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

Koo, Won-Tae; Jang, Ji-Soo; Qiao, Shaopeng; Hwang, WonTae; Jha, Gaurav; Penner, R. M.; Kim, Il-Doo

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

2018

Here, we propose heterogeneous nucleation-assisted hierarchical growth of metal–organic frameworks (MOFs) for efficient particulate matter (PM) removal. The assembly of two-dimensional (2D) Zn-based zeolite imidazole frameworks (2D-ZIF-L) in deionized water over a period of time produced hierarchical ZIF-L (H-ZIF-L) on hydrophilic substrates. During the assembly, the second nucleation and growth of ZIF-L occurred on the surface of the first ZIF-L, leading to the formation of flowerlike H-ZIF-L on the substrate. The flowerlike H-ZIF-L was easily synthesized on various substrates, namely, glass, polyurethane three-dimensional foam, nylon microfibers, and nonwoven 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 the 2D-shaped H-ZIF-L, which is tightly anchored on individual fibers comprising the membrane.

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