Metal-organic frameworks (MOFs) consist of metal centers connected by organic ligands that form networks of pores, giving the material a rich topological and chemical diversity. MOFs have potential applications in chemical conversion, separation and storage as well as in sensing, electronics and medicine.  MOFs and in particular the zeolitic imidazolate frameworks (ZIFs) make superb candidate materials for membranes. However, the fabrication of high-quality MOF membranes remains a challenge due to poor nucleation, adhesion and intergrowth of the MOF crystals. Different strategies, including in-situ and seeded growth methods along with others have been used to prepare supported MOF membranes. Very little work has been done to prepare freestanding MOFs membrane despite the benefits of lower transport resistance and larger surface area.Freestanding ZIF-8 micromembranes were fabricated within the confined space of the microfluidic microchannel. This is achieved by establishing two parallel flows of reactants within the channel and inducing nucleation, crystallization and growth at flow interface. 100 micron thick ZIF-8 was successfully grown along the gap in the microchannel shown below. Tests showed that the freestanding membrane was defect free and impervious to large dye molecules. Samples analyzed under transmission electron microscope showed the ZIF-8 crystals are well crystallized and intergrown. Crack and defect were not evident. The formation of ZIF-8 micromembrane was observed in-situ using a confocal fluorescent microscope and the growth vector was determined from the 3D fluorescent reconstruction images that enable us to propose a mechanism of formation and growth of ZIF-8 micromembrane in microfluidic channel.

Freestanding ZIF-8 metal organic framework membrane in microchannel

246th National Meeting (2013)

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