An isolated doughnut-like molybdenum(V) cobalto-phosphate cluster exhibiting excellent photocatalytic performance for carbon dioxide conversion.

An isolated doughnut-like molybdenum(V) cobalto-phosphate cluster with the formula (C11NH10)2{[Co(H2O)6]@[H29Co16Mo16(H2O)16(PO4)24O36]}(H2PO4)·25H2O has been successfully synthesized by a hydrothermal method. Single crystal X ray diffraction analysis shows that four {Co4O60} tetramers and eight {Mo2O10} dimers are linked by oxygen atoms and phosphate groups to construct a doughnut-type structure for [Co@{Co16Mo16}], in which one [CoII(H2O)6]2+ octahedron is enclosed. More importantly, [Co@{Co16Mo16}] exhibits promising photocatalytic performance for CO2 reduction with the CO formation rate of 6764.3 µmol g-1 h-1 and the selectivity of 96.89%. In addition, the cycling test indicated that [Co@{Co16Mo16}] can be reused for at least four cycles without significant loss of catalytic activity. The result of this work may provide new insight for the synthesis of highly efficient POM-based photocatalysts for CO2 reduction.

A Purely Inorganic Quasi-Keggin Polyoxometalate for Photocatalytic Conversion of Carbon Dioxide to Carbon Monoxide.

A pure inorganic cluster, H47 Na2 Co4 Mo24 (PO4 )11 O72 ⋅ 15H2 O (denoted as {Co4 Mo24 }), has been successfully synthesized by hydrothermal method. Notably, the assembly of a central {Co2 PO4 } tetrahedron and four peripheral {Co[P4 Mo6 ]} fragments gives rise to a rare "quasi-Keggin" structure of {Co4 Mo24 }, in which Co linkers continue to bridge adjacent substructures, resulting in the generation of 3D framework with large cavities. Benefitting from the combination of strong reductive {P4 Mo6 } units and Co active centers, the photocatalytic system with {Co4 Mo24 } as heterogeneous catalyst exhibits excellent activity for CO2 conversion to CO, offering the CO formation rate of 1848.3 µmol g-1 h-1 with high selectivity of 97.0 %. Besides, thermogravimetric and X-ray diffraction analysis confirm that {Co4 Mo24 } can maintain stable during the photocatalytic reaction process.

An Unprecedented Bird Nest Molybdenum(V) Cobalto-Phosphate Nanosized Wheel Constructed from the [H55 (Mo24 O48 )(Co4 O)2 Co16 (PO4 )42 (py)6 (EtOH)2 (H2 O)11 ]3- Anion.

An unprecedented bird-nest high-nuclear molybdenum(V) cobalto-phosphate nanosized wheel modified by imidazole (im) and pyridine (py), {[H55 (Mo24 O48 )(Co4 O)2 Co16 (PO4 )42 (py)6 (EtOH)2 (H2 O)11 ]- @[(Him)2 (Hpy)]}(N-Et-py)(H2 PO4 )(py)7 (EtOH)⋅12 H2 O (1), has been successfully synthesized by self-assembly. The anionic huge wheel consists of two rare {Co4 O} squares, four {Co4 } tetramers, four {Mo4 } tetramers and four {Mo2 } dimers, linked by bridging oxygen atoms and [PO4 ] groups and encloses two imidazolium cations and a protonated pyridium for charge balance. Surprisingly, 1 represents the first twisted wheel-shaped cluster with a record high-nuclear molybdenum(V) cobalto-phosphate. The delocalized electron effects of the cluster are enhanced with the help of coordinated py ligands, which endows 1 with an excellent third-order nonlinear optical (NLO) response. Additionally, 1 also shows a better photocatalytic water oxidation activity than Co(NO3 )2 with the O2 production of 205 µmol during 6 h in the absence of the [Ru(bpy)3 ]2+ photosensitizer.

Two 2D Layered P4Mo6 Clusters with Potential Bifunctional Properties: Proton Conduction and CO2 Photoreduction.

