The Influence of Copper–Copper Interaction on the Structure and Applications of a Metal–Organic Framework Based on Cyanide and 3-Chloropyridine

The structure of the new metal–organic framework, [(CuCN)₂·(3-Clpy)], 1, was characterized by IR, UV–visible, TGA and X-ray single crystal analysis. The structure of 1 consists of CuCN building blocks, which are connected by CN group to form two different chains; one puckered chain with TP-3 geometry around Cu(1) and a linear Cu(2)(CN)₂ chain. The two kinds of chains are bonded by cuprophilic interactions creating a 3D-network. The network structure of 1 is further close-backed by π–π stacking and hydrogen bonds. The electronic absorption and emission spectra as well as the thermodynamic parameters from TGA of the MOF 1 are discussed. MOF 1 was used as an effective heterogeneous catalyst for the oxidative discoloration of methylene blue dye by dilute solution of hydrogen peroxide as the oxidant. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine the in vitro antitumor activity of MOF 1 on human breast cancer cell line, MCF7.     

Microwave-Assisted Solvothermal Synthesis and Photocatalytic Activity of Bismuth(III) Based Metal–Organic Framework

This study aims to synthesize and evaluate the photocatalytic activity of bismuth terephthalate material (Bi-BDC) synthesized by solvothermal (ST) and microwave-assisted solvothermal (MW) methods. Differences in the crystal structure and crystal shape were assessed by analytical methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrum, X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption, Raman spectrum, and thermal gravimetric analysis (TGA). From XRD, IR, Raman, and XPS results, the fully crystallized Bi-BDC materials were achieved regardless of the preparation router. Bi-BDC-MW exhibited spherical-like morphologies, producing between stacked lamellar, while Bi-BDC-ST method exhibited a heterogeneous structure. The TGA data indicated that Bi-BDC is thermally stable up to 300 °C, suggesting the excellent thermal stability of Bi-BDC. The surface area and pore volume of Bi-BDC-MW (18 m²/g and 85 × 10^?3 cm³/g) are higher than those of Bi-BDC-ST (16 m²/g and 52 × 10^?3 cm³/g), which is due to its well-defined lamellar microstructure and homogeneity of the crystals. Compared to Bi-BDC-ST, Bi-BDC-MW has a higher value in the content of oxygen vacancy. Moreover, the photocatalytic efficiency of Bi-BDC-MW was significantly higher than that of Bi-BDC-ST, in which 99.44% rhodamine B (RhB) is removed after 360 min of irradiation. The improved photocatalytic efficiency of Bi-BDC-MW is ascribed to the morphology, specific surface area, and oxygen defects, which exhibited the good separation of electrons and holes, as confirmed by the photoluminescence (PL). The results should open a new approach to enhancing the photocatalytic activity of bismuth terephthalate materials.

     

Nanoarchitectonics of Enzyme/Metal–Organic Framework Composites for Wastewater Treatment

Journal of Inorganic and Organometallic Polymers and Materials - Metal–organic frameworks (MOFs) provide advantages as supporting materials for the immobilization of enzymes due to their...     

Structure,Characterization and Anti-Corrosion Activity of the New Metal–Organic Framework [Ag(qox)(4-ab)]

Yellow crystals of the metal–organic framework (MOF), [Ag(qox)(4-ab)] (1) were obtained at room temperature by the reaction of AgNO₃, quinoxaline (qox) and 4-amino benzoic acid (4-aba). A cluster molecule containing two silver atoms, two qox and two 4-ab ligands is considered the basic building block of the structure of 1. A 3D-network structure is created via H-bonds and π–π stacking. MOF 1 was tested as a corrosion inhibitor for C-steel in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance techniques. It was found that 1 is rich with electron donating groups and the π-systems exhibiting high inhibition efficiency. The adsorption of 1 obeyed the Freundlich adsorption isotherm. Polarization curves indicate that 1 is mixed-type inhibitor. Activation parameters were calculated and discussed. The results obtained from EIS and potentiodynamic polarization are in good agreement.     

Synthesis and Sulfonation of an Aluminum-Based Metal–Organic Framework with Microwave Method and Using for the Esterification of Oleic Acid

Journal of Inorganic and Organometallic Polymers and Materials - In this study, the synthesis of MIL-53(Al) (Material Institute Lavoisier, MIL) material, which is an aluminum-containing...     

