Two-dimensional nanosheets of metal–organic frameworks with tailorable morphologies

The controlled preparation of two-dimensional (2D) nanosheets of metal–organic frameworks (MOFs), with tailorable methodologies, properties, and applications, is of significant importance. Here, in this work, by subtle control of the ultrasonic duration and solvent polarity, the iron(II)-based 2D MOF Fe(pyz)₂Cl₂ (pyz = pyrazine) has been elegantly tailored into 2D nanosheets (lateral size ≥500 nm in aqueous, with ultrasonic duration of 30 min) and one-dimensional (1D) nanoribbons (lateral size ≤100 nm in ethanol solution, with ultrasonic duration of 90 min). The aqueous suspension of 2D nanosheets was featured with thermal-induced spin-state transition at around room temperature and can be used as effective Fenton catalysts for degradation of water-soluble organic dyes, whereas the ethanol suspension of 1D nanoribbons can act as a versatile nanoplatform for trans-to-cis isomerization of 4, 4′-azopyridine. These results may provide a novel strategy for the controlled preparation of layered nanomaterials.     

Adsorption-based characterization of hierarchical metal–organic frameworks

Nitrogen adsorption at 77 K on metal–organic framework (MOF) is investigated by means of molecular simulations. We consider both regular Cu–BTC crystal and a MOF-based hierarchical porous solid consisting of a mesopore carved out of a Cu–BTC crystal. The t-plot method is applied to these solids by using a non-porous Cu–BTC surface as the reference sample. The values of the mesoporous and external surface areas are determined from the t-plot, and the validity of the method for this type of hierarchical solid is discussed.     

In situ construction of metal–organic sulfur-containing heterocycle frameworks

This review outlines three types of in situ methods used for constructing metal–organic sulfur-containing heterocycle frameworks, viz., in situ S–S function reactions, in situ C–S bond cleavage and in situ thiol-S atom reactions. Each method is described in detail in three respects, namely (i) reaction parameters, (ii) the organic transformation and coordination modes involved, and (iii) fascinating structures and functional properties of those in situ-generated metal-coordination compounds.     

The application of Bimetallic metal–organic frameworks for antibiotics adsorption

Fe/Zr-base metal–organic frameworks(Fe/Zr-MOFs) were prepared using a solvothermal method from 1,3,5-phthalic acid (H₃BTC, 98 %) as the organic chain and ferrous heptahydrate (FeSO₄·7H₂O) and zirconium acetate Zr(CH₃COO)₄] as the metal ions. The resulting material was used to remove Doxycycline hydrochloride (DC). The experimental results showed that when the concentration of DC was 10 ppm and the mass of Zr/Fe-MOFs was 100 mg, the maximum removal rate after 5 h was 87.5 %. The results showed that the correlation coefficients (R²) of the pseudo-second-order kinetics model and Freundlich isotherm model of Zr/Fe-MOFs adsorption of DC were greater than 0.99, indicating good consistency. The results showed that the adsorption process of DC by Zr/Fe-MOFs was endothermic and spontaneous. Fe/Zr-MOFs had a high adsorption capacity for DC removal and good application prospects.     

Luminescent nanoscale metal–organic frameworks for chemical sensing

Metal–organic frameworks(MOFs) are a fascinating class of crystalline materials constructed from selfassembly of metal cations/clusters and organic ligands. Both metal and organic components can be used to generate luminescence, and can further interact via antenna effect to increase the quantum yield,providing a versatile platform for chemical sensing based on luminescence emission. Moreover, MOFs can be miniaturized to nanometer scale to form nano-MOF(NMOF) materials, which exhibit many advantages over conventional bulk MOFs in terms of the facile tailorability of compositions, sizes and morphologies, the high dispersity in a wide variety of medium, and the intrinsic biocompatibility. This review will detail the development of NMOF materials as chemical sensors, including the synthetic methodologies for designing NMOF sensory materials, their luminescent properties and potential sensing applications.     

