Mixed-matrix membranes (MMMs) have been investigated to render energy-intensive separations more efficiently by combining the selectivity and permeability performance, robustness, and nonaging properties of the filler with the easy processing, handling, and scaling up of the polymer. However, truly combining all in one single material has proven very challenging. In this work, we filled a commercial polyimide with ultrahigh loadings of a high–aspect ratio, CO 2 -philic Na-SSZ-39 zeolite with a three-dimensional channel system that precisely separates gas molecules. By carefully designing both zeolite and MMM synthesis, we created a gas-percolation highway across a flexible and aging-resistant (more than 1 year) membrane. The combination of a CO 2 -CH 4 mixed-gas selectivity of ~423 and a CO 2 permeability of ~8300 Barrer outperformed all existing polymer-based membranes and even most zeolite-only membranes.
The formation of diaryl ethers is generally achieved via transition metal catalyzed etherification reactions (Ullmann, Chan–Lam, Buchwald–Hartwig) with prefunctionalized aryl halide substrates at elevated temperatures. Herein, we report a protocol for electrochemical C(sp2)–H/O–H cross-dehydrogenative coupling of phenols and tertiary anilines to synthesize diaryl ethers. The C(sp2) H/O–H coupling product can be obtained under metal- and oxidant-free conditions at room temperature in moderate to excellent yield (up to 83% yield) with high regioselectivity (>99% for para-substitution) and with a broad substrate scope (22 examples).
Redox flow batteries (RFB) often operate at extreme pH conditions and may require cooling to prevent high temperatures. The stability of the battery membranes at these extreme pH-values at high temperatures is still largely unknown. In this paper, a systematic screening of the performance and stability of nine commercial membranes at pH 14 and pH ≤ 0 with temperatures up to 80 °C is conducted in an organic aqueous RFB. Swelling, area resistance, diffusion crossover, battery performance and membrane stability after 40–80 °C temperature treatment are shown, after which a recommendation is made for different user scenarios. The Aquivion E98-05 membrane performed best for both the Tiron/2,7-AQDS battery and the DHPS/Fe(CN)6 battery at 40 mA/cm2, with stable results after 1 week of storage at 80 °C. At 80 mA/cm2, E-620-PE performed best in the DHPS/Fe(CN)6 battery, while Sx-050DK performed best in the Tiron/2,7-AQDS battery.
Redox flow batteries (RFBs) are an interesting option for long-term energy storage. A well-performing membrane sits at the heart of the electrochemical battery cell and should effectively mitigate crossover of active species while minimizing resistance. However, current commercial membranes are rather expensive and demonstrate sub-optimal performance, leading to an extensive search for alternatives. Research on membranes for RFBs has long been dominated by dense ion-exchange membranes and porous membranes, both potentially with fillers. In recent years, increased interest in alternative morphologies such as thin-film composites (TFCs) has ignited new research directions. TFCs consist of a thin dense layer on top of a porous support, aiming to merge the advantages of both. Traditionally, TFCs are made using polyamide top layers. In this paper, a novel chemistry is developed with increased chemical stability for RFBs. Poly(vinylbenzyl chloride) is crosslinked interfacially with a diamine, demonstrating for the first time the potential of support-mediated interfacial crosslinking with two immiscible solvents. Optimization of the support, amine crosslinker, reaction time and synthesis procedure allowed a shift of the trade-off between vanadium crossover and proton transport, highlighting the opportunities for this promising TFC chemistry.