Microwave-Assisted Synthesis of the Flexible Iron-based MIL-88B Metal–Organic Framework for Advanced Energetic Systems

The 3D metal–organic framework (MOF), MIL-88B, built from the trivalent metal ions and the ditopic 1,4-Benzene dicarboxylic acid linker (H₂BDC), distinguishes itself from the other MOFs for its flexibility and high thermal stability. MIL-88B was synthesized by a rapid microwave-assisted solvothermal method at high power (850 W). The iron-based MIL-88B [Fe₃.O.Cl.(O₂C–C₆H₄–CO₂)₃] exposed oxygen and iron content of 29% and 24%, respectively, which offers unique properties as an oxygen-rich catalyst for energetic systems. Upon dispersion in an organic solvent and integration into ammonium perchlorate (AP) (the universal oxidizer for energetic systems), the dispersion of the MOF particles into the AP energetic matrix was uniform (investigated via elemental mapping using an EDX detector). Therefore, MIL-88B(Fe) could probe AP decomposition with the exclusive formation of mono-dispersed Fe₂O₃ nanocatalyst during the AP decomposition. The evolved nanocatalyst can offer superior combustion characteristics. XRD pattern for the MIL-88B(Fe) framework TGA residuals confirmed the formation of α-Fe₂O₃ nanocatalyst as a final product. The catalytic efficiency of MIL-88B(Fe) on AP thermal behavior was assessed via DSC and TGA. AP solely demonstrated a decomposition enthalpy of 733 J g^?1, while AP/MIL-88B(Fe) showed a 66% higher decomposition enthalpy of 1218 J g^?1; the main exothermic decomposition temperature was decreased by 71 °C. Besides, MIL-88B(Fe) resulted in a decrease in AP decomposition activation energy by 23% and 25% using Kissinger and Kissinger–Akahira–Sunose (KAS) models, respectively.

     

Clean Baeyer–Villiger Oxidation Using Hydrogen Peroxide as Oxidant Catalyzed by Aluminium Trichloride in Ethanol

Baeyer–Villiger oxidation of ketones was carried out using AlCl₃ as catalyst, H₂O₂ (30%) as oxidant in innocuity and environmentally friendly ethanol conditions. Cyclic ketones and acyclic ketones were transformed into the corresponding lactones or esters in 5–24 h at 40–70 °C with very high conversion and selectivity. A possible reaction mechanism was also given.     

Zinc(II) Metal–Organic Framework with Nano-Sized Channels Based on Paddle-Wheel Units

A Zn(II) metal–organic framework with nano-sized channels from 4,4′-bipyridine (4,4′-bipy) and 4′-sulfo-biphenyl-4-carboxylate (sbpc²⁻) ligands, {[Zn(μ-4,4′-bipy)_1.5(μ-sbpc)]·5H₂O} _n (1), has been synthesized by the hydrothermal method. Compound 1 was characterized by X-ray powder diffraction, IR spectroscopy, elemental analysis and single-crystal X-ray crystallography. The structural studies show the Zn atoms have a six-coordinate geometry with a distorted octahedral environment constructed of paddle-wheel [Zn₂(OOC)₄] building units with 4,4′-bipy and sbpc²⁻ linkers stacked over each other to generate three-dimensional nano-sized channels occupied by guest H₂O molecules.     

UV-induced Decomposition of Ozone and Hydrogen Peroxide in the Aqueous Phase at pH 2–7

The photolysis of ozone and formation of hydrogen peroxide were investigated in solution of pH 2–7, in a 200 cm³ photoreactor in the incident photon flow range 9.6 x 10^?8 - 4.2 x 10^?7 einstein s^?1. The quantum yield of the primary photochemical reactions was measured in a direct way by suppressing the secondary radical reactions. The determined quantum yields of the photo-decompositions of ozone and hydrogen peroxide were 0.42 ± 0.042 ± 0.04 and 0.49 ± 0.04, respectively.

A correct mathematical treatment is given for calculation of the light absorption of the individual components of a multi-absorbent reaction mixture.

On the basis of the literature data and die present results, a probable chemical and reaction kinetic model was proposed to characterize the investigated reaction systems. Reaction kinetic simulations demonstrated that the model predicts a good fit to the measured data with the preferred literature rate constants, except that for the HO₃ radical decomposition reaction. A reasonable reduction of this rate coefficient value is in accordance with the latest published results.     

Synthesis, Crystal Structure and Properties of a New 3D Supramolecular Metal–Organic Framework with Stable Tunnels

A flexible polycarboxyl ligand of tetrahydrofuran-2,3,4,5-tetracarboxylic acid (H₄THFTCA) and a common rigid aromatic ligand of 1,10-phenanthroline (phen) have been successfully co-assembled with Cu(NO₃)₂·3H₂O to give out a novel 3D supramolecular metal–organic framework (MOF) compound, [Cu₂(THFTCA)(phen)(H₂O)₂·CH₃CH₂OH·3H₂O] _n (1), by a solution self-assembly process. Compound 1 has been characterized as a 2D layered coordination polymer constructed by THFTCA^4? and Cu²⁺ ions, and the layer present a novel (3.5²)(3².5³.6⁴.7) topological network. Interestingly, the layers are fused each other via strong π–π stacking interactions among adjacent ligands of the terminal phen, so that a 3D supramolecular MOF with 1D rhomboidal tunnels array is formed. The thermogravimetric analysis and corresponding powder X-ray diffraction analysis have revealed that the tunnels structure of 1 could be retained after all guest molecules are removed, and the framework could resist the collapse even heating up to 210?°C. An opinion has also been proposed that the larger accessible volume of the guests means the larger stress on the backbone of the MOF after the guests are removed, and the stress is harmful to the stability of the supramolecular porous structure. Finally, the application properties based on the porous structure have also been primarily evaluated.     

