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Polyoxometalate (POM)-based materials are ideal candidates for implementing molecular memories, and rational POM molecule design is key to higher resistive switching (RS) performance. In this work, in order to obtain a deep structure–property correlation of POM-based memristors, three Anderson-based hybrids, i.e. two-component hybrids (MV)3(MnMo6O18L2)2·4DMF (1) and (MV)2[Cu(DMF)2](MnMo6O18L1)2·6DMF (2), and the three-component one (MV)2(Cu2I3)(MnMo6O18L2)·4CH3CN (3) (L = 2-(hydroxymethyl)-2-(pyridine-4-yl)-1,3-propanediol) have been structurally determined. These hybrids together with the precursors (methyl viologen (MV2+), CuI, and (MnMo6O18L2)) were further fabricated as memristors with the structure of ITO/active layer/Ag. Interestingly, three precursors are RS silent or have bad RS performance, but the incorporation of MV2+ in 1 and 2 can trigger the RS performances, and the further decoration of iodocuprate in 3 can render enhanced RS behavior (ON/OFF ratio: 2.32 × 102) with high thermal-tolerance temperature (240 °C) and extremely long-term stability. The RS mechanism could be assigned to the valence change (VC) induced by oxygen vacancy migrations. The presence of air-stable (MnMo6O18L2)3−-MV2+ donor–acceptor couples can stabilize the oxygen vacancies, which not only trigger the RS behaviors in ITO/1/Ag and ITO/2/Ag, but also result in extremely long-term stability in ITO/3/Ag. Besides, the oxygen vacancies can also be stabilized by Cu2I3 with intense cuprophilic interactions, which corresponds to enhanced RS properties in ITO/3/Ag. This mechanism could be validated by the following structural characters in 3: the stronger POM-MV2+ interactions, the better planarity of MV2+, the very short Cu⋯Cu distances and the ABAB-type packing fashion. The structure–property correlation in this work can provide a new strategy for the development of highly efficient and reliable memristors. [ABSTRACT FROM AUTHOR]

Atomically precise low‐nuclearity (n<10) silver nanoclusters (AgNCs) have garnered significant interest due to their size‐dependent optical properties and diverse applications. However, their synthesis has remained challenging, primarily due to their inherent instability. The present study introduces a new feasible approach for clustering silver ions utilizing highly negative and redox‐inert polyoxoniobates (PONbs) as all‐inorganic ligands. This strategy not only enables the creation of novel Ag‐PONb composite nanoclusters but also facilitates the synthesis of stable low‐nuclearity AgNCs. Using this method, we have successfully synthesized a small octanuclear rhombic [Ag8]6+ AgNC stabilized by six highly negative [LiNb27O75]14− polyoxoanions. This marks the first PONb‐protected superatomic AgNC, designated as {Ag8@(LiNb27O75)6} (Ag8@Nb162), with an aesthetically spherical core–shell structure. The crystalline Ag8@Nb162 is stable under ambient conditions, What's more, it is water‐soluble and able to maintain its molecular cluster structure intact in water. Further, the stable small [Ag8]6+ AgNC has interesting temperature‐ and pH‐dependent reversible fluorescence response, based on which a multiple optical encryption mode for anti‐counterfeit technology was demonstrated. This work offers a promising avenue for the synthesis of fascinating and stable PONb‐protected AgNCs and sheds light on the development of new‐type optical functional materials. [ABSTRACT FROM AUTHOR]

Two inorganic–organic hybrid polyoxotantalates, H4[Na(H2O)5]2[CoII(en)3]2{[CoIII(en)]2(Ta6O19)2}·22H2O (1) and H2K2Na6 (H2O)24{[CoIII(en)]2(Ta6O19)2}·33H2O (2) have been constructed from {[CoIII(en)(Ta6O19)]2}10− ({Co2Ta12}) dimers. Compound 1 has a three-dimensional supramolecular framework with a pcu-type topology. Compound 2 possesses a three-dimensional structure composed of {Co2Ta12} dimers and alkali metal ions (Na+/K+) via coordination bonds. Polyoxotantalates 1 and 2 have been used as active materials for ITO/1/Ag and ITO/2/Ag RRAM devices. These devices exhibit stable non-volatile storage behavior and rewritable resistive switching with high ON/OFF ratios of 1.43 × 103 and 2.17 × 104 for 1-based and 2-based RRAM devices, respectively, and stable cyclic performance during 100-cycle stability tests. This discovery opens up new opportunities for the development of electrical bistability materials. [ABSTRACT FROM AUTHOR]

