The potential of polymers of intrinsic microporosity (PIMs) and PIM/graphene composites for pervaporation membranes

Polymers of Intrinsic Microporosity Based on Dibenzodioxin Linkage: Design, Synthesis, Properties, and Applications

The development of polymers of intrinsic microporosity (PIMs) over the last two decades has established them as a distinct class of microporous materials, which combine the attributes of microporous solid materials and the soluble nature of glassy polymers. Due to their solubility in common organic solvents, PIMs are easily processable materials that potentially find application in membrane-based separation, catalysis, ion separation in electrochemical energy storage devices, sensing, etc. Dibenzodioxin linkage, Tröger's base, and imide bond-forming reactions have widely been utilized for synthesis of a large number of PIMs. Among these linkages, however, most of the studies have been based on dibenzodioxin-based PIMs. Therefore, this review focuses precisely on dibenzodioxin linkage chemistry. Herein, the design principles of different rigid and contorted monomer scaffolds are discussed, as well as synthetic strategies of the polymers through dibenzodioxin-forming reactions including copolymerization and postsynthetic modifications, their characteristic properties and potential applications studied so far. Towards the end, the prospects of these materials are examined with respect to their utility in industrial purposes. Further, the structure-property correlation of dibenzodioxin PIMs is analyzed, which is essential for tailored synthesis and tunable properties of these PIMs and their molecular level engineering for enhanced performances making these materials suitable for commercial usage.

Ultramicroporous Polyphenylenes via Diels-Alder Polycondensation Approach

Development of new microporous organic polymers attracts significant attention due to a wide scope of promising applications. In addition, the synthesis of soluble, non-crosslinking polymers of high surface area and uniform microporosity is very challenging, and the methods for soluble microporous polymers formation are rather limited. In this work, we report a new approach to construct porous polyphenylenes which employs the Diels-Alder polycondensation of multifunctional ethynyl-containing monomers of different spatial architecture with bis(cyclopentadienone)s. The resulting polymers were soluble in common organic solvents, and their structure and properties were assessed by NMR, TGA, DSC, and SEC studies. The polymers demonstrated a specific surface area up to 751 m²·g^-1 and ultramicroporous (pore size ≤ 0.6 nm) structure. N₂ and CO₂ adsorption-desorption data revealed that porosity parameters, e.g., specific surface area and pore sizes, can be tuned selectively by varying the type of monomers and reaction conditions.

Crosslinking of Branched PIM-1 and PIM-Py Membranes for Recovery of Toluene from Dimethyl Sulfoxide by Pervaporation

Branched forms of the archetypal polymer of intrinsic microporosity PIM-1 and the pyridinecarbonitrile-containing PIM-Py may be crosslinked under ambient conditions by palladium(II) acetate. Branched PIM-1 can arise in polymerizations of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane with tetrafluoroterephthalonitrile conducted at a high set temperature (160 °C) under conditions, such as high dilution, that lead to a lower-temperature profile over the course of the reaction. Membranes of PIM-1 and PIM-Py crosslinked with palladium acetate are sufficiently stable in organic solvents for use in the recovery of toluene from its mixture with dimethyl sulfoxide (DMSO) by pervaporation at 65 °C. With both PIM-1 and PIM-Py membranes, pervaporation gives high toluene/DMSO separation factors (around 10 with a 77 vol % toluene feed). Detailed analysis shows that the membranes themselves are slightly selective for DMSO and it is the high driving force for toluene evaporation that drives the separation.

Breakthroughs on tailoring pervaporation membranes for water desalination: A review

Due to the increase in worldwide population and urbanization, water scarcity is today one of the tough challenges of society. To date, several ongoing initiatives and strategies are aiming to find feasible alternatives to produce drinking water. Seawater desalination is addressed as a latent alternative to solve such an issue. When dealing with desalination, membrane-based technologies (such as reverse osmosis, membrane distillation, pervaporation, among others) have been successfully proposed. Pervaporation (PV) is likely the membrane operation with the less permeation rate but providing high rejection of salts. Thereby, "membranologists" are extensively working in developing new suitable membranes for pervaporation desalination. Therefore, the goal of this review paper is to elucidate and provide a comprehensive outlook of the most recent works (over the last 5-years) at developing new concepts of membranes (e.g. ultra-thin, mixed matrix/composite and inorganic) for desalination, as well as the relevant strategies in fabricating enhanced PV membranes. At this point, an important emphasis has been paid to the relevant insights in the field. This paper also addresses some principles of PV and the main drawbacks of the technique and its membranes. Through reviewing the literature, the future trends, needs, and recommendations for the new researchers are given.

Continuous Flow Upgrading of Selected C2-C6 Platform Chemicals Derived from Biomass

The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C₂ to C₆ bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethylfurfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.