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The combination of electron-deficient viologen ligands with electron-rich POMs is a typical acceptor–donor system that has recently received much attention. Under solvothermal and hydrothermal conditions, by introducing three symmetric viologen ligands into POM-based hybrid materials, we successfully constructed four POMs–viologen inorganic–organic hybrid compounds, namely (1,3-bcbpy)2·(δ-Mo8O26) (1) (1,3-bcbpy·2Cl = 1,1′-bis(3-carboxybenzyl)-4,4′-bipyridine dichloride), {CoII(1,4-bcbpy)2(H2O)2[H2(β-Mo8O26)]}·2H2O·2CH2O (2), (1,4-bcbpy)2·(δ-Mo8O26)·2H2O (3) (1,4-bcbpy·2Cl = 1,1′-bis(4-carboxybenzyl)-4,4′-bipyridine dichloride, CH2O = formaldehyde), and {CuII(1,1-pmbby)2(H2O)[H2(β-Mo8O26)2]}·5H2O·C2H7N (4) (1,1-pmbby·2Cl = 1,1′-[1,4-phenylbis(methylene)]bis-(4,4′-bipyridine)dichloride, C2H7N = dimethylamine). These four compounds exhibit different fascinating structures, especially compound 4 is a typical metal–organic framework. Compounds 1–4 exhibit good discoloration behaviors under various external stimuli. For example, compounds 1–4 showed a positive response to the irradiation from a 300 W Xe lamp. When a positive voltage was applied to the ECD based on compounds 1–4, 1/2/3/4-ECD underwent a significant color conversion. What's more, compound 4 also showed obvious discoloration results after heating. In a word, 1–4 are multifunctional discoloration materials under different external stimuli. In addition, the coated filter paper prepared based on compound 3 can be used as a new printing material medium and can be successfully applied in erasable inkless printing and dual anti-counterfeiting. [ABSTRACT FROM AUTHOR]

A zirconium-MOF with a sulphonic acid functionalized biphenyldicarboxylic acid linker was synthesized by a solvothermal process. The material was characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) analysis, infrared (IR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), and FESEM analysis. The fluorescence sensing experiment towards the detection of Cu2+ was carried out. The detection time for Cu2+ was only 15 s with a very low limit of detection, which is 0.22 μM. The Stern–Volmer constant was found to be 5.5 × 105 M−1. For easy handling and real field application purposes, we developed a paper-strip based sensing device. The systematic study of the mechanism by EDX, PXRD, TRPL, and UV-Vis spectroscopy revealed that the quenching of fluorescence intensity by copper(II) was due to the fluorescence resonance energy transfer. [ABSTRACT FROM AUTHOR]

An ethynyl-modified interpenetrated MOF material with lvt topology, [Cu2(BTEB)(NMF)2]·NMF·8H2O (compound 1, H4BTEB = 4,4′,4′′,4′′′-(benzene-1,2,4,5-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid, NMF = N-Methylformamide), was successfully synthesized by using an alkynyl-functionalized H4BTEB organic ligand under solvothermal conditions. Structural analysis shows that compound 1, consisting of a tetradentate carboxylic acid ligand and classical [Cu2(CO2)4] paddle-wheel structure building units, has a rare 4-connected lvt topology with dual interpenetrating structure, which can improve the framework stability, as well as the gas adsorption capacity and selectivity due to the restricted pore channel. According to the study of gas adsorption performance, compound 1 with a larger surface area, boasts a superior adsorption capacity for small gas molecules. Also, ideal adsorption solution theory (IAST) computational simulation shows that compound 1 has good gas adsorption selectivity for C3H8/CH4, indicating its potential application in gas separation. [ABSTRACT FROM AUTHOR]

