Tungsten and Molybdenum Heteropolyanions with Different Central Ions—Correlation between Theory and Experiment

Density functional theory calculations were carried out to investigate the electronic structures of Keggin-typed [XMo₁₂O₄₀]ⁿ⁻ and [XW₁₂O₄₀]ⁿ⁻ anions with different heteroatoms (X = Zn²⁺, B³⁺, Al³⁺, Ga³⁺, Si⁴⁺, Ge⁴⁺, P⁵⁺, As⁵⁺, and S⁶⁺). The influence of solvent on redox properties of heteropolyanions was discussed. For [XW₁₂O₄₀]ⁿ⁻ systems two linear correlation: first, between the experimental redox potential and energies of LUMO orbital; and second, between the experimental redox potential and total energy interaction (calculated between internal tetrahedron (XO₄ⁿ⁻), and rest of Kegging anion skeleton, (W₁₂O₃₆)) were designated. Taking into account the similarity of XW₁₂O₄₀ⁿ⁻ and XMo₁₂O₄₀ⁿ⁻ systems (in geometry and electronic structure), the estimated redox potential of molybdenum heteropolyanions (with X being p block elements) in different solvent were proposed.

Assembly, structures and properties of polyoxometalate-based supramolecular complexes involving in situ transformation of single-branch N-donor cyano ligands

A series of polyoxometalate-based supramolecular complexes were prepared with in situ transformation of single-branch N-donor cyano ligands, exhibiting diverse structures and good electrocatalytic and photocatalytic properties.

Mixed-Valence Cobalt(II/III) Metal-Organic Framework for Ammonia Sensing with Naked-Eye Color Switching

The construction of colorimetric sensing materials with high selectivity, low detection limits, and great stability provides a significant way for facile device implementation of an ammonia (NH₃) sensor. Herein, with excellent alkaline stability and exposed N sites in molecule as well as with naked-eye color switching nature generated from changeable cobalt (Co) valence, a three-dimensional mixed-valence cobalt(II/III) metal-organic framework (FJU-56) with tris-(4-tetrazolyl-phenyl)amine (H₃L) ligand was synthesized for colorimetric sensing toward ammonia. The activated FJU-56 demonstrates a limit of detection of 1.38 ppm for ammonia sensing, with high selectivity in ammonia and water competitive adsorption, and shows outstanding stability and reversibility in the cyclic test. The NH₃ or water molecules binding to the exposed N sites with the hydrogen-bond are observed by single-crystal X-ray diffraction, determining that the attachment of guest molecules to the FJU-56 framework changes the valence of Co ions with a naked-eye color switching response, which provides an ocular demonstration for ammonia capture and a valuable insight into ammonia sensing.

Construction of 3D metal–organic frameworks bearing heteropolyoxometalate units and multi-azole molecules and exploration of their photocatalytic activities

Two novel 3D metal–organic frameworks consisting of rigid ligand modified polyoxomolybdates were obtained and both of them have efficient photocatalytic activities in the degradation of several dye molecules.

An Effective Strategy To Construct Novel Polyoxometalate-Based Hybrids by Deliberately Controlling Organic Ligand Transformation In Situ

Deliberately controlling organic ligand transformation in situ has remained a challenge for the construction of polyoxometalate (POM)-based inorganic-organic hybrids. In this work, four POM-based hybrids assembled from an in situ bifurcating organic ligand-[Cu2(DIBA)4](H3PMo12O40)·6H2O (1), [Cu2(DIBA)4](H4SiW12O40)·6H2O (2), [Ag(HDIBA)2](H2PMo12O40)·2H2O (3), [Ag3(HDIBA)2(H2O)][(P2W18O62)1/2]·4H2O (4) (DIBAH = 3,5-di(1H-imidazol-1-yl) benzoic acid)-have been designed and obtained under hydrothermal conditions. Compounds 1 and 2 are isostructural, displaying a three-dimensional (3D) 2-fold interpenetrating framework with two types of channels, and the bigger channels are occupied by Keggin polyoxoanions and crystallization water molecules, but only crystallization water molecules in the smaller ones. Compound 3 displays a 3D supramolecular structure constructed from {Ag(HDIBA)2} segments and PMo12O40(3-) polyoxoanions through hydrogen bonding interactions. Compound 4 shows a 3D 2-fold interpenetrating framework based on (3, 3, 4)-connected network, which is constructed from {Ag3(HDIBA)2}n chains and P2W18O62(6-) polyoxoanions as linkers. The DIBAH ligand was generated in situ from 3,5-di(1H-imidazol-1-yl)benzonitrile by deliberate design, which illustrates that the strategy to construct novel POM-based hybrids by controlling ligand transformation in situ is rational and feasible. In addition, the effects of the central metal and POMs on the structures of the target compounds were discussed. Finally, the electrochemical and photocatalytic properties of compounds 1-4 have been investigated in this paper.

