Luminescent zinc and cadmium metal-organic frameworks based on tetrazole ligands

Three metal-organic frameworks with 1D zigzag chain [Zn(dte)(H₂O)₃]·2H₂O (1), 2D double layer [Cd(dtb)(H₂O)(phen)] (2), 3D network [Zn(dte)(phen)] (3) based on tetrazole-based ligands (H₂dtb = 1,3-dis(2H-tetrazol-5-yl)benzene, H₂dte = 1,4-ditetrazolylethylene, phen = 1,10-phenanthroline), have been synthesized and characterized. All the compounds exhibit unusual strong luminescence at room temperature in the solid state and can be potentially used as luminescent materials.     

Hydrothermal synthesis, crystal structure and luminescence of four novel metal-organic frameworks

Using the principle of crystal engineering, four novel metal-organic coordination polymers, {[Cd₁(nic)2(H₂O)]2[Cd₂(nic)2(H₂O)2]}_n (1), [Cd₂(fma)2(phen)2]_n (2), [Cd(fma)(bipy)(H₂O)]_n (3) and [Zn(mal)(bipy)·3H₂O]_n (4) (nic=nicotinate, fma=fumarate, mal=malate, phen=phenanthroline, bipy=2,2′-bipyridine) have been synthesized by hydrothermal reaction of M(CH₃COO)2·2H₂O (M=Zn, Cd) with nicotinic acid, fumaric acid and cooperative L (L=phen, bipy), respectively. X-ray analysis reveals that complex 1 possesses an unprecedented two-dimensional topology structure constructed from three-ply-like layers, complex 2 is an infinite 2D undulating network, complex 3 is a 1D zigzag chain and complex 4 belongs to a 1D chain. The results indicate a transformation of fumarate into malate during the course of hydrothermal treatment of complex 4. The photophysical properties have been investigated with luminescent excitation and emission spectra.     

Syntheses, topological analyses and photoelectric properties of Ag(I)/Cu(I) metal-organic frameworks based on a tetradentate imidazolate ligand

A new tetradentate imidazolate ligand 1,1′,1″,1′′′-(2,2′,4,4′,6,6′-hexamethylbiphenyl-3,3′,5,5′-tetrayl)tetrakis(methylene)(1H-imidazole) (L) and four Ag(I)/Cu(I) coordination polymers, namely [(MCN)₃L]_n (1: M=Ag; 2: M=Cu), and [(MSCN)₂L]_n (3: M=Ag; 4: M=Cu) are described. All four new coordination polymers were fully characterized by infrared spectroscopy, elemental analysis and single-crystal X-ray diffraction. Compound 1 features a 3D supramolecular framework constructed by 1D chains through inter-chain Ag-N(CN) and inter-layer Ag-N(L) weak interactions with an uninodal 6⁶ topology. Complex 2 presents a 3D framework characterized by a tetranodal (3,4)-connected (3·4·5·10²·11)(3·4·5·6·7·9)(3·6·7)(6·10²) topology. Complexes 3 and 4 are isostructural, and both have a 3D network of trinodal 4-connected (4·8⁵)₂(4²·8²·10²)(4²·8⁴)₂ topology. The luminescent properties for these compounds in the solid state as well as the possible ferroelectric behavior of 1 are discussed.     

Metal-directed self-assembly of M3L2 (M=Zn,Cd) metal-organic architectures with a tripodal tris-bidentate chelator

Two discrete M₃L₂ metal-organic architectures, 1 and 2, have been constructed by reaction of a newly designed tripodal tris-bidentate ligand L with M(NO₃)₂ (1: M=Zn; 2: M=Cd). Both complexes together with L have been structurally elucidated by single-crystal X-ray crystallography. Complex 1 exhibits a cationic M₃L₂ coordination architecture bearing three positive charges balanced by three uncoordinated nitrates, while 2 shows a neutral M₃L₂. 1 and 2 both adopt a compressed trigonal prism shape but show no internal cavity due to close ligand-to-ligand interactions. They display totally different intermolecular packing modes in the solid state, which strongly influence the intermolecular π–π interactions. Complex 1 has been arrayed such that each M₃L₂ is surrounded by three neighboring C ₃-symmetry related ones, whereas 2 exhibits a columnar molecular stacking. The distinctive intermolecular packing modes in the solid state between 1 and 2 bring about a small but discernible red shift (4?nm) corresponding to the π–π ^? electronic absorption.     

