•Three new heteronuclear sandwich-type complexes have been synthesized.•They were synthesized by an innovative “pH-controllable degradation approach”.•Complexes 1 and 3 exhibit catalytic activities for electrocatalytic reduction of nitrate.•Complexes 1–3 demonstrated unusual magnetic properties.Three new heteronuclear [FeW9O34]-based sandwich-type complexes [FeIII2MnII2(H2O)2(FeW9O34)2]12− (1), [FeIII2MnIII2(H2O)2(FeW9O34)2]10− (2) and [FeIII2NiII2(H2O)2(FeW9O34)2]12− (3) have been synthesized by an innovative method of pH-controllable degradation in aqueous solution, in which the [FeW12O40]5− precursor could be predominantly degraded into the trivacant [FeW9O34]11− anion. The active ligand of trivacant [FeW9O34]11− anion can catch in situ the mixed transition metal ions to conduce a directed coordination assembly reaction. These three heteronuclear complexes have been characterized by elemental analysis, single-crystal and powder X-ray diffraction analyses, IR spectra, UV–vis spectra, and thermal gravimetric analysis, cyclic voltammetry, magnetic properties, and thermal gravimetric analysis. Complexes 1 and 3 exhibit obvious catalytic activities for electrocatalytic reduction of nitrate. Compared with 1, the magnetic property of 2 shows a remarkable change by only a conversion of Mn(II) into Mn(III), so that a strong ferromagnetic interaction occurs in 2.Three new heteronuclear [FeW9O34]-based sandwich-type complexes have been synthesized by an innovative method of pH-controllable degradation in aqueous solution, in which the [FeW12O40]5− precursor could be predominantly degraded into the trivacant [FeW9O34]11− anion. The active ligand of trivacant [FeW9O34]11− anion can catch in situ the mixed transition metal ions to conduce a directed coordination assembly reaction.Download high-res image (82KB)Download full-size image

•A new tetranuclear pyrophosphate-bridged Cu(II) complex has been hydrothermal synthesized.•The tetranuclear cluster formed with both chelating ligands and linear bridging ligands.•The analysis of the magnetic data shows intramolecular magnetic coupling.A new tetranuclear pyrophosphate-bridged Cu(II) complex with 4,4′-bipyridine and 1,10-phenanthroline [Cu4(phen)4(bpy)2(P2O7)2]·10H2O (1) has been hydrothermal synthesized and characterized by single-crystal X-ray analysis, element analysis, IR spectroscopy, TG analysis, and UV–vis spectra. Variable-temperature magnetic susceptibility measurements show the occurrence of antiferromagnetic interactions between the neighbor Cu(II) centers in 1. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = − 13.16 cm− 1).A new tetranuclear pyrophosphate-bridged Cu(II) complex has been hydrothermal synthesized. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = − 13.16 cm− 1).Download high-res image (251KB)Download full-size image

•The M-G hybrid was fabricated by hydrothermal method.•M-G composite has shown better conversion efficiency as counter electrode than Pt and bare MoS2 in QDSSC.•The fabricated cell shows high efficiency (6.23%) under weak light intensity (25 mW/cm2).MoS2-graphene (M-G) hybrid was prepared by a hydrothermal method and used as counter electrode materials in CdS quantum dot-densitized solar cells (QDSSCs). Under simulated solar light irradiation, the cell with M-G counter electrode has higher efficiency than that of Pt and bare MoS2 counter electrode owing to the synergistic effects between MoS2 and graphene. The electrochemical impedance spectroscopy (EIS) and Tafel-polarization measurements reveal that M-G counter electrodes show better electrocatalytic activity. Moreover, the fabricated cell shows high efficiency (6.23%) under weak light intensity (25 mW/cm2).MoS2-graphene (M-G) hybrid was used as counter electrode materials in quantum dot-densitized solar cells (QDSSCs) and the M-G CEs have higher efficiency than MoS2 or Pt counter electrode.Download high-res image (208KB)Download full-size image

The first Krebs-type tungstoantimonate containing ferrous ions Na2H4[C3H5N2]4[Sb2W20FeII2(H2O)6O70]·12H2O (1) was prepared by a new route of synthesis under mild reaction conditions. The facile synthesis route represented a favourable tactic for the successful synthesis of FeII-based polyoxometalate. Its applications in both catalytic Fenton reaction and electrochemical sensing of ascorbic acid were also investigated primarily.

Herein, we show a new photomagnetic system that gives rise to the magnetic transformation from diamagnetism to paramagnetism by photoinduced intramolecular charge transfer in the polyoxometalate-based organic–inorganic hybrid, [(VMo6O22)2{O2C(CH2)2CO2}3] (1).

A new organically templated molybdenum oxides compound Zn2(bpe)Mo2O8 (bpe = 1,2-bis(4-pyridyl)ethane) has been hydrothermal synthesized and characterized by single X-ray analysis, element analysis, IR spectroscopy, TG analysis, diffuse reflectance UV–Vis spectra. Compound 1 shows a three-dimensional net-like structure, where the bimetallic oxide layers {ZnMoO4} were knitted together with the bpe ligands. The optical band gap for 1 was 2.5 eV, which is comparable to that of TiO2. Moreover, the photoluminescent properties of 1 have been investigated at room temperature.

