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The direct esterification of alcohols with non-noble metal-based catalytic systems faces great challenges. Here, we report a new chrome-based catalyst stabilized by a single pentaerythritol decorated Anderson-type polyoxometalate, [N(C4H9)4]3[CrMo6O18(OH)3C{(OCH2)3CH2OH}], which can realize the efficient transformation from alcohols to esters by H2O2 oxidation in good yields and high selectivity without extra organic ligands. A variety of alcohols with different functionalities including some natural products and pharmaceutical intermediates are tolerated in this system. The chrome-based catalyst can be recycled several times and still keep the original configuration and catalytic activity. We also propose a reasonable catalytic mechanism and prove the potential for industrial applications.

Novel Anderson-type polyoxomanganotungstate clusters with the β-isomer structure, [{R1R2C(CH2O)2}MnIVW6O22]6-, were synthesized and monofunctionalized with derivatives of 1,3-propanediol via a one-pot strategy, and show unprecedented coordination activity as non-lacunary polyoxotungstate clusters and could have potential in the future construction of POM-frameworks.

A highly efficient method to oxidize methylarenes to their corresponding acids with a reusable Cr catalyst was developed. The reaction can be carried out in water with 1 atm oxygen and K2S2O8 as cooxidants, proceeds under green and mild conditions, and is suitable for the oxidation of both electron-deficient and electron-rich methylarenes, including heteroaryl methylarenes, even at the gram level. The excellent result, together with its simplicity of operation and the ability to continuously reuse the catalyst, makes this new methodology environmentally benign and cost-effective. The generality of this methodology gives it the potential for use on an industrial scale. Differing from the accepted oxidation mechanism of toluene, GC-MS studies and DFT calculations have revealed that the key benzyl alcohol intermediate is formed under the synergetic effect of the chromium and molybdenum in the Cr catalyst, which can be further oxidized to afford benzaldehyde and finally benzoic acid.

The carbon–carbon bond cleavage of 1,2-diols is an important chemical transformation. Although traditional stoichiometric and catalytic oxidation methods have been widely used for this transformation, an efficient and valuable method should be further explored from the views of reusable catalysts, less waste, and convenient procedures. Herein an inorganic-ligand supported iron catalyst (NH4)3[FeMo6O18(OH)6]·7H2O was described as a heterogeneous molecular catalyst in acetic acid for this transformation in which hydrogen peroxide was used as the terminal oxidant. Under the optimized reaction conditions, carbon–carbon bond cleavage of 1,2-diols could be achieved in almost all cases and carboxylic acids or ketones could be afforded with a high conversion rate and high selectivity. Furthermore, the catalytic system was used efficiently to degrade renewable biomass oleic acid. Mechanistic insights based on the observation of the possible intermediates and control experiments are presented.

A simple and efficient protocol for the formylation of amines with formic acid, catalyzed by a polyoxometalate-based chromium catalyst, is described. Notably, this method shows excellent activity and chemoselectivity for the formylation of primary amines; diamines have also been successfully employed. Importantly, the chromium catalyst is potentially non-toxic, environmentally benign and safer than the widely used high valence chromium catalysts such as CrO3 and K2Cr2O7. The catalyst can be recycled several times with a negligible impact on activity. Finally, a plausible mechanism is provided based on the observation of intermediate and control experiments.

Organo disulfides represent an abundant class of compounds in chemical biology, pharmaceutical fields, and industry. They are traditionally synthesized by the oxidation of mercaptan in the presence of an organic ligand supported metal catalyst or toxic oxidants under harsh conditions. Here, we disclose a highly-efficient pathway in which disulfide is synthesized by organic boric acid and Na2S2O3 using the catalyst (NH4)3[CrMo6O18(OH)6], demonstrating a high activity and excellent selectivity. Various boric acid derivatives have been successfully transformed into the corresponding disulfides. Mechanistic insights have been furnished based on the observation of intermediate and control experiments.

Two novel supramolecular assemblies built from Keggin-type polyoxometalate and [18]-crown-6 ether building blocks, (K+)4([18]-crown-6)4(CH3CN)2[SiM12O40] (M = Mo (1), W (2)), have been synthesized and characterized via single-crystal/powder X-ray diffraction and a wide range of analytical methods, including FT-IR, UV-vis, Raman, and NMR spectroscopy, thermogravimetric analysis, and density functional theory (DFT) calculations. This POM-based supramolecular architecture is the first example of a Keggin-type POM linked to four 18-crown-6 components forming unique propeller-like supramolecular host–guest structures via crown–metal–O(POM) bonds in the forms of the isostructural compounds 1 and 2. In addition, the electrochemical behaviors and electrocatalytic properties toward the reduction of sodium nitrite (NaNO2) were also investigated via cyclic voltammetry in acidic solution.

