Three-Dimensional Polyoxometalate Organic Frameworks with One-Dimensional Channels Constructed by Multiple Helical Chains Based on 22-Core Ln/Mn/Mo Clusters for Proton Conduction.

Two unique 22-core sandwich {[Mn6Mo6O37]Ln3[MnMo6O24]} (Ln = La or Pr) units have been assembled, featuring an undisclosed {Mn6Mo6} cluster. This assembly is subsequently integrated into two three-dimensional polyoxometalate organic frameworks, which exhibit one-dimensional hydrophilic hexagonal channels formed by six intertwined 63 helical chains, leading to effective proton conduction primarily facilitated by an abundance of water molecules within the channels.

Assembly of Lanthanide-Containing 3D [MnMo9O32]6--Based Metal-Organic Frameworks and Oxidative Desulfurization Performance.

Lanthanide-containing polyoxometalate-based metal-organic frameworks (POMOFs) not only enjoy intriguing architectures but also have good application prospects as catalysts. Herein, three novel three-dimensional (3D) POMOFs with the formulas of {H[Ln3(2,6-pydc)2(H2O)10(MnMo9O32)]·2H2O}n (Ln = La(1), Pr(2), Nd(3)) have been synthesized based on Waugh-type [MnMo9O32]6- anions and pyridine-2,6-dicarboxylate (2,6-H2pydc). Compounds 1-3 are isomorphic, and there are two kinds of one-dimensional (1D) helical chains with opposite handedness staggered into two-dimensional (2D) layers. Interestingly, the coordinated L- and R-[MnMo9O32]6- anions are encapsulated in 1D chains with the same chirality and are further expanded into 3D structures. The catalytic tests indicate that compounds 1-3 exhibit high-efficiency heterogeneous catalytic activity in the oxidative desulfurization reaction for catalyzing the oxidation of sulfides to sulfoxides using tert-butyl hydrogen peroxide (TBHP) as the oxidant. Moreover, a series of control experiments have been conducted to investigate the influence of various parameters such as temperature, time, solvent, catalyst, and substrate on the reaction. Significantly, compound 2, as an example, exhibits good reusability and structural stability in the oxidative desulfurization reaction. It is worth noting that investigations on the oxidative desulfurization of [MnMo9O32]6- anions are scarce. Moreover, their electrochemical properties are also explored.

Design and Synthesis of Amphiphilic Catalyst [C16mim]5VW12O40Br and Its Application in Deep Desulfurization with Superior Cyclability at Room Temperature.

Achieving long-term stable deep desulfurization at room temperature and recovering high value-added sulfone products is a challenge at present. Herein, a series of catalysts [Cnmim]5VW12O40Br (CnVW12, 1-alkyl-3-methylimidazolium bromide tungstovanadate, n = 4, 8, 16) were presented for the room temperature catalytic oxidation of dibenzothiophene (DBT) and its derivatives. Factors affecting the reaction process, such as the amount of catalyst, oxidant, and temperature, were systematically discussed. C16VW12 showed higher catalytic performance, and 100% conversion and selectivity could be achieved in 50 min with only 10 mg. The mechanism study showed that the hydroxyl radical was the active radical in the reaction. Benefiting from the "polarity strategy", the sulfone product accumulated after 23 cycles in a C16VW12 system, and the yield and purity were about 84% and 100%, respectively.

Two three-dimensional Fe(II) frameworks based on {P4Mo6} tetrameric clusters exhibiting efficient visible-light photocatalytic properties for the degradation of Cr(VI) and methylene blue.

