Syntheses, structures and properties of cadmium benzenedicarboxylate metal-organic frameworks

The products isolated from the reaction between Cd(NO3)2 x 4H2O and 1,4-benzenedicarboxylic acid (H2bdc) in DMF are very dependent on the conditions. At 115 degrees C, the reaction gives [Cd(bdc)(DMF)]infinity, which has a three-dimensional network structure, whereas at 95 degrees C, 1 is formed alongside [Cd3(bdc)3(DMF)4]infinity 2, which has a two-dimensional network structure. When the reaction is carried out under pressure, it yields [Cd3(bdc)3(DMF)4]infinity 3, which is a supramolecular isomer of 2. The structure of 3 differs from that of 2 regarding the way the Cd3(O2CR)6 units are interlinked to form layers. When the reaction was carried out in DMF that had undergone partial hydrolysis, the only isolated product was [(NMe2H2)2[Cd(bdc)2] x 2DMF]infinity 4. Compound 4 has a three-dimensional triply-interpenetrated diamondoid structure, with dimethylammonium cations and DMF molecules included within the pores. The reaction between Cd(NO3)2 x 4H2O and H2bdc in DEF gave [Cd(bdc)(DEF)]infinity 5, regardless of the solvent quality. Compound 5 has a three-dimensional network structure. The reaction of Cd(NO3)2 x 4H2O and 1,3-benzenedicarboxylic acid (H2mbdc) in DMF gave [Cd(mbdc)(DMF)]infinity 6 which has a bilayer structure. The thermal properties of the new materials have been investigated, and the coordinated DEF molecules from 5 can be removed on heating to 400 degrees C without any change in the powder X-ray diffraction pattern. The H2 sorption isotherm for the desolvated material shows marked hysteresis between adsorption and desorption, and less adsorption than predicted by simulations. Kinetic data indicate that the hysteresis is not due to mass transfer limitations, and the most likely explanation for this behaviour lies in partial collapse of the framework to an amorphous phase under the conditions of activation.     

Syntheses,structures and properties of four metal-organic frameworks from chlorophenyl imidazole dicarboxylates

Four metal-organic frameworks, [Sr(o-ClPhHIDC)(H₂O)₂]_n (o-ClPhH₃IDC = 2-(o-chlorophenyl)-1H-imidazole-4,5-dicarboxylic acid) (1), [Mg(m-ClPhHIDC)(H₂O)₂]_n (2), [Sr(m-ClPhHIDC)(H₂O)]_n (3) and {[Co₃(m-ClPhIDC)₂(H₂O)₆]·2H₂O}_n (m-ClPhH₃IDC = 2-(m-chlorophenyl)-1H-imidazole-4,5-dicarboxylic acid) (4), have been solvothermally synthesized and structurally characterized. Single-crystal X-ray analyses reveal that 1–3 show 2-D architectures and 4 exhibits a 3-D structure. The o-ClPhH₃IDC and m-ClPhH₃IDC ligands in the polymers can be partly deprotonated and coordinate to metal ions by various modes. The metal ions of 1–4 are coordinated only to oxygens. The thermal and luminescence properties of the polymers have also been investigated.     

Conjugated ligands modulated sandwich structures and luminescence properties of lanthanide metal-organic frameworks

A conjugated ligand, 2-(carboxylic acid)-6-(2-benzimidazolyl) pyridine (Hcbmp), and a series of Lanthanide metal-organic frameworks (MOFs) [Ln(2)(cbmp)(ox)(3)(H(2)O)(2)](2)·2H(3)O(+)·7H(2)O (Ln = Sm (3), Eu (4), and Gd (5), H(2)ox = oxalic acid) have been designed and assembled. To elucidate how the conjugated ligands modulate the structures and luminescence properties, we carried out the structural characterizations and luminescence studies of complexes 3 and 4, and their corresponding oxalate complexes [Ln(ox)(1.5)(H(2)O)(3)]·2H(2)O (Ln = Sm (1) and Eu (2)) were also investigated for comparison. The changes of luminescence behaviors upon dehydration and D(2)O-rehydration processes are presented and discussed in detail. The results indicated that, the cbmp(-) ligands distribute on both sides of the ox(-)-Ln bilayer network to construct a sandwich structure. Moreover, the lowest triplet state of cbmp(-) ligands can match well the energy levels of the Sm(3+) and Eu(3+) cations which allow the preparation of new Ln-MOF materials with enhanced luminescence properties. Meanwhile, the crystallinity of solid states produces more substantial change in the luminescence behaviors than removal or replacement of effective nonradiative relaxers.     