A newly prepared nano-organic–inorganic hybrid compound, videlicet [HPDCD]5[BW12O40]·3H2O (HPDCD = hydrolyzed and protonated 2-cyanoguanidine) (1), has been prepared under reflux condition and analyzed by FT-IR and 1H NMR spectroscopies, TG–DT analysis, FE-SEM, cyclic voltammetry, elemental analyses and also single-crystal and powder X-ray diffraction. Hydrogen bonding is the crucial agent in 1 hybrid structure as can be seen from the X-ray data. In this compound, 3D cage-like cavities are constructed by HPDCD counter-ions through hydrogen bonding. Four types of hydrogen bonds in compound 1 lead to the formation of cage-like cavities. [BW12O40]5− clusters are located into compound 1 cage-like cavities. Five types of HPDCD units create cage-like cavities according to which two types of BW12 clusters are placed between the cavities. Moreover, according to powder X-ray diffraction and field emission SEM analyses, the nano-size of 1 cluster has been confirmed. Furthermore, compound 1 has been considered in terms of the electrocatalytic activity and photocatalytic property.

Two novel polyoxovanadate-iodoBodipy supramolecular assemblies, named as (2I-BDP-C6)2V6 and (2I-BDP-C6)3V10, were first synthesized by the self-assembly of anionic hexavanadate and decavanadate with cationic iodoBodipy for photochemotherapy, respectively. The mechanisms for synergistic photochemotherapy of the anion-cation pairs were determined. In particular, (2I-BDP-C6)3V10 can effectively kill lung cancer cells (HepG2) by synergetic chemotherapy as well as photodynamic therapy.

Direct catalytic oxidation of alcohols to carboxylic acids is very attractive, but economical catalysis systems have not yet been well established. Here, we show that a pure inorganic ligand-supported chromium compound, (NH4)3[CrMo6O18(OH)6] (simplified as CrMo6), could be used to effectively promote this type of reaction in the presence of CO2. In almost all cases, oxidation of various alcohols (aromatic and aliphatic) could be achieved under mild conditions, and the corresponding carboxylic acids can be achieved in high yield. The chromium catalyst 1 can be reused several times with little loss of activity. Mechanism study and control reactions demonstrate that the acidification proceeds via the key oxidative immediate of aldehydes.

The first example of an inorganic-ligand supported iron(III) catalysed coupling of formic acid and amines to form formamides is reported. The pure inorganic catalyst (NH4)3[FeMo6O18(OH)6] (1), which consists of a central FeIII single-atomic core supported within a cycle-shaped inorganic ligand consisting of six MoVIO6 octahedra, shows excellent activity and selectivity, and avoids the use of complicated/commercially unavailable organic ligands. Various primary amines and secondary amines have been successfully transformed into the corresponding formamides under mild conditions, and the formylation of primary diamines has also been achieved for the first time. The Fe catalyst 1 can be reused several times without appreciable loss of activity.

Polyoxometalates (POMs) are a class of discrete molecular inorganic metal-oxide clusters with reversible multielectron redox capability. Taking advantage of their redox properties, POMs are thus expected to be directly involved in the lithium-sulfur batteries (Li-S, LSBs) system as a bidirectional molecular catalyst. Herein, we design a three-dimensional porous structure of reduced graphene-carbon nanotube skeleton supported POM catalyst as a high-conductive and high-stability host material. Based on various spectroscopic techniques and in situ electrochemical studies together with computational methods, the catalytic mechanism of POM clusters in Li-S battery was systematically clarified at the molecular level. The constructed POM-based sulfur cathode delivers a reversible capacity 1110 mAh g-1 at 1.0 C and cycling stability up to 1000 cycles at 3.0 C. Furthermore, Li-S pouch/beaker batteries with a POM-based cathode were successfully demonstrated. This work provides essential inputs to promote molecular catalyst design and its application in LSBs.

One halide ion (X- ) can bind on the surface of nanoscale Anderson-type polyoxometalate (POMs) clusters [(n-C4 H9 )4 N]3 {AlMo6 O18 (OH)3 [(OCH2 )3 CCH3 ]}, and form stable complexes in solution with binding constant K=1.53×103 . Single-crystal structural analysis showed that this binding behavior occurs through multiple hydrogen bonding between X- and three hydroxy groups on the uncapped side of the cluster. This supramolecular interaction in the cluster systems means that their catalytic activities, evaluated from the oxidation of alcohols to aldehydes, can be switched upon the introduction of halide ions and water molecules. The halide ions work as inhibitors by blocking the active sites of the clusters while they can be re-activated by the addition of water.

An efficient oxidation and functionalization of C–H bonds with an inorganic-ligand supported iron catalyst and hydrogen peroxide to prepare the corresponding ketones was achieved using the bromide ion as a promoter. Preliminary mechanistic investigations indicated that the bromide ion can bind to FeMo6 to form a supramolecular species (FeMo6·2Br), which can effectively catalyze the reaction.