A Cu(II)-based metal–organic framework (MOF) [Cu(muco)(3,5-DCP)]n (1) has been synthesized by using linear rigid aliphatic dicarboxylic acid, trans,trans-muconic acid (H2muco) and 3,5-dichloropyridine (3,5-DCP) as an auxiliary ligand. The MOF adopts a square-grid two-dimensional (2D) structure with paddle-wheel [Cu2(OOC)4] robust secondary building units (SBUs). The 3,5-DCP ligands are perpendicularly projected from the SBUs at both sides and undergo interdigitation via antiparallel π⋯π stacking interactions among 3,5-DCP ligands to fabricate three-dimensional (3D) supramolecular architecture. The π⋯π interactions favour the formation of Cl⋯Cl stacking contacts. These non-covalent interactions are further validated by density functional theory (DFT) calculation. In addition, the synthesized MOF is tested for conductivity measurements via current density–voltage characteristics, as well as impedance spectroscopy, which reveal that the MOF is semiconducting in nature and can be used as a Schottky diode. [ABSTRACT FROM AUTHOR]

We show, herein, how the minor ligand modification led to the significant enhancement of both chemical and physical stabilities, as well as the gas sorption property of a Cu(II)-organic framework. Using two analogical bifunctional ligands, two new MOFs, namely {[Cu4Cl(cpt)4]·(NO3)3·4DMF·3H2O}n (1) and {[Cu4(OH)2(tpa)4](NO3)2·2DMA·2H2O}n (2), with similar pore shapes but quite different stabilities were successfully synthesized and fully characterized by performing single crystal X-ray diffraction, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. Although both MOFs show similar pore shapes and topical structures, they have quite different stabilities and gas uptake properties. MOF 1 with a single-walled framework is insufficiently robust after the removal of the solvents, while MOF 2 with a double-walled framework could maintain its framework integrality after the activation. Moreover, MOF 2 exhibits excellent moisture-resist properties and can be easily scaled up with good crystal quality and high phase purity. In addition, the CO2 sorption performances of activated MOF 2 were probed both experimentally and computationally. [ABSTRACT FROM AUTHOR]

Polymorphism is a common phenomenon in crystalline materials but it has barely been studied in the field of metal organic frameworks. The study of polymorphism is useful to investigate structure–property relationships and control over the synthesis of particular polymorphs could be an effective way to fine-tune the physical properties of materials. We report here the preparation and characterization of three polymorphs of a copper(I) coordination polymer 2∞CuCl(4bpytm), 4bpytm = bis(4-pyridylthio)methane. The structural and thermal properties of these compounds were studied to obtain a detailed knowledge of the differences between the three polymorphic forms. [ABSTRACT FROM AUTHOR]

In the last years, chemical research has allowed the obtainment of a large number of new sensing compounds useful in diverse interest areas related to health, environment, food, automotive, and steel industries, among others. Taking into account the interest and demand of sensors on a large scale and the urgent need to reduce the size of devices to nanometric scale, coordination compounds (CCs) -and more specifically those based on copper-have gained full acceptance. CCs present exciting characteristics such as (i) dynamic structures, (ii) ability to form an immense variety of porous structures, or (iii) easy nano processing. Besides, copper is abundant, and an essential ion in the human body with no high toxicity at reachable detectable concentrations. Just this one element copper allows us to obtain porous, non-porous, optoelectronics, and/or magnetic-sensitive compounds that can detect a highly varied range of gases in different devices at economical costs. Several studies show how the properties of this type of compounds can be improved depending on their synthesis conditions or by the technology used in the sensor fabrication. [ABSTRACT FROM AUTHOR]

This mini-review surveys 23 structures of 3D coordination polymers built upon mono-, di- as well as cyclic and acylic polythioethers. An emphasis is put on the Secondary Building Units (SBU) and the physical properties. Importantly, the key feature is that the dominant SBU is not the rhomboid (CuXS), but an inorganic polymer containing at least the chain of the type (CuX). In the latter type of SBU, these chain formations are observed for X = I, but predominantly for X = CN. In addition, a large portion of the surveyed materials exhibit rich photophysical properties, but on several occasions, these materials exhibit properties often attributed to MOFs, mainly solvent exchange. [ABSTRACT FROM AUTHOR]

