Four-connected Nodes Research Articles

High-throughput screening of hypothetical metal-organic frameworks for thermal conductivity

Thermal energy management in metal-organic frameworks (MOFs) is an important, yet often neglected, challenge for many adsorption-based applications such as gas storage and separations. Despite its importance, there is insufficient understanding of the structure-property relationships governing thermal transport in MOFs. To provide a data-driven perspective into these relationships, here we perform large-scale computational screening of thermal conductivity k in MOFs, leveraging classical molecular dynamics simulations and 10,194 hypothetical MOFs created using the ToBaCCo 3.0 code. We found that high thermal conductivity in MOFs is favored by high densities (> 1.0 g cm−3), small pores (< 10 Å), and four-connected metal nodes. We also found that 36 MOFs exhibit ultra-low thermal conductivity (< 0.02 W m−1 K−1), which is primarily due to having extremely large pores (~65 Å). Furthermore, we discovered six hypothetical MOFs with very high thermal conductivity (> 10 W m−1 K−1), the structures of which we describe in additional detail.

Hexanuclear nickel-based [P4Mo11O50] with photocatalytic reduction of CO2 activity

A new polyoxometalate based organic-inorganic hybrid [Ni6(trz)2(Htrz)13][H4P4Mo11O50]·7H2O (1), constructed from a hexanuclear [Ni6(trz)2(Htrz)13] building block and a new polyoxometalate [H4P4Mo11O50] cluster, was synthesized under a hydrothermal condition. In this 3D structure, each [Ni6(trz)2(Htrz)13] secondary building unit (SBU) connects with four neighbored [Ni6(trz)2(Htrz)13] and four [H4P4Mo11O50] clusters, forming an eight-connected node. While each [H4P4Mo11O50] cluster bridges four [Ni6(trz)2(Htrz)13] SBUs as a four-connected node. So the 3D framework of 1 can be simplified to a binodal (4, 8)–connected gsp2 topology with point symbol [44·62][416·612]. The photocatalytic reduction of CO2 under visible light reveals that the highest yield of CO was 689.86 μmol g−1 when 1 is used as catalyst, Ru(bpy)3Cl2 as a photosensitizer and TEOA as a sacrificial agent. The mechanism of the photoreduction of CO2 is confirmed by Mott-Schottky, photocurrent, and fluorescence quenching experiments. This research provides a new strategy for the design of cheap and efficient POM-based photocatalysts.

Square network based upon the molecular salt of the tetraprotonated photoproduct rtct-tetrakis(pyridin-4-yl)cyclobutane and the sulfate anion.

The formation and crystal structure of a hydrated molecular salt that results in a square network is reported. The crystalline solid is based upon the tetraprotonated photoproduct rtct-tetrakis(pyridin-4-yl)cyclobutane (4H-rtct-TPCB)4+ along with two sulfate anions (SO42-) and eight waters of hydration, namely, 4,4',4'',4'''-(cyclobutane-1,2,3,4-tetrayl)tetrapyridinium bis(sulfate) octahydrate, C24H24N44+·2SO42-·8H2O. The fully protonated photoproduct acts as a four-connecting node within the square network by engaging in four charge-assisted N+-H...O hydrogen bonds to the sulfate anion. The observed hydrogen-bonding pattern in this square network is akin to T-silica, which is a metastable form of SiO2. The included water molecules and sulfate anions engage in numerous O-H...O hydrogen bonds to form various hydrogen-bonded ring structures.

A series of new sulfone-functionalized coordination polymers: Fascinating architectures and efficient fluorescent sensing of nitrofuran antibiotics