Polyoxometalates (POMs), an exceptional family of coordination clusters consisting of Mo, W, V, etc. early transition metal ions in their highest oxidation states, have received significant attention over recent years due to their structural versatility and unique and diverse chemical and physical properties. The functionalization of POMs with organic ligands provides a novel strategy to precisely incorporate POMs with advanced functional organic moieties on their surfaces and enhance their compatibility in organic media. Among the various organically functionalized synthetic strategies for POM-based organic–inorganic hybrid materials, alkoxylation of POMs stands for one of the hottest topics during the past decades, since the diverse and tunable alkoxyl ligands are able to anchor on the surface of many POMs clusters, forming novel and flexible organically functionalized POM clusters, which can be further exploited as building blocks to design various functionalized POM-based hybrids with charming catalytic properties, and biomedicine, energy, or functional materials applications. In this review, recent advances in alkoxylation chemistry of POMs from synthetic strategies, structural overviews to their functional applications have been discussed.

The oxidation of alcohols to aldehydes or ketones is a highly relevant conversion for the pharmaceutical and fine-chemical industries, and for biomass conversion, and is commonly performed using stoichiometric amounts of highly hazardous oxidants. The aerobic oxidation of alcohols with transition metal complex catalysts previously required complicated organic ligands and/or nitroxyl radicals as co-catalysts. Herein, we report an efficient and eco-friendly method to promote the aerobic oxidation of alcohols using an inorganic-ligand supported copper catalyst 1, (NH4)4[CuMo6O18(OH)6], with O2 (1 atm) as the sole oxidant. Catalyst 1 is synthesized directly from cheap and commonly available (NH4)6Mo7O24·4H2O and CuSO4, which consists of a pure inorganic framework built from a central CuII core supported by six MoVIO6 inorganic scaffolds. The copper catalyst 1 exhibits excellent selectivity and activity towards a wide range of substrates in the catalytic oxidation of alcohols, and can avoid the use of toxic oxidants, nitroxyl radicals, and potentially air/moisture sensitive and complicated organic ligands that are not commercially available. Owing to its robust inorganic framework, catalyst 1 shows good stability and reusability, and the catalytic oxidation of alcohols with catalyst 1 could be readily scaled up to gram scale with little loss of catalytic activity, demonstrating great potential of the inorganic-ligand supported Cu catalysts in catalytic chemical transformations.

The oxidative esterification of various aldehydes with alcohols could be achieved by a heterogeneous iron(III) catalyst supported on a ring-like POM inorganic ligand under mild conditions, affording the corresponding esters, including several drug molecules and natural products, in high yields. ESI-MS and control experiments demonstrated that POM-FeV(O) was the active catalytic species and the plausible mechanism was presented. More importantly, the 6th run of the iron catalyst recycles shows only a slight decrease in the yield.

Aromatic azo compounds, which play an important role in pharmaceutical and industrial applications, still face great challenges in synthesis. Herein, we report a molybdenum oxide compound, [N(C4 H9 )4 ]2 [Mo6 O19 ] (1), catalyzed selective oxidation of anilines with hydrogen peroxide as green oxidant. The oxidation of anilines can be realized in a fully selectively fashion to afford various symmetric/asymmetric azobenzene and azoxybenzene compounds, respectively, by changing additive and solvent, avoiding the use of stoichiometric metal oxidants. Preliminary mechanistic investigations suggest the intermediacy of highly active reactive and elusive Mo imido complexes.

Direct Hydroxylation of benzene to phenol with high yield and selectivity has been the goal of phenol industrial production. Photocatalysis can serve as a competitive method to realize the hydroxylation of benzene to phenol owing to its cost-effective and environmental friendliness, however it is still a forbidding challenge to obtain good yield, high selectivity and high atom availability meanwhile. Here we show a series of supramolecular catalysts based on alkoxohexavanadate anions and quinolinium ions for the photocatalytic hydroxylation of benzene to phenol under UV irradiation. We demonstrate that polyoxoalkoxovanadates can serve as efficient catalysts which can not only stabilize quinolinium radicals but also reuse H2 O2 produced by quinolinium ions under light irradiation to obtain excellent synergistic effect, including competitive good yield (50.1 %), high selectivity (>99 %) and high atom availability.

A new organic-inorganic hybrid consisting of Keggin-type polyoxometalate ([BW12O40]5−) and protonated piperazine, namely [H5O2]2[Hpip]2.5[BW12O40]·4H2O (pip = piperazine, C4H10N2) (1), has been created under reflux state and identified through material identification devices like single-crystal crystallography, FT-IR and 1H-NMR spectroscopies, Powder XRD, TG-DT Analysis, Field Emission SEM, elemental-analysis and cyclic voltammetry. Crystallography investigation exhibits that the main factor in the formation of 1 is the numerous number of hydrogen bonding between organic and inorganic species. The arrangement of Hpip groups creates holes in which the [BW12O40]5− clusters fit into the holes. Furthermore, the electrochemical and photochemical attributes of 1 have been considered, and the outcomes present that 1 owns privileged electrocatalytic activity against the reduction of nitrite ions as well as an appropriate photochemical effect on methylene blue (MB) dye depredation. A new organic-inorganic hybrid consisting of Keggin-type polyoxometalate ([BW12O40]5-) and protonated piperazine, namely [H5O2]2[Hpip]2.5[BW12O40]·4H2O (pip = piperazine, C4H10N2) (1), has been created under reflux state. The electrochemical and photochemical attributes of 1 have been considered, and the outcomes present that 1 owns privileged electrocatalytic activity against the reduction of nitrite ions as well as an appropriate photochemical effect on methylene blue (MB) dye depredation.