Construction of three new metal-organic frameworks with distinct SBUs: trinuclear {Cd3(COO)6} clusters,inorganic -Cd-O-Cd- chains,and heterometallic trinuclear {Cd2Ba(COO)4} clusters

Three metal-organic frameworks (MOFs), [Cd₃(OABDC)₂(e-urea)₄]_n (1), [Cd₃(OABDC)₂(H₂O)₅)]_n (2) and [Cd₂Ba(OABDC)₂(H₂O)₇]_n (3) (H₃OABDC = 5-oxyacetate isophthalic acid, e-urea = 2-imidazolidinone), were prepared using H₃OABDC and metal salts. Single-crystal X-ray diffraction analyses reveal that 1 features a 2-D layered structure constructed from trinuclear {Cd₃(COO)₆} SBUs and represents a (3,6)-connected kgd topology. Compounds 2 and 3 are 3-D inorganic–organic hybrid frameworks; 2 employs infinite inorganic –Cd–O–Cd– chains as SBUs, whereas (3,6)-connected ant-type 3 employs heterometallic trinuclear {Cd₂Ba(COO)₄} clusters as SBUs. The structures of these three compounds indicate that the SBUs play an important role in the construction of MOFs. Moreover, the thermal stabilities and solid-state photoluminescent properties of these three compounds have also been investigated.     

三维金属有机骨架微孔晶体化合物Cd5(BTC)4(H2O)8·6H2O的合成与晶体结构

通过改变合成条件合成了最大宽度达到2.6 nm的特殊“Z”字形孔道的新型金属有机骨架微孔晶体化合物Cd5(BTC)4(H2O)8·6H2O, 并通过ICP、元素分析、热重(TGA)和X射线单晶衍射分析对其进行了表征.     

Interpenetrating metal-organic frameworks formed by self-assembly of tetrahedral and octahedral building blocks

To investigate the relationship between topological types and molecular building blocks (MBBs), we have designed and synthesized a series of three-dimensional (3D) interpenetrating metal-organic frameworks based on different polygons or polyhedra under hydrothermal conditions, namely [Cd(bpib)_0.5(L¹)] (1), [Cd(bpib)_0.5(L²)]·H₂O (2), [Cd(bpib)_0.5(L³)] (3) and [Cd(bib)_0.5(L¹)] (4), where bpib=1,4-bis(2-(pyridin-2-yl)-1H-imidazol-1-yl)butane, bib=1,4-bis(1H-imidazol-1-yl)butane, H₂L¹=4-(4-carboxybenzyloxy)benzoic acid, H₂L²=4,4′-(ethane-1,2-diylbis(oxy))dibenzoic acid and H₂L³=4,4′-(1,4-phenylenebis(methylene))bis(oxy)dibenzoic acid, respectively. Their structures have been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compounds 1–3 display α-Po topological nets with different degrees of interpenetration based on the similar octahedral [Cd₂(–COO)₄] building blocks. Compound 4 is a six-fold interpenetrating diamondoid net based on tetrahedral MBBs. By careful inspection of these structures, we find that various carboxylic ligands and N-donor ligands with different coordination modes and conformations, and metal centers with different geometries are important for the formation of the different MBBs. It is believed that different topological types lie on different MBBs with various polygons or polyhedra. Such as four- and six-connected topologies are formed by tetrahedral and octahedral building blocks. In addition, with the increase of carboxylic ligands’ length, the degrees of interpenetration have been changed in the α-Po topological nets. And the luminescent properties of these compounds have been investigated in detail.     

