Bai-Qiao Song

Two hybrid materials assembled from transition metal mono-substituted Keggin polyoxoanions as photocatalysts under visible light

Two 2D isostructural organic–inorganic hybrid solid materials based on transition metal mono-substituted Keggin polyoxotungstate with an antenna molecule were synthesized under hydrothermal conditions. Compound 2 with the substituted Co(II) exhibits good photocatalytic activity in the degradation of rhodamine-B (RB) under visible light irradiation.

Coordination assemblies of seven metal-organic frameworks based on a bent connector: structural diversity and properties

Seven new coordination polymers, namely, [Zn(L)(bdc)]·2H2O (1), [Zn(L)(2-NH2-bdc)]·2H2O (2), [Zn(L)(bdc)]·1.75DMF·0.5H2O (3), [Zn(L)(oba)]·H2O (4), [Co(L)(oba)]·H2O (5), [Cd2(L)2(bdc)(NO3)2]·2DMF (6) and [Cd(L)(ndc)(H2O)] (7) (L = 4-amino-3,5-bis(4-imidazol-1-ylphenyl)-1,2,4-triazole, H2bdc = 1,4-benzenedicarboxylic acid, 2-NH2-H2bdc = 2-amino-1,4-benzenedicarboxylic acid, H2oba = 4,4′-oxydibenzoic acid and H2ndc = 1,4-naphthalenedicarboxylic acid), have been synthesized. The structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR, and thermogravimetric (TG) analysis. 1 and 2 feature a similar three-fold interpenetrating network combined with interdigitation which extends the structure into a three-dimensional framework. 3 is a two-fold interpenetrating framework showing intralayer porosity and interdigitation. Compounds 1 and 3 represent a pair of supramolecular isomers where structural motifs and different interpenetration modes exist; compounds 4 and 5 are isostructural and display the same three-fold interpenetrating framework where two types of interlaced triple-stranded helices A and B can be found. The triple-stranded helices with opposite chirality for each type are distributed in adjacent layers. Compound 6 exhibiting a unique simultaneous threading fashion of adjacent polymeric motifs gives the novel (2D → 3D) polythreaded array where coordinated NO3− anions act as the dangling ligands. Compound 7 is a 6-connected 3D self-penetrating network where right- and left-handed single-stranded helical chains (AR and AL) and interlaced triple-stranded helices (BR and BL) coexist. The luminescence properties of compounds 1–7 were also measured and discussed.

Ligand-Directed Assembly of Polyoxovanadate-Based Metal–Organic Polyhedra

Three new polyoxovanadate-based metal-organic polyhedra (VMOPs) have been successfully synthesized and structurally characterized. Single crystals of three VMOPs were obtained by reaction of VCl3 and different carboxylate ligands (2,5-H2TDA = thiophene-2,5-dicarboxylic acid for VMOP-4, m-H2BDC = 1,3-benzenedicarboxylic acid for VMOP-5, 2,6-H2NDC = 2,6-naphthalenedicarboxylic aid for VMOP-6) under solvothermal conditions. Though all of the three hybrids feature the same {V(V)V4(IV)} units, their structures exhibit differences changing from truncated triangular prism to truncated quadrangular prism to octahedron, mainly depending on the nature of carboxylate ligands. Furthermore, the magnetic investigations reveal that VMOP-4-6 show similar ferromagnetic behaviors.

A polyrotaxane-like metal–organic framework exhibiting luminescent sensing of Eu3+ cations and proton conductivity

A novel microporous metal–organic framework (MOF), namely {[Cd2L3(DMF)(NO3)]·2DMF·3H2O}n (1), where L = 1,3-bis(4-carboxyphenyl)imidazolium chloride, was prepared via a hydrothermal process. The structure of 1 shows the first example of 6-fold polyrotaxane-like interpenetration combined with interdigitation which extends the structure into a three-dimensional framework and exhibits reversible and irreversible guest-dependent structural conversion; because of the 1D channels running along the b axis, 1 can serve as a host to encapsulate and sensitize Eu3+ cations in water. Moreover, the framework also exhibits a proton conductivity of over 10−5 S cm−1 at 298 K and 98% relative humidity because the methylene hydrogens of the imidazolium moiety are highly acidic and aligned inside the channels enhancing the proton conductivity.

High-Nuclear Vanadoniobate {Nb48V8} Multiple-Strand Wheel.

An unprecedented octavanadium-substituted polyoxoniobate Na18[Nb48V8(OH)30O130] · 33H2O (1), with a multiple-strand wheel structure, was successfully synthesized via a conventional aqueous method, which represents the largest vanadoniobate cluster reported to date. Single-crystal X-ray diffraction, ESI-MS spectrum, IR spectra, and UV-vis spectra were investigated. In addition, photocatalytic H2 evolution activity for 1 under UV light was observed with TEA as a sacrificial electron donor.