Three new sulfone-functionalized coordination polymers, [Mn(L)(DMF)2]n (1), {[Cd3(L)3(DMA)4]·2DMA·4H2O}n (2) and {[Cd3.5(L)4(DMA)(H2O)]·xsol} n (3), where H2L ​= ​5,5-dioxodibenzothiophen-3,7-dicarboxylic acid, have been synthesized under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction. Complex 1 is a 3D framework based on rod-shaped MnII carboxylate chains as secondary building units (SBUs). Complex 2 is a 2D (4,4) net based on linear trinuclear [Cd3(COO)3] clusters (SBUs1), while 3 presents a rarely binodal (4,6)-connected fsc topological net based on linear trinuclear [Cd3(COO)3] clusters (SBUs1) as four-connected nodes and “chairlike” tetranuclear [Cd4(μ3-OH)2(COO)6] clusters (SBUs2) as six-connected nodes, with the Schläfli symbol of (44·610·8)(44·62). Fluorescence measurements reveal that 2 displays excellent luminescence in EtOH and can selectively detect trace amount of nitrofuran antibiotics via luminescence quenching, with high KSV values (1.673 ​× ​104 ​M−1 for NFT and 2.915 ​× ​104 ​M−1 for NFZ) and low detection limits (0.39 ​μM and 0.22 ​μM for NFT and NFZ). Additionally, the possible mechanisms for the luminescence quenching have been investigated.

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

An Inorganic–Organic Hybrid Polymer Cocatalyst for Photoelectrochemical Water Oxidation with Dual Functions of Accelerating Kinetics and Improving Charge Transfer

Oxygen evolution cocatalysts (OECs) play important roles in improving the efficiency of photocatalysts in solar water splitting. Inorganic–organic hybrid polymers (IOHPs), which have good electroly...

Viologen-Based Cationic Metal-Organic Framework for Efficient Cr2O72- Adsorption and Dye Separation.

A novel cationic metal-organic framework composed of {Cu2(COO)4} paddle-wheel units and a tetracarboxylic viologen derivative, namely, {[Cu2(bdcbp)(H2O)2]·2NO3·2H2O}n (Cu-CMOF, H4bdcbpCl2 = 1,1'-bis(3,5-dicarboxyphenyl)-4,4'-bipyridinium dichloride), has been successfully synthesized and structurally characterized. In Cu-CMOF, the {Cu2(COO)4} unit and viologen derivative both act as four-connected nodes forming an ssb-type cationic network with 42.84 topology, in which the positive charges are distributed on the organic viologen moieties. Deeper insight of the structure indicates that the 3D architecture of Cu-CMOF can be seen as packing of a 26-faceted polyhedral cage and two cuboid cages. Notably, Cu-CMOF displays a highly efficient anion exchange ability for capture and removal of anionic pollutants. UV-vis absorption spectra and digital images demonstrate that Cu-CMOF is capable of adsorbing the dichromate anion and anionic dyes effectively, such as methyl orange (MO-), Congo red (CR2-), and New Coccine (NC3-). Meaningfully, anionic dyes (MO-, CR2-, and NC3-) can be efficiently and selectively removed by Cu-CMOF in the presence of cationic dye methylene blue (MLB+). Such behaviors of anionic pollutant adsorption and dye separation are mainly caused by an ion-exchange process facilitated by the large cavity and decentralized distribution of positive charge in Cu-CMOF.

Simultaneous quantitative recognition of all purines including N6-methyladenine via the host-guest interactions on a Mn-MOF

Simultaneous quantitative recognition of all purines including N6-methyladenine via the host-guest interactions on a Mn-MOF

Supramolecular assembly of a 2D coordination polymer bearing pyridine-N-oxide-2,5-dicarboxylic acid and copper ion: X-ray crystallography and DFT calculations

Abstract As an extension of our interest in pyridine-N-oxide-dicarboxylic acids, we report the design and synthesis of a 2D coordination polymer {[Cu(Hpydco)2]·2H2O}n (1) based on the pyridine-N-oxide-2,5-dicarboxylic acid ligand (H2pydco). Compound 1 was characterized using infrared spectroscopy, CHN-elemental analyses, TGA and single crystal X-ray diffraction (SCXD). Structural analysis showed that this compound is a two-dimensional coordination polymer created by four-connected nodes defined by the copper ion and bridging Hpydco–ligands which created regular tetragons. In the packing, hydrogen bonds connect adjacent 2D sheets to extend the structure into a 3D architecture. Since H2pydco and pyridine-2,5-dicarboxylic acid have similar frameworks, we also highlight some areas of current interest in their coordination behavior by surveying reported structures (Cambridge Structural Database (CSD)) and have investigated the influence of the N-oxide moiety on the coordination mode(s) in the crystal lattice. Finally, DFT calculations have been used to compare H2pydco and pyridine-2,5-dicarboxylic acid ligands and their ability to interact with Cu(II).