Two three-dimensional frameworks based on the {P4Mo6} unit, H(4,4'-bipy)2[Fe4(PO4)(H2O)4Na6][Fe6(H2O)4][(Mo6O12)(HPO4)3(PO4)(OH)3]4·5H2O (4,4'-bipy = 4,4'-bipyridine) (1) and H3(C12H14N2)4[Fe4(PO4)(H2O)4Na4][Fe2(Mo6O12(HPO4)3(PO4)(OH)3)4]·6H2O (2) were successfully synthesized by varying the solvent. The extended structures of the two compounds were formed by transition metal Fe(II) ions bridging the {P4Mo6}-based tetrameric clusters around [NaXFe4(PO4)] (X = 6 (1), or X = 4 (2)) core. The 4,4'-bipy molecules and in situ generated methyl viologen cations as templates induce the formation of two three-dimensional structures, an 8-connected bcu topology framework for 1 and a 4-connected 2-fold interpenetrating diamond-like topological network for 2, respectively. Additionally, multiform hydrogen bonds are found in the framework and also play an important role in stabilizing the structure. The proton conduction mechanism of the two compounds can be mainly classified as the Grotthuss mechanism; the proton conductivity values are 1.06 × 10-3 S cm-1 for 1 and 3.13 × 10-3 S cm-1 for 2 at 75 °C under 98% relative humidity. The visible-light photocatalytic activity was evaluated by photocatalytic decomposition of Cr(VI) and MB dye, and the removal ratios can reach 95.6% (1) and 82% (2) for Cr(VI), and 98% (1) and 99% (2) for MB.

Construction of Water-Stable Rare-Earth Organic Frameworks with Ambient High Proton Conductivity Based on Zirconium Sandwiched Heteropolytungstate.

Water-stable proton-conducting materials owning excellent performances at ambient temperatures are currently one of the crucial challenges. Herein, four water-stable three-dimensional polyoxometalate-based rare-earth organic frameworks have been successfully synthesized and formulated as H{Ln4(L)2(H2O)21[Zr3(OH)3(PW9O34)2]}·15H2O (1-3) (Ln = La (1), Ce (2), Pr (3); L = 3,5-pyridine dicarboxylic acid), which are the first examples of MOFs constructed by a zirconium sandwiched polyoxoanion. There are abundant coordinated water molecules functionalizing the PrIII centers, and simultaneously, plenty of lattice water molecules are fitted into the channel of the framework. A continuous H-bonding network is found between the architectures and plays an important role in stabilizing the structure. Benefiting from the consecutive H-bonding networks, compounds 1-3 showed high proton conductivities at ambient temperature (up to 1.05 × 10-3 S·cm-1 under 98% RH) by a synergistic effect of the combined components.

Ultrastable Polyoxometalate-Encapsulated Supramolecular Metal-Organic Nanotubes for Single-Crystal Proton Conduction.

Two unique polyoxometalate (POM)-encapsulated tubular materials with the formula K(H2O)6[M6(btp)6(H2O)22](P2W18O62)3(Hbtp)5(btp)3·52H2O [M = Mn (1) and Co (2); btp = 2,6-bis(1,2,4-triazol-1-yl)pyridine] were designed and synthesized based on the Dawson POM and V-type btp ligand, as confirmed by IR, X-ray diffraction (XRD), and element analysis. Single-crystal XRD analyses of compound 1 show that two kinds of remarkable metal-organic supramolecular nanotubes, including trigonal and hexagonal nanotubes, are constructed along the c-axis direction via π···π-packing interactions between {Mn3(btp)3} rings and the btp ligands, of which [α-P2W18O62]6- anions are confined in channels, making the entire structure extraordinarily stable. Meanwhile, the coordinated [α-P2W18O62]6- anion within the hexagonal channel makes the channel highly hydrophilic and attracts a number of guest water molecules to fill in the free space, conducive to proton transport. Therefore, the single-crystal sample of 1 exhibits a high proton conductivity of 6.39 × 10-3 S cm-1 along one-dimensional channels, 30 times higher than that of a pellet sample at 358 K and 98% relative humidity.

Isopolymolybdate-Based Cobalt/Nickel Coordination Polymers Constructed by V-Type N-Donor Ligands.

