Mechanistic insights into mechanical behavior of MOF-polymer membranes

Abstract

Efforts to optimize the performance of MOF-polymer mixed matrix membranes (MMMs) are often hindered by a lack of comprehensive understanding of interfacial interaction mechanisms. This study investigates the interfacial structure, dynamics, and mechanical properties of MMMs using molecular dynamics (MD) simulations. Models were developed by incorporating polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), poly(methyl methacrylate) (PMMA), and polystyrene (PS) into optimized slabs of UiO-66, ZIF-8, and ZIF-90. While PEG and PVDF are known for their high compatibility with MOFs due to strong surface coverage, the rigid PS typically exhibits poor surface coverage. However, our findings reveal an intriguing exception: PS enhances the mechanical stability of ZIF-8 membranes through geometry interlocking at the interface, driven by interfacial dynamics. This behavior contrasts with PVDF, where mechanical stability is not significantly improved. These results emphasize that beyond surface coverage, the geometrical fit and interfacial dynamics are critical factors influencing membranes performance. We further evaluated the impact of polymer content by doubling the polymer layer thickness, which maintained stable Young’s modulus and tensile strength while enhancing failure strain. By highlighting the interplay between surface interactions and interfacial dynamics, this work provides valuable insights for optimizing the design and durability of MMMs for advanced applications.