An inorganic hexalanthanide-oxo-cluster-encapsulated antimotungstate, K2Na3H43[Nd6(OH)6(H2O)6(B-α-SbW9O33)4]2·67H2O (1), has been successfully synthesized by a facile one-step hydrothermal reaction method. The tetrahedron-shaped two-shell {Nd6(OH)6(H2O)6(B-α-SbW9O33)4}(1a) polyanion is composed of a novel pure lanthanide-oxo {Nd6(μ3-OH)6(H2O)6} octahedron and {(B-α-SbW9O33)4} tetrahedron. After being effectively loaded onto a glassy carbon electrode (GCE) by electrostatic adsorption using polydiallyldimethyl ammonium chloride (PDDA)-functionalized multi-walled carbon nanotubes (MWCNTs), compound 1 exhibits electrochemical activity for the reduction of bromate ions with good selectivity, a high sensitivity of 186 μA mM−1 and a detection limit that has reached 1.9 μM. To the best of our knowledge, this is the first example of an amperometric bromate sensor based on Ln-containing antimotungstates, which will provide new materials for electrochemical sensors. [ABSTRACT FROM AUTHOR]

Three new group IIIA metal phosphate–oxalate (MPO) compounds, namely [(CH3)2NH2]2[M2(HPO4)2(H2PO4)2(C2O4)] (M = Al (1), Ga (2)) and [(CH3)2NH2]2[In2(HPO4)2(H2PO4)2(C2O4)]·H2O (3), have been synthesized. Their crystal structures feature an anionic layer with the sql topology net. In particular, 1 displays a proton conductivity (σ) of 9.09 × 10−3 S cm−1 at 85 °C and under 98% relative humidity, which is the highest among MPOs. This study not only endows the main group metal-based MPO family with new members, but also contributes to further understanding of the structure-directing roles of amines and provides a feasible idea for improving the proton conductivity of MPOs. [ABSTRACT FROM AUTHOR]

Inspired by the metal‐oxo cluster structural feature and charge separation behaviour of the oxygen evolving center (OEC) in photosystem II (PS‐II) under photoirradiation, a new crystalline photochromic polyoxomolybdate, MV2[β‐Mo8O26] (1, MV=methyl viologen cation), is designed as a biomimetic oxygen evolution reaction (OER) catalyst in neutral electrolytes. After photoinduced electron transfer (PIET) with colour change from colourless to grey, it remains in an ultra‐stable charge‐separated state over a year under ambient conditions. The observed overpotential at 10 mA ⋅ cm−2 and Tafel slope decrease by 49 mV and 62.8 mV ⋅ dec−1 after coloration, respectively. The outstanding OER performance of the coloured state in neutral electrolytes even outperforms the commercial RuO2 benchmark. Experimental and theoretical studies show that oxygen holes within polyanions after irradiation serve as sites for enhancing direct O−O coupling, thus effectively promoting OER. This is the first successful application of electron‐transfer photochromism to realize OER activity gain. [ABSTRACT FROM AUTHOR]

Only rarely have polyoxometalates been found to form core–shell nanoclusters. Here, we succeeded in isolating a series of rare giant and all‐inorganic core–shell cobalt polyoxoniobates (Co−PONbs) with diverse shapes, nuclearities and original topologies, including 50‐nuclearity {Co12Nb38O132}, 54‐nuclearity {Co20Nb34O128}, 62‐nuclearity {Co26Nb36O140} and 87‐nuclearity {Co33Nb54O188}. They are the largest Co−PONbs and also the polyoxometalates containing the greatest number of Co ions and the largest cobalt clusters known thus far. These molecular Co−PONbs have intriguing and atomically precise core–shell architectures comprising unique cobalt oxide cores and niobate oxide shells. In particular, the encapsulated cobalt oxide cores with different nuclearities have identical compositions, structures and mixed‐valence Co3+/Co2+ states as the different sized Co−O moieties of the bulk cubic‐spinel Co3O4, suggesting that they can serve as various molecular models of the cubic‐spinel Co3O4. The successful construction of the series of the Co−PONbs reveals a feasible and versatile synthetic method for making rare core–shell heterometallic PONbs. Further, these new‐type core–shell bimetal species are promising cluster molecular catalysts for visible‐light‐driven CO2 reduction. [ABSTRACT FROM AUTHOR]

