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Hydrogen has the highest gravimetric energy density of any energy carrier and produces water as the only oxidation product, making it extremely attractive for both transportation and stationary power applications. However, its low volumetric energy density causes considerable difficulties, inspiring intense efforts to develop chemical-based storage using metal hydrides, liquid organic hydrogen carriers and sorbents. The controlled uptake and release of hydrogen by these materials can be described as a series of challenges: optimal properties fall within a narrow range, can only be found in few materials and often involve important trade-offs. In addition, a greater understanding of the complex kinetics, mass transport and microstructural phenomena associated with hydrogen uptake and release is needed. The goal of this Perspective is to delineate potential use cases, define key challenges and show that solutions will involve a nexus of several subdisciplines of chemistry, including catalysis, data science, nanoscience, interfacial phenomena and dynamic or phase-change materials. Hydrogen, which possesses the highest gravimetric energy density of any energy carrier, is attractive for both mobile and stationary power, but its low volumetric energy density poses major storage and transport challenges. This Perspective delineates potential use cases and defines the challenges facing the development of materials for efficient hydrogen storage.

C(sp3)-rich bicyclic hydrocarbon scaffolds, as exemplified by bicyclo[1.1.1]pentanes, play an increasingly high-profile role as saturated bioisosteres of benzenoids in medicinal chemistry and crop science. Substituted bicyclo[2.1.1]hexanes (BCHs) are emerging bicyclic hydrocarbon bioisosteres for ortho- and meta-substituted benzenes, but are difficult to access. Therefore, a general synthetic route to BCHs is needed if their potential as bioisosteres is to be realized. Here we describe a broadly applicable catalytic approach that delivers substituted BCHs by intermolecular coupling between olefins and bicyclo[1.1.0]butyl (BCB) ketones. The SmI2–catalysed process works for a wide range of electron-deficient alkenes and substituted BCB ketones, operates with SmI2 loadings as low as 5 mol% and is underpinned by a radical relay mechanism that is supported by density functional theory calculations. The product BCH ketones have been shown to be versatile synthetic intermediates through selective downstream manipulation and the expedient synthesis of a saturated hydrocarbon analogue of the broad-spectrum antimicrobial, phthalylsulfathiazole.Substituted bicyclo[2.1.1]hexanes (BCHs) are emerging bicyclic hydrocarbon bioisosteres for ortho- and meta-substituted benzenes, but are difficult to access. Now a SmI2-catalysed intermolecular coupling of bicyclo[1.1.0]butyl ketones and alkenes provides a general approach to access substituted BCHs, thus promoting their widespread use in medicinal chemistry and crop science.

Transition-metal single-atom catalysts present extraordinary activity per metal atomic site, but suffer from low metal-atom densities (typically less than 5 wt% or 1 at.%), which limits their overall catalytic performance. Here we report a general method for the synthesis of single-atom catalysts with high transition-metal-atom loadings of up to 40 wt% or 3.8 at.%, representing several-fold improvements compared to benchmarks in the literature. Graphene quantum dots, later interweaved into a carbon matrix, were used as a support, providing numerous anchoring sites and thus facilitating the generation of high densities of transition-metal atoms with sufficient spacing between the metal atoms to avoid aggregation. A significant increase in activity in electrochemical CO2 reduction (used as a representative reaction) was demonstrated on a Ni single-atom catalyst with increased Ni loading.Transition-metal single-atom catalysts display excellent activity per metal atom site, but suffer from low metal atom densities (typically less than 5 wt% or 1 at.%), which limits their overall catalytic performance. Now, the use of a graphene-quantum-dot primary support, later interweaved into a carbon matrix, has enabled the synthesis of single-atom catalysts with high transition-metal atom loadings of up to 40 wt% or 3.84 at.%.

Ferroptosis, an iron-dependent form of cell death driven by lipid peroxidation, provides a potential treatment avenue for drug-resistant cancers and may play a role in the pathology of some degenerative diseases. Identifying the subcellular membranes essential for ferroptosis and the sequence of their peroxidation will illuminate drug discovery strategies and ferroptosis-relevant disease mechanisms. In this study, we employed fluorescence and stimulated Raman scattering imaging to examine the structure–activity–distribution relationship of ferroptosis-modulating compounds. We found that, although lipid peroxidation in various subcellular membranes can induce ferroptosis, the endoplasmic reticulum (ER) membrane is a key site of lipid peroxidation. Our results suggest an ordered progression model of membrane peroxidation during ferroptosis that accumulates initially in the ER membrane and later in the plasma membrane. Thus, the design of ER-targeted inhibitors and inducers of ferroptosis may be used to optimally control the dynamics of lipid peroxidation in cells undergoing ferroptosis. Ferroptosis is a lipid-peroxide-driven cell death with promising therapeutic applications. Although peroxidation of various subcellular membranes can initiate ferroptosis, the authors found that the endoplasmic reticulum is an essential site.

