Molecular vanadium oxides, or polyoxovanadates (POVs), have recently emerged as a new class of molecular energy conversion/storage materials, which combine diverse, chemically tunable redox behavior and reversible multielectron storage capabilities. This Review explores current challenges, major breakthroughs, and future opportunities in the use of POVs for energy conversion and storage. The reactivity, advantages, and limitations of POVs are explored, with a focus on their use in lithium and post‐lithium‐ion batteries, redox‐flow batteries, and light‐driven energy conversion. Finally, emerging themes and new research directions are critically assessed to provide inspiration for how this promising materials class can advance research in sustainable energy technologies.

Filtration is an established water-purification technology.H owever,d ue to lowf low rates,t he filtration of large volumes of water is often not practical. Herein, we report an alternative purification approach in whichamagnetic nanoparticle composite is used to remove organic, inorganic, microbial, and microplastics pollutants from water.T he composite is based on ap olyoxometalate ionic liquid (POM-IL) adsorbed onto magnetic microporous core-shell Fe 2 O 3 / SiO 2 particles,g iving am agnetic POM-supported ionic liquid phase (magPOM-SILP). Efficient, often quantitative removal of several typical surface water pollutants is reported together with facile removal of the particles using apermanent magnet. Tuning of the composite components could lead to new materials for centralized and decentralized water purification systems.

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The enhanced redox-activity of a molecular vanadium oxide cluster upon functionalization with redox-inert Ca2+ ions is reported together with initial insights into its performance as a lithium ion battery cathode.

Low-valent iron centers are critical intermediates in chemical and bio-chemical processes. Herein, we show the first example of a low-valent Fe center stabilized in a high-valent polyoxometalate framework. Electrochemical studies show that the Fe -functionalized molecular vanadium(V) oxide (DMA)[Fe ClV O Cl] (DMA=dimethylammonium) features two well-defined, reversible, iron-based electrochemical reductions which cleanly yield the Fe species (DMA)[Fe ClV O Cl] . Experimental and theoretical studies including electron paramagnetic resonance spectroscopy and density functional theory computations verify the formation of the Fe species. The study presents the first example for the seemingly paradoxical embedding of low-valent metal species in high-valent metal oxide anions and opens new avenues for reductive electron transfer catalysis by polyoxometalates.

The visible‐light‐driven hydrogen evolution reaction (HER) by covalent photosensitizer–catalyst dyads is one of the most elegant concepts in supramolecular homogeneous solar energy conversion. The intricacies of catalyst reactivity and photosensitizer–catalyst interactions require a detailed fundamental understanding of the system to rationalize the observed reactivities. Here, we report three dyads based on the covalent imine‐bond linkage of an iridium photosensitizer and an organo‐functionalized Anderson polyoxometalate anion [MMo6O18{(OCH2)3CNH2}2]3− (M=Mn3+, Fe3+, Co3+). Modification of the central metal ion M is used to modulate the HER activity. Detailed theoretical and experimental studies examine the role of the central metal ion M and provide critical understanding of the redox activity and light‐driven HER activity of the novel dyads. Thus, the study enables a knowledge‐based optimization of HER dyads by chemical modification of the reactive metal oxide components.

Molecular vanadium oxides – polyoxovanadates (POVs) – have recently received widespread interest as new, high performance active materials in lithium ion and sodium ion battery electrodes. This is due to their low molecular weight and their high redox activity. However, little attention has been paid to the structural and chemical stability of the POVs under typical electrode fabrication processes. Here, we report how molecular polyoxovanadates can be differentiated from solid‐state vanadium oxides as active materials in battery electrodes using combined spectroscopic, X‐ray diffraction and element‐analytical data. Our study highlights that novel electrode fabrication processes are required as prototype POVs are not stable under classical fabrication conditions. We explore POV degradation pathways and show how thermal POV conversion leads to the formation of layered solid‐state lithium vanadium oxide phases. A facile protocol is presented to detect and prevent POV degradation. In future, this will enable energy materials science to unambiguously identify and use molecular or solid‐state vanadium oxides as next‐generation active materials in lithium or post‐lithium battery electrodes.

The solid-state stabilization of a molecular vanadium oxide cluster using molecular crystal engineering is reported together with its performance in electrochemical energy storage.