Polymer Membrane Cavities Tuned by a Removable Inorganic-Phase Additive for Enhanced CO₂ Separation

Polyether block amide (Pebax) is a commercially available polymer that has gained attention for capturing CO₂ from flue gas. However, its relatively low permeance and CO₂/N₂ selectivity limit its large-scale industrial applications. Herein, we proposed an approach to adjust the interchain cavities and improve the permeance of the Pebax membrane by adding a water-soluble additive, ammonium carbonate (AC), into the Pebax polymer, aiming to form removable inorganic phases in the Pebax membrane. A series of Pebax membranes with varying concentrations of AC content were fabricated via a spin-coating process. The AC was decomposed by subsequent thermal treatment, thus creating subnanometer pores in the Pebax membrane substrate while preserving the membrane's integrity. The optimized Pebax-AC membranes achieved a CO₂ permeance of 111 GPU and a CO₂/N₂ selectivity of 74, showing increments of 68% and 37% in comparison with pure Pebax membranes. Our results indicate that incorporating removable inorganic phases is a promising strategy for advancing membrane-based CO₂ capture.