Simultaneously enhanced CO2 permeability and CO2/N2 selectivity at sub-ambient temperature from two novel functionalized intrinsic microporous polymers

A twisted imidazole-tethered aromatic polymer for high-performance membranes in vanadium-based redox flow batteries

We report on a twisted aromatic polymer, the first xanthene-based example bearing protonated imidazole groups. Its special architecture enables superior ion selectivity, conductivity, and chemical stability, providing excellent performance in both all-vanadium and iron-vanadium redox flow batteries.

Recent Advances in Direct Synthesis of Functional Polymers of Intrinsic Microporosity Based on (Super)Acid Catalysis

Polymers of intrinsic microporosity (PIMs) are an emerging class of amorphous organic porous materials with solution processability, which are widely used in a multitude of fields such as gas separation, ion conduction, nanofiltration, etc. PIMs have adjustable pore structure and functional pore wall, so it can achieve selective sieving for specific substances. In order to meet the functional requirements of PIMs, two principal methods are used to synthesize functional PIMs, namely, post-modification of PIMs precursors and functionalization of monomers. A number of post-modification routes have been reported, however, the direct synthesis of functional PIMs with diverse groups still remains a challenge. The synthesis of PIMs through the acid-catalyzed polyhydroxyalkylation has been demonstrated to be an effective solution, exhibiting the advantages of wider substrates range, milder reaction conditions, and higher molecular weight. Recently, a series of functional substrates for direct synthesis of PIMs have been proposed. This article presents a review and summary of recent advances in synthesizing PIMs via acid-catalyzed polyhydroxyalkylation, and the synthesis route and structure-activity relationship are emphasized, which provides a versatile platform for the direct synthesis of functional PIMs.

Hydroxyl-functionalized microporous polymer membranes with tunable para position substituent benzaldehydes for gas separation

We report hydroxyl-functionalized microporous polymers with tunable benzaldehyde groups for gas separation membranes. These polymers were synthesized via acid-catalyzed Friedel-Crafts polycondensation. The tunability in d-spacing and fractional free volume of these polymers depends on the para position substituents (-H, -F, -Cl, and -Br) of the benzaldehyde. Specifically, the size and polarity of the para position substituent influence the polymer chain-packing structure. Consequently, the hydroxyl-functionalized microporous polymer membrane with a larger para position substituent in the benzaldehyde group exhibited improved gas permeability. This improvement is due to enhanced gas diffusivity resulting from the inefficient polymer chain-packing structure. Furthermore, these membranes demonstrated enhanced CO2 plasticization resistance, attributable to the rigid, contorted polymer structure and the hydrogen bonding interactions between hydroxyl groups. This study provides insights into the relationship between the polymer chain-packing structure, tunable para position substituents, and molecular transport.

Penetrant-induced plasticization in microporous polymer membranes

Penetrant-induced plasticization has prevented the industrial deployment of many polymers for membrane-based gas separations. With the advent of microporous polymers, new structural design features and unprecedented property sets are now accessible under controlled laboratory conditions, but property sets can often deteriorate due to plasticization. Therefore, a critical understanding of the origins of plasticization in microporous polymers and the development of strategies to mitigate this effect are needed to advance this area of research. Herein, an integrative discussion is provided on seminal plasticization theory and gas transport models, and these theories and models are compared to an exhaustive database of plasticization characteristics of microporous polymers. Correlations between specific polymer properties and plasticization behavior are presented, including analyses of plasticization pressures from pure-gas permeation tests and mixed-gas permeation tests for pure polymers and composite films. Finally, an evaluation of common and current state-of-the-art strategies to mitigate plasticization is provided along with suggestions for future directions of fundamental and applied research on the topic.