Electrochemical and Biocatalytic Signal-Controlled Payload Release from a Metal-Organic Framework.

A metal-organic framework (MOF), ZIF-8, which is stable at neutral and slightly basic pH values in aqueous solutions and destabilized/dissolved under acidic conditions, is loaded with a pH-insensitive fluorescent dye, rhodamine-B isothiocyanate, as a model payload species. Then, the MOF species are immobilized at an electrode surface. The local (interfacial) pH value is rapidly decreased by means of an electrochemically stimulated ascorbate oxidation at +0.

Metal-Organic Framework as a Fluorescent and Colorimetric Dual-Signal Readout Biosensor Platform for the Detection of a Genetic Sequence from the SARS-CoV-2 Genome.

The quest for the development of high-accuracy, point-of-care, and cost-effective testing platforms for SARS-CoV-2 infections is ongoing as current diagnostics rely on either assays based on costly yet accurate nucleic acid amplification tests (NAAT) or less selective and less sensitive but rapid and cost-effective antigen tests. As a potential solution, this work presents a fluorescence-based detection platform using a metal-organic framework (MOF) in an effective assay, demonstrating the potential of MOFs to recognize specific targets of the SARS-CoV-2 genome with high accuracy and rapid process turnaround time. As a highlight of this work, positive detection of SARS-CoV-2 is indicated by a visible color change of the MOF probe with ultrahigh detection selectivities down to single-base mismatch nucleotide sequences, thereby providing an alternative avenue for the development of innovative detection methods for diverse viral genomes.

Systematic Study on the Removal of Per- and Polyfluoroalkyl Substances from Contaminated Groundwater Using Metal-Organic Frameworks.

Harmful per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in aquatic environments, but their remediation remains challenging. Metal-organic frameworks (MOFs) have been recently identified as an advanced material class for the efficient removal of PFAS, but little is known about the fundamentals of the PFAS@MOF adsorption process. To address this knowledge gap, we evaluated the performance of 3 different MOFs for the removal of 8 PFAS classes from aqueous film-forming foam-impacted groundwater samples obtained from 11 U.

Force-Induced Near-Infrared Chromism of Mechanophore-Linked Polymers.

A near-infrared (NIR) mechanophore was developed and incorporated into a poly(methyl acrylate) chain to showcase the first force-induced NIR chromism in polymeric materials. This mechanophore, based on benzo[1,3]oxazine (OX) fused with a heptamethine cyanine moiety, exhibited NIR mechanochromism in solution, thin-film, and bulk states. The mechanochemical activity was validated using UV-vis-NIR absorption/fluorescence spectroscopies, gel permeation chromatography (GPC), NMR, and DFT simulations.

Design and Characterization of Metal Nanoparticle Infiltrated Mesoporous Metal-Organic Frameworks.

The infiltration of palladium and platinum nanoparticles (NPs) into the mesoporous metal-organic framework (MOF) CYCU-3 through chemical vapor infiltration (CVI) and incipient wetness infiltration (IWI) processes was systematically explored as a means to design novel NP@MOF composite materials for potential hydrogen storage applications. We employed a traditional CVI process and a new ″green″ IWI process using methanol for precursor infiltration and reduction under mild conditions. Transmission electron microscopy-based direct imaging techniques combined with synchrotron-based powder diffraction (SPD), energy-dispersive X-ray spectroscopy, and physisorption analysis reveal that the resulting NP@MOF composites combine key NP and MOF properties.

Direct Imaging of Isolated Single-Molecule Magnets in Metal-Organic Frameworks.

Practical applications involving the magnetic bistability of single-molecule magnets (SMMs) for next-generation computer technologies require nanostructuring, organization, and protection of nanoscale materials in two- or three-dimensional networks, to enable read-and-write processes. Owing to their porous nature and structural long-range order, metal-organic frameworks (MOFs) have been proposed as hosts to facilitate these efforts. Although probing the channels of MOF composites using indirect methods is well established, the use of direct methods to elucidate fundamental structural information is still lacking.

Systematic Investigation of Controlled Nanostructuring of Mn Single-Molecule Magnets Templated by Metal-Organic Frameworks.

