Magnetic functionalities in MOFs: from the framework to the pore

Covalent and Ionic Capacity of MOFs To Sorb Small Gas Molecules

In this work, the aim is to characterize how an Fe-based metal-organic framework (MOF) behaves when gases, like carbon dioxide, are inserted through their channels and to characterize the nature and strength of those interactions. Despite the computational nature of the project, it is based on the experimental results obtained in 2016 by Mı́nguez-Espallargas and co-workers ( J. Am. Chem. Soc. 2013, 135, 15986 - 15989 ). Those MOFs were found to selectively allocate/adsorb CO₂, having as a drawback that apparently each cavity allocates only one CO₂ molecule. Despite truncating the MOF to its unitary cell, the whole cavity of the MOF can be described in detail by precise ab initio calculations. Another computational goal is to unravel why experimentally CO₂ was preferred with respect to N₂, and for the sake of consistency, a list of common gases will be further studied, such as H₂, O₂, H₂O, CH₄, C₂H₆, N₂O, or NO.

Control of the Speed of a Light-Induced Spin Transition through Mesoscale Core-Shell Architecture

The rate of the light-induced spin transition in a coordination polymer network solid dramatically increases when included as the core in mesoscale core-shell particles. A series of photomagnetic coordination polymer core-shell heterostructures, based on the light-switchable Rb _aCo _b[Fe(CN)₆] _c· mH₂O (RbCoFe-PBA) as core with the isostructural K _jNi _k[Cr(CN)₆] _l· nH₂O (KNiCr-PBA) as shell, are studied using temperature-dependent powder X-ray diffraction and SQUID magnetometry. The core RbCoFe-PBA exhibits a charge transfer-induced spin transition (CTIST), which can be thermally and optically induced. When coupled to the shell, the rate of the optically induced transition from low spin to high spin increases. Isothermal relaxation from the optically induced high spin state of the core back to the low spin state and activation energies associated with the transition between these states were measured. The presence of a shell decreases the activation energy, which is associated with the elastic properties of the core. Numerical simulations using an electro-elastic model for the spin transition in core-shell particles supports the findings, demonstrating how coupling of the core to the shell changes the elastic properties of the system. The ability to tune the rate of optically induced magnetic and structural phase transitions through control of mesoscale architecture presents a new approach to the development of photoswitchable materials with tailored properties.

Ru/UiO-66 Catalyst for the Reduction of Nitroarenes and Tandem Reaction of Alcohol Oxidation/Knoevenagel Condensation

A 3.1% Ru/UiO-66 material was prepared by adsorption of RuCl₃ from ethyl acetate on to MOF UiO-66, followed by reduction with NaBH₄. The presence of acid-base and ox-red sites allows this 3.1% Ru/UiO-66 material acting as a bifunctional catalyst for the reduction of nitroarenes and tandem reaction of alcohol oxidation/Knoevenagel condensation. The high efficiency of 3.1% Ru/UiO-66 was demonstrated in the reduction of nitroarenes to amines. This system can be applied as a catalyst for at least six successive cycles without loss of activity. The 3.1% Ru/UiO-66 catalyst also was active in the tandem aerobic oxidation of alcohols/Knoevenagel condensation with malononitrile. However, the activity of this catalyst strongly decreased in the second cycle. A combination of physicochemical and catalytic experimental data indicated that Ru nanoparticles are the active sites both for the catalytic reduction of nitro compounds and the aerobic oxidation of alcohols. The activity for the Knoevenagel condensation reaction was from the existence of the "Zr ⁿ⁺-O^2- Lewis acid-base" pair in the framework of UiO-66.

A thermoelectric copper-iodide composite from the pyrolysis of a well-defined coordination polymer

Coordination polymer 1 was prepared from CuI and a flexible [SNS] ligand L in acetonitrile. The thermal decomposition of 1 yielded a CuI-rich thermoelectric carbon composite 2, which is relatively light, thermally stable and robust. Composite 2 possesses high Seebeck coefficients (700-950 μV K-1) from rt to 204 °C after an optimization cycle.

Magnetization relaxation in the single-ion magnet DySc2N@C80: quantum tunneling, magnetic dilution, and unconventional temperature dependence

Quantum tunneling and relaxation of magnetization in single molecule magnet DySc₂N@C₈₀ is thoroughly studied as a function of magnetic dilution, temperature, and magnetic field.