The direct catalytic oxidation of alcohols to esters is very appealing, but the economical-friendly catalysis systems are not yet well established. Herein, we show that a pure inorganic ligand-supported single-atomic cobalt compound, (NH 4 ) 3 [CoMo 6 O 18 (OH) 6 ] (simplified as CoMo 6 ), could be used as a heterogeneous catalyst and effectively promote this type of reaction in the presence of 30% H 2 O 2 using KCl as an additive. The oxidative cross-esterification of various alcohols (aromatic and aliphatic) could be achieved under mild conditions in nearly all cases, affording the corresponding esters in high yields, including several drug molecules and natural products. Detailed studies have revealed that chloride ion is able to bind to the CoMo 6 to form a supramolecular dimer 2(CoMo 6 ∙Cl), which can effectively catalyze the reaction via a synergistic effect from chloride ion and CoMo 6 . Mechanism studies and control reactions demonstrate that the esterification proceeds via the key oxidative immediate of aldehydes.

Polyoxometalates (POMs) are an exceptional family of inorganic oxide anions consisting of Mo, W, V, etc. early transition metal ions at their highest oxidization states with structural versatility. The Anderson-type hetreopolyanions are one of the most important subclass since their most flexibility benefited from the central heteroatom. Among the frontier of current POMs investigations, organic modification and functionalization of POMs stands for one of most hot topics. The organic modification of POMs can incorporate POMs with advanced functional organic moieties on their surfaces to make the structure versatility more accessible and the design of advanced functional materials more rational. In this review, recent advances in controllable alkoxylation chemistry of Anderson-type polyoxometalates are briefly summarized into 9 parts as following: (1) the synthesis strategy development of direct modification protocol for the synthesis of single-side triol-functionalized Anderson δ isomer organic hybrids. (2) Based on direct modification protocol, the synthesis strategy development of μ 2-O atom pronation and activation chemistry in Anderson cluster to afford single-side triol-functionalized Anderson χ and ψ isomer organic hybrids. The proton-controlled isomer transformation between the δ , χ and ψ isomer was discovered. This will open up a new era for developing chemical reactivity of μ 2-O atoms in the Anderson cluster. (3) By precise proton control, the synthesis strategy development to obtain diol functionalized Anderson organic hybrids. Such diol functionalization mode not only works for some specific triol ligands but also can readily be extended to the diol ligands, which will greatly enrich the species of alkoxo-derivatized Anderson POM clusters. (4) Based on direct modification protocol, extending special tripodal ligands with carboxyl group to symmetrically functionalized the Anderson cluster. Such Anderson organic hybrids cannot be obtained for the traditional reconstruction protocol. This has extended the versatility of tripodal ligands applied for Anderson-type POMs modification. (5) Through stepwise synthesis strategy, single-side δ isomer was utilized as a precursor to efficiently synthesized asymmetrically triol-functionalized Anderson organic hybrids. (6) The synthesis strategy development of direct parent Anderson alkoxylation protocol for triol-functionalized butterfly-shaped β isomers of Anderson POMs hybrids. (7) The synthesis strategy development to extend the triol-functionalized Anderson from polymolybdates(Mo6O24) to polyoxotungstates(W6O24). (8) The newly development and revised synthesis strategy of Mo8 reconstruction protocol. (9) The original concept proposed by our group, organic ligand protected and inorganic-ligand supported atomically precise Anderson nanocluster based molecular armor hybrid material design as effective catalysts for green aerobic oxidation catalysis applications. In summary, the synthetic strategies and structures of novel alkoxyl-functionalized Anderson cluster have been discussed in this review. These newly developed synthesis strategies have greatly enriched the category of organoalkoxylation derivatives of Anderson cluster, providing a reliable and convenient synthetic methodology for the controllable design of triol-functionalized Anderson organic hybrids with specific and desirable functionalization modes. The extension of triol ligands with functional groups to other POMs units are still need to be developed. One of the important application fields for POMs is catalysis, however, the exploration of catalysis of alkoxyl-functionalized Anderson nanoclusters is quite limited to the recent cases we mentioned in this review. It is worth exploring to develop more alkoxyl-functionalized Anderson nanoclusters as catalysts for useful reactions, because alkoxyl-functionalized Anderson nanoclusters have multiple active sites and special properties derived from functional groups of alkoxyl ligands as well as cooperativities. The charge transfer properties between POMs and organic moieties in alkoxyl-functionalized Anderson nanoclusters have also attracted widely attentions. Using alkoxyl ligands with conjugated groups to functionalize Anderson nanoclusters may enhance the ability of electron transfer to improve the intrinsic redox properties of Anderson nanoclusters. It can be concluded with confidence that the persistent and dedicated efforts of chemists have revealed a vast advance in alkoxylation of Anderson nanoclusters, which may in fact just be the reason why the alkoxylation chemistry of Anderson nanoclusters research field has flourished in recent years. Of course, more Anderson nanoclusters-based materials with novel structures, interesting and functional properties remain to be explored and the alkoxylation chemistry of Anderson nanoclusters still has great growing opportunities in the future.