Dicarboxylate ligand-modulated assembly of new luminescent zinc(ii) coordination polymers with in situ formed tetrazole ligands: an experimental and theoretical study

In situ hydrothermal reactions of 4-(1H-imidazol-1-yl)benzonitrile, Zn(NO₃)₂ and NaN₃ with H₂DPA or H₂PYDC gave rise to two new zinc(ii) coordination polymers, which exhibit different intriguing architectures and photoluminescence properties.

A series of organic–inorganic hybrid materials consisting of flexible organic amine modified polyoxomolybdates: synthesis, structures and properties

A series of hybrid materials consisting of Tris[(2-pyridyl)methyl]amine modified polyoxomolybdates were obtained and some complexes have efficient photocatalytic activities to degrade pararosaniline hydrochloride dye molecules.

Architectural chemistry of polyoxometalate-based coordination frameworks constructed from flexible N-donor ligands

Polyoxometalate-based coordination frameworks (POMCFs) constructed from flexible N-donor ligands can exhibit diverse properties and fascinating architectures, extending the families of material chemistry and structural chemistry.

Color tunable and near white-light emission of two solvent-induced 2D lead(ii) coordination networks based on a rigid ligand 1-tetrazole-4-imidazole-benzene

Two solvent-induced Pb(ii)-tzib⁻ (Htzib = 1-tetrazole-4-imidazole-benzene) coordination polymers display color tunable and near white-light emissions upon varying excitation wavelengths.

A series of polyoxometalate-based compounds including infinite Ag belts and circles constructed by two tolyl-1H-tetrazole isomers

Three novel Keggin-based complexes constructed by two new isomeric ligands 5-o-tolyl-1H-tetrazole and 5-m-tolyl-1H-tetrazole have been synthesized under hydrothermal conditions via changing the types of POM anions and organic ligands.

Recent advances in porous polyoxometalate-based metal–organic framework materials

POM-based MOF materials, which combine the advantages of both POMs and MOFs, have received increasing attention. In this review, we present the recent developments in porous POM-based MOF materials for the first time, including their classification, synthesis strategies and applications, especially in the field of catalysis.

pH-controlled assembly of hybrid architectures based on Anderson-type polyoxometalates and silver coordination units

Three new architectures based on Anderson-type polyoxometalates, (3-H2pya)[(3-Hpya)2Ag][AgAlMo6H6O24]·3H2O 1, HNa2[(3-pya)(3-Hpya)Ag]2[AlMo6H6O24]·8H2O 2 and [(3-Hpya)2Ag][(H2O)2Ag]2[AlMo6H6O24]·2H2O 3 (3-Hpya = 3-(3-pyridyl)acrylic acid), have been synthesized at the different pH values and characterized by elemental analysis, IR spectroscopy, TG analysis, powder X-ray diffraction and single crystal X-ray diffraction. Compound 1 was obtained at lower pH value (2.50), and represents a 3D host-guest compound containing the Ag-3-Hpya coordination complex guest and the 3D [AgAlMo6H6O24](2-) host. The host framework exhibits a 4-connected diamond topology, and is constructed from [AlMo6H6O24](3-) clusters connected by Ag(+) cations. When the pH value was increased slightly, compound 2 was obtained with a 1D chain structure built up of Anderson polyoxoanions, Ag-3-Hpya coordination complexes and binuclear sodium clusters. By further increasing the pH value (3.50), compound 3 was isolated as a 2D network in which [AlMo6H6O24](3-) clusters are linked together by Ag(+) cations and Ag-3-Hpya coordination complexes. Their structural differences reveal that the pH value of the reaction system is the key factor influencing the structure and topology of three compounds. The UV-visible-NIR diffuse reflectivity spectra of 1-3 show that they can be regarded as a wide gap semiconductor. Furthermore, the pyrolysis of 1-3 produces three nanocomposites 1'-3' composed of silver microparticles dispersed in the metal oxides. The photocatalytic properties of 1'-3' have been investigated.