Ultrathin Water-Cast Polymer Membranes for Hydrogen Purification

Thermally Annealed High-Aspect-Ratio ZIF-8 Nanoplates-Incorporated Mixed Matrix Membranes for Improved H2/CO2 Selectivity

The main challenge in the preparation of MOF-based mixed matrix membranes is to construct a good interface morphology to improve the gas separation performance and stability of the membranes. Herein, high-aspect-ratio ZIF-8 nanoplates for H2/CO2 separation membranes were synthesized by direct template conversion. The ZIF-8 nanoplates were prepared with the commercial Matrimid polymer to form MMMs by the flat scraping method. The homogeneous dispersion of high-aspect-ratio nanoplates in the membrane and the good compatibility between the filler and the matrix caused by the thermal annealing operation improve the gas separation performance and mechanical properties of MMMs. The H2/CO2 selectivity of MMMs loaded with 30 wt % ZIF-8 nanoplates increased to 10.3, and the H2 permeability was 330.1 Barrer. This synthesis method can be extended to prepare various ZIF nanoplates with elevated aspect ratios to obtain excellent performance fillers for gas separation of MMMs. In addition, the thermal annealing operation allows more efficient gas separation in polymer membranes and is a feasible way to design excellent and stable MMMs.

Graphene in Polymeric Nanocomposite Membranes—Current State and Progress

One important application of polymer/graphene nanocomposites is in membrane technology. In this context, promising polymer/graphene nanocomposites have been developed and applied in the production of high-performance membranes. This review basically highlights the designs, properties, and use of polymer/graphene nanocomposite membranes in the field of gas separation and purification. Various polymer matrices (polysulfone, poly(dimethylsiloxane), poly(methyl methacrylate), polyimide, etc.), have been reinforced with graphene to develop nanocomposite membranes. Various facile strategies, such as solution casting, phase separation, infiltration, self-assembly, etc., have been employed in the design of gas separation polymer/graphene nanocomposite membranes. The inclusion of graphene in polymeric membranes affects their morphology, physical properties, gas permeability, selectivity, and separation processes. Furthermore, the final membrane properties are affected by the nanofiller content, modification, dispersion, and processing conditions. Moreover, the development of polymer/graphene nanofibrous membranes has introduced novelty in the field of gas separation membranes. These high-performance membranes have the potential to overcome challenges arising from gas separation conditions. Hence, this overview provides up-to-date coverage of advances in polymer/graphene nanocomposite membranes, especially for gas separation applications. The separation processes of polymer/graphene nanocomposite membranes (in parting gases) are dependent upon variations in the structural design and processing techniques used. Current challenges and future opportunities related to polymer/graphene nanocomposite membranes are also discussed.