Pervaporation has been regarded as a promising separation technology in separating azeotropic mixtures, solutions with similar boiling points, thermally sensitive compounds, organic-organic mixtures as well as in removing dilute organics from aqueous solutions. As the pervaporation membrane is one of the crucial factors in determining the overall efficiency of the separation process, this article reviews the research and development (R&D) of polymeric pervaporation membranes from the perspective of membrane fabrication procedures and materials.

High‐performance zeolitic imidazolate frameworks (ZIFs)/polybenzimidazole (PBI) nanocomposites are molecularly designed for hydrogen separation at high temperatures, and demonstrate it in a useful configuration as dual‐layer hollow fibers for the first time. By incorporating as‐synthesized nanoporous ZIF‐8 nanoparticles into the high thermal stability but extremely low permeability polybenzimidazole (PBI), the resultant mixed matrix membranes show an impressive enhancement in H2 permeability as high as a hundred times without any significant deduction in H2/CO2 selectivity. The 30/70 ZIF‐8/PBI dense membrane has a H2 permeability of 105.4 Barrer and a H2/CO2 selectivity of 12.3. This performance is far superior to ZIF‐7/PBI membranes and is the best ever reported data for H2‐selective polymeric materials in the literature. Meanwhile, defect‐free ZIF‐8‐PBI/Matrimid dual‐layer hollow fibers are successfully fabricated, without post‐annealing and coating, by optimizing ZIF‐8 nanoparticle loadings, spinning conditions, and solvent‐exchange procedures. Two types of hollow fibers targeted at either high H2/CO2 selectivity or high H2 permeance are developed: i) PZM10‐I B fibers with a medium H2 permeance of 64.5 GPU (2.16 ×10−8 mol m−2 s−1 Pa−1) at 180°C and a high H2/CO2 selectivity of 12.3, and, ii) PZM33‐I B fibers with a high H2 permeance of 202 GPU (6.77 ×10−8 mol m−2 s−1 Pa−1) at 180°C and a medium H2/CO2 selectivity of 7.7. This work not only molecularly designs novel nanocomposite materials for harsh industrial applications, such as syngas and hydrogen production, but also, for the first time, synergistically combines the strengths of both ZIF‐8 and PBI for energy‐related applications.

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in Wiley Online Library (wileyonlinelibrary.com).Acetone dehydration via pervaporation is challenging, because acetone and water have close molecular sizes, and acetone has a much higher vapor pressure than water. Acetone is also a powerful solvent, which dissolves or swells most polymers. We have developed novel polybenzimidazole/BTDA-TDI/MDI (PBI/P84) dual-layer hollow fibers for pervaporation dehydration of acetone for industrial and biofuel separations. Both thermal and chemical crosslinking modifications were applied to the membranes to investigate their effectiveness to overcome acetone-induced swelling. Thermal treatment can effectively enhance separation performance, but performance stability can only be achieved through the crosslinking modification of PBI. Crosslinking by p-xylene dichloride followed by a thermal treatment above 250 C show significant effectiveness to improve and stabilize pervaporation performance. The fractional free volume of the PBI selective layer reduces from 3.27 to 1.98% and 1.33%, respectively, after thermal treatment and a combination of chemical/thermal crosslinking modifications characterized by positron annihilation spectroscopy.The as-spun PBI/P84 dual-layer hollow fiber membrane shows an acetone/water separation factor of only 2.2 and a Figure 2. Sorption results of PBI and P84 dense films after one-week and one-month immersion in acetone and water.Figure 3. FE-SEM images of the cross-section morphology of the original PBI/P84 dual-layer hollow fiber. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] Figure 7. FE-SEM images of the cross-section morphology of the outer layer outer edge of original and thermaltreated PBI/P84 dual-layer hollow fibers at various temperatures.

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