Chitosan-Gallic acid tailored thin-film nanocomposite membrane with ZIF-8 metal–organic frameworks toward improved CO2/CH4 and CO2/N2 separation performance

In the present work, ZIF-8-incoporated TFN membranes were prepared via a facile one-pot in situ synthesis approach, enabling uniform incorporation of ZIF-8 nanoparticles within a Chitosan-Gallic acid (CS-GA) selective layer. Structural and morphological analyses confirmed effective integration and uniform distribution of ZIF-8 throughout the polymer matrix, while preserving the thermal stability of the membranes following the introduction of ZIF-8 nanoparticles. The gas separation behavior of the TFN membranes was systematically investigated by varying the ZIF-8 content (5-15 wt%) and the applied operating pressure (2-10 bar). Compared to the pure CS-GA membrane, incorporation of ZIF-8 significantly enhanced CO 2 transport without compromising selectivity. The membrane loaded with 10 wt% ZIF-8 demonstrated the optimal balance between permeance and selectivity, achieving a 25% increase in CO 2 permeance (from 487.2 to 647.1 GPU) at 35°C and 10 bar. At this loading, CH 4 and N 2 permeances remained relatively low (30.8 and 24.5 GPU, respectively), indicating effective molecular sieving behavior. Consequently, the CO 2 /CH 4 selectivity increased from 17.5 to 21.0 (16.5% improvement), while the CO 2 /N 2 selectivity improved by nearly 10%, rising from 23.8 to 26.4 compared to the unmodified membrane. These enhancements are attributed to the combined effects of increased CO 2 uptake due to specific interactions with the ZIF‑8 framework and facilitated molecular pathways introduced by the ZIF‑8 porous structure, which together promote preferential CO 2 transport relative to CH 4 and N 2 .