We report on the synthesis of a new metal-organic framework (MOF) composed of Sn(OCH3)2-tetrakis(pyridin-4-yl)porphyrin linkers, Cu+ connecting nodes and [CuCl2]− counter-ions, namely poly[[bis(methanolato-κ O)[μ5-5,10,15,20-tetrakis(pyridin-4-yl)porphyrin-κ81κ N5:1′κ N10:1′′κ N15:1′′′κ N20:2κ4 N21, N22, N23, N24]copper(I)tin(II)] dichloridocuprate(I)], [CuSn(C40H24N8)(CH3O)2][CuCl2]. Its crystal structure consists of a single-framework coordination polymer of the organic ligand and the CuI ions. The latter are characterized by a tetrahedral coordination geometry [with CN (coordination number) = 4], linking to the pyridyl N-atom sites of four different ligands and imparting to the positively charged polymeric assembly a diamondoid PtS-type topology. Correspondingly, every porphyrin unit is coordinated to four different CuI connectors. The [CuCl2]− anions occupy the intra-lattice voids, along with disordered molecules of the water crystallization solvent. The asymmetric unit of this structure consists of two halves of the porphyrin scaffold, located on centres of crystallographic inversion, and the Cu+ and [CuCl2]− ions. This report provides unique structural evidence for the formation of tetrapyridylporphyrin-based three-dimensional MOFs with a diamondoid architecture that have been observed earlier only on rare occasions. [ABSTRACT FROM AUTHOR]

The simultaneous use of 2-pyridyl oximes (pyridine-2 amidoxime, H2pyaox; 2-methyl pyridyl ketoxime, Hmpko) and 1,3,5-benzenetricarboxylic acid (H3btc) provided access to five new compounds, namely [Zn(H2btc)2(H2pyaox)2]•2H2O (1•2H2O), [Zn(Hbtc)(H2pyaox)2]n (2), [Cu(Hbtc)(H2pyaox)]n (3), [Cu(Hbtc)(HmpKo)]n (4) and [Cu2(Hbtc)2(Hmpko)2(H2O)2]•4H2O (5•4H2O). Among them, 3 is the first example of a metal-organic framework (MOF) containing H2pyaox. Its framework can be described as a 3-c uninodal net of hcb topology with the layers being parallel to the (1,0,1) plane. Furthermore, 3 is the third reported MOF based on a 2-pyridyl oxime in general. 2 and 4 are new members of a small family of coordination polymers containing an oximic ligand. 1–5 form 3D networks through strong intermolecular interactions. Dc magnetic susceptibility studies were carried out in a crystalline sample of 3 and revealed the presence of weak exchange interactions between the metal centres; the experimental data were fitted to a theoretical model with the fitting parameters being J = −0.16(1) cm−1 and g = 2.085(1). The isotropic g value was also confirmed by electronic paramagnetic resonance (EPR) spectroscopy. Reactivity studies were performed for 3 in the presence of metal ions; the reaction progress was studied and discussed for Fe(NO3)3 by the use of several characterization techniques, including single crystal X-ray crystallography and IR spectroscopy. [ABSTRACT FROM AUTHOR]

Several important synthesis pathways for metal-organic frameworks (MOFs) were applied to determine how the synthesis methods and conditions affect the structure and adsorption capacity of the resulting samples. In the present work, three different synthesis routes were used to obtain copper trimesinate coordination polymer: Slow evaporation (A), solvothermal synthesis using a polyethylene glycol (PEG-1500) modulator (B), and green synthesis in water (C). This MOF was characterized by elemental analysis, infrared spectrometry, X-ray diffraction, scanning electron microscopy, thermogravimetry and volumetric nitrogen adsorption/desorption. The samples have permanent porosity and a microporous structure with a large surface area corresponding to the adsorption type I. The obtained MOF was tested as a sorbent to remove organic dyes methylene blue (МВ), Congo red (CR) and methyl violet (MV) as examples. Dye adsorption followed pseudo-first-order kinetics. The equilibrium data were fitted to the Langmuir and Freundlich isotherm models, and the isotherm constants were determined. Thermodynamic parameters, such as changes in the free energy of adsorption (∆G0), enthalpy (∆H0), and entropy (∆S0), were calculated. Thermolysis of copper trimesinate leads to the formation of carbon materials Cu@C with a high purity. [ABSTRACT FROM AUTHOR]