Lanthanide-organic frameworks constructed from multi-functional ligands: Syntheses, structures, near-infrared and visible photoluminescence properties

A series of multi-functional ligands supported lanthanide-organic frameworks, formulated as [Ln(HL₁)(H₂L₂)_0.5(H₄L₂)_0.5(H₂O)]·(H₂O)_1.5·{Ln=La (1), Pr (2), Nd (3), Sm (4), Eu (5); H₃L₁=5-Sulfosaclicylic acid; H₄L₂=N,N′-piperazine (bis-methylene phosphonic acid)}, have been synthesized by hydrothermal reactions. Single crystal X-ray diffractions and powder XRD patterns confirm they are isostructural. They feature 3D framework structures based on extension of a “zigzag” inorganic chain by organic linkers. Moreover, the photoluminescence properties of 5 and 3 have been investigated, and they show strong solid-state emissions in the visible and near-infrared (IR) regions at room temperature.     

One dense and two open chiral metal-organic frameworks: crystal structures and physical properties

Three 3D robust homochiral helical coordination polymers, [Cu(2,2',3,3'-H2odpa)(bpy)] (1), {[Ni4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)16} (2), and {[Co4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)14} (3), have been hydrothermally synthesized from a flexible ligand of 2,2',3,3'-odpda (2,2',3,3'-oxydiphthalic dianhydride). Compound 1 crystallized in space group P3(1)21 and has a rare chiral dense qzd 7.(5)9 topology that incorporates single helical substructures with the same accessibility, whereas compounds 2 and 3 crystallized in the space group C2 and possessed isostructural 3D chiral open frameworks based on the homochiral 2D sheets and 4,4'-bpy pillars. TGA and PXRD analyses show that the porous framework of 2 is stable after the removal of solvent water molecules. In contrast, 3 changed its structure to an amorphous one because of the simultaneous loss of solvent and coordination water molecules. 1 is nearly paramagnetic, whereas weak ferromagnetic interactions between M(II) (M = Ni, Co) ions have been found in 2 and 3.     

Ln(III) metal-organic frameworks with 5-nitroisophthalate ligands: Crystal structures and luminescent properties

Two new Ln(III) metal-organic frameworks (MOFs) based on 5-nitroisophthalic acid (H₂L), namely [Pr₄(L)₆(H₂O)₄] _n (I) and [Gd(L)(FA)(H₂O)₂] _n (II) (HFA = formic acid), were prepared by solvothermal reactions and structurally characterized by IR, elemental analysis, XRD, and single crystal X-ray diffraction (CIF files CCDC nos. 971379 (I) and 971380 (II)). A 3D {4.6²}{4¹⁰.6¹⁷.8⁹}{4³}₂ topology framework of I and a 3D {4.6² ₂}{4².6¹⁰.8³} topology network of II are constructed respectively with different synthetic conditions. Four kinds of coordination modes are observed for dicarboxylate in these two MOFs in total. Notably, the in situ hydrolysis of DMF solvates leads to the formation of formate ions that was observed in the structure of II. Moreover, the luminescent properties of both complexes and corresponding ligand have been investigated.     

Syntheses,crystal structures,and electrochemical properties of transition metal complexes with new tetrathiafulvalene-derivatized acetylacetonate ligands

Two new tetrathiafulvalene (TTF) derivatives of acetylacetone, namely, 3-[{6,7-benzo-2-(methylthio)-TTF-3-yl}-thio]-2,4-pentanedione (L₁) and 3-[{6,7-(ethylenedithio)-2-(methylthio)-TTF-3-yl}-thio]-2,4-pentanedione (L₂), have been synthesized. Four transition metal(II) complexes of these ligands, of general formulae [Zn(L₁)₂(THF)₂] and [M(L₂)₂(THF)₂] (M = Zn, Mn, and Ni), have been prepared and structurally characterized. The redox properties of both the ligands and their complexes were investigated by cyclic voltammetry. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Peng Zheng and Yun-Jun Guo contributed equally to this work.     

