Rapid Generation of Metal-Organic Framework Phase Diagrams by High-Throughput Transmission Electron Microscopy

Metal-organic frameworks (MOFs) constructed from Zr₆ nodes and tetratopic carboxylate linkers display high structural diversity and complexity in which various crystal topologies can result from identical building units. To determine correlations between MOF topologies and experimental parameters, such as solvent choice or modulator identity and concentration, we demonstrate the rapid generation of phase diagrams for Zr₆-MOFs with 1,4-dibromo-2,3,5,6-tetrakis(4-carboxyphenyl)benzene linkers under a variety of conditions. We have developed a full set of methods for high-throughput transmission electron microscopy (TEM), including automated sample preparation and data acquisition, to accelerate MOF characterization. The use of acetic acid as a modulator yields amorphous, NU-906, NU-600, and mixed-phase structures depending on the ratio of N,N-dimethylformamide to N,N-diethylformamide solvent and the quantity of the modulator. Notably, the use of formic acid as a modulator enables direct control of crystal growth along the c direction through variation of the modulator quantity, thus realizing aspect ratio control of NU-1008 crystals with different catalytic hydrolysis performance toward a nerve agent simulant.

Two isomeric metal-organic frameworks bearing stilbene moieties for high volatile iodine uptake

The efficient, green, and economical removal of radioactive iodine (I2) has drawn worldwide attention in the safe development of nuclear energy. Metal-organic frameworks (MOFs) have been demonstrated to be a...

The solvent influenced coordination variation of flexible ligands to Y(iii) towards MOF structural diversity

Coordination variation by solvent environment change leading to various yttrium-based MOFs with flexible ligands.

Solvent-Effected Coordination Variation of Flexible Ligands to Cu(II) for the Formation of 1D and 2D Secondary Building Units for Metal-Organic Frameworks

Producing more than one structure from the same set of metal and ligand precursors will grant structural diversity in metal-organic framework (MOF) systems. One of the biggest obstacles of getting structural diversity for the late transition metals is that the coordination mode is pretty much fixed by nature. Herein, we show that two different coordination modes to Cu(II) are possible for flexible ligands containing hydrophilic terminal groups through solvent guidance. It is demonstrated that trans,trans-muconic acid (H₂muco) ligands coordinate to Cu(II) to form Cu(II) muconate MOFs having a 1D chain structure and a 2D plane structure in water-rich and DMF-rich water-DMF mixed solvent systems, respectively. It is suggested that the interaction between ligands and solvent is responsible for the selective coordination. A similar result was observed from the attempts using the fumaric acid ligand. Our results provide a new direction to obtain diverse secondary building units for the construction of diverse MOFs.

Electrolytic synthesis of porphyrinic Zr-metal-organic frameworks with selective crystal topologies

The thermodynamic (PCN-222) and kinetic (PCN-224) products of porphyrinic Zr-metal-organic frameworks (MOFs) were synthesized via an anodic dissolution approach for the first time. To the best of our knowledge, this is the first report of MOF polymorphs being controlled by electrolysis. The selective formation of PCN-222 requires an amorphous component to be present on the electrode during the initial reaction process.

Tuning dimensionality between 2D and 1D MOFs by lanthanide contraction and ligand-to-metal ratio

2D/1D dimensionality tuning in LnMOFs is related to both (i) ligand-to-metal ratio and (ii) lanthanide contraction, this is only possible with Er/Tm, lighter lanthanides e.g. Pr only produced 2D MOFs, despite different ligand-to-metal ratios were used.

Dysprosium Chlorocyanoanilate-Based 2D-Layered Coordination Polymers

A series of two-dimensional (2D)-layered coordination polymers (CPs) based on the heterosubstituted anilate ligand ClCNAn^2- derived from 3-chloro-6-cyano-2,5-dihydroxybenzoquinone and Dy^III are reported. By changes in the synthetic methods (layering technique, solvothermal or conventional one-pot reactions) and conditions (solvent, concentration, etc.), different types of 2D extended networks could be prepared and structurally characterized. Compounds 1 and 1', two polymorphs with the formula [Dy₂(ClCNAn)₃(DMSO)₆]_n·(H₂O)_x [x = 7 (1), 0 (1')], were prepared by a conventional one-pot reaction and recrystallized at different concentrations. Compound 2, formulated as [Dy₂(ClCNAn)₃(DMF)₆]_n, was prepared by a layering technique, while compound 3, formulated as {(Me₂NH₂)₂[Dy₂(ClCNAn)₄(H₂O)₂]·(DMF)₂·(H₂O)₅}_n, was obtained by a solvothermal method. Compounds 1 and 2 are neutral 2D CPs of the ClCNAn^2- ligand and Dy^III ions, while 3 presents 2D anionic layers of [Dy₂(ClCNAn)₄(H₂O)₂]^2- alternating with cationic layers of Me₂NH₂⁺ ions. These compounds show very diverse networks, with compound 1 forming 2D (8,3) and (4,3) topology with eight- and four-membered rings with square cavities, 1' and 2, respectively, a 2D (6,3) topology with six-membered rings (a rectangular cavity for 1' and a regular hexagonal cavity for 2), and 3 a 2D (4,4) topology with distorted square cavities. In this respect, 1 and 1' represent the first examples of polymorphism in the family of anilate-based CPs. Thermal analysis measurements (differential scanning calorimetry and thermogravimetry) show an exothermic polymorphic transformation from the kinetically stable 1' phase to the thermodynamically stable phase 1. The magnetic behavior of 1-3 very likely indicates depopulation of the m_J levels, while the presence of weak antiferromagnetic coupling between the Dy^III centers mediated by the anilate bridge cannot be excluded.