Hydrothermal synthesis, characterization and properties of a d10 metal coordination polymer with a layered structure based on carboxyphosphinate ligand, 4,4′-bipyridine and four-coordinated zinc ion

Hydrothermal reaction of Zn(NO3)2 · 6 H2O with 2-carboxyethyl(phenyl)phosphinate (H2L) and 4,4'-bipyridine (4,4′-bipy) led to a novel zinc(II) carboxyphosphinate [ZnL(4,4′-bipy)0.5]n (1). The zinc ion is tetrahedrally coordinated by two phosphinate oxygen atoms, one carboxylate oxygen atom, and one nitrogen atom of 4,4′-bipy ligand. The L2- ligand and zinc ion can be seen as three- and four-connected nodes, respectively. Compound 1 shows a layered network with (3,4)-connected topology. It exhibits a broad blue fluorescent emission band at 459 nm, which can be attributed to 4,4′-bipy intraligand emission as well as to H2L emission. It is a diamagnetic system between 300 K and 11 K.

Structural variation and luminescence properties of d10 metal ions complexes from 5-Aminotetrazolate ligand

Three new d10 complexes with 5-aminotetrazolate (5-HATZ), [Zn2(5-ATZ)3(N3)]n (1), {[Cd6(5-ATZ)8Cl5]n·(H2O)4}n (2), and {[Cd12(5-ATZ)12Cl8(N3)4]·2H2O}n (3) have been obtained under hydrothermal conditions and structurally characterized. Single-crystal X-ray structural analyses reveal that complex 1 can be rationalized to be 3D dia topological nets with the metal ZnII centers acting as four-connected nodes and L acting as linkers, and the Schläfli symbol is 66, while 2 exhibits a 3D architecture based on six crystallographically independent hexahedral coordinated CdII centers linked by 5-ATZ anion and Cl anion. Complex 3 also possesses a 3D network linked by 5-ATZ anion, Cl anion as well as N3 anion. The ligand 5-ATZ anion adopts μ1,4-bridging coordination mode in complex 1, μ1,2,3, μ1,2,4, μ1,2,3,4-bridge coordination mode in complex 2, while μ1,2,4, μ1,2,3,4-bridge coordination mode in complex 3. Also, the fluorescent properties of complexes 1 and 2 have been investigated.

Nanocage containing metal-organic framework constructed from a newly designed low symmetry tetra-pyrazole ligand

1368-Tetra(1H-pyrazol-4-yl)-9H-carbazole (H4CTP), a tetra-pyrazole ligand with Cs symmetry, has been synthesized based on a carbazole core. A solvothermal reaction of this ligand with NiCl2·6H2O gave a three-dimensional (3-D) metal-organic framework (MOF), [Ni(H4CTP)Cl2]·nS (BUT-41), which crystallized in the cubic space group Pm-3 in spite of H4CPT with a central carbazole core and four peripheral pyrazole rings has low symmetry. The framework of BUT-41 can be regarded as a four-connected 3-D net with the rhr topology when both the organic ligand and the metal center are considered as four-connected nodes. Nanocages with internal diameter of 2 nm are present in the framework of BUT-41, which are formed by interconnecting 12 H4CTP ligands and 20 Ni(II) ions. Each nanocage connects with six adjacent cages through sharing hexagonal windows with diameter over 7 Å, resulting in 3-D intersecting channels of the MOF. Although the tetra-pyrazole ligand is not deprotonated after coordination with the metal ions, powder X-ray diffraction and N2 adsorption experiments reveal that the framework of BUT-41 is rigid and permanently porous with the Brunauer-Emmett-Teller surface area up to 1551 m2 g−1. Furthermore, gas adsorption experiments show that this MOF selectively adsorbs CO2 over N2 and CH4.