Four novel isopolymolybdate-based coordination polymers (CPs), constructed from 2,6-bis(1,2,4-triazol-1-yl)pyridine (btp), 1,3-bis(4H-1,2,4-triazol-4-yl)benzene (btb), and 3,5-bis(1-imidazolium)pyridine (bip), have been synthesized under a hydrothermal method: {[Co(btp)(H2O)2(ß-Mo8O26)0.5]·3H2O}n (1), [Ni(btp)(H4Mo6O22)0.5]n (2), [Co(btb)(H2O)(ß-Mo8O26)0.5]n (3), and {[Co(Hbip)2(H2O)2(γ-Mo8O26)]·6H2O}n (4). Complex 1 exhibits one 3D framework with an unexpected 3-nodal 2,4,6-c net topology containing the 1D {ß-Mo8O26}n chains, 6-connected CoII centers, and V-type coordinated btp ligands. The neighboring [Mo6O22]4- anions of complex 2 are bridged by the NiII centers to build one 2D {Ni2(Mo6O22)} network, which is arranged into the 3D framework through the weak π···π stacking interactions. In compound 3, one 3D framework is formed by the adjacent 1D {Co2(btp)2}n chains connected by {ß-Mo8O26}n units, which demonstrates a rare 4,6-c fsc topology. In complex 4, one 2D {Co(Hbip)2(γ-Mo8O26)} layer with a (4, 4) network is connected to one 3D hydrogen-bonding framework via N-H···O and O-H···O hydrogen bonds. Magnetic data indicate that complexes 1 and 4 exhibit antiferromagnetic behaviors, whereas complexes 2 and 3 reveal spin-canting magnetic behavior and metamagnetic behavior, respectively. In addition, the proton conductivity of complexes 3 and 4 was investigated, showing that compound 4 has good proton conductivity at 85 °C and a relative humidity of 98% RH.

Three-Dimensional Interpenetrating Frameworks Based on {P4Mo6} Tetrameric Clusters and Filled with In Situ Generated Alkyl Viologens.

Four novel three-dimensional interpenetrating frameworks based on {P4Mo6} units, H[C12H14N2]4[TM4(PO4)(H2O)4Na6][TM2(Mo6O12(HPO4)3(PO4)(OH)3)4]·8H2O (1, 2) and H[C14H18N2]4[TM4(PO4)(H2O)4Na6][TM2(Mo6O12(HPO4)3(PO4)(OH)3)4]·8H2O (3, 4) (TM = Co2+ (1, 3), Mn2+ (2, 4)) were synthesized and characterized using infrared spectroscopy, elemental analyses, thermogravimetric analysis, and single-crystal X-ray diffraction. In situ generated methyl viologen (compounds 1 and 2) or ethyl viologen (compounds 3 and 4) cations function as templates to induce the generation of 2-fold interpenetrating structures in which the {P4Mo6} tetrameric clusters with [TM4(PO4)Na6] (TM = Co2+ (1, 3) and Mn2+ (2, 4)) as the core were bridged by transition metal ions. Compounds 1-4 possess high thermal stabilities and the decomposition temperature of the inorganic frameworks were all >500 °C. It is worth noting that the four compounds all exhibited the bifunctional catalytic performance that they not only had an excellent photocatalytic activity for the reduction of hexavalent chromium (Cr(VI)) under visible light irradiation but also showed a good electrocatalytic activity for the reduction reaction of hydrogen peroxide.

Ionothermal Synthesis of an Antimonomolybdate Cluster, [Sb8MoVI13MoV5O66]5-, and Its Catalytic Behavior to the Reduction of Nitrobenzene.

The largest antimonomolybdate monomer, [Sb8MoVI13MoV5O66]5- (1-Sb8Mo18), has been isolated and displays a new breakthrough of polyoxometalates (POMs) with an ionothermal synthesis strategy. 1-Sb8Mo18 features the first hexanuclear sandwich-type polymolybdate (POMo) with an unexpected metal ring {Sb6O12} to make its debut in Sb clusters. Furthermore, 1-Sb8Mo18 exhibits a prominent catalytic activity for reducing nitrobenzene to aniline with excellent sustainability.

Long-range magnetic ordering in a metal-organic framework based on octanuclear nickel(ii) clusters.

A novel three-dimensional metal-organic framework [Ni3(BTC)2(bpp)2(H2O)]·3H2O (1) based on mixed ligands H3BTC (1,2,4-benzenetricarboxylic acid) and bpp (1,3-bis(4-pyridyl)propane) was obtained under hydrothermal conditions. Crystal structure analysis reveals that 1 is a framework based on cage-like Ni8(COO)12 units. Furthermore, long-range magnetic ordering is observed at low temperature.

