Biphenyl-based covalent triazine framework-incorporated polydimethylsiloxane membranes with high pervaporation performance for n-butanol recovery

Continuous Covalent Organic Framework Membranes with Ordered Nanochannels as Tunable Transport Layers for Fast Butanol/Water Separation

Polymeric membranes with high permselective performance are desirable for energy-saving bioalcohol separations. However, it remains challenging to design membrane microstructures with low-resistance channels and a thin thickness for fast alcohol transport. Herein, we demonstrate highly crystalline covalent organic framework (COF) membranes with ordered nanochannels as tunable transport layers for efficient butanol/water separation. The thickness was well-regulated by altering the concentration and molar ratio of two aldehyde monomers with different reactivity. The surface-integrated poly(dimethylsiloxane) produced defect-free and hydrophobic COF membranes. The membrane with continuous transport channels exhibited an exceptional flux of up to 18.8 kg m-2 h-1 and a pervaporation separation index of 217.7 kg m-2 h-1 for separating 5 wt % n-butanol/water. The separation efficiency exceeded that of analogous membranes. The calculated mass-transfer coefficient of butanol followed an inverse relationship with the COF membrane thickness. Consequently, this work reveals the great potential of crystalline polymeric membranes with high-density nanopores for biofuel recovery.

Superlithiation Performance of Pyridinium Polymerized Ionic Liquids with Fast Li+ Diffusion Kinetics as Anode Materials for Lithium-Ion Battery

Polymerized ionic liquids (PILs) with super ion diffusion kinetics have aroused considerable attention in rechargeable batteries, which are very promising to solve the problem of the slow ion diffusion kinetics in organic electrode materials. Theoretically, PILs incorporated redox groups are very suitable as anode materials to realize "superlithiation" performance, achieving high lithium storage capacity. In this study, redox pyridinium-based PILs (PILs-Py-400) have been synthesized through trimerization reactions by pyridinium ionic liquids with cyano groups under an appropriate temperature (400 °C). The positively charged skeleton, extended conjugated system, abundant micropores, and amorphous structure for PILs-Py-400 can boost the utilization efficiency of redox sites. A high capacity of 1643 mAh g-1 at 0.1 A g-1 (96.7% of the theoretical capacity) has been obtained, indicating intriguing 13 Li+ redox reactions in per repeating unit of one pyridinium ring, one triazine ring, and one methylene. Moreover, PILs-Py-400 exhibit excellent cycling stability with a capacity of around 1100 mAh g-1 at 1.0 A g-1 after 500 cycles, and the capacity retention is 92.2%.

Controllable hydrogen-bonded poly(dimethylsiloxane) (PDMS) membranes for ultrafast alcohol recovery

The lack of efficient separation membranes limits the development of bio-alcohol purification via a pervaporation process. In this work, novel controllable hydrogen-bonded poly(dimethylsiloxane) (PDMS) membranes are prepared from self-synthesized supramolecular elastomers for alcohol recovery. Different from the conventional covalently-bonded PDMS membranes, the hydrogen-bonding content and therefore the crosslinking degree in the as-synthesized PDMS membranes can be exactly regulated, by the suitable molecular design of the supramolecular elastomers. The effects of hydrogen-bonding content on the flexibility of the polymer chains and the separation performance of the resultant supramolecular membranes are investigated in detail. In comparison with the state-of-the-art polymeric membranes, the novel controllable hydrogen-bonded supramolecular PDMS membrane exhibits ultrahigh fluxes for ethanol (4.1 kg m-2 h-1) and n-butanol (7.7 kg m-2 h-1) recovery from 5 wt% alcohol aqueous solutions at 80 °C, with comparable separation factors. The designed supramolecular elastomer is therefore believed to provide valuable insights into the design of next-generation separation membrane materials for molecular separations.

Pt/WO3 Nanoparticle-Dispersed Polydimethylsiloxane Membranes for Transparent and Flexible Hydrogen Gas Leakage Sensors

Hydrogen gas is a promising, clean, and highly efficient energy source. However, to use combustible H₂ gas safety, high-performance and safe gas leakage sensors are required. In this study, transparent and flexible platinum-catalyst-loaded tungsten trioxide (Pt/WO₃) nanoparticle-dispersed membranes were prepared as H₂ gas leakage sensors. The nanoparticle-dispersed membrane with a Pt:W compositional ratio of 1:13 was transparent and exhibited a sufficient color change in response to H₂ gas. The membrane containing 0.75 wt.% of Pt/WO₃ nanoparticles exhibited high transparency over a wide wavelength range and the largest transmittance change in response to H₂ gas among the others. The heat treatment of the particles at 573 K provided sufficient crystallinity and an accessible area for a gasochromic reaction, resulting in a rapid and sensitive response to the presence of H₂ gas. The lower limit of detection of the optimized Pt/WO₃ nanoparticle-dispersed membrane by naked eye was 0.4%, which was one-tenth of the minimum explosive concentration. This novel membrane was transparent as well as flexible and exhibited a clear and rapid color response to H₂. Therefore, it is an ideal candidate sensor for the safe and easy detection of H₂ gas leakage.