High hydrogen permeable ZIF-8 membranes on double modified substrates

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Heterogeneous nucleation on the substrate surface is an advantage for inducing the synthesis of a thin and continuous membrane. Here, high hydrogen permeable ZIF-8 membranes were fabricated by combining the dopamine functionalized substrate and seed-induced growth method. In addition to providing abundant functional groups, polydopamine also can chelate metal ions (Zn2+) to accelerate the nucleation on the substrate surface. Furthermore, polydopamine can anchor the seeds for promoting the heterogeneous nucleation on the substrate surfaces, and prevent the seeds from entering into the substrate porous. The characterization results by the X-ray diffraction and scanning electron microscopy showed a continuous and thin ZIF-8 layer was synthesized on the modified substrate, resulting in a low gas permeance resistance. For the single gas permeation performance, the membrane showed a marked hydrogen permeance of 1.8 × 10−6 mol·m−2·s−1·Pa−1, and the idea selectivity for H2/CO2, H2/N2, H2/CH4 and H2/C3H8 is 4.1, 8.5, 11.3 and 294, respectively. The H2 permeance of the obtained membrane is about one order of magnitude higher than that of similar substrate supported membrane. The membrane also demonstrated a comparable separation performance for mixed gas separation.