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Recent demonstrations of melting in the metal-organic framework (MOF) family have created interest in the interfacial domain between inorganic glasses and amorphous organic polymers. The chemical and physical behaviour of porous hybrid liquids and glasses is of particular interest, though opportunities are limited by the inaccessible melting temperatures of many MOFs. Here, we show that the processing technique of flux melting, 'borrowed' from the inorganic domain, may be applied in order to melt ZIF-8, a material which does not possess an accessible liquid state in the pure form. Effectively, we employ the high-temperature liquid state of one MOF as a solvent for a secondary, non-melting MOF component. Differential scanning calorimetry, small- and wide-angle X-ray scattering, electron microscopy and X-ray total scattering techniques are used to show the flux melting of the crystalline component within the liquid. Gas adsorption and positron annihilation lifetime spectroscopy measurements show that this results in enhanced, accessible porosity to a range of guest molecules in the resultant flux melted MOF glass.

Metal–organic frameworks (MOFs) exhibit large surface areas and low thermal conductivity, making them promising for thermoelectric generation. However, their limited electrical conductivity poses a significant hurdle to be practically useful. Traditionally, enhancing the electrical conductivity of MOFs typically comes at the cost of reducing surface area, thereby increasing thermal conductivity. This study introduces an approach to simultaneously boost the electrical conductivity and porosity of a MOF‐based material while maintaining remarkably low thermal conductivity. The electrically conductive poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) is deployed to nucleate the growth of Cu3(BTC)2 (or simply CuBTC, where BTC = benzene‐1,3,5‐tricarboxylic acid), resulting in the synthesis of composites labeled CPP‐y (where y denotes wt% PEDOT:PSS). Predictably, the CPP‐y composites are more electrically conductive than pure CuBTC, achieving an electrical conductivity exceeding 1.40 S cm−1 at room temperature. Furthermore, the CPP‐y composites exhibit consistently high Brunauer–Emmett–Teller (BET) surface areas of ≈1600 m2 g−1, comparable to pristine CuBTC, while maintaining thermal conductivities below 0.04 W m−1 K−1 at room temperature. With a high Seebeck coefficient in the range 180–373 µV K−1, CPP‐15 and CPP‐23 demonstrate a figure‐of‐merit (zT) of 0.25 and 0.11, respectively, at 285 K, marking a substantial achievement for MOF‐based materials. [ABSTRACT FROM AUTHOR]

Free-volume of polymers governs transport of penetrants through polymeric films. Control over free-volume is thus important for the development of better membranes for a wide variety of applications such as gas separations, pharmaceutical purifications and energy storage. To date, methodologies used to create materials with different amounts of free-volume are based primarily on chemical synthesis of new polymers. Here we report a simple methodology for generating free-volume based on the self-assembly of polyethylene-b-polydimethylsiloxane-b-polyethylene triblock copolymers. We have used this method to fabricate a series of membranes with identical compositions but with different amounts of free-volume. We use the term artificial free-volume to refer to the additional free-volume created by self-assembly. The effect of artificial free-volume on selective transport through the membranes was tested using butanol/water and ethanol/water mixtures due to their importance in biofuel production. We found that the introduction of artificial free-volume improves both alcohol permeability and selectivity.

Solid polymer electrolytes (SPEs) are long sought after for versatile applications due to their low cost, light weight, flexibility, ease of scale-up, and low interfacial impedance. However, obtaining SPEs with high Li+ conductivity (σ+) and high voltage stability to avoid concentrated polarization and premature capacity loss has proven challenging. Here a stretchable dry-SPE is reported with a semi-interpenetrating, supermolecular architecture consisting of a cross-linked polyethylene oxide (PEO) tetra-network and an alternating copolymer poly(ethylene oxide-alt-butylene terephthalate). Such a unique supermolecular architecture suppresses the formation of Li+/PEO intermolecular complex and enhances the oxidation stability of PEO-based electrolyte, thus maintaining high chain segmental motion even with high salt loading (up to 50 wt%) and achieving a wide electrochemical stability window of 5.3 V. These merits enable the simultaneous accomplishment of high ionic conductivity and high Li+ transference number (t+) to enhance the energy efficiency of energy storage device, and electrochemical stability. [ABSTRACT FROM AUTHOR]

