Constructing Two Cu-Modified Organophosphomolybdates from a Nanocluster to a One-Dimensional Chain for Boosted Visible-Light-Driven Hydrogen Production

Photocatalytic decomposition of water to produce hydrogen H2 is an ideal way to solve energy and environmental problems, and the development of highly efficient polyoxometalate catalysts for photocatalytic hydrogen production has attracted wide attention. Herein, two Cu-modified Strandberg-type organophosphomolybdates were successfully synthesized, [Cu(C8H7N3)(H2O)2]2[(C6H5PO3)2Mo5O15]·4H2O (1) and [Cu(phen)(H2O)][Cu(phen)(H2O)2][(C6H5PO3)2Mo5O15]·2H2O (2) ([(C6H5P)2Mo5O21]Cu2) (C8H7N3 = 2-(1H-pyrazol-3-yl)pyridine, phen = 1,10-phenanthroline). Two Strandberg-type organophosphomolybdates can be used for visible-light-driven hydrogen production. Also, compound 2 exhibits an H2 production rate of 6399 μmol g-1 h-1 after 8 h light exposure in the presence of photosensitization agent [Ir(dtbbpy)(ppy)2][PF6] and TEOA. In addition, cyclic tests showed that compound 2 could be recycled four times without a significant reduction in catalytic performance. This work offers fresh insight into the development of novel polyoxometalates for efficient hydrogen evolution.

A polyoxomolybdate-based hybrid nano capsule as an antineoplastic agent

Polyoxometalates (POMs) are versatile anionic clusters which have attracted a lot of attention in biomedical investigations. To counteract the increasing resistance effect of cancer cells and the high toxicity of chemotherapeutic treatments, POM-based metallodrugs can be strategically synthesized by adjusting the stereochemical and physicochemical features of POMs. In the present report a polyoxomolybdate (POMo) based organic-inorganic hybrid solid (C6H16N)(C6H15N)2[Mo8O26]·3H2O, solid 1, has been synthesized and its antitumoral activities have been investigated against three cancer cell lines namely, A549 (Lung cancer), HepG2 (Liver cancer), and MCF-7 (Breast cancer) with IC50 values 56.2 μmol L-1, 57.3 μmol L-1, and 55.2 μmol L-1 respectively. The structural characterization revealed that solid 1 consists of an octa molybdate-type cluster connected by three triethylamine molecules via hydrogen bonding interactions. The electron microscopy analysis suggests the nanocapsule-like morphology of solid 1 in the size range of 50-70 nm. The UV-vis absorption spectra were used to assess the binding ability of synthesized POM-based solid 1 to calf thymus DNA (ctDNA), which further explained the binding interaction between POMo and ctDNA and the binding constant was calculated to be 2.246 × 103 giving evidence of groove binding.

Hybrid Cu-Containing Compounds Based on Lacunary Strandberg Anions: Synthesis under Mild Conditions, Crystal Structure, and Magnetic Properties

A one-pot reaction of a copper source (metallic powder Cu⁰ or Cu²⁺ salts) and bpy (bpy = 2,2'-bipyridine) in the presence of (NH₄)₂HPO₄ and (NH₄)₆Mo₇O₂₄·4H₂O yields heterometallic hybrid compounds of the general type {[Cu(bpy)_n(H₂O)_m]_p[P₂Mo_xO_y]}. The structures exhibit a number of phosphomolybdate POMs including not only a common Strandberg anion [P₂Mo₅O₂₃]^6- but also its unprecedented bi- and trilacunary derivatives [P₂Mo₃O₁₈]^8- and [P₂Mo₂O₁₅]^8-. The structural determinants including the metal source (copper powder vs copper salts), counterion of the salts, and stoichiometry of the reagents were examined. An ex situ EPR study revealed the formation of different Cu^II complexes in the reaction mixture depending on the copper precursor. The obtained compounds have been found to possess selectivity toward the sorption of methylene blue in a mixture of organic dyes. DC magnetic measurements of 1-3 indicate rather strong antiferromagnetic metal-metal exchange interactions. Compound 1 exhibits field-induced slow magnetic relaxation in AC magnetic measurements, which is a rarely observed phenomenon among Cu(II) complexes.

