Dual Interaction Assembly of Functionalized Tannic Acid and Zinc Based Metal–Organic Framework Membranes for CO 2 Separation from Simulated Post-Combustion Gas Mixtures

In this study, PEI-based composite membranes were fabricated using MOF nanoparticles, ZIF-8, and tannic-acid-functionalized HKUST-1 (TA-HKUST-1) for enhancing structural and energy efficiency properties for CO2 separation from postcombustion gases. Five different membranes, including bare PEI, ZIF-8/PEI blend, TA-HKUST-1/PEI blend, ZIF-8/PEI coated, and PEI/TA-HKUST-1 coated, were fabricated using a solution casting method. The successful incorporation of MOF fillers was confirmed using FT-IR and XRD, showing the integrity of the PEI backbone. The thermal stability of all membranes was above 500 °C, demonstrating excellent interfacial interactions and uniform distribution of MOF fillers in the PEI matrix. The mechanical stability of the membranes showed that the TA-HKUST-1/PEI coated membrane possessed excellent mechanical properties, including flexibility, with a Young’s modulus of 70.8 MPa. Gas permeation tests for all membranes using CO2, N2, and O2 gases showed that the TA-HKUST-1/PEI blend possessed better gas separation properties, including a CO2 permeance of 137.6 GPU and a CO2/N2 selectivity of 2.28 at 4 bar and 35 °C. Moreover, the highest cost-efficiency index was observed for the TA-HKUST-1-coated membrane (0.0958), whereas the ZIF-8-coated membrane possessed the lowest specific energy consumption of 3.73 kWh/kg of CO2. Overall, the surface-coated composite membranes possessed improved properties, making PEI-based membrane materials suitable for CO2 capture applications.