This is the first systematic study exploring metal-organic frameworks (MOFs) as platforms for the controlled nanostructuring of molecular magnets. We report the incorporation of seven single-molecule magnets (SMMs) of general composition [MnO(OCR)(OH)], with R = CF (1), (CH)CCH (2), CHCl (3), CHBr (4), CHCl (5), CHBu (6), and CH (7), into the hexagonal channel pores of a mesoporous MOF host. The resulting nanostructured composites combine the key SMM properties with the functional properties of the MOF.

Design, structural diversity and properties of novel zwitterionic metal-organic frameworks.

Seven new zwitterionic metal-organic frameworks (ZW MOFs) of compositions {[Cd(L1)(OH)]·2HO} (1), {[Mn(L1)(OH)]·HO} (2), {[Cu(HL1)(OH)]·9HO} (3), {[Mn(L2)(OH)]·3HO} (4), [Co(L2)(OH)]·HO (5), [Ni(L2)(OH)] (6), and {[Cd(L2)(OH)]·4HO} (7), where HL1Br = 3-carboxy-1-(3,5-dicarboxybenzyl)pyridinium bromide and HL2Br = 4-carboxy-1-(3,5-dicarboxybenzyl)pyridinium bromide, have been synthesized under hydrothermal conditions. We demonstrate that the diversity of these crystal structures suggests that the tridentate and flexible nature of ZW ligands L1 and L2 make them excellent candidates for the synthesis of new ZW MOFs. A multi-charged anionic nature is a common feature of L1 and L2, and therefore, allows the rational design of ZW MOFs without the presence of additional counterions for charge compensation.

Evaluation of Metal-Organic Frameworks and Porous Polymer Networks for CO2 -Capture Applications.

This manuscript presents experimental data for 20 adsorption materials (metal-organic frameworks, porous polymer networks, and Zeolite-5A), including CO2 and N2 isotherms and heat capacities. With input from only experimental data, working capacities per energy for each material were calculated. Furthermore, by running seven different carbon-capture scenarios in which the initial flue-gas composition and process temperature was systematically changed, we present a range of performances for each material and quantify how sensitive each is to these varying parameters.

The Importance of Polymorphism in Metal-Organic Framework Studies.

Polymorphic phase transitions remain frequently undetected in routine metal-organic framework (MOF) studies; however, their discovery is of major importance in interpreting structure-property relationships. We herein report a reversible enantiotropic single-crystal to single-crystal polymorphic phase transition of a new microporous MOF [Eu(BDC)(NO3)(DMF)2]n (H2BDC = 1,4-benzenedicarboxylic acid; DMF = dimethylformamide). While modification 1LT at 170 K crystallizes in the monoclinic space group P21/c with unit cell dimensions of a = 17.

Metal-Organic Frameworks as Platforms for the Controlled Nanostructuring of Single-Molecule Magnets.

The prototypical single-molecule magnet (SMM) molecule [Mn12O12(O2CCH3)16(OH2)4] was incorporated under mild conditions into a highly porous metal-organic framework (MOF) matrix as a proof of principle for controlled nanostructuring of SMMs. Four independent experiments revealed that the SMM clusters were successfully loaded in the MOF pores, namely synchrotron-based powder diffraction, physisorption analysis, and in-depth magnetic and thermal analyses. The results provide incontrovertible evidence that the magnetic composite, SMM@MOF, combines key SMM properties with the functional properties of MOFs.

Crystal structure of tetra-aqua-bis-(thio-cyanato-κN)nickel(II)-2,5-di-methyl-pyrazine (1/4).

In the crystal structure of the title compound, [Ni(NCS)2(H2O)4]·4C6H8N2, the Ni(II) cations are coordinated by four water ligands and two trans-coordinated terminally N-bonded thio-cyanate anions in a slightly distorted octa-hedral geometry. The asymmetric unit consists of a Ni(2+) cation located on a centre of inversion, two water mol-ecules and one thio-cyanate ligand, as well as two uncoordinated 2,5-di-methyl-pyrazine ligands in general positions. In the crystal, discrete complex mol-ecules are linked into a three-dimensional network by O-H⋯N hydrogen bonding between the water H atoms and the 2,5-di-methyl-pyrazine N atoms.

A new design strategy to access zwitterionic metal-organic frameworks from anionic viologen derivates.