The significant interest in developing hierarchical materials to overcome the traditional limitations of microporous catalysts, has led to a wide range of synthesis protocols being developed. In this work we modify traditional synthetic procedures known to yield highly crystalline microporous materials, by adding a hydrocarbon surfactant, leading to the formation of hierarchical solid-acid zeotypes; silicoaluminophosphates. We show for the first time, that small angle neutron scattering can build a qualitative description of the porosity in hierarchical materials, probing the exact nature of the micropores and mesopores within our system, that can be adapted to any hierarchical system. When combined with positron annihilation lifetime spectroscopy and porosimetry measurements we gain greater insight by exploring the accessibility and interconnectivity of the micropores and mesopores. We show that by varying the quantity of mesoporogen the size and nature of the mesopores can be finely tuned. Further, small angle neutron scattering reveals that mesopores are lined with a silica layer, that strongly influences the accessibility of the micropores. As such we show that our hierarchical materials contain distinct micropores housing stronger Brønsted acid sites, whilst the mesopores are lined with weaker silanol groups. This is complemented with a catalytic study focussing on n-butane isomerisation and ethanol dehydration that highlights the advantages and disadvantages of this design and further probes the influence of these bimodal porous systems on catalytic performance. [ABSTRACT FROM AUTHOR]

Physical aging is a slow structural relaxation process characteristic of glassy polymers that results in reduced membrane permeabilities. In this study, PIM-1, the archetypal polymer of intrinsic microporosity (PIM), was post-synthetically modified to introduce components that are known to influence physical aging, such as hydrogen bonds and crosslinks. The effects of physical aging were monitored by permeation and sorption experiments, and structural changes were examined by positron annihilation lifetime spectroscopy (PALS) and other characterization techniques. The results suggest that higher initial fractional free volume is the primary factor contributing to higher rates of physical aging and that the introduction of hydrogen bonds and crosslinks reduces the initial free volume of PIM-1. In contrast, structural factors such as hydrogen bonds and crosslinks were the key factors in determining how permselectivity changed with physical aging. This study provides useful structure–property correlations and design principles related to free volume, hydrogen bonds, and crosslinks on physical aging behavior of microporous polymer membranes. [ABSTRACT FROM AUTHOR]

The regulation of water content in polymeric membranes is important in a number of applications, such as reverse electrodialysis and proton-exchange fuel-cell membranes. External thermal and water management systems add both mass and size to systems, and so intrinsic mechanisms of retaining water and maintaining ionic transport (1-3) in such membranes are particularly important for applications where small system size is important. For example, in proton-exchange membrane fuel cells, where water retention in the membrane is crucial for efficient transport of hydrated ions (1,4-7), by operating the cells at higher temperatures without external humidification, the membrane is self-humidified with water generated by electrochemical reactions (5,8). Here we report an alternative solution that does not rely on external regulation of water supply or high temperatures. Water content in hydrocarbon polymer membranes is regulated through nanometre-scale cracks ('nanocracks') in a hydrophobic surface coating. These cracks work as nanoscale valves to retard water desorption and to maintain ion conductivity in the membrane on dehumidification. Hydrocarbon fuel-cell membranes with surface nanocrack coatings operated at intermediate temperatures show improved electrochemical performance, and coated reverse-electrodialysis membranes show enhanced ionic selectivity with low bulk resistance., Ion-exchange membranes are used in a wide range of applications for separations, energy conversion and energy storage systems, where selective barrier properties are essential for high performance in membrane-integrated systems. [...]