Opportunities and Challenges in Biomedical Applications of Metal–Organic Frameworks

Journal of Inorganic and Organometallic Polymers and Materials - Unique chemical and physical properties of metal–organic framework (MOF) nanoparticles suggest them as promising candidates...     

Biofunctionalization of Metal–Organic Framework Nanoparticles via Combined Nitroxide-Mediated Polymerization and Nitroxide Exchange Reaction

Surface engineering of metal–organic framework nanoparticles (MOF NPs), and enabling their post-synthetic modulation that facilitates the formation of bio-interfaces has tremendous potential for diverse applications including therapeutics, imaging, biosensing, and drug-delivery systems. Despite the progress in MOF NPs synthesis, colloidal stability and homogeneous dispersity—a desirable property for biotechnological applications, stands as a critical obstacle and remains a challenging task. In this report, dynamic surfaces modification of MOF NPs with polyethylene glycol (PEG) polymer is described using grafting-from PEGylation by employing nitroxide-mediated polymerization (NMP) and inserting arginylglycylaspartic acid (RGD) peptides on the surface via a nitroxide exchange reaction (NER). The dynamic modification strategy enables tailoring PEG-grafted MOF NPs of the type UiO-66-NH₂ with improved colloidal stability, and high dispersity, while the morphology and lattice crystallinity are strictly preserved. The interaction of PEG-grafted MOF NPs with human serum albumin (HSA) protein under physiological conditions is studied. The PEG-grafted colloidal MOF NPs adsorb less HSA protein than the uncoated ones. Therefore, the described approach increases the scope of bio-relevant applications of colloidal MOF NPs by reducing nonspecific interactions using NMP based PEGylation, while preserving the possibility to introduce targeting moieties via NER for specific interactions.     

High Performance of UiO-66 Metal–Organic Framework Modified with Melamine for Uptaking of Lead and Cadmium from Aqueous Solutions

Journal of Inorganic and Organometallic Polymers and Materials - In this paper, UiO-66 metal–organic framework (MOF) was prepared by a hydrothermal method and modified consequently with...     

Effect of the OH Radical Scavenger Hydrogen Peroxide on Secondary Organic Aerosol Formation from α-Pinene Ozonolysis

Hydrogen peroxide (HOOH) is a potentially valuable hydroxyl radical (OH) scavenger in secondary organic aerosol experiments focused on ozonolysis yields. Here, we present results for α-pinene ozonolysis. The OH scavenging produces solely HO₂ radicals and the resulting high [HO₂]/[RO₂] ratio causes an increase in aerosol formation from α-pinene ozonolysis, compared to experiments performed with butanol OH scavengers. The majority of the increase comes in the 100 μg m^?3 volatility range, suggesting that instead of more volatile products formed under higher RO₂ conditions, less volatile, multifunctional hydroperoxides form under the high-HO₂ conditions here. This dependence on the [HO₂]/[RO₂] ratio can be parameterized in a similar fashion to the way high- and low-NO _x yields are currently treated in models.     

Response Surface Optimisation of an Oxalate–Phosphate–Amine Metal–Organic Framework (OPA-MOF) of Iron and Urea

Metal–organic framework (MOF) materials are well known for various application fields, such as engineering, and medical sciences. Here, the synthesis, and synthesis-optimisation of a novel oxalate-phosphate-amine MOF (OPA-MOF) for innovative agricultural applications is described, with urea as a structure-directing agent in a hydrothermal synthesis. Product properties conducive to proposed applications included yield, purity, elemental content (N, P, C), and oxalate-solubility, as important driving forces for functionality, which is based on the biomineralisation processes for the material’s decomposition in soil. A four-factors/two levels plus one (4²+1) factorial design included replicated zero-point and factors of time, temperature, urea input rate and dilution factor. 19 experimental runs results provided data for a Response Surface Method optimisation to determine factors resulting in a desired product at highest efficiency. The saddle-ridge shaped response surface highlighted system robustness for two factors (time/urea-input), and sensitivity for temperature and dilution factor. Optimal factor combinations initially appeared counterintuitive compared to expected results from factorial design outcomes, however confirmatory experiments validate model predictions. Consequently, the optimisation process was strongly justified for accurate determination of the optimal OPA-MOF synthesis conditions.