Organic Framework Structures Research Articles

CoII Immobilized on Aminated Magnetic-Based Metal–Organic Framework: An Efficient Heterogeneous Nanostructured Catalyst for the C–O Cross-Coupling Reaction in Solvent-Free Conditions

In this paper, we report the synthesis of Fe3O4@AMCA-MIL53(Al)-NH2-CoII NPs based on the metal–organic framework structures as a magnetically separable and environmentally friendly heterogeneous nanocatalyst. The prepared nanostructured catalyst efficiently promotes the C–O cross-coupling reaction in solvent-free conditions without the need for using toxic solvents and/or expensive palladium catalyst.

Metal organic framework top-down and bottom-up patterning techniques.

Metal organic frameworks (MOFs) have recently attracted considerable research interest in several fields from coordination chemistry and materials science to engineering and medicine not only due to energy and environmental issues but also due to the need for new paradigms of efficiency and sustainability according to the requirements of the 21st century global society. Because of their crystalline and organic-inorganic nature, they are able to crystallize constituting intergrown architectures ductile enough to be patterned, with the use of appropriate techniques, as nano- and micro-devices with multiple applications. This perspective comprehensively summarizes the recent state of the art in the use of top-down and bottom-up methodologies to create MOF structures with a defined pattern at the nano- and micro-scale.

Sonication-assisted synthesis of a new heterostructured schiff base ligand Silver-Guar gum encapsulated nanocomposite as a visible light photocatalyst

A heterostructured Schiff base ligand (Benzildiethylenetriamine)-Silver-Guar gum encapsulated nanocomposites was intended to prepare by simple sonication assisted reflux method. Appropriate composition of purified guar gum, Schiff base ligand and silver nitrate were used for the synthesis. The synthesised nanocomposites were characterised by photoluminescence spectrum, UV-vis diffuse reflectance spectrophotometer, Fourier transform infra-red spectroscopy, X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. The crystalline peaks of XRD and FTIR reveals that Schiff base ligand and guar gum forms metal-organic matrix. Morphology studies have confirmed the organic framework structure and metallic silver nanoparticles are embedded on the organic framework. The efficiency of nanocomposites depends on adsorption capacity and silver nanoparticles that are encapsulated thereby increasing the visible light absorption through surface plasma resonance. The nanocomposite was proved to be highly selective in hydrogenation reaction which favoured the formation of aniline from nitrobenzene as single product with short reaction time and 90% conversion.

Advances, Updates, and Analytics for the Computation-Ready, Experimental Metal–Organic Framework Database: CoRE MOF 2019

Over 14 000 porous, three-dimensional metal–organic framework structures are compiled and analyzed as a part of an update to the Computation-Ready, Experimental Metal–Organic Framework Database (Co...

Lanthanides based metal organic frameworks for luminescence sensing of toxic metal ions

Two set of lanthanides-based metal organic framework structures incorporating 2,6-naphthalenedicarboxylic acids and 1,5 dihydroxy-2,6-naphthalenedicarboxylic have been successfully synthesized and fully characterized. Interestingly, when 1,5 dihydroxy-2,6-naphthalenedicarboxylic was employed as organic linker, the hydroxyl groups were not involved in the coordination to the lanthanide clusters and therefore hydroxyl-functionalized lanthanides MOFs (AUBM-3) were obtained. The photophysical properties of both set of MOFs were studied and their sensing properties for toxic elements Pb(II), Cr(III), As(III), Cd(II), and Hg(II) and for paraquat were investigated. The hydroxyl-functionalized structures have shown to be promising luminescent sensory materials with high selectivity and sensitivity to mercury.

Photochemically Induced Water Harvesting in Metal–Organic Framework

Harvesting water from air is one of the key environmental related issues facing humanity in recent years. In this study, we demonstrate that tha Ni-IRMOF74-III metal–organic framework structure att...

New Molecular Sieve Materials: Composites Based on Metal–Organic Frameworks and Ionic Liquids

The review discusses aspects of the synthesis and application of new composite materials with molecular sieve properties, formed on the basis of metal–organic framework (MOF) structures and ionic liquids (ILs). Ways of creation, physicochemical characteristics, and problems of practical application of IL/MOF systems to selective adsorption and gas separation are considered.

