced microstructure rearrangement (MSR) technique was developed to fabricate Pebax 2533 MSR membranes by adjusting the type and concentration of acidic/alkaline solutions. Gas permeation tests revealed that CO₂/N₂ separation performance first increased and then decreased with increasing alkali concentration. The membrane subjected to MSR in 1 mol L⁻¹ NaOH solution exhibited a CO₂ permeability of 1076.5 Barrer, while maintaining a stable CO₂/N₂ selectivity of 27.4. In contrast, MSR treatment under acidic conditions consistently resulted in deteriorated separation performance across all tested concentrations. A long-term stability test showed that the Pebax-NaOH 1 mol L⁻¹ membrane maintained good CO₂ separation stability throughout the 7-day continuous testing period. Physical–chemical characterization studies, such as transmission electron microscope (TEM), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC), indicate that the key mechanism for the improvement of CO₂ permeability may be achieved through non-solvent-induced physical structural rearrangement rather than the regulation of crystallinity.