Freestanding Zeolitic Imidazolate Frameworks Membrane in Microchannel

Metal-organic frameworks (MOFs) have a wide range of applications including chemical separation, hydrogen storage, sensing, electronics and medicine [1,2]. They incorporate metal clusters and coordinate organic ligands to form networks of pores, giving the material a rich topological and chemical diversity. MOFs, in particular the zeolitic imidazolate frameworks (ZIFs), have a promising future in membrane technology. However, it is still a challenge to prepare high-quality MOF membranes due to poor nucleation, adhesion and intergrowth of the crystals. Although 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 fabricate freestanding MOFs membrane despite the benefits of lower transport resistance and a larger surface area.

Freestanding ZIF-8 micromembranes are 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 the flow interface. 100 micron thick ZIF-8 was successfully grown along the gap in the microchannel. The freestanding membrane was defect-free and impervious to large dye molecules. Cracks and defects were not evident. The formation of ZIF-8 micromembrane was observed using a confocal fluorescent microscope that enables us to propose a mechanism of formation and growth of ZIF-8 micromembrane in a microfluidic channel.

References:

[1]  O. Shekhah, et al., "MOF thin films: existing and future applications," Chemical Society Reviews, vol. 40, pp. 1081-1106, 2011.

[1]  J. Lee, et al., "Metal-organic framework materials as catalysts," Chemical Society Reviews, vol. 38, pp. 1450-1459, 2009