Syntheses,characterization and luminescent properties of two lead(II) fumarate metal-organic frameworks

It is of interest that the hydrous 3D metal-organic framework (MOF) {[Pb₂(fum)₂(H₂O)₄] · 2H₂O}_n (1) has been synthesized by the reaction of the fum dianion with the lead(II) ion (fum = fumarate) in the presence of pyrazole, while the anhydrous 3D MOF [Pb(fum)]_n (2) is obtained by the reaction of the fum dianion with the lead(II) ion in the presence of pyrazine. These complexes were further characterized by FT-IR spectroscopy, thermogravimetric analysis (TG), X-ray analysis and solid state photoluminescence spectra. The arrangement of the ligands displays a coordination gap around the Pb atom, occupied possibly by a stereoactive lone pair of electrons on lead(II), with the coordination around both the eight-coordinated lead atom in 1 and six-coordinated lead atom in 2 exhibiting a hemidirected geometry. The fum ligand shows different ligation behavior toward the lead(II) ions in these complexes. These compounds exhibit photoluminescence with the maximum emission located in the UV region.     

Templated metal-organic frameworks: synthesis, structures, thermal properties and solid-state transformation of two novel calcium-adipate frameworks

Two novel calcium-adipate framework materials have been synthesized hydrothermally. GWMOF-7 ([Ca(C6H8O4)(H2O)2]*(C10H8N2)) and GWMOF-8 ([Ca(C6H8O4)(H2O)2]*(C12H12N2)) both formed three-dimensional structures and were characterized with single-crystal X-ray diffraction, powder X-ray diffraction, IR spectroscopy and elemental analysis. Thermal properties were also studied with thermogravimetric analysis, and show that these structures undergo a solid-state transformation into a denser three-dimensional framework.     

Toward templated metal-organic frameworks: synthesis, structures, thermal properties, and luminescence of three novel lanthanide-adipate frameworks

Three novel praseodymium-adipate frameworks were synthesized hydrothermally. GWMOF-3 ([Pr(2)(adipic acid)(3)(H(2)O)(4)].adipic acid.4H(2)O) and GWMOF-6 ([Pr(2)(adipic acid)(3)(H(2)O)(2)].4,4'-dipyridyl) formed three-dimensional structures, whereas GWMOF-4 ([Pr(2)(adipic acid)(3)(H(2)O)(2)].H(2)O) produced a more dense, two-dimensional topology. Single-crystal X-ray and powder diffraction, IR spectroscopy, fluorescence spectroscopy, thermogravimetric analysis, and elemental analysis were employed to characterize all samples. GWMOF-6 represents an innovative step forward in metal-organic framework synthesis where a neutral molecular species not used in the construction of the framework is utilized as a structure-directing agent, or template. Furthermore, this template molecule (4,4'-dipyridyl) is shown to sensitize the fluorescence of lanthanide metal centers in a europium analogue of GWMOF-6.     

Synthesis, structures and luminescent properties of Co(II) and Ni(II) metal-organic frameworks with semirigid diphthalic ligands

A series of transition metal coordination polymers [Co(H₃L)₂(4,4′- bpy)(H₂O)₂]_n?n(4,4′-bpy) (1), [Ni(H₂L)(4,4′-bpy)(H₂O)₂]_n (2), [Co₂(L)(phen)₂(H₂O)₄]_n?(H₂O)_2n (3), and [Ni₂(L)(phen)₂(H₂O)₄]_n?(H₂O)_2n (4) have been assembled from a semirigid multicarboxylate ligand 3,3′-(1,4-phenylenebis(oxy))diphthalic acid (H₄L) with the help of 4,4′-bipyridine (4,4′-bpy) ligand or 1,10-phenanthroline (phen) ligand. X-ray single crystal diffraction analysis reveals that complex 1 crystallizes in the space group of P − 1 and displays a one-dimensional (1D) chain structure constructed from 4,4′-bpy ligand and H₃L ligand, which was further interlinked to form a three-dimensional network via hydrogen bonds. In complex 2, Ni(II) atoms are coordinated by L ligand in monodentate fashion to form alternate left- and right-helices, which are further bridged together by the coordination interactions between Ni(II) atoms and 4,4′-bpy, leading to a 2-fold (4, 4)-connected interpenetrating network. Isostructural complexes 3 and 4 belong to the space group P − 1 and display a 1D chain structure constructed from phen and L ligands, which was further interlinked to form a 2D plane via π–π interactions. In addition, their thermal and luminescent properties were also investigated.     