Nitrogen-Doped Graphene-Based Catalyst with Metal-Reduced Organicframework: Chemical Analysis and Structure Control

Here we report an advanced nitrogen-doped graphene-based catalyst with metal-reduced organic framework structure (N-G/MOF) prepared by functionalizing ZIF-8 and nitrogen-functionalized graphene oxide using the nanoscale high energy wet ball milling method. The chemical structure control of N-G/MOF was studied by characterizing the variation of the chemical structure of synthesized samples throughout targeted grinding speeds. The results proved that the chemical interaction between ZIF-8 and N-G caused the reduction of nitrogen, oxygen and zinc atoms, and the variation of chemical bonding composition in N-G/MOF. The reduction rate of zinc was gradually increased with the increasing grinding speed and reached 82% of zinc loss at 650 RPM. The characterization of carbon and nitrogen bonding composition confirmed that the reduction of nitrogen, oxygen and zinc atoms was caused by the decomposition of C-N-Zn heteroatom contents in ZIF-8 and the O-containing functional groups in N-G which were influenced by the grinding speed. The decomposition of ZIF-8 not only affected the framework and the pore structure but also modified the chemical structure and the surface distribution of C-N-containing functional groups-constituted active sites. The variation of physical and chemical properties enhanced the electrochemical performance of N-G/MOF and made it comparable to the 10 wt% Pt/C catalyst.

Correlation of metal–organic framework structures and catalytic performance in Fischer–Tropsch synthesis process

Two typical metal–organic frameworks (MOFs), i.e. tris(pyridine-2-carboxylato)-cobalt(III) monohydrate (MOF-1) and (μ2-pyridine 2,6-dicarboxylato)(pyridine 2,6-dicarboxylato) pentaaqua dicobalt(II)dihydrate (MOF-2) were employed for preparation of cobalt Fischer–Tropsch catalysts. Both MOF-derived catalysts were obtained by direct pyrolysis in N2 atmosphere at 500 °C. The pyrolysis of desired MOFs resulted nanoparticles embedded in the porous carbon matrix. Such catalysts can serve as useful catalysts for FT synthesis. Co-MOF-1 derived catalyst exhibited carbon monoxide conversion of 74.8% and selectivity towards long-chain hydrocarbons (C5+) of 49.2%. Also, it showed selectivity for short-chain hydrocarbons (C2–C4) of 36.19% for 50 h on steam while Co-MOF-2 derived catalyst displayed CO conversion of 81.6% and selectivity for long-chain hydrocarbons (C5+) and short-chain hydrocarbons of 56.8% and 28.2%. The superb activity and catalytic efficiency can be ascribed to the MOF precursors structures. This study investigated the relationship between MOF structure and catalytic performance and presented a new approach to design novel super active catalysts with preferable selectivity for Fischer–Tropsch synthesis by opting the suitable MOF precursors.

Control of SEI Formation for Stable Potassium-Ion Battery Anodes by Bi-MOF-Derived Nanocomposites.

Bismuth (Bi)-based electrodes are highly attractive for potassium-ion batteries (PIBs) while suffering from a short cycle life due to the larger diameter of K ion, leading to unstable solid electrolyte interface (SEI) films during continuous potassiation/depotassiation. Herein, we developed novel ultrathin carbon film@carbon nanorods@Bi nanoparticle (UCF@CNs@BiN) materials for the long cycle life anode of PIBs. Bi nanoparticles are uniformly distributed in carbon nanorods, which not only provides a high-speed channel for ion transport but also accommodates the volume change of Bi nanoparticles during continuous potassiation/depotassiation processes. The UCF@CN matrix can direct most SEI film formation on the surface of the carbon film, not on the surface of individual Bi nanoparticles, avoiding the fracture of the matrix. Benefiting from their unique structure, the UCF@CNs@BiN anodes exhibit an outstanding capacity of ∼425 mAh g-1 at 100 mA g-1 and a capacity decay of 0.038% per cycle over 600 cycles. Even at a higher current density of 1000 mA g-1, there is a capacity decay as low as 0.036% per cycle during 700 cycles. Meanwhile, this work provides a new way of utilizing the metal-organic framework structure and reveals a highly promising PIB anode.

Inclusion of ethanol in a nano-porous, bio-based metal organic framework

More than 15,000 types of metal–organic framework (MOF) structures have been synthesized to date. The vast majority of these structures have been synthesized by linking transition metal ions with organic linkers, which limits their potential applications due to toxicity and environmental concerns. In this study we synthesized, bio-based nano-porous crystalline MOF using γ-Cyclodextrin (γ-CD) and potassium ions by vapor diffusion process. Gamma-cyclodextrin MOF (CDMOF) crystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). We hereby report inclusion complex (IC) formation between nano-porous γ-CDMOF and ethanol molecules. Ethanol, a generally recognized as safe compound and well-known antibacterial and antimicrobial compound, can be used for various industrial applications such as energy, food packaging, pharmaceuticals, gas sensing devices etc. Around ~ 20% ethanol encapsulation was observed in the CDMOF as substantiated by FTIR, TGA and differential scanning calorimetry. Observations from XRD supported the IC formation. CDMOF analyzed before and after IC formation using SEM and XRD indicated that CDMOF crystals retained the crystal structure after the complex formation. This study helps advance our understanding of ethanol-CDMOF host–guest interactions.

