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UV-Rearranged PIM-1 Polymeric Membranes for Advanced Hydrogen Purification and Production

Authors

  • Fu Yun Li,

    1. Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576, Singapore
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  • Youchang Xiao,

    1. Suzhou Faith & Hope Membrane Technology Co. Ltd., Suzhou Industrial Park, Jiangsu Province, 215123, PR China
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  • Yee Kang Ong,

    1. Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576, Singapore
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  • Tai-Shung Chung

    Corresponding author
    1. Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576, Singapore
    • Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576, Singapore.
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Abstract

Polymers of intrinsic microporosity (PIM-1) have been known for their super high permeability but average selectivity for medium-size gas pairs. They have unimpressive selectivity for H2 and CO2 separation (i.e., α (H2/CO2) = 0.6). For the first time, we have discovered that ultraviolet (UV)-rearranged polymers of PIM-1 membranes can be used for H2/CO2 separation with far superior separation performance to others in literatures. The PIM-1 membrane after UV radiation for 4 hours shows H2 permeability of 452 barrer with H2/CO2 selectivity of 7.3. Experimental data and molecular simulation reveal that the polymer chains of PIM-1 undergo 1,2-migration reaction and transform to close-to-planar like rearranged structure after UV radiation. As a result, the UV-irradiated PIM-1 membrane shows considerable drops in both fractional free volume (FFV) and size of micro-pores. Positron annihilation lifetime (PAL) results have confirmed the chemical and structural changes, suggesting the FFV and pore size drops are mainly ascribed to the destructed spiro-carbon centre during UV radiation. Sorption and x-ray diffractor (XRD) analyses indicate that the impressive H2/CO2 selectivity arises from the significantly enhanced diffusivity selectivity induced by UV radiation, followed by molecular rearrangement, conformation change and chain packing.

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