Engineering photoredox-triggered chemical transformation via visible light has been an emerging area in organic synthesis. However, most of the well-established photocatalysts are based upon either transition metal complexes involved with noble metals and organic ligands or photosensitive organic dyes, the development of pure inorganic molecular photocatalysts that could provide better stability and durability is greatly retarded. Herein we discover that the Anderson polyoxometalate (POM) Na-4[NiMo6O18(OH)(6)] (1), which consists of pure inorganic framework built from a central Ni-II core supported by six (MoO6)-O-VI inorganic scaffold/ligands, can be used as a powerful photocatalyst. Upon irradiation with visible light (>400 nm), the compound can catalyze, in high efficiency, a wide range of reactions, including the oxidative cross-coupling reaction of chlorides with amines, as well as oxidation of chlorides using molecular oxygen, affording various imines, aldehydes, and ketones, respectively in high selectivity and good yields. Owing to the robust inorganic framework, this catalyst exhibits excellent stability during the catalysis and reusability with little loss of the catalytic activity, thus providing an alternative without use of complicated organic ligands and expensive noble metal-based photosensitizers.

Sub-nanoscaled polyalkoxyvanadates (PAOVs) functionalized with various aliphatic acids are evaluated for their insulin-sensitizing activity in lowering the blood glucose levels of diabetic mice in typical glucose tolerance tests. All the PAOVs can restore the blood glucose to normal levels after a single oral administration of PAOVs. Among them, the myristic acid-modified PAOVs enable the response of insulin to the repeated glucose challenges, lasting for up to 13 h. The combined administration of PAOVs exerts better glucose control over insulin alone, while the capric acid- and myristic acid-modified ones can enhance the responsiveness of insulin to glucose challenge and is comparable to a clinical-used derivative of insulin. Interestingly, continuous glucose monitoring shows that myristic acid-modified PAOV derivatives sensitize the responsiveness of insulin, almost matching with that of a healthy pancreas. These discoveries open up new opportunities for the application of PAOVs to promote glucose-responsive and long-lasting activity of insulin, which are expected to aid the accurate blood glucose control in insulin therapy while reducing the number of insulin administrations.

The synthesis of a new organic-inorganic nano-hybrid material [H5O2][pip]2.5[SiMoV2W9O40]. 7H2O (pip = Piperazine) (1), in which piperazine is connected to a mixed-addenda Keggin structure of polyoxometalate by hydrogen bonding interaction, is reported. This nano-hybrid is characterized by single-crystal X-ray diffraction, fourier transform infrared (FT-IR), proton nuclear magnetic resonance (1H NMR), powder X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTA), field emission scanning electron microscopy (FESEM) and cyclic voltammetry (CV). Single crystal X-ray analysis reveals that compound 1 has been assembled by hydrogen bonding among polyoxometalate, piperazine and crystallization water units. In this compound, polyoxometalates are located in the cavities which are created by piperazine groups in the zigzag form. In addition, based on XRD and FESEM analyzes, the nano composition of compound 1 can be verified. Moreover, the electrochemical properties of 1 were perused, which represent that 1 has an appropriate electrocatalytic activity towards reduction of nitrate (NO2−) ion attributed to the metal-center and piperazine units.

A series of rod-shaped polyoxometalates (POMs) [Bu4 N]7 [Mo6 O18 NC(CH2 O)3 MnMo6 O18 (OCH2 )3 CNMo6 O18 ] and [Bu4 N]7 [ArNMo6 O17 NC(CH2 O)3 MnMo6 O18 (OCH2 )3 CNMo6 O17 NAr] (Ar=2,6-dimethylphenyl, naphthyl and 1-methylnaphthyl) were chosen to study the effects of cation-π interaction on macroionic self-assembly. Diffusion ordered spectroscopy (DOSY) and isothermal titration calorimetry (ITC) techniques show that the binding affinity between the POMs and Zn2+ ions is enhanced significantly after grafting aromatic groups onto the clusters, leading to the effective replacement of tetrabutylammonium counterions (TBAs) upon the addition of ZnCl2 . The incorporation of aromatic groups results in the significant contribution of cation-π interaction to the self-assembly, as confirmed by the opposite trend of assembly size vs. ionic strength when compared with those without aromatic groups. The small difference between two aromatic groups toward the Zn2+ ions is amplified after combining with the clusters, which consequently triggers the self-recognition behavior between two highly similar macroanions.

A practical, efficient and environmentally benign catalytic protocol for the oxidative cross-coupling reaction of halides with amines, oxidative self-coupling of amines and oxidation of halides was developed with inorganic-ligand supported ZnPOM (NH4)4[ZnMo6O18(OH)6] using molecular oxygen. This method mainly utilizes an inorganic polymolybdate ligand to support the Zn2+ ion, avoiding the use of complicated organic ligands.