Solid-Solution Mixed-Linker Synthesis of Isoreticular Al-Based MOFs for an Easy Hydrophilicity Tuning in Water-Sorption Heat Transformations

The solid-solution mixed-linker approach, where a linker is partially replaced by a similar one under retention of the isoreticular metal–organic framework (MOF) structure, offers an easy and inexpensive way to fine-tune MOF properties to design tailored compounds. A total of 10 aluminum mixed-linker MOFs, [Al(OH)(X)a(Y)1–a] (X = IPA, isophthalate; Y = FDC, 2,5-furandicarboxylate) spanning between the isostructural MOFs CAU-10-H (a = 1) and MIL-160 (a = 0), were synthesized by employing different ratios of the aforementioned linkers. CAU-10-H and MIL-160 have been reported as highly promising materials for cycling water sorption for heat transformation applications. A detailed characterization with a focus on the changes in the sorption properties for water vapor showed that the hydrophilicity is readily and easily tuned through the mixed-linker approach between the limits of MIL-160 and CAU-10-H. An increasing fraction of IPA shifts the steep increase in the S-shaped water adsorption isotherm in small steps from p/p0 = ∼0.05 for MIL-160 to p/p0 = ∼0.18 for CAU-10-H. Higher coefficient of performance (COPH) values for the mixed-linker materials over MIL-160 illustrate the well-balanced hydrophobicity/hydrophilicity of the former under the exemplary calculation conditions.

Desiccant-Based Air Handling Unit Alternatively Equipped with Three Hygroscopic Materials and Driven by Solar Energy

The energy demand for the air-conditioning of buildings has shown a very significant growth trend in the last two decades. In this paper three alternative hygroscopic materials for desiccant wheels are compared considering the operation of the air handling unit they are installed in. The analyses are performed by means of the TRNSYS 17® software, simulating the plant with the desiccant wheel made of: silica-gel, i.e., the filling actually used in the experimental plant desiccant wheel of the University of Sannio Laboratory; MIL101@GO-6 (MILGO), a composite material, consisting of graphite oxide dispersed in a MIL101 metal organic framework structure; Campanian Ignimbrite, a naturally occurring tuff, rich in phillipsite and chabazite zeolites, widespread in the Campania region, in Southern Italy. The air-conditioning system analyzed serves a university classroom located in Benevento, and it is activated by the thermal energy of a solar field for which three surfaces are considered: about 20, 27 and 34 m2. The results demonstrate that a primary energy saving of about 20%, 29%, 15% can be reached with silica-gel, MILGO and zeolite-rich tuff desiccant wheel based air handling units, respectively.

Cyclohexene Oxidation with H2O2 over Metal-Organic Framework MIL-125(Ti): The Effect of Protons on Reactivity

The catalytic performance of the titanium-based metal–organic framework MIL-125 was evaluated in the selective oxidation of cyclohexene (CyH) with environmentally friendly oxidants, H2O2 and tBuOOH. The catalytic activity of MIL-125 as well as the oxidant utilization efficiency and selectivity toward epoxide and epoxide-derived products can be greatly improved by acid additives (HClO4 or CF3SO3H). In the presence of 1 molar equivalent (relative to Ti) of a proton source, the total selectivity toward CyH epoxide and trans-cyclohexane-1,2-diol reached 75–80% at 38–43% alkene conversion after 45 min of reaction with 1 equivalent of 30% H2O2 at 50 °C. With 50% H2O2 as the oxidant, the total selectivity toward heterolytic oxidation products increased up to 92% at the same level of alkene conversion. N2 adsorption, powder X-ray diffraction (PXRD), and infrared (IR) spectroscopy studies before and after the catalytic oxidations confirmed the absence of structural changes in the Metal–organic framework (MOF) structure. MIL-125 was stable toward titanium leaching, behaved as a truly heterogeneous catalyst, and could easily be recovered and reused several times without any loss of the catalytic properties.

Tunable Twisting Motion of Organic Linkers via Concentration and Hydrogen-Bond Formation