Vapour- and solvent-mediated crystalline transformations in Mo(vi) hydrazone complexes controlled by noncovalent interactions

Through the use of hydrogen bond driven solid-state synthesis, mononuclear complexes are transformed into crystalline materials.

An efficient approach to modulate the coordination number of yttrium ions for diverse network formation

Hidden role of water! It acts as a key to determine the coordination number of yttrium by controlling the active ligand concentration.

Molybdenum(vi) complexes of hemilabile aroylhydrazone ligands as efficient catalysts for greener cyclooctene epoxidation: an experimental and theoretical approach

The focus of this work was on the synthesis, characterization and catalytic activity of Mo(vi) complexes with hemilabile 2-aminobenzhydrazone ligands.

Temperature tuned syntheses of two new d10-based Cd(ii) cluster metal–organic frameworks: luminescence sensing and photocatalytic properties

The solvothermal reactions of 5,5′-(1,4-phenylenebis(methyleneoxy))diisophthalic acid (H₄L) and the N-donor ancillary ligand 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (bpz) with cadmium(ii) salts at two different reaction temperatures yielded two new metal–organic frameworks (MOFs), viz., [Cd(H₂L)(bpz)]_n (1) and [Cd₂(H₄L)(L)(bpz)₂]_n (2), which have been characterized by FTIR and single crystal X-ray diffraction. The single crystal X-ray diffraction studies revealed that 1 displays a 3-periodic network with monometallic SBU, while 2 exhibits a 3-periodic network with a 2-fold interpenetration feature. The effects of variation in reaction temperature on the architecture of MOFs 1 and 2 have been discussed. The luminescence investigation indicates that both 1 and 2 displayed good turn-off luminescence sensing against nitroaromatic compounds (NACs), especially m-nitrophenol (MNP), via a decrease in their luminescence intensities with a K_sv value of 6.43 × 10³ for 1 and 2.03 × 10⁴ for 2 and LOD values of 1.09 and 0.81 ppm for 1 and 2, respectively. The plausible mechanism for the decline in luminescence intensity of the MOFs with NACs has been addressed using theoretical calculations. The photocatalytic properties for both the MOFs demonstrated that they display efficient photocatalytic performances to degrade methyl violet (MV) under UV irradiation. The plausible mechanism through which these MOFs exhibited photocatalytic properties has been suggested using band gap calculations.

Two new d¹⁰-based Cd(ii) MOFs were synthesized and their photoluminescence sensing to selectively detect m-nitrophenol (MNP) and ability to decompose the organic dye methyl violet (MV) were explored.

Synthesis and characterization of two one-dimensional CdII coordination polymers (CPs) with 5-amino-2,4,6-tribromoisophthalic acid and flexible N-donor bipyridyl ligands

The bromo-substituted aromatic dicarboxylic acid 5-amino-2,4,6-tribromoisophthalic acid (H₂ATBIP) was used to assemble with Cd^II ions in the presence of the N-donor flexible bipyridyl ligands 3,3'-(diazene-1,2-diyl)dipyridine (mzpy) and 1,3-bis(pyridin-3-ylmethyl)urea (3bpmu), leading to the formation of two chain coordination polymers by adopting solution methods, namely, catena-poly[[[triaqua(5-amino-2,4,6-tribromoisophthalato-κO)cadmium(II)]-μ-3,3'-(diazene-1,2-diyl)dipyridine-κ²N¹:N^1'] dihydrate], {[Cd(C₈H₂Br₃NO₄)(C₁₀H₈N₄)(H₂O)₃]·2H₂O}_n or {[Cd(ATBIP)(mzpy)(H₂O)₃]·2H₂O}_n, (1), and catena-poly[[[tetraaquacadmium(II)]-μ-1,3-bis(pyridin-3-ylmethyl)urea-κ²N¹:N^1'-[diaquabis(5-amino-2,4,6-tribromoisophthalato-κO)cadmium(II)]-μ-1,3-bis(pyridin-3-ylmethyl)urea-κ²N¹:N^1'] octahydrate], {[Cd(C₈H₂Br₃NO₄)(C₁₂H₁₂N₄O)(H₂O)₃]·4H₂O}_n or {[Cd(ATBIP)(3bpmu)(H₂O)₃]·4H₂O}_n, (2). Both complexes were characterized by FT-IR spectroscopic analysis, thermogravimetric analysis (TGA), solid-state diffuse reflectance UV-Vis spectroscopic analysis, and single-crystal and powder X-ray diffraction analysis (PXRD). The mzpy and 3bpmu ligands bridge the Cd^II metal centres in (1) and (2) into one-dimensional chains, and the ATBIP^2- ligands show a monodentate coordination to the Cd^II centres in both coordination polymers. A discrete water tetramer exists in (1). Within the chains of (1) and (2), there are halogen bonds between adjacent ATBIP^2- and mzpy or 3bpmu ligands, as well as hydrogen bonds between the ATBIP^2- ligands and the coordinated water molecules. With the aid of weak interactions, the structures of (1) and (2) are further extended into three-dimensional supramolecular networks. An analysis of the solid-state diffuse reflectance UV-Vis spectra of (1) and (2) indicates that a wide indirect band gap exists in both complexes. Complexes (1) and (2) exhibit irreversible and reversible dehydration-rehydration behaviours, respectively, and the solid-state fluorescence properties of both complexes have been studied.