Synergistic Photocatalytic-Adsorption Removal of Basic Magenta Effect of AgZnO/Polyoxometalates Nanocomposites

The bifunctional photocatalytic-adsorbent AgZnO/polyoxometalates (AgZnO/POMs) nanocomposites were synthesized by combining AgZnO hybrid nanoparticles and polyoxometalates [Cu(L)₂(H₂O)]H₂[Cu(L)₂(P₂Mo₅O₂₃)]⋅4H₂O (HL = C₆H₆N₂O) into nanostructures via a sonochemical method. Transmission electron microscopy (TEM) indicated that AgZnO/POMs nanocomposites were uniform with narrow particle size distribution and without agglomeration. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the nanostructure and composition of AgZnO/POMs nanocomposites. The ultraviolet-visible spectra (UV-Vis) and photoluminescence spectra (PL) confirmed excellent optical properties of the AgZnO/POMs nanocomposites. 94.13% ± 0.61 of basic magenta (BM) in aqueous solution could be removed using the AgZnO/POMs nanocomposites through adsorption and photocatalysis. The kinetic analysis showed that both the adsorption and photocatalysis process conform to pseudo-second-order kinetics. In addition, the removal rate of AgZnO/POMs nanocomposites was found to be almost unchanged after 5 cycles of use. The bifunctional photocatalytic-adsorbent AgZnO/POMs nanocomposites with high stability and cycling performance have broad application prospects in the treatment of refractory organic dye wastewater containing triphenylmethane.

In Vitro Anti-tumoral and Anti-bacterial Activity of an Octamolybdate Cluster-Based Hybrid Solid Incorporated with a Copper Picolinate Complex

Inorganic drugs, especially polyoxometalate-based hybrids, are expected to be developed as promising future metallodrugs. Herein, an organic-inorganic hybrid solid based on pyridine-2-carboxylic acid or picolinic acid (pic), [(Cu(pic)₂)₂(Mo₈O₂₆)]·8H₂O (1), was synthesized. A single-crystal structure of a solid possesses a discrete β-type octamolybdate cluster that supramolecularly aggregates with a {Cu₂(pic)₄}^4- complex and eight lattice water molecules. The study indicates that the solid is stable in aqueous medium and less toxic toward normal cell lines. The in vitro anti-bacterial and anti-tumor properties of the solid 1 were investigated. The results of the anti-tumor action against various human cancer cell lines, namely, lung (A549), breast (MCF-7), and liver (HepG2) cancer cells suggest that this β-octamolybdate-based solid yielded the lowest IC₅₀ value reported so far among octamolybdate anion-based hybrid solids, i.e., 24.24 μM for MCF-7, 21.56 μM for HepG2, and 25 μM for A549, indicating significant anti-cancer activity. The cell cycle analysis further reveals the observed anti-tumor effect to be governed by the arrest of breast cancer cells in the G2/M phase while that of lung and liver cancer cells in the S phase of the cell cycle. A fluorescence quenching study suggests the binding interaction between solid and ctDNA, which in turn induces apoptosis and necrosis pathways leading to cancer cell death. This is also the first study of {Mo₈O₂₆}^4- cluster-based solids as an anti-bacterial agent against Escherichia coli, and it was found to be very effective with a minimal inhibitory concentration value of ∼135 μg/mL, which is the lowest so far reported for any octamolybdate-based solid.

Structure, optical and magnetic properties of a novel homometallic coordination polymers: Experimental and Computational studies

Single crystal of 1D homometallic coordination polymer involving cobalt metal ion and P₂Mo₅ Strandberg type polyoxometallate cluster (C₆H₁₀N₂)₂[Co(H₂O)₄P₂Mo₅O₂₃].6H₂O, is prepared in aqueous solution and characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance, fluorescence and magnetism. Single crystal X-ray diffraction analysis reveals that this compound crystallizes in the triclinic system with space group P \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\,\bar{1}$$\end{document}1¯. The 3-(ammoniomethyl)pyridine C₆H₈N₂ organic fragment is used merely as stabilizer for the promotion of topological structure. DRS data indicate that the synthesized material can be identified as a ferromagnetic semiconductor with optical bands gaps energy of 1.81 and 2.74 eV, respectively. The large value of refractive index observed in the visible region make the simple a promising candidate for visible optical communication devices and fluorescent emisson result provides that the complex belongs to a blue luminescent compounds. Moreover, magnetic measurements and electronic structure calculations show that P₂Mo₅ Strandberg polyoxoanion can be reported as a new class of ligand that is candidate to construct metal-inorganic framworks with long distance ferromagnetic superechange between Co(II) centers. The evidence from this study suggests that the syntesized polymer can become a great multifunctional material openning the door for the developpement of new coordination polymers based on Strandberg type polyxoxmetalate with potential applications.

