Ceramic-based composite membranes decorated by incorporating ZIF-8 and PDMS for highly efficient CO2/N2 separation

The development of high-performance composite membranes for efficient CO2/N2 separation is essential for reducing CO2 emissions. However, achieving a balance between permeance and selectivity remains a challenge. In this work, two CO2 permeable mullite ceramic-based composite membranes were made using fly ashes and α-Al2O3 as raw materials for mullite substrates, ZIF-8 nanofillers, and PDMS rubber polymer as gas separation materials. To enhance CO2 permeance and CO2/N2 selectivity, the M/PDMS@ZIF-8 composite membrane was prepared by dip-coating a ZIF-8 doped PDMS active layer (PDMS@ZIF-8) on the surface of the mullite-based substrate (M0). Subsequently, the M/ZIF-8/PDMS@ZIF-8 composite membrane was fabricated by in-situ growing ZIF-8 and followed by coating a PDMS@ZIF-8 functional layer on the M0 surface. The results indicated that the optimal M/PDMS@ZIF-8 membrane with 1 % of ZIF-8 exhibited an ultrahigh CO2 permeance of 4756 GPU and a good CO2/N2 selectivity of 10.07 at room temperature under 0.2 MPa. While the optimized composite membrane M/ZIF-8/PDMS@ZIF-8 with 0.8 wt% of ZIF-8 achieved a high CO2 permeance of 3050 GPU and superior CO2/N2 selectivity of 10.7. Furthermore, the latter displayed long-term permeation stability at 80 °C. The facile preparation process and cost-effective nature of the ceramic-based composite membrane demonstrate great potential for applications in CO2 capture from flue gas.