A fluorescent 3-D metal-organic framework with unusual tetranuclear zinc secondary building units

A 3-D metal-organic framework (MOF) {Zn₄(μ₃-OH)₂(bdc)₃(pad)₂}·2H₂O (1, H₂bdc = 1,4-benzenedicarboxylic acid, pad = 1,10-phenanthroline-5,6-dione) with unusual Zn₄(μ₃-OH)₂(COO)₆(N₂)₂ secondary building units (SBUs) has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, elemental analysis, and infrared spectroscopy. The tetranuclear Zn₄ SBU was formed through two dinuclear Zn₂ clusters by sharing two μ₃-OH bridges. Considering this Zn₄ SBU as a six-connected node, the overall framework of 1 has a pcu topology. This tetranuclear Zn₄ SBU can be used as a node in construction of MOFs.     

A new 8-connected self-penetrating metal-organic framework based on dinuclear cadmium clusters as secondary building units

A new metal-organic framework（MOF） based on metal clusters as secondary building units（SBU）,has been synthesized and structurally characterized.The reported MOF presents an interesting 8-connected self-penetrating coordination network based on dinuclear cadmium cluster with a 4²⁴·5·6³ topology. Moreover,the thermal stability and luminescence property of this compound have been investigated.     

羧基配体金属有机骨架材料作为催化剂的研究进展

<正>金属有机骨架材料(MOFs)是由无机金属中心与多齿有机配体通过配位键形成的立体网络结构多孔晶体材料[1].MOFs具有多孔性、大比表面积、结构规整、有机配体的可修饰性、金属离子的可选择性等特点,在气体吸附、气体分离、磁性材料、光学材料和催化剂等领域得到广泛的应用[2-6].尤其是在催化方面,MOFs结合了金属有机配合物和分子筛的优点,可以直接用作催化剂,也可作为催化剂载体使用.     

Three-dimensional (3-D) metal-organic frameworks with 3-pyridin-4-yl-benzoate defining new (3,6)-connected net topologies

Reactions of different metal salts with 3-pyridin-4-yl-benzoic acid (3,4-Hpybz) under ambient condition afford a series of 3-D metal-organic frameworks with two new types of (3,6)-connected net topologies. In the isomorphic complexes [M₂(μ-H₂O)(3,4-pybz)₄]_n (M^II=Mn^II for 1, Zn^II for 2, or Cd^II for 3), the octahedral metal nodes are extended by the 3-connected pybz tectons to constitute 3-D arrays with the Schläfli symbol of (3.4.5)(3².4⁴.5⁵.6².7²), whereas [Pb(3,4-pybz)₂]_n (4) shows a completely different 3-D (4².6)₂(4⁴.6².8⁹) framework, which represents a subnet of the (4,8)-connected fluorite lattice.     

Two- and three-dimensional photoluminescent Cd(II)-carboxylate coordination frameworks bridged by benzenepentacarboxylate and N-donor ligands

Reactions of Cd(OAc)₂·H₂O, benzenepentacarboxylic acid (H₅bpc), 2,2′-bpy/4,4′-bpy, and Et₃N yield two new coordination polymers [Cd₅(bpc)₂(2,2′-bpy)₄(H₂O)₄] (1) and [Cd₅(bpc)₂(4,4′-bpy)₂(H₂O)₄]·3H₂O (2). Complex 1 is a 2-D structure based on six-connected Cd-carboxylate layers. Adjacent layers are linked by π–π interactions and hydrogen bonds to generate a layered supramolecular network. Complex 2 is a 3-D coordination framework. The bpc ligands adopting μ ₇-bridging mode connect Cd(II) ions to form a 3-D open framework with elliptic channels, in which the coordinated 4,4′-bpy ligands fill to support the whole framework. Complex 2 exhibits strong photoluminescence at room temperature.     