Effective inhibitory activity against MCF-7, A549 and HepG2 cancer cells by a phosphomolybdate based hybrid solid

A novel P₂Mo₅ cluster based hybrid solid [{4,4′-H₂bpy}{4,4′-Hbpy}₂{H₂P₂Mo₅O₂₃}]·5H₂O with effective anti-proliferation activity against MCF-7, HepG2 and A549 cancer cells comparable with a routinely used chemotherapeutic agent, methotrexate (MTX).

Synthesis, characterization and bioactivities of a new covalent copper(II) compound derived from {P2Mo5O23}6- and thiosemicarbazones

In this article, a new compound H₂[{Cu(HL)(H₂O)}₂(P₂Mo₅O₂₃)]·5H₂O (1) (HL = 2-acetylpyrazine thiosemicarbazone) has been synthesized and structurally characterized by single-crystal X-ray diffraction of and other detection techniques. Interestingly, the structure of 1 is different from many reported copper-based complexes, in which the [P₂Mo₅O₂₃]^6-, two Cu²⁺ ions and two HL were directly connected by covalent bands. Biological studies demonstrated that 1 indicated moderate antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and a better cytotoxicity against human hepatic cancer line (SMMC-7721) than Mitoxantrone (Mito), the current clinical anticancer drug. Besides, the antibacterial mechanisms of 1 have been studied by the membrane integrity disruption, the destructive reactive oxygen species generation (ROS), the glutathione (GSH) depletion and the depressed enzymatic activity of respiratory chain dehydrogenases (RCD). These results revealed that the combination of HL, Cu²⁺, [P₂Mo₅O₂₃]^6- shows a higher antibacterial and cytotoxic activity.

Synthesis, Characterization and Dye Removal Behavior of Core-Shell-Shell Fe3O4/Ag/Polyoxometalates Ternary Nanocomposites

The ternary nanocomposites Fe3O4/Ag/polyoxometalates (Fe3O4/Ag/POMs) with core-shell-core nanostructure were synthesized by coating [Cu(C6H6N2O)2(H2O)]H2[Cu(C6H6N2O)2(P2Mo5O23)]·4H2O polyoxometalates on the surface of Fe3O4/Ag (core-shell) nanoparticles. The transmission electron microscopy/high resolution transmission electron microscopy (HR-TEM) and X-ray powder diffraction (XRD) analyses show that the Fe3O4/Ag/POMs ternary nanocomposites reveal a core-shell-core nanostructure, good dispersibility, and high crystallinity. The vibrating sample magnetometer (VSM) and physical property measurement system (PPMS) demonstrated the good magnetic properties and superparamagnetic behavior of the nanocomposites at 300 K. The UV-vis spectroscopy displayed the broadband absorption of the Fe3O4/Ag/POMs with the maximum surface plasmon resonance of Ag nanostructure around 420 nm. The dye removal capacity of Fe3O4/Ag/POMs was investigated using methylene blue (MB) as a probe. Through adsorption and photocatalysis, the nanocomposites could quickly remove MB with a removal efficiency of 98.7% under the irradiation of visible light at room temperature. The removal efficiency was still as high as 97.5% even after six runs by magnetic separation of photocatalytic adsorbents after processing, indicating the reusability and high stability of the nanocomposites. These Fe3O4/Ag/POMs photocatalytic adsorbents with magnetic properties will hopefully become a functional material for wastewater treatment in the future.

Dyes Adsorption Behavior of Fe3O4 Nanoparticles Functionalized Polyoxometalate Hybrid

The magnetic adsorbent, Fe₃O₄@[Ni(HL)₂]₂H₂[P₂Mo₅O₂₃]·2H₂O (Fe₃O₄@1), is synthesized by employing the nanoparticles Fe₃O₄ and polyoxometalate hybrid 1. Zero-field-cooled (ZFC) and field-cooled (FC) curves show that the blocking temperature of Fe₃O₄@1 was at 120 K. Studies of Fe₃O₄@1 removing cationic and anionic dyes from water have been explored. The characterization of Fe₃O₄@1, effects of critical factors such as dosage, the concentration of methylene blue (MB), pH, adsorption kinetics, isotherm, the removal selectivity of substrate and the reusability of Fe₃O₄@1 were assessed. The magnetic adsorbent displayed an outstanding removal activity for the cationic dye at a broad range of pH. The adsorption kinetics and isotherm models revealed that the adsorption process of Fe₃O₄@1 was mainly governed via chemisorption. The maximum capacity of Fe₃O₄@1 adsorbing substance was 41.91 mg g⁻¹. Furthermore, Fe₃O₄@1 showed its high stability by remaining for seven runs of the adsorption-desorption process with an effective MB removal rate, and could also be developed as a valuable adsorbent for dyes elimination from aqueous system.