Isolation of hemoglobin with metal–organic frameworks Y(BTC)(H_2O)_6

The hierarchical metal-organic frameworks(MOFs),such as Y(BTC)(H_2O)_6,are prepared with yttrium nitrate and benzene-1,3,5-tricarboxylic acid at room temperature.The product is characterized by Fourier transform infrared(FT-IR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA).The Y(BTC)(H_2O)_6 particles are sufficiently rigid for performing solid phase extraction and they exhibit favorable selectivity toward the adsorption of hemoglobin.The adsorption behavior of hemoglobin onto the Y(BTC)(H_2O)_6 fits the Langmuir adsorption model with a theoretical adsorption capacity of 555.6 mg g 1.An adsorption efficiency of 87.7%for 100μg mL 1hemoglobin in 1 mL sample solution(at pH 6.0)is achieved with 0.40 mg Y(BTC)(H20)6.77.3%of the retained hemoglobin is readily recovered using a 0.5%(m/v)SDS solution as the stripping reagent.Circular dichroism spectra indicated that the conformation of hemoglobin is maintained during the adsorption-desorption process.The MOFs material is applied for the isolation of hemoglobin from human blood and the purity of the obtained hemoglobin is further verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE).     

Quasi-solid electrolyte membranes with percolated metal–organic frameworks for practical lithium-metal batteries

High-energy Li-metal batteries (LMBs) suffer from short cycle life and safety issues due to severe parasitic reactions and dendrite growth of Li metal anode (LMA) in liquid electrolytes [1–3].It is generally believed that replacing liquid electrolytes with solidstate electrolytes (SSEs) would be a feasible approach for practical LMBs [4,5]. Conventional SSEs including ceramic and polymer electrolytes have been studied for decades.     

Investigation of interface compatibility in stiff polymer/metal–organic frameworks

Polymers with excellent comprehensive performance toward enhanced stability and mechanical strength are attractive for matrix loading of tunable porous and inherently brittle metal?organic frameworks (MOFs). Polyethersulfone (PES) with high mechanical strength (elastic modulus = ~2.6 GPa) is one of the best polymeric materials widely applied in gas and liquid separations but hindered by its ability to adhere to MOFs surface. The combination of the interface width, porosity, atomic density, and hydrogen bonding number and strength strongly influences MOFs/PES compatibility. ZIF-8 is one of the most frequently investigated MOFs, and exhibits excellent interface compatibility with PES, which is confirmed by both computational and experimental analyses. The desired porosity and adsorption properties of ZIF-8 are retained in ZIF-8/PES composites. This study sheds light on the theoretical understanding and characterization of hybrid material systems with diverse differences between brittle MOFs and stiff polymers.     

A novel exploration of metal–organic frameworks in flame-retardant epoxy composites

In this work, a series of transition metal–organic frameworks (MOFs) were prepared through self-assembly of organic bridging ligands and transition metal ions. The structure of MOFs samples was analyzed by XRD, FTIR, TG, and TEM. The influences of MOFs on flame resistance, toxicity reduction, and smoke suppression of epoxy were explored in detail. The findings presented that low addition amount of MOFs had a positive effect on decreasing the fire hazards of epoxy. Loading of 2 mass% MOFs into epoxy led to the decrease in thermal degradation rate and increase in char yields. Meanwhile, the values of peak heat release rate, total heat release, and average mass loss rate of epoxy composites were cut down effectively, in comparison with neat epoxy. Moreover, the remarkable decrease in smoke production rate, total smoke production, and CO, CO₂ yield could be provided by cone calorimeter test. The char residues after cone calorimeter test were investigated by SEM and Raman spectra, and the flame-retardant mechanism was discussed.

     

Irradiation and isolation of fission products from uranium metal–organic frameworks

Journal of Radioanalytical and Nuclear Chemistry - A customized single-stage cylindrical combined air lift mixer-settler (C-CALMIX) device has been developed and its performance was evaluated by...     

Structural identification of multidimensional metal–organic frameworks using soft x-ray tomography

This paper mainly discusses the applicability of using soft x-ray tomography technology to examine the multidimensional structure of metal–organic frameworks, such as their core-shell and hollow framework, by visually observing their corresponding images in different energy bands by different excitation energies for different elements. The results show that the use of soft x-ray tomography (SXT) can effectively observe the distribution of metals in the structure, as well as observe the type of hollow pores the metal – organic framework (MOF) possesses. This pioneering evaluation of MOFs via SXT shows excellent performance in the structure identification of multidimensional metal–organic frameworks.     

