Effect of zeolitic imidazolate frameworks on the gas transport performance of ZIF8-poly(1,4-phenylene ether-ether-sulfone) hybrid membranes

This work reports the permeability of hydrogen, nitrogen, oxygen, carbon dioxide, methane, ethane and ethylene across ZIF-8/poly(1,4-phenylen ether-ether-sulfone) hybrid membranes containing 0, 0.10, 0.20 and 0.30 weight fractions of ZIF-8. The glass transition temperature is independent on the filler content suggesting that the filler does not affect the polymer chains mobility. The study was carried out at 1 bar in the range of 283-313 K and the diffusion coefficient of the gases was obtained in this range of temperature by means of the lag time method. The permeability and diffusion coefficients obey Arrhenius behavior and the activation energies associated with this processes were obtained from the slopes of the respective plots. The performance of the membranes as determined by the closeness of their selectivity to the Robeson's upper bounds increases as the ZIF-8 content of the hybrid membranes increases. The membrane with 30% (w/w) content exhibits at 303 K pretty good selective properties for O-2/N-2 and H-2/N-2. The selectivity for C2H4/C2H6 is of the order of 3 with P(C2H4)congruent to 3 Barrer. Extrapolation of the permeability data for H-2/N-2 at high temperatures gives a selectivity that coincides with that predicted by the Robeson limit for this pair of gases. (C) 2011 Elsevier B.V. All rights reserved.