In this work we introduce a sustainable membrane-based synthesis–separation platform for enantioselective organocatalysis. An azido derivatized cinchona-squaramide bifunctional catalyst was synthesized and subsequently grafted to the surface of a polybenzimidazole-based nanofiltration membrane. The favorable effect of the covalent graftingdue to the change in geometry and increased secondary interactionson the catalytic activity due to conformational changes was confirmed by quantum chemical calculations. Asymmetric Michael and aza-Michael reactions of 1,3-dicarbonyl and indole, pyrazole, and triazole derivatives to β-nitrostyrene were performed with as high as 99% enantiomeric excess. This report on the enantioselective aza-Michael reaction of pyrazoles and triazoles opens new frontiers in the application of squaramide-based cinchona catalysts. A catalytic membrane cascade reactor was developed for an integrated synthesis–purification process allowing at least 98% product and substrate recovery, and quantitative in situ solvent recycling. The sustainability of the synthetic methodology was assessed through E-factor and carbon footprint.

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Robust, readily scalable, high-flux graphene oxide (GO) mixed matrix composite membranes were developed for organic solvent nanofiltration. Hydroxylated polybenzimidazole was synthesized by N-benzylation of polybenzimidazole with 4-(chloromethyl)benzyl alcohol, which was confirmed by FTIR and NMR spectroscopy. Flat-sheet composite membranes comprising of polybenzimidazoles and 1 or 2 wt % GO were fabricated via conventional blade coating and phase inversion. Subsequently, GO was covalently anchored to the hydroxyl groups of the polymer using a diisocyanate cross-linking agent. The even distribution of GO in the membranes was mapped by visible-light microscopy. Hydroxylation and incorporation of GO in the polymer matrix increased the permeance up to 45.2 ± 1.6 L m h bar in acetone, nearly 5 times higher than the unmodified benchmark membrane. The enhancement in permeance from the addition of GO did not compromise the solute rejection. The composite membranes were found to be tight in seven organic solvents, having molecular weight cut-offs (MWCO) as low as 140 g mol. Permeance increased with increasing solvent polarity, while rejection of a 420 g mol pharmaceutical remained over 93%. The covalent anchoring resulted in robust composite membranes that maintained constant performance over 14 days in a continuous cross-flow configuration.

In order to address the increasing demand for fresh water due to accelerated social and economic growth in the world, water treatment technologies, such as desalination, have been rapidly developed in attempts to safeguard water security. Electromembrane desalination processes, such as electrodialysis and membrane capacitive deionization, belong to a category of desalination technologies, which involve the removal of ions from ionic solutions with the use of electrically charged membranes termed ion exchange membranes. The challenges associated with ion exchange membranes have drawn the attention of many researchers, who have investigated various approaches to enhance their properties. The incorporation of nanomaterials is one of the popular approaches employed. Much research on nanomaterials incorporated ion exchange membranes was conducted for the purpose of fuel cell applications rather than electromembrane desalination. This review reports on the advances in nanomaterials incorporated ion exchange membranes applicable to desalination. The nanomaterials employed in ion exchange membranes fabrication include carbon nanotubes, graphene-based nanomaterials, silica, titanium (IV) oxide, aluminum oxide, zeolite, iron (II, III) oxide, zinc oxide, and silver. The aims of this article are to provide a snap shot of the current status of nanomaterials incorporation in ion exchange membranes, to assess the status of nanomaterials-facilitated ion exchange membranes research for electromembrane desalination, and to stimulate progress in this area.

Reaching beyond the upper limits of electromembrane desalination processes with novel graphene-based nanocomposite anion exchange membranes.

Greener synthetic routes, physical–chemical properties, green metrics performance and applications for the eco-friendly polar aprotic solvent, methyl 5-dimethylamino-2-methyl-5-oxopentanoate (PolarClean).

Membrane capacitive deionization (MCDI) for water desalination is an innovative technique that could help to solve the global water scarcity problem. However, the development of the MCDI field is hindered by the limited choice of ion-exchange membranes. Desalination by MCDI removes the salt (solute) from the water (solvent); this can drastically reduce energy consumption compared to traditional desalination practices such as distillation. Herein, we outline the fabrication and characterization of quaternized anion-exchange membranes (AEMs) based on polymer blends of polyethylenimine (PEI) and polybenzimidazole (PBI) that provides an efficient membrane for MCDI. Flat sheet polymer membranes were prepared by solution casting, heat treatment, and phase inversion, followed by modification to impart anion-exchange character. Scanning electron microscopy (SEM), atomic force microscopy (AFM), nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy were used to characterize the morphology and chemical composition of the membranes. The as-prepared membranes displayed high ion-exchange capacity (IEC), hydrophilicity, permselectivity and low area resistance. Due to the addition of PEI, the high density of quaternary ammonium groups increased the IEC and permselectivity of the membranes, while reducing the area resistance relative to pristine PBI AEMs. Our PEI/PBI membranes were successfully employed in asymmetric MCDI for brackish water desalination and exhibited an increase in both salt adsorption capacity (>3×) and charge efficiency (>2×) relative to membrane-free CDI. The use of quaternized polymer blend membranes could help to achieve greater realization of industrial scale MCDI.

legislated to minimize the discharge of industrial pollutants to protect freshwater resources. [2] One of the largest volumes and the most problematic types of wastewater is the effluent from the textile industry, whose water consumption can reach as high as 216 million m 3 day −1 . [3] Millions of metric tons of synthetic dyes are produced globally every year, with the main demand coming from the textile industry. [4] Exact numbers have not been established, but they surely exceed the commonly cited-even in 2020numbers of "100 000 dyes and 7.5 × 10 5 tons" as those appear as early as 1981. [5] Due to the incomplete binding of the dyes to the fabric material, it is estimated that a significant portion, around 5-20% of the total amount of dyes used remain in the effluent water. [6] The treatment of this dye-laden wastewater is essential for multiple reasons. Some dyes are directly and acutely toxic to the natural water ecosystem, but even those dyes that are not toxic absorb sunlight and thus decrease photosynthesis. [7] This effect, combined with the high oxygen demand from the decomposition of dyes, deprives natural waters of dissolved oxygen. Apart from environmental pollution, many dyes are toxic to humans and cause allergic reactions or even potential mutagenic or carcinogenic effects. [7] Biological and chemical treatment, membrane processes, and adsorption or a combination of these processes are used for the treatment of textile wastewater. Electrospinning technology has attracted attention for the production of adsorptive membranes due to the excellent control it provides over structural properties that can be tailored for specific applications. Owing to their high surface-to-volume ratio, high pore volume, low density, and increased flexibility compared with their film counterparts, [8] electrospun nanofibrous membranes are thus effective adsorbents that can scavenge pollutants. However, most polymers used in the preparation of electrospun membranes, such as cellulose acetate, poly(vinyl alcohol), poly(vinylidene fluoride), or poly(acrylic acid), either have poor adsorptive properties as stand-alone materials due to the lack of high-affinity binding sites or inadequate stability in water. They are therefore mostly used in composites with other materials, such as cyclodextrin [9,10] or polydopamine, [11,12] that provide binding sites for adsorption. Recently, Chen et al. tested multifunctional cellulose acetate nanofibers for the adsorption of ionic dyes. [13]