Hydrothermal synthesis, crystal structures and fluorescence properties of three novel frameworks constructed with mixed ligands of isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq): [M(1,3-BDC)(Dpdq)(H2O)m] · nH2O (M = Co, Cd or Zn)

Three novel metal-organic frameworks [M(1,3-BDC)(Dpdq)(H₂O)_m] · nH₂O, (M = Co^II (1), Cd^II (2) or Zn^II (3); m = 0, 1; n = 0, 1, 2, respectively) have been obtained from hydrothermal reactions of three different metal(II) nitrates with the same mixed ligands [isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq)], and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that each pair of metal ions are bridged by various coordination modes of 1,3-BDC ligands to form left- and right-handed helical chains in 1, linear chains in 2, and double chains in 3, respectively. N-containing flexible ligand Dpdq takes a chelating coordination mode acting as terminal ligand. In the compound 1, adjacent left- and right-handed helical chains are packed through hydrogen bonds to form a two-dimensional (2-D) structure. In the compounds 2 and 3, adjacent chains are further linked by hydrogen bonds and/or π-π stacking interactions to form a three-dimensional (3-D) distorted hexagon meshes supramolecular framework for 2 and a ZnS-related three-dimensional (3-D) topology for 3, respectively. The different structures of compounds 1-3 illustrate that the influence of the metal ions in the self-assembly of polymeric coordination architectures. In addition, compounds 2 and 3 exhibit blue emission in the solid state at room temperature.     

A series of metal-organic frameworks constructed with arenesulfonates and 4,4′-bipy ligands

Five transition metal compounds containing arenesulfonates and 4,4′-bipy ligands, namely [Zn₂(N,N′-4,4′-bipy)(N-4,4′-bipy)₂(H₂O)₈](bpds)₂ · 5H₂O (1), [Ag₂(N,N′-4,4′-bipy)₂(bpds)] (2), [Cd(N,N′-4,4′-bipy)(H₂O)₄]₂(4-abs)₄ · 5H₂O (3), [Cu(N,N′-4,4′-bipy) (O-bs)₂(H₂O)₂] · 4H₂O (4), and [Zn(N,N′-4,4′-bipy)₂(H₂O)₂](4,4′-bipy)(bs)₂ · 4H₂O (5) (4,4′-bipy = 4,4′-bipyridine, bpds = 4,4′-biphenyldisulfonate, 4-abs = 4-aminobenzenesulfonate, bs = benzenesulfonate), have been synthesized and characterized by X-ray single crystal diffraction, elemental analyses and TG analyses, in order to investigate the coordination chemistry of arenesulfonates and 4,4-bipy, as well as to construct novel coordination frameworks via mixed-ligand strategy. Compounds 2, 4 and 5 could be obtained via hydrothermal or aqueous reactions. Compound 1 forms a binuclear octahedral metal complex. Compounds 2–4 form polymeric chains. Compound 5 consists of 2D square grids with one intercalated 4,4′-bipy molecule. Weak Ag–Ag interactions are observed in compound 2. These complexes show great structural varieties and there are three different coordination modes observed for both the 4,4′-bipy and the sulfonate ligands.     

Controlling structural topology of metal-organic frameworks with a desymmetric 4-connected ligand through the design of metal-containing nodes

Two new metal-organic frameworks(MOFs),[Cu2(H_2O)_2(BCPIA)](BUT-20)and(Me_2NH_2)[In(BCPIA)](BUT-21)were designed and synthesized through the solvothermal reaction between a newly created desymmetric 4-connected ligand,5-(2,6-bis(4-carboxyphenyl)pyridin-4-yl)isophthalic acid(H_4BCPIA)and Cu(NO_3)2 2.5H_2O or In(NO_3)_3·5H_2O,respectively,and characterized by single-crystal and powder Xray diffraction,thermogravimetric analysis,infrared spectroscopy,and elemental analysis.The two MOFs have three-dimensional structures,in which both the BCPIA 4 ligand and metal-containing entities,Cu_2(COO)_4(H_2O)_2 and In(COO)_4 act as 4-connected nodes.However,different linkage configurations of the two metal-containing nodes,quadrilateral Cu_2_TD_2(COO)_4(H_2O)_2and tetrahedral In(COO)_4,lead to distinct structural networks of BUT-20 and 21,with Nbo and Unc topologies,respectively.     