Oxidation is a powerful methodology that is widely used for the production of fine chemicals and pharmaceutical intermediates, however, this process often involves the use of toxic reagents and harsh reaction conditions. Herein we report an efficient and eco-friendly way to promote the aerobic oxidation of organic halides to aldehydes/ketones and oxidative coupling of amines to imines using an inorganic-ligand supported iron catalyst 1a (NH4)3[FeMo6O18(OH)6] with O2 (1 atm) as the sole oxidant. 1a is synthesized directly from cheap and commonly available (NH4)6Mo7O24·4H2O and Fe2(SO4)3, which consist of a pure inorganic framework built from a central FeIII core supported by six MoVIO6 inorganic scaffolds. The iron catalyst 1a exhibits better activity towards a wide range of substrates in the catalytic oxidation of halides and amines, and the use of toxic oxidants and potentially air/moisture sensitive and complicated organic ligands that are not commercially available is avoided. Owing to the robust inorganic framework, 1a shows good stability and reusability and the catalytic oxidation of halides and amines could be readily scaled up to gram-scale with little loss of catalytic activity, demonstrating the great potential of inorganic-ligand supported catalysts in catalytic chemical transformation.

Several novel triol-ligands functionalized Anderson–Evans type polyoxotungstates, K3Na3[{HOCH2C(CH2O)3}AlO3W6O18], K3Na3[{HOCH2C(CH2O)3}CrO3W6O18], K3Na3[{HOCH2C(CH2O)3}CoO3W6O18], and K3Na3[{H3CC(CH2O)3}CoO3W6O18], were successfully synthesized and characterized, in which some of the central metal ions have never been found in the Anderson-type polyoxotungstates. The single crystal X-ray diffraction analysis indicated that the clusters were on a status, in which only one-side μ3-O was protonated. This indicates that the three-protonated cluster is a common type of Anderson cluster aside zero-protonated (A-type) and six-protonated (B-type), which could be named as the T-type.

By controlling the terminal organic ligands, various fascinating supramolecular assemblies originating from hydrogen bonding interactions in different dimensions in a series of hexavanadate hybrids were synthesized via step-by-step organic modification. These hybrids were characterized, and their structures were determined by single-crystal X-ray diffraction. Moreover, the introduction of a rigid bridging ligand has a positive influence on the assembly of supramolecular architectures, providing a new vision for the design and synthesis of advanced inorganic–organic materials.

An unprecedented class of benzoyldiazenido functionalized polyoxometalates, (Bu4N)3[Mo6O18(=N=NCOAr)] (Ar = Ph, 1; Ph-o-Cl, 2; Ph-m-Cl, 3; Ph-p-Cl, 4; Ph-o, p-Cl2, 5; Ph-p-Br, 6; Ph-m-NO2, 7; Ph-p-NO2, 8; Ph-p-OMe, 9) are prepared via the refluxing reaction of α-octamolybdates and corresponding hydrazides in dry acetonitrile using dicyclohexylcarbodiimide (DCC) as dehydrating agent. Single crystal X-ray diffraction structural analysis reveals that their anions demonstrate typical structural features of mono-functionalized hexamolybdates with different organic substituents. 1H NMR indicates that the [Mo6O18(NN)] fragment in these compounds is an electron-donating group rather than an electron-withdrawing group, which is further validated by the calculation of atomic charge distribution(natural bond orbital (NBO) and Mulliken). Bond valence sum (BVS) shows that the oxidation state of all molybdenum atoms is +6. Cyclic voltammetry (CV) indicates that they are more difficult to be reduced than hexamolybdate and its organoimido derivatives. Anti-tumour activity test against K562 shows that most hybrid compounds have an enhanced inhibitory activity compared to hexamolybdate and corresponding hydrazide ligands.

A redox-responsive hybrid of polyoxometalate and conducting oligomer including its self-assemblies with controllable morphologies are reported. To this end, a hybrid molecule, containing a Lindqvist hexamolybdate as the polar head group and N,N'-bis(4'-amino-2,6-dimethylphenyl)-1,4-quinonediimine as the redox-responsive and aggregating group, is prepared. This hybrid exhibits redox-responsive behavior with controllable assembling morphological transition from spherical vesicles to short cylindrical vesicles. Besides, the hybrid-based self-assemblies are transferred to the surface, thus the surface wettability can be well-tuned owing to the morphological transitions of the self-assemblies. By marrying conducting materials with polyoxometalate chemistry, this research opens a new horizon of polyoxometalate-based self-assembled systems with potential applications in functional materials.

The first example of a heterogeneous iron(III)-catalyzed aerobic oxidation of aldehydes in water was developed. This method utilizes 1 atmosphere of oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification. Its operational simplicity, gram-scale oxidation, and the ability to successively reuse the catalyst, make this new methodology environmentally benign and cost effective. The generality of this methodology gives it the potential to be used on an industrial scale.