Compounds with redox activities have appealing applications in catalytic, electronic and magnetic properties, but the redox inert of polyoxoniobates (PONbs) significantly limits their applications for a long time. In this work, we are able to integrate organophosphate and lanthanide cluster into PONb to create the first family of inorganic‐organic hybrid organophosphate‐Ln‐PONb composite clusters. These novel species not only present the first family of redox active PONbs that can be reduced to form long‐lived "heteropoly blues" under ambient conditions, but also a new photochromic system. More importantly, the analyses of the electronic configurations and photochromic properties for a series of designed proof‐of‐concept PONbs models allow us to discover a D‐f‐A electron transfer mechanism, that is, photoinduced electron is transferred from a photosensitive organophosphate electron donor (D) to the NbV electron acceptor (A) through the unoccupied 4 f‐orbitals of Ln (f). This work paves the way for developing diverse PONb‐based redox materials and expanding the possibility of the applications of PONbs in the redox chemistry. [ABSTRACT FROM AUTHOR]

An oxalate-assisted strategy was first developed for creating new polyoxotantalates (POTas). With this strategy, two brand-new POTa supramolecular frameworks based on uncommon dimeric POTa secondary building units (SBUs) were constructed and characterized. Interestingly, the oxalate ligand can not only serve as a coordination ligand to form unique POTa SBUs but also act as a key hydrogen bond acceptor to construct supramolecular architectures. Besides, the architectures show outstanding proton conductivity. The strategy opens up new opportunities for developing new POTa materials. [ABSTRACT FROM AUTHOR]

A rare cadmium-containing windmill-like heteropolyoxoniobate macrocycle has been successfully synthesized with stable 1-D cyclic cluster aggregates. The compound exhibited promising basic catalytic ability for Knoevenagel condensation with a high yield under mild reaction conditions and high cycling stability. The theoretical calculation showed that the promising basic catalytic ability is due to the dense and stronger basic sites of the surface terminal O atoms. [ABSTRACT FROM AUTHOR]

This work reports the interesting and unique cation‐exchange behaviors of the first indium‐bridged purely inorganic 3D framework based on high‐nuclearity polyoxoniobates as building units. Each nanoscale polyoxoniobate features a fascinating near‐icosahedral core–shell structure with six pairs of unique inorganic "molecular tweezers" that have changeable openings for binding different metal cations via ion‐exchanges and exhibit unusual selective metal‐uptake behaviors. Further, the material has high chemical stability so that can undergo single‐crystal‐to‐single‐crystal metal‐exchange processes to produce a dozen new crystals with high crystallinity. Based on these crystals and time‐dependent metal‐exchange experiments, we can visually reveal the detailed metal‐exchange interactions and mechanisms of the material at the atomic precision level. This work demonstrates a rare systematic and atomic‐level study on the ion‐exchange properties of nanoclusters, which is of significance for the exploration of cluster‐based ion‐exchange materials that are still to be developed. [ABSTRACT FROM AUTHOR]

Herein, a giant Sb‐rich polyoxometalate (POM) {Sb21Tb7W56} is reported, which contains the largest number of Sb atoms in a POM so far. The Sb‐rich POM has many interesting structural features and is a rare example of a soluble and water‐stable giant POM. Biomedical studies indicate that the Sb‐rich POM exhibits broad‐spectrum antitumor activity against various cancer cell lines by reactivating the P53‐dependent apoptotic processes and disrupting the mitochondrial membrane. In addition, this Sb‐rich POM was capable of suppressing the growth and metastasis of a breast cancer in vivo. This work demonstrates that Sb‐rich POMs are promising candidates for the development of new anticancer drugs. [ABSTRACT FROM AUTHOR]