基于柔性羧酸配体和含氮辅助配体的金属有机配位聚合物的合成、结构及表征

本文通过水热合成的方法制备得到了一个新型的二维金属有机配位聚合物[Co2(L1)(4,4’-bipy)(3H2O).2H2O]n (1), (H4L1 = 3,3'-(1,4-苯二氧基)二邻苯二甲酸; 4,4’-bipy = 4,4’-联吡啶),并对其结构进行了系统的表征。研究表明3,3'-(1,4-苯二氧基)二邻苯二甲酸配体中的羧酸采用μ1-η1-η0和μ1-η1-η1两种桥联的方式跟两个钴离子配位形成十四圆环,形成的十四圆环被3,3'-(1,4-苯二氧基)二邻苯二甲酸配体连接进一步形成之字形的一维链状结构。最终,辅助配体4,4’-联吡啶将这些一维链状结构连接起来形成二维的(44)-sql网状拓扑结构。在本文中,我们还一步研究了这个配位聚合物的红外光谱以及热稳定性。     

Construction of metal-organic frameworks through coordination and hydrogen bonding interactions: Syntheses, structures and photoluminescent properties of metal complexes with macrocyclic ligand

A macrocyclic ligand L with two diethylenetriamine units linked by two rigid biphenylene spacers was used as building block for construction of metal-organic frameworks. A silver(I) complex with macrocyclic and open-chain mix-type ligands [Ag₂(L)(L′)](ClO₄)₂ (1) [L′=1,6-bis(4-imidazol-1′-ylmethylphenyl)-2,5-diazahexane] was obtained by reaction of L and L′ together with AgClO₄·H₂O. It is interesting that the open-chain tetradentate ligand L′ only served as a bidentate ligand to bridge the Ag₂L units into an infinite one-dimensional (1D) cationic chain. Neutral 1D chain coordination polymer [Cu₂(L)(μ-SO₄)₂]·3H₂O·3MeOH (2) is formed by sulfate bridges between the neighboring Cu₂L units. When L reacted with nickel(II) sulfate instead of copper(II) sulfate, a monomacrocycle molecular complex [Ni₂(L)(H₂O)₄(SO₄)₂] (3) was obtained in which the sulfate anion acts as monodentate ligands rather than as bridges. When Cd(II) salts were used for the reactions with L, another two neutral 1D coordination polymers, [Cd₂(L)(μ-Cl)₂Cl₂]·2H₂O (4) and [Cd₂(L)(μ-Br)₂Br₂] (5), with the same structure were isolated. All the synthesized complexes exhibit three-dimensional framework structures linked by various hydrogen bonds. The photoluminescent properties of the synthesized complexes were studied in the solid state at room temperature, and the Ag(I) and Cd(II) complexes were found to show strong blue luminescence.     

Microporous metal-organic frameworks incorporating 1,4-benzeneditetrazolate: syntheses, structures, and hydrogen storage properties