The exploration and discovery of new POM species with novel structural motifs are core prerequisites and permanent missions in the field of POM chemistry. It has been nearly 30 years since the first butterfly-shaped Anderson-type hetreopolyanions with a centred pentavalent Sb atom, [Sb(OH)2Mo6O22]5−, named as the β isomer, was discovered in 1988. Yet the corresponding β isomers with a lower valence metal as the central heteroatom and its triol-functionalized organic derivatives have never been obtained. Herein, for the first time, two novel triol-functionalized butterfly-shaped heteropolyanions, β-{Cr[RC(CH2O)3]2Mo6O18}3− (R = NH2, 1; C2H5, 2), were synthesized by the reaction of common flat Anderson-type POM, α-[Cr(OH)6Mo6O18]3−, and triol ligands in hot DMF. Single crystal XRD analysis reveals that β-{Cr[RC(CH2O)3]2Mo6O18}3− is the first triol-functionalized β isomer of common α-type Anderson POMs. This study will enrich the family of POMs and provide an oportunity for the discovery of more potential POMs-based organic–inorganic hybrid materials.

Three novel bis(Triol)-functionalized Anderson cluster derivatives (POM-L-POM, POM-L, L-POM-L) were efficiently synthesized, which manifest interesting self-assembly and synergistic effects. They provided strong support in synthons, applications in syntheses and properties for designing organic-inorganic hybrid chains.

The first molybdovanadate cluster with a polyarylimido trimetal fragment, [V4Mo3O14(NAr)3(μ2-NAr)3]2−, was in situ synthesized by using (TBA)3[H3V10O28] as proton and vanadium sources. Additional aniline hydrochlorides will give rise to the formation of phenyl guanidines, which will serve as cations and proton donors to form chain-like and dimeric supermolecules via H-bonding.

A new synthetic approach to tri-substituted trisalkoxy-hexavanadate clusters containing different organic groups was developed in this work. Four mixed-valence or fully reduced POV hybrids were synthesized and structurally characterized, including an amino-containing derivative of hexavanadate, Na2[VIV3VV3O10{NH2C(CH2O)3}3] (1). Furthermore, a novel mixed-valence POV hybrid was prepared via the amidation of 1, indicating that 1 can be used as an excellent building block for the design and synthesis of mixed-valence POV functional materials.

Three new derivatives of hexavanadate with remote methacryl, phthalyl and tetrahydrophthalyl groups, respectively, were synthesized by esterification of pentaerythritol-derivatized hexavanadate. These new compounds were characterized by FT-IR, 1H NMR, UV-vis, elemental analysis and single-crystal X-ray diffraction. Their thermal stabilities were also tested by TGA analyses. Through such syntheses, we have successfully introduced the carbon–carbon double bond and/or carboxylic groups into the polyoxovanadates which could be utilized to build more complex structures. We also discuss the influence of anhydrides with different functional groups on the esterification of the pentaerythritol derivatized hexavanadate.

Over the past two decades, there have been major developments in the transition iron-catalyzed selective oxidation of alkenes to epoxides; a common structure found in drug, isolated natural products, and fine chemicals. Many of these approaches have enabled highly efficient and selective epoxidation of alkenes via the design of specialized ligands, which facilitates to control the activity and selectivity of the reactions catalyzed by iron atom. Herein, we report the development of the olefin epoxidation with inorganic-ligand supported iron-catalysts using 30% H2O2 as an oxidant, and the mechanism is similar to iron-porphyrin type. With the catalyst 1, (NH4)3[FeMo6O18(OH)6], various aromatic and aliphatic alkenes were successfully transformed into the corresponding epoxides with excellent yields as well as chemo- and stereo-selectivity. This catalytic system possesses the advantages of being able to avoid the use of expensive, toxic, air/moisture sensitive and commercially unavailable organic ligands. The generality of this methodology is simple to operate and exhibits high catalytic activity as well as excellent stability, which gives it the potential to be used on an industrial scale, and maybe opens a way for the catalytic oxidation reaction via inorganic-ligand coordinated iron catalysis.

The influence of three functionalized hexavanadates (V6): Na2 [V6O13{(OCH2)3CCH3}2], [H2]2 [V6O13{(OCH2)3CCH2OCOCH2CH3}2] and [(C4H9)4N]2 [V6O13{(OCH2)3CCH2OOC(CH3)2-COOH}2 on Na+/K+-ATPase activity, was investigated in vitro. Including compounds already tested by Xu et al. (Journal of Inorganic Biochemistry 161 (2016) 27–36), all functionalized hexavanadates inhibit the activity of Na+/K+-ATPase in a dose-dependent manner but with different inhibitory potencies. Na2 [V6O13{(OCH2)3CCH3}2] was found to have the best inhibition properties - showing 50% inhibition IC50 = 5.50 × 10−5 M, while [(C4H9)4N]2 [V6O13{(OCH2)3CCH2OOC(CH3)2-COOH}2] showed the lowest inhibitory power, IC50 = 1.31 × 10−4 M. In order to understand the bioactivity of functionalized hexavanadates series, we have also used a combined theoretical approach: determination of electrostatic potential from ab initio theoretical calculations and computation of the molecular interaction field (MIF) surface.