Systematic design of secondary building units by an efficient cation-directing strategy under regular vibrations of ionic liquids.

A cobalt-1,4-naphthalenedicarboxylic acid system in a systematic series of ionic liquids with different alkyl chain lengths of imidazolium cations governed the construction of four MOFs with regular changes of secondary building units (SBUs).

Cation-size-controlled assembly of the Ni(Ac)2-1,4-H2NDC system: geminal dicationic ionothermal syntheses, crystal structures and magnetic properties.

Geminal dicationic ionic liquids with different alkyl spacer lengths regularly tune four MOF structures of two structure types in the Ni(Ac)2-1,4-H2NDC system, which in turn bring about the magnetic properties divided into antiferromagnetic and ferromagnetic couplings consistent with the structures.

Crystal structures and spectral properties of two polyoxometalate-based inorganic-organic compounds from silver-azine building blocks with bis-bidentate and tridentate ligands.

Two polyoxometalate-based inorganic-organic hybrid compounds constructed from silver(I)-L species and saturated Keggin type polyoxoanion, [Ag2L2(1)]2(SiMo12O40)·1.5DMF·0.5CH3OH⋅H2O 1 and [{Ag4L2(2)(DMF)5}(SiMo12O40)] 2 (L(1) = phenyl 2-pyridyl ketone azine, L(2) = 3-phenyltriazolo[1,5-a]pyridine), have been synthesized and structurally characterized by IR, UV, elemental analysis, XRPD and complete single crystal structure analyses, where the ligands L(1) and L(2) are bis-bidentate and tridentate azines synthesized with the same materials under different conditions. The structure of 1 exhibits a dinuclear double-helicate with [SiMo12O40](4)(-) anions as counter ions, where all of the Ag centers coordinate to bis-bidentate chelating ligands. Compound 2 displays a two-dimensional sheet formed by the Ag-organic infinite chains and the [SiMo12O40](4)(-) alternately arranged in a "rail-like" fashion. The luminescent properties of 1 and 2 in the solid state were investigated.

A novel cobalt (I) coordination polymer with mixed thiocyanate and quinoline ligands: crystal structure, magnetism and luminescent properties.

A new Co(I) one-dimensional coordination polymer [Co(SCN)(ql)]n (ql=quinoline) (1) has been synthesized and characterized by IR, elemental analysis, TG technique and X-ray crystallography. Co(I) atom has a distorted trigonal pyramidal N2S2 (1) environment with two S atoms and one N atom from three µ-1,1,3-thiocyanate bridge ligands and one N atom from ql ligand. Two S atoms from two µ-1,1,3-SCN- bridging ligands bridge two centers to obtain bimetallic 4-membered ring. Adjacent 4-membered rings are linked by a pair of µ-1,1,3-SCN- bridging ligands to form a 1D stair-case like chain. The luminescent properties and magnetic properties of the polymer 1 were investigated in the solid state.

Two polyoxometalate-based coordination polymers constructed from Mn(II)-4,4'-bipyridine-N,N'-dioxide building blocks and Keggin-type clusters: Syntheses, crystal structures and spectral properties.

Two polyoxometalate-based coordination polymers {[Mn2(dpdo)4(H2O)6](GeMo12O40)(H2O)4}n (1) and {[Mn2(dpdo)4(H2O)6](GeW12O40)(H2O)3}n (2) (dpdo=4,4'-bipyridine-N,N'-dioxide) have been synthesized and characterized by IR, elemental analysis, XRPD, TG technique and X-ray crystallography. The polymers 1 and 2 are basically isostructural and feature a 3D supramolecular framework decorated with Keggin-type polyanion clusters based on one-dimension polymeric chains, which formed through the coordination interaction of Mn(II) and dpdo. The luminescent properties of the polymers were investigated in the solid state at room temperature.

One new dicoumarol-based fluorescent compound: synthesis, crystal structure and metal ions recognition.

