Ionic Microporous Polymer Membranes for Advanced Gas Separations

Abstract

Microporous polymers are uniquely attractive for membrane-mediated gas separations; however, conventional microporous polymers suffer a ubiquitous trade-off between gas permeability and selectivity, leading to bottlenecks in their practical applications. Functionalization of microporous polymers via molecule engineering is an effective way to enhance their gas separation performance and processability. This review outlines the research progress of ionization to improve the gas separation performance of typical microporous polymers (e.g., polymers of intrinsic microporosity (PIM), perfluorinated polymers, microporous polyimides, etc.) and summarizes the different ionization methods, including carboxylation, sulfonation, quaternization, and other ionization processes. Additionally, the review also explores the research progress of ionization to regulate the processability, microporosity, and gas separation properties of microporous polymers. Specifically, ionization can effectively tailor the microporosity, improve the solubility coefficients of gas molecules, especially CO 2 , and enhance gas selectivities. In addition, ionization can improve the processability of PIMs and enhance the membrane plasticization resistance. Ionic microporous polymers provide an essential platform for developing energy-efficient and high-performance gas separation membranes.

Hierarchically microporous membranes for highly energy-efficient gas separations

“…66 , Copyright (2020) Elsevier) and (b) plasticization of typical crosslinked polyimide and PIM membranes (Reprinted with permission from Ref. 67 , Copyright (2023) American Chemical Society).…”

Troger's base polymeric membranes for CO2 separation: a review

“…[135][136][137] For TB polymers, on one hand, the easy protonation of the tertiary nitrogen of TB units enables the TB polymer to form a rigid poly-cationic framework, and thus, This journal is © The Royal Society of Chemistry 2023 quaternization is commonly employed to functionalize a TB polymer. 138,139 On the other hand, the incorporation of an imidazole ring, which is prone to quaternization, in the formation of TB polymers is also feasible. Thus, there can be two methods to prepare functionalized TB polymers: pre-functionalization (monomers) and post-functionalization (polymers).…”

“…Thus, there can be two methods to prepare functionalized TB polymers: pre-functionalization (monomers) and post-functionalization (polymers). 138 In terms of the functionalization of monomers, starting from commercially available imidazole, 2-uoronitrobenzene (2-FNB) or 4-uoronitrobenzene (4-FNB), Kammakakam et al 69,140 synthesized the TB base monomers having "ortho"and "para"substituted diimidazole (Im-TB(o) and Im-TB(p)). Then a series of imidazolium-mediated TB-based ionene polymers (Im-TBionene) (shown in Fig.…”

“…Thus, there can be two methods to prepare functionalized TB polymers: pre-functionalization (monomers) and post-functionalization (polymers). 138…”

Preface for Membranes for Sustainability

“…Polymers of intrinsic microporosity (PIMs) are soluble in common organic solvents and can be easily processed into membranes. The functionalization of PIMs with different ionization methods, such as carboxylation, sulfonation, and quaternization, is an effective way to improve their processability and plasticization resistance, as well as tailor their microporous structure for separations including CO 2 capture and separation …”