Understanding and manipulating gas bubble evolution during electrochemical water splitting is a crucial strategy for optimizing the electrode/electrolyte/gas bubble interface. Here gas bubble dynamics are investigated during the hydrogen evolution reaction on a well-defined platinum microelectrode by varying the electrolyte composition. We find that the microbubble coalescence efficiency follows the Hofmeister series of anions in the electrolyte. This dependency yields very different types of H2 gas bubble evolution in different electrolytes, ranging from periodic detachment of a single H2 gas bubble in sulfuric acid to aperiodic detachment of small H2 gas bubbles in perchloric acid. Our results indicate that the solutal Marangoni convection, induced by the anion concentration gradient developing during the reaction, plays a critical role at practical current density conditions. The resulting Marangoni force on the H2 gas bubble and the bubble departure diameter therefore depend on how surface tension varies with concentration for different electrolytes. This insight provides new avenues for controlling bubble dynamics during electrochemical gas bubble formation.Although gas bubble dynamics during electrochemical processes dramatically affect performance, the fundamental understanding and manipulation of such dynamics have been limited. Now, electrolyte composition is found to be a key factor in inducing a solutal Marangoni instability that impacts both H2 gas detachment and coalescence between H2 microbubbles.

Recently, there has been an increased interest in sodium-ion batteries (SIBs), in which cathodes that directly determine the performance of batteries play a critical role. Among the cathode materials, layered oxide cathodes are the most fascinating electrode materials for SIBs. However, irreversible phase transition, low capacity, poor air stability, and inferior cycling stability limit the application of layered oxides. In this study, hollow P2-Na 0.62 K 0.05 Mn 0.7 Ni 0.2 Co 0.1 O 2 polyhedra consisting of nanosheets with exposed stable {001} facets and a small amount of large-size K + ions partly replacing Na + ions were successfully obtained. By virtue of the high redox potential of Ni 2+/4+ , it can be stored in air for several days. It also exhibits a high discharge capacity of 115.0 mA h g −1 after 100 cycles at 100 mA g −1 . A preeminent discharge capacity of 104.1 mA h g −1 can be achieved even at 500 mA g −1 . Results showed that such performances are related to the block of phase transition from P2 to O2 and to the riveting of K + ions, which expands the interlayer space ( d (O—Na—O) ) and accelerates the transfer of sodium. Thus, the P2-Na 0.62 K 0.05 Mn 0.7 Ni 0.2 Co 0.1 O 2 cathode is one of the promising cathode materials for SIBs.

Lithium metal batteries represent a promising technology for next-generation energy storage, but they still suffer from poor cycle life due to lithium dendrite formation and cathode cracking. Fluorinated solvents can improve battery longevity by improving LiF content in the solid–electrolyte interphase; however, the high cost and environmental concerns of fluorinated solvents limit battery viability. Here we designed a series of fluorine-free solvents through the methylation of 1,2-dimethoxyethane, which promotes inorganic LiF-rich interphase formation through anion reduction and achieves high oxidation stability. The anion-derived LiF interphases suppress lithium dendrite growth on the lithium anode and minimize cathode cracking under high-voltage operation. The Li + -solvent structure is investigated through in situ techniques and simulations to draw correlations between the interphase compositions and electrochemical performances. The methylation strategy provides an alternative pathway for electrolyte engineering towards high-voltage electrolytes while reducing dependence on expensive fluorinated solvents. Lithium metal batteries are an attractive energy storage technology, but their development relies on the complex interplay between the components’ chemical, physical and mechanical properties. Now, selective methylation of dimethoxyethane ether electrolytes is shown to improve electrolyte, electrode and solid–electrolyte interphase stabilities to enable high-performance 4.3 V lithium metal batteries.

In 1931, Erich Hückel published a landmark paper — the seed of the now famous 4 n + 2 rule for aromaticity in annulenes that bears his name. Electron counting has since been extended to other classes of compounds, resulting in a multitude of rules aiming to capture the concept of aromaticity and its impact in chemistry.

Statistical tools based on machine learning are becoming integrated into chemistry research workflows. We discuss the elements necessary to train reliable, repeatable and reproducible models, and recommend a set of guidelines for machine learning reports.

Porous materials are very promising for the development of cost- and energy-efficient separation processes, such as for the purification of ethylene from ethylene/ethane mixture—an important but currently challenging industrial process. Here we report a microporous hydrogen-bonded organic framework that takes up ethylene with very good selectivity over ethane through a gating mechanism. The material consists of tetracyano-bicarbazole building blocks held together through intermolecular CN···H–C hydrogen bonding interactions, and forms as a threefold-interpenetrated framework with pores of suitable size for the selective capture of ethylene. The hydrogen-bonded organic framework exhibits a gating mechanism in which the threshold pressure required for guest uptake varies with the temperature. Ethylene/ethane separation is validated by breakthrough experiments with high purity of ethylene (99.1%) at 333 K. Hydrogen-bonded organic frameworks are usually not robust, yet this material was stable under harsh conditions, including exposure to strong acidity, basicity and a variety of highly polar solvents.Porous materials are promising candidates for the cost- and energy-efficient separation of ethylene and ethane from gas mixtures: an important but challenging industrial process. Now, a hydrogen-bonded organic framework has been reported that is stable under harsh conditions and can take up ethylene at practical temperatures—with very high selectivity over ethane—through a gating mechanism.