Self-Assembled 8-Ti-Containing Polyoxomolybdate for the Photocatalytic Hydrogen Evolution

An S-shaped 8-Ti-containing polyoxomolybdate (NH4)Cs2Na6H3[Ti8(GeMo9O34)2(GeMo5O23)2]·44H2O (1) has been prepared under the one-pot hydrothermal method and further characterized. According to single-crystal X-ray, compound 1 consists of two {GeMo9O34} and two {GeMo5O23} segments, which are linked with a {Ti8O34} cluster. Moreover, the {GeMo5O23} fragment is rare and the first discovery, which enriches the lacunary Keggin-type family and offers the possibility of obtaining new structures. Among all of the reported polyoxomolybdates, compound 1 has the highest nuclearity of Ti centers. From the photocatalytic hydrogen evolution studies, compound 1 can be used as the heterogeneous catalyst with an H2 evolution rate of 2392.6 μmol g-1 h-1 under minimally optimized conditions.

A Lanthanide-Incorporated Phospho(III)tungstate Aggregate Constructed from [HPIIIW8O31]10- and [W11O39]12- Building Blocks and Its Nanocomposite with CdS for Ultrasensitive Photoelectrochemical Detection of Oxytetracycline

A novel tartronic acid decorated hexa-CeIII-incorporated phospho(III)tungstate aggregate (C4H12NO)6Na18H2[(HPW8O31)2[W11O39]2(H2TAD)4(H2O)4W4Ce6H2P2O14]·84H2O (1, H3TAD = tartronic acid) was synthesized by a one-step assembly strategy. Its main skeleton is constructed from two [W11O39]12- fragments, two [HPIIIW8O31]10- segments and one H2TAD--ornamented dodecanuclear heterometallic [W4Ce6H2PIII2O14(H2TAD)4(H2O)4]18+ cluster. In the structure, the [HPIIIO3]2- groups not only work as the heteroatom template to induce the formation of lacunary [HPIIIW8O31]10- segments but also function as the connector to bridge Ce3+ cations. With the help of a reaction strategy of combining ultrasonication treatment with the continuous ion layer adsorption method, the 1/CdS composite was constructed and exhibits prominent photoelectrochemical activity. The 1/CdS composite was used as a photoelectrochemical sensor for oxytetracycline detection at 0 V (vs Ag/AgCl), which displays excellent properties with quick response and low limit of detection (0.042 nM). This work can provide some helpful references in the construction of novel PIII-induced polyoxometalates consisting of different building blocks and can extend the applications of polyoxometalate-based nanocomposites into photoelectrochemical detection for antibiotics as well as biomolecules.

Synthesis and Characterization of 6-Ti-Substituted Polyoxomolybdate with High Catalytic Activity for Sulfide Oxidation

A 6-Ti-substituted polyoxometalate, (NH4)5Cs7Na3H2[Cs@(Ti2GeMo10O39)3]·34H2O (1), was synthesized by reacting (NH4)6Mo7O24·4H2O, GeO2, and TiOSO4 through the conventional aqueous method. Polyanion 1a is composed of three {Ti2GeMo10} segments linked by Ti-O-Ti linkages and shows a trefoil-shaped structure. Furthermore, one Cs+ cation is encapsulated in the cavity of 1a. Notably, it possesses the highest number of Ti centers among the reported polyoxomolybdates. In addition, serving as a high-efficiency heterogeneous catalyst, 1 enables the conversion of methyl phenyl sulfide within 20 min, yielding 96.4% of the corresponding sulfoxide with good recyclability.

Gold Nanoparticles Capped with a Novel Titanium(IV)-Containing Polyoxomolybdate Cluster: Selective and Enhanced Bactericidal Effect Against Escherichia coli

Bacterial infections are a public health threat of increasing concern in medical care systems; hence, the search for novel strategies to lower the use of antibiotics and their harmful effects becomes imperative. Herein, the antimicrobial performance of four polyoxometalate (POM)-stabilized gold nanoparticles (Au@POM) against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as Gram-negative and Gram-positive bacteria models, respectively, is studied. The bactericidal studies performed, both in planktonic and sessile forms, evidence the antimicrobial potential of these hybrid nanostructures with selectivity toward Gram-negative species. In particular, the Au@GeMoTi composite with the novel [Ti2 (HGeMo7 O28 )2 ]10- POM capping ligand exhibits outstanding bactericidal efficiency with a minimum inhibitory concentration of just 3.12 µm for the E. coli strain, thus outperforming the other three Au@POM counterparts. GeMoTi represents the fourth example of a water-soluble TiIV -containing polyoxomolybdate, and among them, the first sandwich-type structure having heteroatoms in high-oxidation state. The evaluation of the bactericidal mechanisms of action points to the cell membrane hyperpolarization, disruption, and subsequent nucleotide leakage and the low cytotoxicity exerted on five different cell lines at antimicrobial doses demonstrates the antibiotic-like character. These studies highlight the successful design and development of a new POM-based nanomaterial able to eradicate Gram-negative bacteria without damaging mammalian cells.

pH-Controlled assembly of [ZnW12O40]6--based hybrids from a 0D dimer to a 2D network: synthesis, crystal structure, and photocatalytic performance in transformation of toluene into benzaldehyde

Polyoxometalate-based organic-inorganic hybrids have attracted considerable attention due to their fascinating structures and wide application prospects. In this work, using the same building blocks, ligands and metal ions (ZnW₁₂O₄₀^6-(ZnW₁₂), 2,2'-bipyridine (2,2'-bipy), and Cu²⁺), we synthesized three new POM-based hybrids by controlling the pH values of the reaction systems. These three compounds {(Zn_0.6(H₂)_0.4W₁₂O₄₀)[Cu(2,2'-bipy)(H₂O)][Cu(2,2'-bipy)(H₂O)₂][Cu(2,2'-bipy)(H₂O)₃]}₂·6H₂O (1), (Me₄N)₂{ZnW₁₂O₄₀[Cu(2,2'-bipy)(H₂O)][Cu(2,2'-bipy)(H₂O)₃]}·5H₂O (2), and {(Zn_0.5(H₂)_0.5W₁₂O₄₀)[Cu(2,2'-bipy)][Cu(2,2'-bipy)(H₂O)][Cu(2,2'-bipy)(H₂O)₂]}·5H₂O (3) have been structurally characterized by single-crystal X-ray diffraction. Compound 1 appears as a dimeric cluster structure, while compounds 2 and 3 appear as a 1D chain structure and a 2D network, respectively. The semiconducting properties of compounds 1-3 are different, which was demonstrated by band gap (E_g) and photocurrent response measurements. Compound 3 can efficiently catalyze the photooxidation of toluene to benzaldehyde with high selectivity using molecular oxygen as the oxidant component. Moreover, compound 3 was recycled and reused three times without significant degradation in conversion and selectivity. In addition, the mechanism of the photocatalytic reaction was also investigated.

A series of A- and B-type Anderson compounds with Al, Te and Cr as centers by tuning different ligands: syntheses, electrochemical, photocatalytic and CO2RR properties

A series of N- and N/O-containing ligands were used, inducing the 2D structures of compounds 1, 3, 4 and 6, a discrete unit containing the tri-nuclear [Cu^II₃(tybm)₃(H₂O)₄]⁶⁺ cluster of 2, and a 3D framework of 5.