Oriented Zeolitic imidazolate framework membranes within polymeric matrices for effective N2/CO2 separation

Rational Design of Superhydrophobic and Flexible Oriented MOF Nanosheet Membrane for Highly Efficient Ethanol-Water Separation

Highly efficient and energy-conserving membrane separation technology holds vast potential for applications in the bioethanol production process. This work reports a strategy for the fast preparation of an oriented and flexible two-dimensional metal-organic framework (MOF) nanosheet membrane by an electrochemical deposition method. The oriented MOF nanosheet membrane growth, followed by spin-coating of polydimethylsiloxane, resulted in an efficiently formed superhydrophobic and ethanol affinity membrane for separating ethanol from aqueous solution. Vertically aligned MOF nanosheets with strong ethanol affinity and superhydrophobic membrane surfaces simultaneously promote the transport process, thus delivering a relatively high flux of 1.63 kg·m-2·h-1 and good separation factor of 14.89 in the pervaporation of 5 wt % ethanol aqueous solution. The oriented arrangement of MOF nanosheets combined with polydimethylsiloxane can significantly enhance the pervaporation selectivity and flux, creating a preferential pathway for the production of biofuel.

Development of cellulose-based self-healing hydrogel smart packaging for fish preservation and freshness indication

Biomass-based composite packaging materials loaded with functional fillers have good application prospects in food preservation and freshness detection. Self-healing hydrogel packaging films based on nanocellulose (CNF), polyvinyl alcohol (PVA), and ZIF-8 embedded with curcumin (Cur@ZIF-8) were developed in this study. The synthesis of Cur@ZIF-8 was demonstrated by characterization experiments. The addition of Cur@ZIF-8 enhanced the water vapor barrier property, tensile strength, and elongation at break of hydrogel films by 49.2 %, 193.5 %, and 172.9 %, respectively, and endowed them with excellent antimicrobial, antioxidant, and ammonia sensitivity. In packaging tests with fish, hydrogel films loaded with Cur@ZIF-8 inhibited spoilage and microbial growth to extend the shelf life of fish to 9 days, and the color change of hydrogel films allowed for real-time monitoring of fish freshness. This study provided a new solution for smart packaging materials with dual functions of preservation and freshness indication.

Effective Separation of CO2 Using Metal-Incorporated rGO Membranes

Graphene-based materials, primarily graphene oxide (GO), have shown excellent separation and purification characteristics. Precise molecular sieving is potentially possible using graphene oxide-based membranes, if the porosity can be matched with the kinetic diameters of the gas molecules, which is possible via the tuning of graphene oxide interlayer spacing to take advantage of gas species interactions with graphene oxide channels. Here, highly effective separation of gases from their mixtures by using uniquely tailored porosity in mildly reduced graphene oxide (rGO) based membranes is reported. The gas permeation experiments, adsorption measurement, and density functional theory calculations show that this membrane preparation method allows tuning the selectivity for targeted molecules via the intercalation of specific transition metal ions. In particular, rGO membranes intercalated with Fe ions that offer ordered porosity, show excellent reproducible N₂ /CO₂ selectivity of ≈97 at 110 mbar, which is an unprecedented value for graphene-based membranes. By exploring the impact of Fe intercalated rGO membranes, it is revealed that the increasing transmembrane pressure leads to a transition of N₂ diffusion mode from Maxwell-Stefan type to Knudsen type. This study will lead to new avenues for the applications of graphene for efficiently separating CO₂ from N₂ and other gases.

Molecular Modeling Investigations of Sorption and Diffusion of Small Molecules in Glassy Polymers

With a wide range of applications, from energy and environmental engineering, such as in gas separations and water purification, to biomedical engineering and packaging, glassy polymeric materials remain in the core of novel membrane and state-of the art barrier technologies. This review focuses on molecular simulation methodologies implemented for the study of sorption and diffusion of small molecules in dense glassy polymeric systems. Basic concepts are introduced and systematic methods for the generation of realistic polymer configurations are briefly presented. Challenges related to the long length and time scale phenomena that govern the permeation process in the glassy polymer matrix are described and molecular simulation approaches developed to address the multiscale problem at hand are discussed.