Structure Direction, Solvent Effects, and Anion Influences in Halogen-Bonded Adducts of 2,6-Bis(iodoethynyl)pyridine

A new divergent and self-complementary halogen bond donor–acceptor molecule 2,6-bis(iodoethynyl)pyridine L has been prepared and structurally characterized, and used to generate a series of extended halogen-bonded adducts with tetrabutylammonium halide salts. The reaction between L and anions such as either bromide or chloride gives the one-dimensional polymeric species {L·TBABr} or {L·TBACl}, respectively, which contains helical strands linked by C–I···X– halogen bonds which partially encapsulate the associated organic cations. Varying the reaction solvent from ethyl acetate to 5:95 methanol/ethyl acetate gives rise to another polymeric phase on combining L with tetrabutylammonium chloride, the one-dimensional looped chain structure {L2·TBACl} in which each chloride ion acts as a four-connected square planar node for halogen bonding interactions originating from L. Similar solvent effects are observed in the discrete macrocyclic species {L·TBAI}-α and {L·TBAI}-β, both consisting of cyclic (L2I2)2– specie...

Versatile Coordination Mode of LiNaB8O13 and α- and β-LiKB8O13 via the Flexible Assembly of Four-Connected B5O10 and B3O7 Groups

Three new alkali-metal mixed borates, LiNaB8O13, α-LiKB8O13, and β-LiKB8O13, containing a (3)∞[B8O13] three-dimensional network have been successfully synthesized. Their fundamental building block is [B8O16](8-) formed by the vertex-sharing [B5O10](5-) and [B3O7](5-) groups, which are topologically identical when they are considered as four-connected nodes. The viewpoints give us a feasible way to investigate the versatile structure assembly of borates with a complex network.

A novel [4 + 3] interpenetrated net containing 7-fold interlocking pseudo-helical chains and exceptional catenane-like motifs.

A novel interpenetrating metal-organic framework, namely [Zn(3)L(2)(oba)(3)(H(2)O)(2)]·(4)H(2)O (1), has been synthesized under hydrothermal conditions. Its structure was determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR, and thermogravimetric (TG) analysis. In the structure of 1, the rigid and flexible V-shaped ligands link Zn(ii) to form a 3D structure where two types of helices and four types of pseudo-helical chains containing three pairs of enantiomers and two pairs of conformational isomers have been characterized. One such 3D framework incorporates six identical networks to form a 7-fold interpenetrated 3D framework. From the topological analysis, the Zn(ii) ions act as three- and four-connected nodes, and oba as well as L are linkers. The framework of compound can be classified as a new (6(3))2(6(5)·8) topology, which is a novel (3,3,4)-connected [4 + 3] 7-fold interpenetrating net showing 7-fold interlocking pseudo-helical chains and a unique catenane-like motif with Hopf links. In addition, the luminescence properties of the compound are discussed.

Preparation of open and closed forms of the lvt network with Cu(ii) complexes of structurally related 1,2-diazole ligands

Reported here are the synthesis and structural characterisation of two topologically related coordination polymers: [Cu(L1)(CH3CONH2)], 1, and [Cu(L2)(NMP)]·0.5NMP·0.5H2O, 2, (NMP = N-methyl-pyrrolidinone) prepared from 1H-indazole-3-carboxylic acid, H2L1, and 1H-pyrazole-3-carboxylic acid, H2L2, respectively. Both 1 and 2 crystallise in the tetragonal space group I41/a and form 3-dimensional coordination polymers described by the lvt topology, in which [Cu2L2] dimers form four-connected nodes linked through carboxylate groups. Within 1 the presence of a Cu-bound acetamide molecule (formed in situ by the solvothermal hydration of acetonitrile) propagates hydrogen bonding between dimer units that, combined with the steric bulk of the indazole fragment, yield a closed (non-porous) framework. In 2, however, Cu-bound NMP, which does not participate in hydrogen bonding, coupled with the less bulky nature of the pyrazole-backbone, gives rise to an open framework of an otherwise isostructural network.