Preparation of Fe3O4@polyoxometalates Nanocomposites and Their Efficient Adsorption of Cationic Dyes from Aqueous Solution

In this work, two magnetic adsorbents Fe₃O₄@1 and Fe₃O₄@2 were prepared by combining Fe₃O₄ nanoparticles and polyoxometalate hybrids [Ni(HL)₂]₂H₂[P₂Mo₅O₂₃]·4H₂O (1), [H₂L]₅H[P₂Mo₅O₂₃]·12H₂O (2) (HL = 2-acetylpyridine-thiosemicarbazone). The temperature-dependent zero-field-cooled (ZFC) and field-cooled (FC) measurements indicated the blocking temperature at 160 K and 180 K, respectively. The Brunauer–Emmett–Teller (BET) surface area of Fe₃O₄@1 and Fe₃O₄@2 is 8.106 m²/g and 1.787 m²/g, respectively. Cationic dye methylene blue (MB) and anionic dye methyl orange (MO) were investigated for selective dye adsorption on Fe₃O₄@1 and Fe₃O₄@2. The two adsorbents were beneficial for selective adsorption of cationic dyes. The adsorption efficiency of MB was 94.8% for Fe₃O₄@1, 97.67% for Fe₃O₄@2. Furthermore, the two adsorbents almost maintained the same adsorption efficiency after seven runs. The maximum MB adsorption capacity of Fe₃O₄@1 and Fe₃O₄@2 is 72.07 and 73.25 mg/g, respectively. The fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) spectra of the adsorbents collected after adsorption of MB are very similar to the initial as-synthesized Fe₃O₄@polyoxometalates indicating the high stability of the two adsorbents. The adsorption kinetics indicated that the MB removal followed the pseudo-second-order model. These results showed that the two adsorbents had a potential application in treating wastewater.

A Comprehensive Study on the Dye Adsorption Behavior of Polyoxometalate-Complex Nano-Hybrids Containing Classic β-Octamolybdate and Biimidazole Units

Six new hybrids based on β-[Mo₈O26]4- polyoxometalates, [Ni(H₂biim)₃]₂[β-Mo₈O26]•8DMF(1); (DMA)₂[M(H₂biim)₂(H₂O)₂][β-Mo₈O26]•4DMF (M = Ni (2), Co (3)), DMA = dimethyl-ammonium, H₂biim=2,2'-biimidazole); [M(H₂biim)(DMF)₃]₂[β-Mo₈O26]•2DMF (M = Zn (4), Cu (5)); [(DMA)₂[Cu(DMF)₄][β-Mo₈O26]•2DMF]n (6), have been successfully synthesized and characterized. Compounds 2⁻5 show favorable capacity to adsorb methylene blue (MB) at room temperature, and they can selectively capture MB molecules from binary-mixture solutions of MB/MO (MO = Methyl Orange), or MB/RhB (RhB = Rhodamine B). Compound 3 can uptake up to 521.7 mg g-1 MB cationic dyes rapidly, which perform the maximum adsorption in an hour among the reported materials as far as we know. The compounds are stable and still work very efficiently after three cycles. For compound 3, the preliminary adsorption mechanism studies indicated that the adsorption is an ion exchange process and the adsorption behavior of polyoxometalate-complex can be benefited from additional exchangeable protons in the complex cations.

Copper-containing hybrid compounds based on extremely rare [V2Mo6O26]6– POM as water oxidation catalysts

Hybrid Cu/V/Mo compounds with rare [α-V₂Mo₆O₂₆]^6– and oxides prepared by their thermal degradation were used as catalysts for water oxidation.

Immobilization of enzymes on an organic–inorganic hybrid network consisting of Dawson-type polyoxotungstate and a zinc(ii)-biimidazole complex moiety

A new polyoxometalate (POM)-based organic–inorganic hybrid compound {[(Zn(H₂biim)₂)₃(P₂W₁₈O₆₂)]·6H₂O}_n (1) shows excellent enzyme-loading capability for horseradish peroxidase (HRP) and can be used as a new catalyst for trace H₂O₂ detection in solution.