Synthesis and characterization of two new metal–organic frameworks with interpenetrated structures and luminescent properties

Two new metal–organic compounds, [Ag₂(HADC)₂(bimh)] (1) and [Cd(ADC)(bpp)]_n (2) [H₂ADC = 1,3-adamantanedicarboxylic acid, bimh = 1,6-bis(2-methyl-imidazole-1-yl)hexane, bpp = 1,3-bis(4-pyridyl)propane], have been synthesized and characterized. Compound 1 exhibits a discrete symmetric unit with 0D→2D interpenetrating structure. Compound 2 crystallizes in a chiral space group P212121 and presents a threefold interpenetrated 3D diamondoid network containing three helical chains. Thermal stability, X-ray powder diffraction, and luminescence for 1 and 2 are also measured and discussed.     

Advanced metal–organic frameworks for aqueous sodium-ion rechargeable batteries

Inexpensive and abundant sodium resources make energy storage systems using sodium chemistry promising replacements for typical lithium-ion rechargeable batteries(LIBs).Fortuitously,aqueous sodium-ion rechargeable batteries(ASIBs),which operate in aqueous electrolytes,are cheaper,safer,and more ionically conductive than batteries that operate in conventional organic electrolytes;furthermore,they are suitable for grid-scale energy storage applications.As electrode materials for storing Na~+ ions in ASIBs,a variety of multifunctional metal-organic frameworks(MOFs) have demonstrated great potential in terms of having porous 3 D crystal structures,compatibility with aqueous solutions,long cycle lives(≥1000 cycles),and ease of synthesis.The present review describes MOF-derived technologies for the successful application of MOFs to ASIBs and suggests future challenges in this area of research based on the current understanding.     

Alkaline earth metal–organic frameworks supported by ditopic carboxylates

Hydrothermal reactions of alkaline earth metal nitrates with two ditopic carboxylic acids, trans-1,4-cyclohexanedicarboxylic acid (H₂CDC) and 1,4-phenylenedipropionic acid (H₂PDP), generate two 3-D metal–organic frameworks (MOFs) with empirical formulas [Ca(CDC)(H₂O)₂]·H₂O (1) and [Sr(PDP)(H₂O)] (2), respectively. Compound 1 consists of Ca–COO–H₂O chains cross-linked through the –C₆H₁₀– spacers of the CDC anions, showing slightly open 1-D channels along the crystallographic c axis that accommodate the guest water molecules. Compound 2 exhibits a MOF consisting of wavy 2-D Sr–COO–H₂O nets linked by –CH₂CH₂C₆H₄CH₂CH₂– tethers, and the condensed structure appears to arise from conformational flexibility of the ligand spacer.     

Structural diversity of metal–organic frameworks via employment of azamacrocycles as a building block

Research on incorporating macrocycles into metal–organic frameworks (MOFs) has been performed intensively due to the opportunities afforded by merging a merit of macrocycles with MOF chemistry, which lead to novel hybrid materials for potential application. Among the numerous kinds of macrocycles, azamacrocycles are used as traditional and popular chelating agents in supramolecular coordination chemistry, because they are very easily functionalized by joining pendant arms and possess a strong propensity to complex metal cations, accounting for the amine functionalities. With this as background, many types of azamacrocyclic MOFs have been synthesized, granting compositionally and topologically new MOFs. The macrocyclic rings can serve as additional adsorption sites or catalytic sites, and the pendant arms on the macrocycles can also play versatile roles such as structure-directing agents, pore-decorating moieties, or rotatable molecular gates for opening/closing pores. In this review, we comprehensively discuss the syntheses, structures, and features of azamacrocyclic MOFs reported to date. Based on representative studies, advantages of these compounds are described, such as how the azamacrocycles increase the structural diversity and complexity of the MOFs and induce novel structural properties within the architectures.     

Selective adsorption of potassium and rubidium by metal–organic frameworks supported supramolecular materials

Journal of Radioanalytical and Nuclear Chemistry - A new MOFs-based adsorbent UiO-66@iPCC5 was prepared by hybridization of 25,27-bis(iso-propoxyl)-calix[4]arene-26,28-crown-5 (iPCC5) into the...