Benzothiadiazole dibenzoic acid (BTDB) derivative is a well-known organic linker in various metal–organic framework structures as well as a fluorescent probe in biological systems. Here, we demonstrate that the radiative and nonradiative decay channels of BTDB can be interplayed and precisely controlled through concentration and hydrogen-bond interactions as directly evidenced experimentally and theoretically. This leads to excited-state structural changes that significantly suppress the torsional motion around the benzothiadiazole moiety, leading to an enormous increase in the emission quantum yields from ∼1 to 70%. These changes are associated with the existence of two equilibria, where dimers and small oligomers form in dimethylformamide (DMF), with high formation constants of 18 000 M–1 and 1.2 × 1013 M–3, respectively. These evolving species, i.e., the dimers and oligomers, are formed via hydrogen bonds between carboxylic acid groups present at the far edge of the rodlike BTDB molecules. The estimated repeating number for this small-oligomer formation via bonded monomers is eight in DMF, as shown by emission spectra analysis. With deprotonation as a control experiment, these associated species can easily collapse with the initial monomer species, confirming the role of the hydrogen-bond formation in the observed phenomena. Theoretical studies and NMR experiments not only confirm the existence of the dimers, but also demonstrate the important role of the hydrogen bonds in the excited-state dynamics. These new findings provide a better understanding of the photophysical behaviors of organic linkers used in a wide range of chemical and biological applications.

A survey of interactions in crystal structures of pyrazine-based compounds.

The important role of pyrazine (pz) and its derivatives in fields such as biochemistry and pharmacology, as well as in the study of magnetic properties, is surveyed. Recognition of these properties without extensive investigations into their structural properties is not possible. This review summarizes interactions that exist between these organic compounds by themselves in the solid state, as well as those in coordination polymers with metal ions and in polyoxometalate-based hybrids. Complexes based on pyrazine ligands can generate metal-organic framework (MOF) structures that bind polyoxometalates (POMs) through covalent and noncovalent interactions. Some biological and magnetic properties involving these compounds are considered and the effect of hydrogen bonding on their supramolecular architectures is highlighted.

Metal Organo-Polymeric Framework via [2 + 2] Cycloaddition Reaction: Influence of Hydrogen Bonding on Depolymerization

In the doubly interpenetrated metal–organic framework (MOF) structure with cds topology, [Zn2(bpeb)(dhbdc)(fa)2], 1 (where bpeb = trans,trans,trans-1,4-bis[2-(4′-pyridyl)ethenyl]benzene, dhbdc = 2,...

Synthesis, crystal structure and efficient SOD activity of transition compounds constructed with 5-aminoisophthalic acid ligand

Three new superoxide dismutase model compounds: [CoL(H2O)]·2H2O (1), [CdL(H2O)]·H2O (2) and [PbL] (3) were successfully synthesized by the reaction of a transition metal salt and 5-aminoisophthalic acid under hydrothermal conditions (L: 5-aminoisophthalic acid). The three compounds were characterized by elemental analysis, infrared spectroscopy, ultraviolet–visible spectroscopy, PXRD analysis and TG analysis. X-ray single crystal diffraction analysis showed that compounds 2 and 3 were 3D inorganic–organic framework structures while compound 1 was a 2D structure. These simulations contained pores structures with maximum sizes of 4.08–14.67 Å. To further explore the functional properties of these compounds, we firstly analyzed their SOD activity, and the results demonstrated that they have different SOD activities. The IC50 values of the three mimics are much smaller than the international standard for SOD standards, demonstrating that these mimics have superior Reactive Oxygen Species resistance.

Methane Adsorption on the Metal–Organic Framework Structure Al-BTC

Adsorption of natural gas (methane) on the synthesized metal–organic framework (MOF) Al-BTC with specific surface area SBET = 1422 m2/g was studied at pressures up to 40 MPa and temperatures of 303, 313, 323, and 333 K. The maximum adsorption of methane on Al-BTC reaches 10.36 mmol/g at 303 K and 40 MPa, and the initial heat of adsorption is ~14 kJ/mol. The amount of methane accumulated in a system with Al-BTC attains a value of 120–130 m3(NTP)/m3 in a range of pressures from 3.5 to 10.0 MPa, which is the most relevant for methane accumulation. The volumes of methane stored in the systems with Al-BTC and without an adsorbent differ by a factor of about 2 at 3.5 MPa, there is almost no distinction between these options of methane storage at 7.0 and 20.0 MPa, and the amount of gas in the system without an adsorbent exceeds by 25% that in Al-BTC. The pressure range from 3.5 to 6.0 MPa is most efficient for the methane adsorption accumulation in the MOF structure Al-BTC. The absolute efficiency of methane adsorption accumulation increases with lowering of temperature.

Ab initio structure determination of [Eu5(C2H4O2)6(CH3CO2)3] n by X-ray powder diffraction

The compound [Eu5(C2H4O2)6(CH3CO2)3] n was synthesized by dissolving acetate europium salt in ethylene glycol solvent and heating under reflux for a short time. Its structure was solved ab initio from synchrotron powder diffraction data using optimization methods in direct space. The compound has a very large unit-cell volume of 23679 Å3 and the highest centred cubic symmetry space group, Ia{\bar 3}d (No. 230). The porous metal–organic framework structure is similar to those usually observed in zeolites, with pores volumes of 82 Å3, which is of potential interest for gas storage.