The potential of tetrazolate-based ligands for forming metal-organic frameworks of utility in hydrogen storage is demonstrated with the use of 1,4-benzeneditetrazolate (BDT(2)(-)) to generate a series of robust, microporous materials. Reaction of H(2)BDT with MnCl(2).4H(2)O and Mn(NO(3))(2).4H(2)O in N,N-diethylformamide (DEF) produces the two-dimensional framework solids Mn(3)(BDT)(2)Cl(2)(DEF)(6) (1) and Mn(4)(BDT)(3)(NO(3))(2)(DEF)(6) (2), whereas reactions with hydrated salts of Mn(2+), Cu(2+), and Zn(2+) in a mixture of methanol and DMF afford the porous, three-dimensional framework solids Zn(3)(BDT)(3)(DMF)(4)(H(2)O)(2).3.5CH(3)OH (3), Mn(3)(BDT)(3)(DMF)(4)(H(2)O)(2).3CH(3)OH.2H(2)O.DMF (4), Mn(2)(BDT)Cl(2)(DMF)(2).1.5CH(3)OH.H(2)O (5), and Cu(BDT)(DMF).CH(3)OH.0.25DMF (6). It is shown that the method for desolvating such compounds can dramatically influence the ensuing gas sorption properties. When subjected to a mild evacuation procedure, compounds 3-6 exhibit permanent porosity, with BET surface areas in the range 200-640 m(2)/g. The desolvated forms of 3-5 store between 0.82 and 1.46 wt % H(2) at 77 K and 1 atm, with enthalpies of adsorption in the range 6.0-8.8 kJ/mol, among the highest so far reported for metal-organic frameworks. In addition, the desolvated form of 6 exhibits preferential adsorption of O(2) over H(2) and N(2), showing promise for gas separation and purification applications.     

Syntheses, structures and properties of silver-organic frameworks constructed with 1,2,3,4-benzenetetracarboxylic acid

The reactions of 1,2,3,4-benzenetetracarboxylic acid (H(4)mpda) and different silver(I) salts under hydrothermal or solvent evaporation conditions yielded four unusual coordination complexes with interesting frameworks: [Ag(4)(mpda)](n) (1), {[Ag(2.5)(mpda)(bpy)(2)]·[Ag(bpy)]·[Ag(bpy)(H(2)O)]·(NO(3))(0.5)·(H(2)O)(9)}(n) (2), {[Ag(5)(mpda)(2)(bpy)(4)]·[Ag(bpy)]·[Ag(bpy)(H(2)O)]·[Ag(bpy)(H(2)O)]·(H(2)O)(16)}(n) (3), {[Ag(2)(mpda)(H(2)O)]·[Ag(bpy)]·[Ag(bpy)]}(n) (4) (bpy = 4,4'-bipyridine). Complex 1 displays a novel (3,4,7)-connected {4.6(2)}{4.6(5)}{4(2).6(13).8(5).10} topology, in which the carboxylic groups of the mpda(4-) ligand adopt variable coordination modes. In 1, besides Ag-O coordination bonding, AgAg and Agaromatic intermolecular interactions also make their appearance. In complexes 2-4, rare architectures comprising three or four isolated coordination polymers within the same crystalline structure have been obtained, respectively. In 2 and 3, neighboring layers are linked together through water tapes into a three-dimensional supramolecular architecture, which is also consolidated by π···π stacking, while independent infinite rod-like polymer chains fill the void space between layers. Interestingly, an anionic (H(2)O-NO(3)(-))(n) layer, built from water tapes and nitrate anions as well as consolidated by the mpda(4-) ligands, has been structurally identified in compound 2. A new water tape constructed from alternating tetramers and decamers has been obtained in compound 3. In compound 4, a right-handed helical chain and two rod-like polymeric chains are interconnected through host-guest molecular recognition to generate a three-dimensional chiral supramolecular architecture. Bulk materials for 1 and 4 have second-harmonic generation activity, being approximately 0.6 and 0.4 times that of urea. The IR spectra, thermogravimetric analysis and luminescent properties of all compounds were also investigated.     

Syntheses, structures, photoluminescence, and magnetic properties of (3,6)- and 4-connected lanthanide metal-organic frameworks with a semirigid tricarboxylate ligand

Lanthanide coordination polymers [LnL(DMF)(2)]·0.25H(2)O [Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), and Tm (12)], and [GdL(H(2)O)(3)] (7') (H(3)L = 5-(4-carboxy-2-nitrophenoxy)-isophthalic acid), have been synthesized under hydro- and solvothermal conditions, respectively. Compounds 1-12 exhibit the same three-dimensional (3D) architecture, which is built up from binuclear paddle-wheel building blocks, and their resulting frameworks can be rationalized as rarely reported flu-3,6-C2/c topology. Compound 7' crystallizes in the monoclinic system, space group P2(1)/c. The ligands (L) bridge the Gd(III) centers to form 3D frameworks featuring a zeolite BCT topology, which have been unreported based on rare earth metals until now. Moreover, compound 6 exhibits characteristic red luminescent properties of Eu(III) complexes. The magnetic susceptibilities, over a temperature range of 2.0-300 K, of 7 and 7' have also been investigated.     