A new dicoumarol-based compound (C6H4)[CH2NHCO(C9O2H4)N(C2H5)2]21 was synthesized and characterized by IR, UV spectroscopy and single-crystal X-ray diffraction analysis. The structure of 1 exhibits a transoid formation with the two coumarin-containing arms sited on the two sides of the center benzene ring. In the crystal packing the molecule further interact with each other and form a three-dimensional framework through π-π stacking interactions and multiform hydrogen bonds. The compound 1 shows the main emission peak at 540 nm corresponding to the green hue in the solid state. The fluorescence recognition behaviors for various metal ions were investigated and 1 exhibits a highly fluorescence-quenching selectivity for Fe(III) ion in the mixed CH3CN-H2O solvent.

Three-dimensional homochiral manganese-lanthanide frameworks based on chiral camphorates with multi-coordination modes.

A series of 3D homochiral manganese-lanthanide frameworks have been synthesized based on chiral camphoric acid. In the heterometallic features, D-camphoric acids are unprecedentedly embedded in three coordination modes.

Two 2D Cd(II) coordination polymers based on asymmetrical Schiff-base ligand: synthesis, crystal structures and luminescent properties.

Two new two-dimensional coordination polymers [Cd(3)L(2)(SCN)(6)](n) (1) and [CdLI(2)](n) (2) have been synthesized and characterized by IR spectroscopy, elemental analysis, TG technique, XRPD and complete single crystal structure analysis, where L is 4-(pyridine-2-yl)methyleneamino-1,2,4-trizaole. Asymmetrical Schiff-base ligand L with five- and six-membered N-containing heterocyclic rings acts as a tridentate bridging ligand to bind two Cd(II) centers through one terminal N(triazolyl) and one pyridylimine chelate unit in 1 and 2. For polymer 1, tridentate bridging ligands link Cd-(1,3-µ-SCN(-)) 1D inorganic chains to form a 2D layer network. The existence of C-H···π and π-π stacking interactions between 2D hybrid layers further gives rise to a 3D supramolecular network. In comparison with 1, polymer 2 shows a 2D layer network containing hexanuclear macrometallacyclic units. The 2D layers are staggered together through the combination of C-H···π and π-π stacking interactions and forming a 3D supramolecular structure. The luminescent properties of the polymers 1 and 2 were investigated in the solid state at room temperature.

Assembly of a phospho-molybdic Wells-Dawson-based silver coordination polymer derived from Keggin polyoxoanion cluster.

A 2D Wells-Dawson-based silver(I) coordination polymer was achieved based on silver-Schiff base building blocks and [P(2)Mo(18)O(62)](6-) clusters using AgNO(3), N,N'-bis(furan-2-ylmethylene)hydrazine and Keggin [PMo(12)O(40)](3-) as original materials at room temperature. It is structurally characterized by IR spectroscopy, (31)P NMR, XRPD, thermogravimetric (TG) analyses and X-ray crystallography. The structure of 1 exhibits a novel crystalline 2D coordination polymer constructed by the coordination interaction between the Wells-Dawson polyoxoanion [P(2)Mo(18)O(62)](6-) and Ag-L species. The luminescent property of 1 in the solid state is investigated.

Synthesis, crystal structures and luminescent properties of two one-dimensional cadmium(II) coordination polymers generated from polydentate Schiff-base ligand.

Two new one-dimensional coordination polymers {[CdL(2)(H(2)O)(2)](NO(3))(2)(H(2)O)(6)}(n) (1) and {[CdLI(2)](H(2)O)(CH(3)OH)}(n) (2) have been synthesized and characterized by IR, elemental analysis, TG technique, XRPD and complete single crystal structure analyses, where L is bis(pyridin-4-ylmethylene)biphenyl-2,2'-dicarbohydrazide. The Cd(II) atom has a distorted octahedral coordination geometry with N(4)O(2) donors from four ligands and two water molecules in 1 and a distorted tetrahedral coordination geometry with NOI(2) donors from two ligands and two I(-) anions in 2, respectively. Polymer 1 shows a 1D framework structure containing bimetallic 42-membered quadrangular ring units. The adjacent 1D chains are interacted forming a 3D supramolecular network structure through multiform hydrogen bond interactions. In comparison with 1, polymer 2 is a new rampart-type chain and each chain is interacted with each other through hydrogen bond interactions to lead a 2D layer. The luminescent properties of the polymers 1 and 2 were investigated in the solid state at room temperature.