Fabrication of thin-film composite mixed matrix membrane with 2D magnesium oxide for gas separation application

BACKGROUND: Increased concentration of carbon dioxide (CO2) emission leads to climate change. Hollow-fibre membrane technology seems feasible due to its high packing density, facile processability and easily tuneable properties. A mixed matrix membrane is designed to overcome the balance of solution-dissolution phenomena. However, ensuring optimized dispersion of fillers at the outermost selective skin layer region appears to be challenging. In this study, a thin-film composite mixed matrix membrane (TFCMMM) is fabricated with a facile dip-coating method comprising a PES substrate, polydimethylsiloxane (PDMS) coating layer and magnesium oxide (MgO) nanosheet as the additive filler in the coating layer. RESULTS: The loading of the MgO nanosheet was varied from 0 to 10 wt% in the PDMS coating solution. Mixed gas performance showed a similar trend to the single gas permeation test, with lower gas permeance and selectivity due to the effect of competitive sorption between the binary gas mixtures. The permeance-selectivity trade-off was absent until the MgO loading of 1.00 wt%, when CO2/N-2 and CO2/CH4 improved by 35.13% and 27.55%, respectively, over pristine TFCMMM. When the MgO loading was increased beyond 2.5 wt%, filler agglomeration and leaching caused the formation of non-selective voids, reducing CO2/N-2 and CO2/CH4 selectivity. The improvement in selectivity observed in this study was due to an increased tortuous pathway of the gas penetrant due to the presence of a high-aspect-ratio MgO nanosheet, resulting in slower diffusion of gas through the PDMS selective layer of the TFCMMM. CONCLUSION: Our findings provide additional insights into the fabrication of TFCMMM using an MgO nanosheet as an additive filler in the coating layer, specifically for CO2/N-2 and CO2/CH4 separation. (c) 2025 Society of Chemical Industry (SCI).