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In recent years, European Union member states have hastened energy policy deliberations to address supply and sustainability concerns, placing a significant emphasis on nuclear energy as a means to achieve decarbonization goals. However, despite its significant role in power generation, nuclear energy faces significant challenges linked to fuel reprocessing and waste disposal, that hinder its broader expansion. In this context, the separation of technetium represents a concerning issue. Indeed, technetium's catalytic activity can impede the extraction of uranium, neptunium, and plutonium, affecting waste reprocessing efficiency. Additionally, the stable form of technetium in aerobic conditions, pertechnetate (TcO 4 - ), poses risks of groundwater contamination due to its mobility and solubility. Hence, sensing and separation of TcO 4 - is imperative for both nuclear fuel processing and minimising radioactive contamination in the environment. However, the binding of TcO 4 - and its separation from contaminated solutions present challenges due to the acidic (or basic) waste components and the high ionic strength in real matrices. Supramolecular chemists have addressed these issues by designing receptors inspired by molecular recognition principles. This article explores recent advancements and future directions in TcO 4 - sensing and separation (using extraction and sorption) with a focus on molecular hosts. Metal-organic receptors will also be discussed., (© 2024 Wiley-VCH GmbH.)

The synthesis and characterization of a novel film-forming organic cage and of its smaller analogue are here described. While the small cage produced single crystals suitable for X-ray diffraction studies, the large one was isolated as a dense film. Due to its remarkable film-forming properties, this latter cage could be solution processed into transparent thin-layer films and mechanically stable dense self-standing membranes of controllable thickness. Thanks to these peculiar features, the membranes were also successfully tested for gas permeation, reporting a behavior similar to that found with stiff glassy polymers such as polymers of intrinsic microporosity or polyimides. Given the growing interest in the development of molecular-based membranes, for example for separation technologies and functional coatings, the properties of this organic cage were investigated by thorough analysis of their structural, thermal, mechanical and gas transport properties, and by detailed atomistic simulations., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Two novel imide/imine-based organic cages have been prepared and studied as materials for the selective separation of CO 2 from N 2 and CH 4 under vacuum swing adsorption conditions. Gas adsorption on the new compounds showed selectivity for CO 2 over N 2 and CH 4 . The cages were also tested as fillers in mixed-matrix membranes for gas separation. Dense and robust membranes were obtained by loading the cages in either Matrimid® or PEEK-WC polymers. Improved gas-transport properties and selectivity for CO 2 were achieved compared to the neat polymer membranes., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Invited for the cover of this issue are the groups of Valeria Amendola at the University of Pavia, Mariolino Carta at the University of Swansea, and Johannes C. Jansen at the CNR-ITM. The image depicts one of the novel imide/imine organic cages that were employed as fillers in mixed-matrix membranes for the selective separation of CO 2 from N 2 and CH 4 . Read the full text of the article at 10.1002/chem.202201631., (© 2022 Wiley-VCH GmbH.)