pH-Controlled Assembly of 3D and 2D Zinc-Based Metal-Organic Frameworks with Tetrazole Ligands

We report the synthesis and structural diversity of Zn(II) metal-organic framework (MOF) with in situ formation of tetrazole ligand 3-ptz [3-ptz = 5-(3-pyridyl)tetrazolate] as a function pH. By varying the initial reaction pH, we obtain high-quality crystals of the noncentrosymmetric three-dimensional MOF Zn(3-ptz)2 , mixed phases involving the zinc-aqua complex [Zn(H2O)4(3-ptz)2]·4H2O, and two-dimensional MOF crystals Zn(OH)(3-ptz) with a tunable microrod morphology, keeping reaction time, temperature, and metal-ligand molar ratio constant. Structures are characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and UV-vis spectroscopy. We discuss the observed structural diversity in terms of the relative abundance of hydroxo-zinc species in solution for different values of pH.

Packing polymorphism in 3-amino-2-pyrazinecarboxylate based tin(ii) complexes and their catalytic activity towards cyanosilylation of aldehydes

3-Amino-2-pyrazinecarboxylic acid is used to synthesize two new mononuclear interconvertible packing polymorphs of tin(ii) which act as heterogeneous catalysts for the cyanosilylation of aldehydes with trimethylsilyl cyanide.

General strategy for lanthanide coordination polymers constructed from 1,1′-ferrocenedicarboxylic acid under hydrothermal conditions

26 lanthanide CPs were synthesized under different reaction conditions. As well, their fluorescence and magnetism properties were investigated.

Synthesis, structure, thermostability and luminescence properties of Zn(II) and Cd(II) coordination polymers based on dimethysuccinate and flexible 1,4-bis(imidazol-1-ylmethyl)benzene ligands

The design and synthesis of functional coordination polymers is motivated not only by their structural beauty but also by their potential applications. Zn(II) and Cd(II) coordination polymers are promising candidates for producing photoactive materials because these d(10) metal ions not only possess a variety of coordination numbers and geometries, but also exhibit luminescence properties when bound to functional ligands. It is difficult to predict the final structure of such polymers because the assembly process is influenced by many subtle factors. Bis(imidazol-1-yl)-substituted alkane/benzene molecules are good bridging ligands because their flexibility allows them to bend and rotate when they coordinate to metal centres. Two new Zn(II) and Cd(II) coordination polymers based on mixed ligands, namely, poly[[μ2-1,4-bis(imidazol-1-ylmethyl)benzene-κ(2)N(3):N(3')]bis(μ3-2,2-dimethylbutanoato-κ(3)O(1):O(4):O(4'))dizinc(II)], [Zn2(C6H8O4)2(C14H14N4)]n, and poly[[μ2-1,4-bis(imidazol-1-ylmethyl)benzene-κ(2)N(3):N(3')]bis(μ3-2,2-dimethylbutanoato-κ(5)O(1),O(1'):O(4),O(4'):O(4))dicadmium(II)], [Cd2(C6H8O4)2(C14H14N4)]n, have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. Both complexes crystallize in the monoclinic space group C2/c with similar unit-cell parameters and feature two-dimensional structures formed by the interconnection of S-shaped Zn(Cd)-2,2-dimethylsuccinate chains with 1,4-bis(imidazol-1-ylmethyl)benzene bridges. However, the Cd(II) and Zn(II) centres have different coordination numbers and the 2,2-dimethylsuccinate ligands display different coordination modes. Both complexes exhibit a blue photoluminescence in the solid state at room temperature.

A series of coordination polymers based on varied polycarboxylates and different imidazole-containing ligands: syntheses, crystal structures and physical properties

To investigate the effect of organic ligands on the coordination frameworks, seven nickel(ii) coordination polymers, based on varied polycarboxylates and different imidazole-containing ligands, are synthesized under hydrothermal method.

Tuned synthesis of two coordination polymers of Cd(ii) using substituted bent 3-pyridyl linker and succinate: structures and their applications in anion exchange and sorption properties

Two new coordination polymers of Cd(ii) have been synthesized using disodium succinate and a substituted bent N,N'-donor ligand where the substitution on N,N'-donor ligand controlled the formation of the product.