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

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 (O 3 -PIMs) within minutes. The FT-IR spectra and XPS results suggested that C O 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 O 3 oxidation, the O 3 -PIMs showed a large drop in gas permeability whereas huge increases in gas pair selectivity, resulting in large improved overall performance for H 2 /N 2 , H 2 /CH 4 and H 2 /CO 2 that beat the latest trade-off lines. The O 3 -PIM-60 showed a H 2 permeability of 1294 Barrer and H 2 /N 2 , H 2 /CH 4 and H 2 /CO 2 selectivity of 93.7, 121, and 2.92, respectively. The increased selectivity of O 3 -PIMs is due to their remarkably enhanced size sieving effect induced enhanced diffusion selectivity. Theoretical simulation showed that this is caused by the O 3 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. • O 3 -PIMs was obtained by in-situ ozone oxidation of PIM-1 for the first time. • This method is simple, controllable and highly efficient. • The O 3 oxidation happened at the surface within 10 μm in depth. • The performance improvement originated from the enhanced diffusion selectivity. • O 3 -PIM-60 membrane exceed the 2015 Robeson upper bounds for H 2 /N 2 and H 2 /CH 4 .