Two hourglass-type molybdophosphate hybrids with the formulas [Cd(H2O)2DABT]4[Cd(H7P4Mo6O31)2]·19H2O (1) and (C2H5OH)(C3H5N2)6[Co3(H6P4Mo6O31)2]·H2O (2) (DABT= 3,3'-diamino-5,5'-bis(1H-1,2,4-triazole)) have been successfully designed and synthesized via a hydrothermal method. Structure analysis revealed that the inorganic moieties in compounds 1 and 2 are made up of hourglass-type {M[P4Mo6]2} (M = Cd/Co) structure, which were constructed by two (P4Mo6) units with single transition metal (TM) (Cd/Co) atom as the central metal. The {M[P4Mo6]2} (M = Cd/Co) structures were then further connected by TM to constitute a 2D layered structure. Surprisingly, under the condition of 60 °C and 98% RH, compounds 1 and 2 exhibited excellent proton conductivity of 1.35 × 10-3 and 3.78 × 10-3 S cm-1, respectively. Furthermore, compound 2 can act as heterogeneous catalyst for CO2 photoreduction, which indicates that it may be a bifunctional POM-based material with great promise.

Synthesis, crystal structures and magnetic properties of two heterometallic {Ln8Cr4} (Ln = Gd3+ and Tb3+) complexes with one-dimensional wave chain structure.

Two isomorphic heterometallic 3d-4f cluster-based materials, formulated [Gd8Cr4(IN)18(µ3-O)2(µ3-OH)6(µ4-O)4(H2O)10]·13H2O (1) and [Tb8Cr4(IN)18(µ3-O)2(µ3-OH)6(µ4-O)4(H2O)10]·13H2O (2) (abbreviation: {Ln8Cr4}: Ln = Gd3+ (1); Tb3+ (2); HIN = isonicotinic acid), were achieved by hydro-/solvothermal method through using the ligand HIN. X-ray diffraction analysis illustrates eight lanthanide ions (Ln = Gd3+, Tb3+) and four transition-metal ions (Cr3+) of {Ln8Cr4} were constructed from two classical "drum-like" {Ln4Cr2} structures associated by organic ligands HIN, displaying a one-dimensional wave chain structure, which is rare. The magnetic properties of {Gd8Cr4} were inspected and showed the existence of antiferromagnetic coupling interactions between contiguous metal ions. On top of this, the magnetic entropy change of ΔS m can attain 23.40 J kg-1 K-1 (44.90 mJ cm-3 K-1) at about 3 K and ΔH = 7 T. Besides, fluorescence measurements of {Tb8Cr4} display typical characteristic Tb-based luminescence.

Lewis Acid Dominant Windmill-Shaped V8 Clusters: A Bifunctional Heterogeneous Catalyst for CO2 Cycloaddition and Oxidation of Sulfides.

Carbon dioxide (CO2) and sulfides in gasoline are the main causes of air pollution. Considerable attention has been devoted to solving the problems, and the catalytic reaction seems to be a good choice. Owing to the high density of Lewis acid (LA) active sites and large numbers of open methoxide groups, polyoxovanadates (POVs) are an undisputed option as a heterogeneous catalyst for the CO2 cycloaddition reaction and catalytic oxidation of sulfides. On the basis of the above, a series of V8 clusters, [(C2N2H8)4(CH3O)8VIV8O12]·CH3OH (V8-1a), [(C2N2H8)4(CH3O)4VIV4VV4O16]·4CH3OH (V8-1), [(C3N2H10)4(CH3O)4VIV4VV4O16]·5H2O (V8-2), [(C6N2H14)4(CH3O)4VIV4VV4O16]·5CH3OH·2H2O (V8-3), have been legitimately designed and triumphantly isolated. In the synthesis process, three different kinds of Lewis bases (LBs), ethanediamine, 1,2-diaminopropane, and 1,2-cyclohexanediamine, were used to modify LA {V8} clusters to form four diverting windmill-shaped configuration. Among them, the vanadium atoms in V8-1a are +4 valence of VIV, while the vanadium atoms in V8-1-3 are mixed valence states of VIV and VV. Magnetic property investigation indicates that the antiferromagnetic coupling interactions between VIV ions all exist in the four compounds. The compound V8-1 also demonstrated high catalytic activity in the cycloaddition of CO2 to several epoxides under relatively mild conditions (70 °C, 0.5 MPa). More importantly, the reaction pressure 0.5 MPa is the lowest among the high nuclear polyoxometallates (POMs). Furthermore, V8-1 also has an excellent catalytic conversion for the oxidation of sulfides. The catalytic tests manifested that V8-1 was a very efficient difunctional heterogeneous catalyst for CO2 cycloaddition reaction and catalytic oxidation of sulfides.