A new hexamolybdate-based copper-2,2'-biimidazole coordination polymer serving as an acid catalyst and support for enzyme immobilization

The hydrothermal reaction of (NH₄)₃[CoMo₆O₂₄H₆]·7H₂O (CoMo₆), CuCl₂·2H₂O and 2,2'-biimidazole (H₂biim) led to the formation of a new coordination polymer, namely poly[diaquabis(2,2'-biimidazole)hexa-μ₃-oxo-octa-μ₂-oxo-hexaoxodicopper(II)hexamolybdate(VI)], [Cu₂Mo₆O₂₀(C₆H₆N₄)₂(H₂O)₂]_n (Cu-Mo₆O₂₀), at pH 2-3. It is obvious that in the formation of crystalline Cu-Mo₆O₂₀, the original Anderson-type skeleton of heteropolymolybdate CoMo₆ was broken and the new isopolyhexamolybdate Mo₆O₂₀ unit was assembled. In Cu-Mo₆O₂₀, one Mo₆O₂₀ unit connects four [Cu(H₂biim)(H₂O)]²⁺ ions in a pentacoordinate mode via four terminal O atoms, resulting in a tetra-supported structure, and each Cu^II ion is shared by two adjacent Mo₆O₂₀ units. Infinite one-dimensional chains are established by linkage between two adjacent Mo₆O₂₀ units and two Cu^II ions, and these chains are further packed into a three-dimensional framework by hydrogen bonds, π-π interactions and electrostatic attractions. The catalytic performance of this crystalline material used as an efficient and reusable heterogeneous acid catalyst for carbonyl-group protection is discussed. In addition, Cu-Mo₆O₂₀ was applied as a new support for enzyme (horseradish peroxidase, HRP) immobilization, forming immobilized enzyme HRP/Cu-Mo₆O₂₀. HRP/Cu-Mo₆O₂₀ showed good catalytic activity and could be reused.

A Magnetic Adsorbent for the Removal of Cationic Dyes from Wastewater

In this article, a study was presented on the adsorption activity of a new nanocomposite particle Fe₃O₄@1, which was synthesized by combining [Cu(HL)₂]₂H₂[P₂Mo₅O23]·10H₂O (1) (HL = 2-acetylpyridine semicarbazone) and Fe₃O₄ nanoparticles. Transmission electron microscopy and X-ray powder diffraction analyses revealed that Fe₃O₄@1 possessed high crystallinity with an average particle size of 19.1 nm. The adsorption activity of the as-prepared Fe₃O₄@1 was investigated by photometrically monitoring the removal of methylene blue, rhodamine B, safranine T, gentian violet, fuchsin basic, and methyl orange from aqueous solutions. Significantly, we could easily separate Fe₃O₄@1 from the reaction media by applying an external magnet. Furthermore, the recycling performance was observed using methylene blue, revealing the recyclability and high stability of Fe₃O₄@1. It was shown that Fe₃O₄@1 is a promising candidate material for adsorbing cationic dyes in aqueous media.

Three new Strandberg-type phenylphosphomolybdate supports for immobilizing horseradish peroxidase and their catalytic oxidation performances

Three new Strandberg-type polyoxometalate TM-(PhP)2Mo5 supports for immobilizing HRP showed high adsorption capacity and good catalytic oxidation activity.

Two novel bi-functional hybrid materials constructed from POMs and a Schiff base with excellent third-order NLO and catalytic properties

The first polyoxometalates modified by a porphyrin-resembling planar Schiff base have been successfully designed and synthesized under hydrothermal conditions. The third-order NLO responses indicated that they are excellent third-order NLO materials. Their catalytic performances are also investigated.

Synthesis and adsorption properties of [Cu(L)2(H2O)]H2[Cu(L)2(P2Mo5O23)]·4H2O/Fe3O4 nanocomposites

Multifunctional [Cu(L)₂(H₂O)]H₂[Cu(L)₂(P₂Mo₅O₂₃)]·4H₂O/Fe₃O₄ (HL = pyridine-2-carboxamide) nanocomposites were successfully synthesized by combining [Cu(L)₂(H₂O)]H₂[Cu(L)₂(P₂Mo₅O₂₃)]·4H₂O and Fe₃O₄ nanoparticles.

Controllable assembly, characterization and catalytic properties of a new Strandberg-type organophosphotungstate

A new Strandberg-type organophosphotungstate was assembled under hydrothermal conditions and displayed good fluorescence properties and catalytic activity.

Heterogeneous Catalysis of Polyoxometalate Based Organic-Inorganic Hybrids

Organic–inorganic hybrid polyoxometalate (POM) compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic–inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.

Three novel polyoxoanion-supported compounds: confinement of polyoxoanions in Ni-containing rigid concave surfaces with enhanced NLO properties

Three new polyoxometalates confined in metal-containing rigid concave surfaces were developed. All of them gave a strong third-order NLO response.