Preparation,structure and photocatalysis of metal-organic frameworks derived from aromatic carboxylate and imidazole-based ligands

Three 3-D metal-organic frameworks (MOFs), [Cd(NDC)(biim-4)]·0.5H₂O (1), [Cd₂(TDC)₂(biim-4)₂(H₂O)₂] (2) and [Zn₂(biim-4)₂(TDC)₂]·2.5H₂O (3) (biim-4 = 1,4-bis(1-imidazolyl) butyric alkyl; H₂NDC = 1,4-naphthalene dicarboxylic acid; H₂TDC = thiophene-2,5-dicarboxylic acid), have been synthesized under hydrothermal conditions and structurally characterized by single X-ray diffraction. The three MOFs have high photocatalytic degradation effects on methyl orange under UV irradiation. Through electronic structure analysis combined with time-dependent density functional theory calculations, catalytic performances of these materials are correlated with the molecular composition and the optoelectronic properties of the samples.     

Synthesis,structures and magnetic properties of three metal-organic frameworks containing manganese(II)

Two new Mn(II) coordination polymers formed with molecular formula [Mn(H₂O)₂(HBTC)·(H₂O)] 1 and [Mn(H₂O)₂(4,4′bipy)(HBTC)₂]·(H4,4′bipy)₂ 2, where BTC = 1,2,4-benzenetricarboxylate and 4,4′bipy = 4,4′bipydine, have been synthesized via hydrothermal approach and characterized by single crystal X-ray diffraction techniques. 1 is composed of Mn–H₂O–Mn 1D chains and further the chains are linked by HBTC ligands to form a 2D network in the ab plane; 2 is constructed by Mn–4,4′bipy–Mn 1D chains along the b direction with Mn²⁺ ions coordinated to H₂BTC and water as terminal ligands to form a 2D network. We also prepared a third compound with the molecular formula of [Mn(H₂O)(HBTC)·(H₂O)] which has been recently structurally reported elsewhere. The magnetic properties of the three compounds have been studied in detail under variable temperatures.     

Synthesis, structures, and properties of two three-dimensional metal-organic frameworks, based on concurrent ligand extension

A tritopic carboxylate ligand, tris(4'-carboxybiphenyl)amine (L-H(3)), has been synthesized and applied in the construction of microporous metal-organic frameworks (MOFs). Two novel metal-organic frameworks (MOFs), {[Zn(2)(L)(OH)]·2DMF·H(2)O}(∞) (1) and {[Cu(L-H)(DMA)]·DMA·2H(2)O}(∞) (2), have been constructed out of L-H(3), Zn(2+), and Cu(2+), respectively. 1 has a 2-fold interpenetrating three-dimensional framework formed by L connectors and the [Zn(2)(CO(2))(3)] secondary building units (SBUs). As for 1, it is worth pointing out that one μ(2)-OH group links two Zn atoms between two neighboring SBUs to produce interesting Zn-O-Zn zigzag chains in the structure. 2 has a two-dimensional grid sheet formed by L-H connectors and the typical paddle-wheel [Cu(2)(CO(2))(4)] SBUs. Two-dimensional (2D) sheets nest with each other, which finally forms a three-dimensional (3D) nested framework. Two MOFs are characterized by infrared (IR) spectroscopy, thermogravimetry, single-crystal and elemental analyses, and powder X-ray diffraction methods. Framework 1' exhibits high permanent porosity (Langmuir surface area = 848 m(2)/g), high thermal stability (up to 450 °C), highly active properties for Friedel-Crafts alkylation reaction, as well as the potential application for the CO(2) gas storage and luminescent material. The catalytic results reveal that 2' is indeed an efficient heterogeneous catalyst for olefin epoxidation reactions.