ZIF-8/GO sandwich composite membranes through a precursor conversion strategy for H2/CO2 separation

Abstract

It is difficult to control the heterogeneous nucleation and growth of crystals on porous supports, the preparation of thin ZIF-8 membranes is still extremely challenging. Herein, a two-dimensional transformation strategy is demonstrated for constructing a ZIF-8/GO ‘sandwich’ composite membrane with a thickness of ∼0.9 μm, which was prepared from Zn-EG-AC (EG: ethylene glycol, AC: CH3COO-groups, abbreviated as ZnEG) on alumina hollow fiber support for the first time by precursor conversion method in 2-methylimidazole methanol solution. The effects of the amount of precursor, reaction time and membrane thickness on the membrane structure and H2/CO2 separation performance are explored. The sieving effect of ZIF-8 and the adsorption effect of 2-methylimidazole rings on CO2, as well as the strong interaction between GO and CO2 hinder the permeation of CO2 into the membrane, thus exhibiting a good H2/CO2 ideal separation selectivity of 30.8 with the H2 permeance of 1.36 × 10−7 mol·Pa−1·m−2·s−1 under the optimized preparation conditions. The separation factor of the equimolar H2/CO2 binary-mixture gases stabilizes to ∼25 after 30 h. This precursor conversion strategy is expected to be extended to other MOF/graphene oxide (GO) composite membrane systems.