Two cyanometalate-functionalized heteropolytungstates (C4H10ON)23[HN(CH2CH2OH)3]11H[FeIII(CN)6(α2-P2W17O61NiII)4]·31H2O (1) and (C4H10ON)23[HN(CH2CH2OH)3]10H2[FeIII(CN)6(α2-P2W17O61CoII)4]·27H2O (2) (C4H10ON = morpholine, HN(CH2CH2OH)3 = triethanol amine) have been successfully synthesized in aqueous solution under conventional reaction conditions, which demonstrated that it is a successful strategy to incorporate the cyanometalate fragment into lacunary heteropolytungstates. These polyanions were characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, thermogravimetric analysis, magnetic studies, and electrochemistry. Interestingly, the electrochemical studies have shown that the two complexes have bifunctional electrocatalytic activities towards not only the reduction of potassium iodate (KIO3) ascribed to the function of POM, but also the oxidation of the biological molecule ascorbic acid (AA) ascribed to the Fe-center in [MII4FeIII(CN)6]5+. Significantly, the magnetic investigations demonstrate the presence of ferromagnetic exchange interactions in 1 (Ni4Fe) and antiferromagnetic interactions in 2 (Co4Fe).

An efficient photocatalyst was designed through dual modification of CdS by cobalt polyoxotungstosilic (SiW11Co) and MoS2/graphene (M/G). The activity of CdS is increased up to 21.3 times with 1 wt% SiW11Co and 5 wt% M/G loaded. In the absence of noble metals, the as-prepared sample reached a H2 evolution rate of 1.7 mmol h−1.

A highly active and stable photocatalyst MoS2–graphene/CdS nanoparticles/nanorods was prepared using a facile two-step hydrothermal method. The noble-metal-free photocatalyst achieved a remarkable quantum yield of 65.8% at 420 nm for photocatalytic H2 evolution from water.

Three multi-copper molybdovanadate cluster compounds [Cu8(OH)2(H2O)2V10Mo30O132]20− (1), {[CuNa(H2O)6][Cu(H2O)4]2[Cu8(OH)2(H2O)2V9Mo30O128]}10− (2), {[Cu0.5Na0.5(H2O)3][Cu(H2O)4]2 [Cu6(OH)2(H2O)2V9Mo23O108]}9.5− (3), containing a novel [VMo7O28]9− fragment, have been isolated by using a one-pot self-assembly method. These three compounds were characterized by elemental analysis, single-crystal X-ray diffraction, IR spectroscopy, UV-vis spectroscopy, cyclic voltammetry, magnetic properties analysis, and thermal gravimetric analysis. The Z-shaped [Cu8(OH)2(H2O)2V9Mo30O128]17− anions of compound 2 can transform into the banana-shaped {Cu6(OH)2(H2O)2V9Mo23O108} units of compound 3 by only changing the pH from 4.5 to 5.0, while the introduction of nitrilotriacetic acid as an assistant ligand ensures the formation of the zero-dimensional compound 1. Magnetic studies indicate the presence of strong antiferromagnetic interactions in compounds 1–3, and the three compounds also exhibit obvious electrocatalytic activities for nitrate reduction. The semiconducting properties of these solid state compounds were revealed from the measurements of the diffuse reflectance UV-vis spectra, in which the band gap values at ca. 2.5 eV are similar to inorganic semiconductor materials, suggesting potential applications in areas of photocatalysis and light-to-electricity conversion.

Composite photocatalyst K7HNb6O19–NiS/Cd0.65Zn0.35S is demonstrated to be highly active for H2 evolution under visible light due to the introduction of K7HNb6O19 and NiS as cocatalysts. In the absence of noble metals, a high quantum yield of 42% was achieved at 420 nm.

A highly active and stable photocatalyst MoS2–graphene/CdS nanoparticles/nanorods was prepared using a facile two-step hydrothermal method. The noble-metal-free photocatalyst achieved a remarkable quantum yield of 65.8% at 420 nm for photocatalytic H2 evolution from water.

The first Krebs-type tungstoantimonate containing ferrous ions Na2H4[C3H5N2]4[Sb2W20FeII2(H2O)6O70]·12H2O (1) was prepared by a new route of synthesis under mild reaction conditions. The facile synthesis route represented a favourable tactic for the successful synthesis of FeII-based polyoxometalate. Its applications in both catalytic Fenton reaction and electrochemical sensing of ascorbic acid were also investigated primarily.

Herein, we show a new photomagnetic system that gives rise to the magnetic transformation from diamagnetism to paramagnetism by photoinduced intramolecular charge transfer in the polyoxometalate-based organic–inorganic hybrid, [(VMo6O22)2{O2C(CH2)2CO2}3] (1).

Two cyanometalate-functionalized heteropolytungstates (C4H10ON)23[HN(CH2CH2OH)3]11H[FeIII(CN)6(α2-P2W17O61NiII)4]·31H2O (1) and (C4H10ON)23[HN(CH2CH2OH)3]10H2[FeIII(CN)6(α2-P2W17O61CoII)4]·27H2O (2) (C4H10ON = morpholine, HN(CH2CH2OH)3 = triethanol amine) have been successfully synthesized in aqueous solution under conventional reaction conditions, which demonstrated that it is a successful strategy to incorporate the cyanometalate fragment into lacunary heteropolytungstates. These polyanions were characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, thermogravimetric analysis, magnetic studies, and electrochemistry. Interestingly, the electrochemical studies have shown that the two complexes have bifunctional electrocatalytic activities towards not only the reduction of potassium iodate (KIO3) ascribed to the function of POM, but also the oxidation of the biological molecule ascorbic acid (AA) ascribed to the Fe-center in [MII4FeIII(CN)6]5+. Significantly, the magnetic investigations demonstrate the presence of ferromagnetic exchange interactions in 1 (Ni4Fe) and antiferromagnetic interactions in 2 (Co4Fe).