Preparation of continuous NH2–MIL-53 membrane on ammoniated polyvinylidene fluoride hollow fiber for efficient H2 purification

• PVDF fiber is ammoniated by ethanediamine to produce –NH2 and improve stability.
• Continuous NH2–MIL-53/PVDF membrane is synthesized in DMF solution directly.
• H2 permeance and H2/CO2 selectivity increase 330 and 5.46 times by activation.
• Permeance reaches 42.13×10−7 mol s−1 m−2 Pa−1 with selectivity of 32.35 for H2/CO2.

A thin and continuous NH2–MIL-53 layer composed of Al(III) and 2-amino terephthalic acid has been successfully deposited on an ammoniated polyvinylidene fluoride (PVDF) hollow fiber under harsh synthetic conditions in N,N-dimethyl formamide (DMF) precursor solution at 423 K. In order to enhance the solvent resistance and thermal stability of membrane, the hollow fiber was ammoniated by ethanediamine to become cross-linked. The amino groups formed on its surface provided high-density heterogeneous nucleation sites for strong adhesive growth of NH2–MIL-53. Results showed that the thin NH2–MIL-53 layer on ammoniated PVDF hollow fiber was inter-grown with thickness of only about 8 μm. After activation by DMF at 423 K for 5 h and drying under vacuum at 423 K for 12 h, its permeance and ideal separation factor of H2/CO2 increased 330 and 5.46 times respectively. The prepared NH2–MIL-53/PVDF hollow fiber membrane exhibited excellent H2 permeance of 54.20×10−7 mol s−1 m−2 Pa−1 as well as the high ideal separation factor of 30.37, 24.07, 27.85 and 27.31 for H2/CO2, H2/O2, H2/N2 and H2/CH4, respectively. The composite membrane can also efficiently separate the H2/CO2 mixture with H2 permeance of 42.13×10−7 mol s−1 m−2 Pa−1 and separation factor of 32.35, which showed to be the highest separation factors among those reported for polymer supported MOF membranes.

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