In-situ generation of polymer molecular sieves in polymer membranes for highly selective gas separation

ZIF-8 @polycarbonate nanocomposite membranes for improved permeability and selectivity for hydrogen gas

Through this work, we are reporting high-performance ZIF-8 @polycarbonate nanocomposite membranes with satisfactory structural stability for improving the gas separation performance. ZIF-8 nanoparticles were synthesised using the wet chemical route with cubic morphology and controlled size using CTAB as a surfactant. The membranes were prepared using the solution casting method by adding ZIF-8 filler at various concentrations. The synthesised filler material and MMMs were characterised through X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and RAMAN spectroscopy techniques. The gas separation measurements were taken using H2, CO2, and N2 gas in the purest form. The SEM results confirm the formation of spherulite-like morphology with the addition of ZIF-8 due to the crystallisation of the polymer, which increased the membrane's free volume and opened up additional pathways for the transportation of the gas molecules. The gas separation results confirmed that the 15 wt% ZIF-8/PC nanocomposite membrane showed the maximum H2 permeability of 180,970 barrer with an increment of 316.03%, while H2/CO2 and H2/N2 selectivity showed the increments of 89.43% and 103.64%, respectively. Therefore, this PC/ZIF-8 system seems to be a promising approach to developing new H2 selective membranes with high gas permeability and gas selectivity values.

In situ nanoarchitectonics of magnesium hydroxide particles for property regulation of carboxymethyl cellulose/poly(vinyl alcohol) aerogels

Carboxymethyl cellulose (CMC)-based aerogels with low density, low thermal conductivity, and biodegradability are promising candidates for environmentally friendly heat-insulating materials. However, the application of CMC-based aerogels as insulation materials in building exterior walls is limited by the high water sensitivity, poor mechanical properties and high flammability of these aerogels. In this work, a simple hydration method was used to generate magnesium hydroxide (MH) directly from CMC/polyvinyl alcohol (PVA) mixed sol with active MgO obtained by calcined magnesite as the raw material. A series of composite aerogels with different MH contents were prepared through the freeze-drying method. Scanning electron microscopy showed that nanoflower-like MH was successfully synthesised in situ in the 3D porous polymer aerogel matrix. Compared with the mechanical properties and water resistance of the original CMC/PVA composite aerogels, those of the composite aerogels were significantly improved. In addition, the flame retardancy of the CMC/PVA composite aerogels was greatly enhanced by the introduction of MH into the polymer matrix, and the limiting oxygen index reached 35.5% when the MH loading was 60%.

Recent Progress in Mixed-Matrix Membranes for Hydrogen Separation

Membrane separation is a compelling technology for hydrogen separation. Among the different types of membranes used to date, the mixed-matrix membranes (MMMs) are one of the most widely used approaches for enhancing separation performances and surpassing the Robeson upper bound limits for polymeric membranes. In this review, we focus on the recent progress in MMMs for hydrogen separation. The discussion first starts with a background introduction of the current hydrogen generation technologies, followed by a comparison between the membrane technology and other hydrogen purification technologies. Thereafter, state-of-the-art MMMs, comprising emerging filler materials that include zeolites, metal-organic frameworks, covalent organic frameworks, and graphene-based materials, are highlighted. The binary filler strategy, which uses two filler materials to create synergistic enhancements in MMMs, is also described. A critical evaluation on the performances of the MMMs is then considered in context, before we conclude with our perspectives on how MMMs for hydrogen separation can advance moving forward.