Structural and Gas Permeation Properties of Pebax/ <scp> AlPO ₄ </scp> ‐5 Mixed Matrix Membrane

ABSTRACT The rapid increase in CO 2 emissions has intensified global warming and environmental challenges, highlighting the need for efficient gas separation technologies. In this study, aluminophosphate (AlPO 4 ‐5) crystals were synthesized, calcined, functionalized, and employed as fillers (0–30 wt.%) in Pebax 2533 polymer matrices to enhance CO 2 separation performance. Comprehensive characterization using FESEM, FTIR, TGA, and mechanical strength analysis confirmed successful incorporation and strong interfacial adhesion between AlPO 4 ‐5 particles and the polymer. Gas permeability tests for N 2 , CH 4 , and CO 2 were conducted at 2, 4, and 6 bar. At low filler loadings (2–10 wt.%), membranes showed reduced CO 2 and CH 4 permeability compared to the neat polymer, while N 2 permeability remained nearly unchanged. A marked improvement was observed at 20 wt.% filler, with increased permeabilities and the highest selectivity at 6 bar and 25°C (CO 2 permeability: 335.35 barrer; CO 2 /N 2 : 43.83; CO 2 /CH 4 : 10.46). The most effective membrane featured 20 wt.% piperazine‐functionalized AlPO 4 ‐5, achieving CO 2 permeability of 542.18 barrer, CO 2 /N 2 selectivity of 55.04, and CO 2 /CH 4 selectivity of 17.09. These results demonstrate that PZ‐functionalization significantly enhances CO 2 affinity and transport, making these mixed matrix membranes promising candidates for advanced CO 2 separation applications.