The two-dimensional (2D) nanostructures comprised of polyoxometalate based building blocks are of great value in nanoarchitectures, which have unique properties and widespread potential applications, but it is still challenging in mature preparation. Herein a new strategy to build Cr(III) centered Anderson type polyoxometalate 2D nanostructures based on the modulation of host–guest interaction between cationic pillar[5]arenes and sodium dodecyl sulfonate (SDS) in aqueous media was exploited in this work. Through regulating stoichiometry of SDS, the morphology of assemblies vary from nanobones to 2D nanosheets. The fine assembled structure was discovered by combined 1H NMR, SAXS, and element analyses. The nanomaterials can be used as adsorbents for I2 in various solutions, including n-hexane, cyclohexane, water, and chloroform, where the polyoxometalates play a key role in the effective adsorption of iodine since they can expand the interspace between pillar[5]arenes in the as-prepared nanostructure. Furth...

Formamides represent an abundant class of compounds in organic synthesis. They can be made efficiently by the direct catalytic coupling of methanol with amines in the presence of metal-based catalysts. However, these catalysts require complicated organic ligands, susceptible to oxidative self-degradation, restricting their practical applications. Here, we describe an inorganic ligand-supported chromium (III) catalyst, (NH4)3[CrMo6O18(OH)6], which consists of a central chromium (III) single-atomic core supported by a cycle-shaped inorganic ligand consisting of six MoVIO6 octahedra, shows excellent activity and selectivity. Various primary amines and secondary amines are successfully transformed into the corresponding formamides under mild conditions, and the formylation of primary diamines is also achieved. The chromium catalyst can be reused several times with little loss of the activity. Mechanistic insight is provided based on the observation of an intermediate and control experiments. Several catalytic methods for N-formylation of amines using noble metals or manganese pincer complexes are known. Here an air-stable and reusable chromium-based polyoxometalate is shown to catalyze the N-formylation of amines and diamines using methanol and hydrogen peroxide.

Electrocatalytic CO2 reduction reaction (CO2RR) is a promising pathway for storage of renewable electricity and converting CO2 into value-added products. It`s highly desired to obtain acetic acid via CO2RR since it`s an important chemical feedstock and high energy-density liquid fuel. However, developing highly efficient electrocatalysts for selective CO2RR toward acetate remains formidable challenge. We report an interface engineering strategy to modify copper nanocubes with polyoxometalate (POM) to generate Cu–O–Mo interface as active sites for CO2RR, achieving state-of-the-art activity with 48.68% acetate formation Faradaic efficiency and current density of ∼110 mA cm−2 at -1.13 V vs RHE. DFT calculations suggest the interface of Cu planes and polyoxometalate clusters with abundant Cu–O–Mo active sites promote the generation of *CH3 and successive coupling with CO2 insertion, showing a potential dependence of acetate production. This work provides a Cu–O–Mo interface model for the rational design of earth-abundant metal based electrocatalysts for CO2RR and other renewable energy conversions.

A water-soluble single-sided tris-functionalized Anderson-type polyoxometalate (POM) with counter ammonium cations, (NH4)2{[NH3C(CH2O)3]Cr(OH)3Mo6O18}·5H2O(1), has been synthesized by a hydrothermal reaction of parent Anderson-type POMs, [NH4]3[Cr(OH)6Mo6O18] (CrMo6) and tris ligand (HOCH2)3CNH2·HCl (Tris) in aqueous solution. Single-crystal X-ray diffraction analysis has revealed that compound 1 crystallizes in triclinic space group P-1. Each asymmetric unit contains one protonated single-side tris-functionalized Anderson-type POMs anion cluster, {[NH3C(CH2O)3]Cr(OH)3Mo6O18}2- (CrMo6-tris-NH3), and two NH4+ counter cations and five crystallized H2O solvent molecules, which can assemble into a layer-by-layer structure via hydrogen bonding interactions. Furthermore, compound 1 was characterized by elemental analysis, FT-IR, 1H NMR, UV–Vis and TGA. Such a water-soluble tris-functionalized POM with the remote amino reactive group has not been reported before and it may serve as a valuable synthon for further post-functionalization in aqueous solution.

Two-dimensional nanomaterials have become a hot research topic, and progress in research on them in the past decade has been substantial. Here we demonstrate a molecule-based bottom-up method to synthesize freestanding polyoxometalatebased nanosheets in two different ways. The trans substitution of ligands with carboxylate functionality promoted the coordination of organically derivatized hexavanadate with zinc ions with preferential directionality, which led to the formation of coordination polymer nanosheets. Characterization with transmission electron microscopy, powder X-ray diffraction, and infrared spectroscopy confirmed the morphology, structural composition, and preferential direction of the nanosheets. The microwave-assisted heating method and solvent addition method were proved to be effective for the preparation of POM-based nanosheet structures. The nanosheets were found to catalyze the aerobic oxidation of propanethiol (n-PrSH) to its corresponding disulfide (PrSSPr) under mild conditions.