ZIF-8 continuous membrane on porous polysulfone for hydrogen separation

• Continuous ZIF-8 membrane is fabricated on a flexible and porous polymer support.
• Micro and nanosized crystals are combined to ensure adhesion between MOF and support.
• High H2 separation factors (αH2/CH4=10.5αH2/CH4=10.5, αH2/N2=12.4αH2/N2=12.4) from mixtures are obtained.
• Separation shows molecular sieving effect and activated transport with temperature.

A thick continuous zeolitic imidazolate framework-8 (ZIF-8) membrane is crystallized on a highly porous flexible polymer (polysulfone) surface by in-situ synthesis. Micro and nanosized metal organic framework (MOF) particles are combined to avoid holes or defects in the membranes, which are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analyses (TGA) and N2 sorption analysis. ZIF-8 content of the membrane exceeds 75 wt%, indicating an almost self-supported MOF-layer membrane. Permeation tests show high H2/CH4 (10.5±0.6) and H2/N2 (12.4±0.9) selectivities in separation of gas mixtures, confirming the expected molecular sieving effect due to MOF microporosity. These selectivity values are the highest among those reported for polymer-supported ZIF-8 membranes. Finally, in the H2/CH4 mixture the measurements carried out as a function of temperature (35–80 °C) show activated transport.

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