Temperature effect-driven assembly of [CunXn]-based coordination polymers from CuX and 1,4-bis(imidazol-1-yl)butane

Three [CunXn]-based (X=Br, I) coordination polymers, {[Cu2(μ-I)2(bimb)2]·iodobenzene}n (1), {[Cu4(μ3-I)4(bimb)2][Cu2(μ-I)2(bimb)]}n (2) and {[Cu2Br(bimb)2]Br}n (3) were prepared from solvothermal reactions of CuX (X=I, Br) with 1,4-bis(imidazol-1-yl)butane (bimb) at different temperatures. These compounds were characterized by elemental analysis, IR, and single crystal X-ray diffraction. Compound 1 contains a rhombic [Cu2(μ-I)2] dimer that acts as a planar four-connected node to link four equivalent ones via bimb bridges to form a 2D (4,4) network. Each layer is further stacked by π–π interactions to form a 3D structure with 1D rhombic channels occupied by the guest iodobenzene molecules. Compound 2 consists of [Cu2(μ-I)2] dimers and [Cu4(μ3-I)4] tetramers which are interconnected by bimb bridges to generate another 2D network. Compound 3 contains [Cu2Br(bimb)2]+ cations that are linked by bimb ligands to form a 1D cationic chain. We also investigated the solid state photoluminescent properties of 1–3 at ambient temperature. The results provide an interesting insight into how reaction temperatures exert a great effect on the assembly of [CunXn]-based coordination polymers.

Syntheses, Structures and Properties of Two 2D Transition Metal Coordination Polymers Based on Oxalate and Two Types of N-donor Auxiliary Ligands

Two new two-dimensional (2D) metal–organic coordination polymers [Co(ox)(bbbm)]·H2O (1) and [Cu(ox)(bppdca)]·2H2O (2) (H2ox = oxalic acid, bbbm = 1,1-(1,4-butanediyl)bis-1H-benzimidazole and bppdca = N,N′-bis(pyridin-3-yl)-2,6-pyridinedicarboxamide) were synthesized under hydrothermal conditions and structurally characterized. Both 1 and 2 exhibit a 2D four-connected network formed by the CoII/CuII ions as four-connected nodes; and, the ox anions and bbbm/bppdca ligands as linkers with a (44.62) topology as determined by single crystal X-ray diffraction. In addition, the thermal stability, electrochemical and luminescent properties for 1 and 2 were investigated.

A three-dimensional manganese(II) metal–organic framework based on 5-methoxybenzene-1,3-dicarboxylic acid and exhibiting a pts net

The solvothermal reaction of MnCl2·H2O and 5-methoxybenzene-1,3-dicarboxylic acid (MeO-m-H2BDC) led to a three-dimensional Mn(II) metal-organic framework, namely poly[(dimethylformamide-κO)(μ4-5-methoxybenzene-1,3-dicarboxylato-κ(4)O(1):O(1'):O(3),O(3'):O(3))manganese(II)], [Mn(C9H6O5)(C3H7NO)]n or [Mn(MeO-m-BDC)(DMF)]n (DMF is dimethylformamide). The Mn(II) atom is six-coordinated and exhibits a distorted octahedral geometry formed by five carboxylate O atoms from four different MeO-m-BDC(2-) anionic ligands and by one DMF O atom. The three-dimensional framework of (I) formed by the bridging MeO-m-BDC(2-) ligands and the Mn(II) atoms exhibits a pts topological network when MeO-m-BDC(2-) and Mn(II) are viewed as four-connected nodes.

Two different dimensional bbbm-based cobalt(II) coordination polymers tuned by benzenedicarboxylates: Assembly, structures and properties

Two new metal–organic coordination polymers [Co4(bbbm)4(1,2-BDC)4(H2O)]·2H2O (1) and [Co(bbbm)(1,4-BDC)] (2) (bbbm=1,1-(1,4-butanediyl)bis-1H-benzimidazole, 1,2-H2BDC=1,2-benzenedicarboxylic acid and 1,4-H2BDC=1,4-benzenedicarboxylic acid) were obtained under hydrothermal conditions and structurally characterized. Polymer 1 exhibits a two-dimensional (2D) 4-connected network with the CoII ions as four-connected nodes, and the bbbm and 1,2-BDC ligands as linkers. Polymer 2 possesses a novel three-dimensional (3D) 3-fold interpenetrated framework. The position of carboxyl groups for benzenedicarboxylates dominates the final structures of 1 and 2. Furthermore, elemental analysis, IR spectroscopy, thermogravimetric analysis, electrochemical properties and solid state fluorescence for 1 and 2 were investigated.