Relaxation of magnetization in endohedral metallofullerenes DySc₂N@C₈₀ is studied at different temperatures, in different magnetic fields, and in different molecular arrangements. Magnetization behavior and relaxation are analyzed for powder sample, and for DySc₂N@C₈₀ diluted in non-magnetic fullerene Lu₃N@C₈₀, adsorbed in voids of a metal–organic framework, and dispersed in a polymer. The magnetic field dependence and zero-field relaxation are also studied for single-crystals of DySc₂N@C₈₀ co-crystallized with Ni(ii) octaethylporphyrin, as well as for the single crystal diluted with Lu₃N@C₈₀. Landau–Zener theory is applied to analyze quantum tunneling of magnetization in the crystals. The field dependence of relaxation rates revealed a dramatic dependence of the zero-field tunneling resonance width on the dilution and is explained with the help of an analysis of dipolar field distributions. AC magnetometry is used then to get access to the relaxation of magnetization in a broader temperature range, from 2 to 87 K. Finally, a theoretical framework describing the spin dynamics with dissipation is proposed to study magnetization relaxation phenomena in single molecule magnets.

A highly stable and hierarchical tetrathiafulvalene-based metal-organic framework with improved performance as a solid catalyst

A highly stable Metal–Organic Framework with a hierarchical structure based on the Fe₃O cluster and a TTF-based ligand is presented.

Herein we report the synthesis of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, which shows a non-interpenetrated hierarchical crystal structure with mesoporous one-dimensional channels of ca. 3 nm and orthogonal microporous channels of ca. 1 nm. This highly stable MOF (aqueous solution with pH values ranging from 2 to 11 and different organic solvents), which possesses the well-known [Fe₃(μ₃-O)(COO)₆] secondary building unit, has proven to be an efficient catalyst for the aerobic oxidation of dibenzothiophenes.

Two isostructural Ln-MOFs showing luminescent sensing (Eu) and slow magnetic relaxation (Dy) properties

Two isostructural lanthanide-based MOFs are reported. The Eu-MOF exhibiting luminescence properties can be utilized in ion detection and the Dy-MOF displays SMM behavior with an energy barrier (ΔU_eff) of 54 K.

Rare azido and hydroxido bridged tetranuclear Co(ii) complexes of a polynucleating Mannich base ligand with a defect dicubane core: structures, magnetism and phenoxazinone synthase like activity

Triply azido/hydroxido bridged defect dicubane tetranuclear Co(ii) complexes of a Mannich base ligand show ferromagnetic/antiferromagnetic coupling and phenoxazinone synthase like activity.

3D isomorphous lanthanide coordination polymers displaying magnetic refrigeration, slow magnetic relaxation and tunable proton conduction

Four lanthanide 3D coordination frameworks with 1D hydrophilic channels along the crystallographic c direction have been investigated for their proton conduction and magnetic properties.

Implementation of slow magnetic relaxation in a SIM-MOF through a structural rearrangement

Dehydration of a Dy-based MOF causes the appearance of slow-magnetic relaxation due to the changes of the charge density of the coordination environment.

A one dimensional coordination polymer composed of antiferromagnetically coupled disk-like [Mn7] units

A single-chain magnet (SCM) was constructed from disk-like Mn₇ clusters linked by azide units.

Rare earth phosphors based on spherical infinite coordination polymers

New spherical lanthanide infinite coordination polymer (ICP)-based phosphors were obtained and show great potential for light-emitting applications.

Porous substrates as platforms for the nanostructuring of molecular magnets

This article highlights recent advances in the newly emerging field on the nanostructuration of molecular magnets using porous substrates.

Two MOFs as dual-responsive photoluminescence sensors for metal and inorganic ion detection

Two MOFs were synthesized and explored as dual-responsive photoluminescent sensors: 1 for Fe³⁺ and Cr₂O₇²⁻ ions, and 2 for Hg²⁺ and Cr₂O₇²⁻ ions.

Construction of two Zn(ii)/Cd(ii) multifunctional coordination polymers with mixed ligands for catalytic and sensing properties

Two Zn(ii)/Cd(ii) coordination polymers with different networks were constructed with mixed ligands. The former compound shows high catalytic activity for Knoevenagel condensation, and the latter compound can selectively recognize l-cysteine through the luminescence quenching effect.