Facile tailoring molecular sieving effect of PIM-1 by in-situ O3 treatment for high performance hydrogen separation

Abstract

Highly efficient hydrogen separation membrane is critical in the future hydrogen powered zero carbon society. However, challenges left in searching for hydrogen separation membranes with high permeability, selectivity and easy accessibility. Here, this target was partially achieved by a series of membranes made from in-situ ozone oxidized intrinsic mciroporous polymer membranes (O3-PIMs) within minutes. The FT-IR spectra and XPS results suggested that CO and OH groups were formed after the oxidation reaction. The TGA and EDS mapping results indicated that the oxidation reaction happened only on the skin surface of PIM-1 membrane within 10 μm in depth. After O3 oxidation, the O3-PIMs showed a large drop in gas permeability whereas huge increases in gas pair selectivity, resulting in large improved overall performance for H2/N2, H2/CH4 and H2/CO2 that beat the latest trade-off lines. The O3-PIM-60 showed a H2 permeability of 1294 Barrer and H2/N2, H2/CH4 and H2/CO2 selectivity of 93.7, 121, and 2.92, respectively. The increased selectivity of O3-PIMs is due to their remarkably enhanced size sieving effect induced enhanced diffusion selectivity. Theoretical simulation showed that this is caused by the O3 reaction induced pore blocking effect that shifted the mciropore of PIM-1 to the ultra-micropore region, and thus, significantly improved the hydrogen sieving efficiency. In all, this facile and highly efficient ozone oxidation method provides a great perspective in searching for high performance hydrogen separation membranes.