A 3-D metal-organic framework constructed with cobalt(II), 1,3-di(4-pyridyl)propane (bpp) and 3,5-dinitrobenzoate (DNBA) with methyl-3,5-dinitrobenzoate (MDNBA) by in-situ synthesis as a guest

A new 3-D cobalt(II) mixed ligand, metal-organic framework {[Co₂(bpp)₂(DNBA)₄H₂O] ·?MDNBA} (1), (bpp =?1,3-di(4-pyridyl)propane, DNBA =?3,5-dinitrobenzoate and MDNBA =?methyl-3,5-dinitrobenzoate) was synthesized in aqueous-methanol medium. X-ray structural analysis of 1 revealed that the dinuclear cobalt clusters interlinked by two μ-carboxylates and a μ ₂ water molecule, acting as a node, are connected to four other clusters through bridging bpp to generate an extended neutral 3-D network. MDNBA was in-situ synthesized and encapsulated in the framework as a guest molecule. Moreover, the fluorescence spectrum shows 1 exhibits blue fluorescent emission in the solid state at room temperature.     

Multi-functional sites catalysts based on post-synthetic modification of metal-organic frameworks

Multi-functional sites MOFs have been explored as a new type of heterogeneous catalytic materials, which can be constructed by various post-synthetic modifications.     

Ligand-controlled assembly of Cd(II) coordination polymers based on mixed ligands of naphthalene-dicarboxylate and dipyrido[3,2-d:2′,3′-f]quinoxaline: From 0D+1D cocrystal, 2D rectangular network (4,4), to 3D PtS-type architecture

Three novel Cd(II) coordination polymers, namely, [Cd(Dpq)(1,8-NDC)(H₂O)₂][Cd(Dpq)(1,8-NDC)]·2H₂O (1), [Cd(Dpq)(1,4-NDC)(H₂O)] (2), and [Cd(Dpq)(2,6-NDC)] (3) have been obtained from hydrothermal reactions of cadmium(II) nitrate with the mixed ligands dipyrido [3,2-d:2′,3′-f]quinoxaline (Dpq) and three structurally related naphthalene-dicarboxylate ligands [1,8-naphthalene-dicarboxylic acid (1,8-H₂NDC), 1,4-naphthalene-dicarboxylic acid (1,4-H₂NDC), and 2,6-naphthalene-dicarboxylic acid (2,6-H₂NDC)]. Single-crystal X-ray diffraction analysis reveals that the three polymers exhibit novel structures due to different naphthalene-dicarboxylic acid. Compound 1 is a novel cocrystal of left- and right-handed helical chains and binuclear complexes and ultimately packed into a 3D supramolecular structure through hydrogen bonds and π-π stacking interactions. Compound 2 shows a 2D rectangular network (4,4) bridged by 1,4-NDC with two kinds of coordination modes and ultimately packed into a 3D supramolecular structure through inter-layer π-π stacking interactions. Compound 3 is a new 3D coordination polymer with distorted PtS-type network. In addition, the title compounds exhibit blue/green emission in solid state at room temperature.     

Synthesis,characterization and catalytic performance of Mo based metal-organic frameworks in the epoxidation of propylene by cumene hydroperoxide

Two types of Mo containing metal-organic frameworks, denoted as Mo@COMOC-4 and PMA@MIL-101 (Cr), were synthesized respectively by a post-synthetic modification and a ship-in-bottle approach. The catalytic performance of both compounds in the epoxidation of propylene using cumene hydroperoxide (CHP) as oxidant was compared with MoO₃@SiO₂. A higher conversion (46.2%) and efficiency (87.4%) of CHP was observed for Mo@COMOC-4, whereas the heteropoly acids supported MIL-101 resulted in the decomposition of CHP due to its strong acidic character. Regenerability tests demonstrated that Mo@COMOC-4 could be reused for multiple runs without significant loss in both activity and stability. © 2017 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.