Effect of MIL-53 on phase inversion and gas separation performance of mixed matrix hollow fiber membranes

Abstract

In this paper the θ-composition for the Ultem®1000/NMP/EtOH ternary phase system was determined firstly and based on this, membranes with different non-solvent ratios (lower, slightly lower, and larger than the θ-composition) were prepared. It was found that dopes with a non-solvent ratio slightly lower than the θ-composition gave membranes the most attractive gas separation performance. Then the metal–organic framework (MOF) of MIL-53 was incorporated into Ultem®1000 to fabricate asymmetric mixed matrix hollow fiber membranes (MMHFMs). MIL-53, which was grouped with EtOH as a non-solvent, turned out to influence the phase inversion more significantly than EtOH did. Similar to the pure Ultem®1000 membrane, MMHFMs formed with the dopant close to the θ-condition for the Ultem®1000/MIL-53/NMP/EtOH phase system possessed the best permeation performance: MMHFMs with 5 wt% MIL-53 loading exhibited an O₂ and CO₂ permeance of 8.1 GPU and 27.9 GPU, an increase of 138% and 129% respectively compared with the pure Ultem membrane. Meanwhile, the O₂/N₂ and CO₂/CH₄ selectivity was almost unchanged. Moreover, the rule was also embodied in MMHFMs with different filler loadings. This study quantitatively revealed the pseudo non-solvent effect of MOFs, which offers an effective method for the fabrication of MMHFMs with a low MOF loading but high performance.