Toward an Understanding of the Microstructure and Interfacial Properties of PIMs/ZIF‑8 Mixed Matrix Membranes

• Published in: ACS applied materials & interfaces Vol. 8; no. 40; pp. 27311 - 27321
• Main Authors: Benzaqui, Marvin, Semino, Rocio, Menguy, Nicolas, Carn, Florent, Kundu, Tanay, Guigner, Jean-Michel, McKeown, Neil B, Msayib, Kadhum J, Carta, Mariolino, Malpass-Evans, Richard, Le Guillouzer, Clément, Clet, Guillaume, Ramsahye, Naseem A, Serre, Christian, Maurin, Guillaume, Steunou, Nathalie
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.10.2016; Washington, D.C. : American Chemical Society
• Subjects: Chemical Sciences; chemical structure; colloids; image analysis; light scattering; microstructure; nanoparticles; physicochemical properties; polymers; solvents; texture; transmission electron microscopy; X-radiation; mixed matrix membrane; transmission electron microscopy; ZIF-8; molecular modeling; polymer of intrinsic microporosity; MOF/polymer interface
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.6b08954

A study integrating advanced experimental and modeling tools was undertaken to characterize the microstructural and interfacial properties of mixed matrix membranes (MMMs) composed of the zeolitic imidazolate framework ZIF-8 nanoparticles (NPs) and two polymers of intrinsic microporosity (PIM-1 and PIM-EA-TB). Analysis probed both the initial ZIF-8/PIM-1 colloidal suspensions and the final hybrid membranes. By combination of dynamic light scattering (DLS) and transmission electron microscopy (TEM) analytical and imaging techniques with small-angle X-ray scattering (SAXS), the colloidal suspensions were shown to consist mainly of two distinct kinds of particles, namely, polymer aggregates of about 200 nm in diameter and densely packed ZIF-8-NP aggregates of a few 100 nm in diameter with a 3 nm thick polymer top-layer. Such aggregates are likely to impart the granular texture of ZIF-8/PIMs MMMs as shown by SEM-XEDS analysis. At the molecular scale, modeling studies showed that the surface coverage of ZIF-8 NPs by both polymers appears not to be optimal with the presence of microvoids at the interfaces that indicates only a moderate compatibility between the polymer and ZIF-8. This study shows that the microstructure of MMMs results from a complex interplay between the ZIF-8/PIM compatibility, solvent, surface chemistry of the ZIF-8 NPs, and the physicochemical properties of the polymers such as molecular structure and rigidity.