Hierarchical Metal-Organic Framework Assembled Membrane Filter for Efficient Removal of Particulate Matter.

Here, we propose heterogeneous nucleation assisted hierarchical growth of metal-organic framework (MOF) for efficient particulate matter (PM) removal. The assembly of 2-dimensional (2D) Zn based zeolite imidazole framework (2D-ZIF-L) in deionized water over a period time produced hierarchical ZIF-L (H-ZIF-L) on hydrophilic substrates. During the assembly, the 2nd nucleation and growth of ZIF-L occurred on the surface of 1st ZIF-L, leading to the formation of flower-like H-ZIF-L on the substrate. The flower-like H-ZIF-L was easily synthesized on various substrates, including glass, polyurethane 3D foam, nylon microfibers, and non-woven fabrics. We demonstrated H-ZIF-L assembled polypropylene microfibers as a washable membrane filter with highly efficient PM removal property (92.5% ± 0.8% for PM2.5 and 99.5% ± 0.2% for PM10), low pressure drop (10.5 Pa at 25 L min-1), long-term stability, and superior recyclability. These outstanding particle filtering properties are mainly attributed to the unique structure of 2D-shaped H-ZIF-L, which is tightly anchored on individual fibers comprising the membrane.