Two isostructural microporous zwitterionic metal-organic frameworks (ZW MOFs), {[M(bdcbpy)(OH2)4]·4H2O}n with M = Mn (1) and Ni (2), were synthesized by the rational design of the flexible anionic viologen derivate, 1,1'-bis(3,5-dicarboxybenzyl)-4,4'-bipyridinium dibromide dihydrate solvate (H4bdcbpyBr2·2H2O), and its self-assembly with metal(II) acetates in an aqueous medium. Single-crystal structure analyses revealed that both compounds exhibit three-dimensional hydrogen-bonded supramolecular frameworks with one-dimensional channel pores. Significantly, the pore surfaces are lined with charge gradients employed by the ZW ligand bdcbpy(2-) leading to the adsorption of hydrogen attributed to polarization effects.

Unprecedented activation and CO2 capture properties of an elastic single-molecule trap.

The activation and CO2 capture properties of a microporous metal-organic framework with elastic single-molecule traps were systematically investigated. This material shows a unique low-energy gas-purge activation capability, high CO2 adsorption selectivities over various gases and optimized working capacities per energy of 2.9 mmol kJ(-1) at 128 °C.

High-throughput analytical model to evaluate materials for temperature swing adsorption processes.

In order for any material to be considered in a post-combustion carbon capture technology, it must have high working capacities of CO₂ from flue gas and be regenerable using as little energy as possible. Shown here is an easy to use method to calculate both working capacities and regeneration energies and thereby predict optimal desorption conditions for any material.

Reversible switching from antiferro- to ferromagnetic behavior by solvent-mediated, thermally-induced phase transitions in a trimorphic MOF-based magnetic sponge system.

Hydrothermal reactions of copper(II) acetate, tetrazolate-5-carboxylate (tzc), and the neutral N-donor spacer ligand 1,3-di(4-pyridyl)propane (dpp) lead in a single reaction vial to the simultaneous formation of three different single-crystalline solvates [Cu(tzc)(dpp)]n·0.5C6H14·0.5H2O (1), [Cu(tzc)(dpp)]n·4.

Synthesis, crystal structure, and magnetic properties of the coordination polymer [Fe(NCS)2(1,2-bis(4-pyridyl)-ethylene)]n showing a two step metamagnetic transition.

Reaction of iron(II) thiocyanate with an excess of trans-1,2-bis(4-pyridyl)-ethylene (bpe) in acetonitrile at room temperature leads to the formation of [Fe(NCS)(2)(bpe)(2)·(bpe)] (1), which is isotypic to its Co(II) analogue. Using slightly different reaction conditions the literature known compound [Fe(NCS)(2)(bpe)(2)(H(2)O)(2)] (2) was obtained as a phase pure material. Simultaneous differential thermoanalysis and thermogravimetry prove that the hydrate 2 transforms into the anhydrate [Fe(NCS)(2)(bpe)(2)] (3), that decomposes on further heating into the new ligand-deficient 1:1 compound of composition [Fe(NCS)(2)(bpe)](n) (4), which can also be obtained directly by thermal decomposition of 1.

Low-energy selective capture of carbon dioxide by a pre-designed elastic single-molecule trap.

Single-molecule trap: Easy activation of the water-stable metal-organic framework PCN-200 provides a new route to low-energy selective CO(2) capture through stimuli-responsive adsorption behavior. This elastic CO(2) trapping effect was confirmed by single-component and binary gas-adsorption isotherms and crystallographic determination.

Tetra-kis(pyridazine-κN)bis-(seleno-cyanato-κN)nickel(II) pyridazine disolvate.

The reaction of nickel(II) nitrate with potassium seleno-cyanate and pyridazine leads to crystals of the title compound, [Ni(NCSe)(2)(C(4)H(4)N(2))(4)]·2C(4)H(4)N(2). The Ni(II) atom is coordinated by two terminal N-bonded seleno-cyanate anions and four pyridazine ligands within a slightly distorted octa-hedral geometry. The crystal structure contains two crystallographically independent pyridazine molecules in cavities of the structure, which are not coordinated to the metal centres.

Tetra-kis(pyridazine-κN)bis-(seleno-cyanato-κN)cobalt(II) pyridazine disolvate.

Reaction of cobalt(II) nitrate with potassium seleno-cyanate and pyridazine leads to single crystals of the title compound, [Co(NCSe)(2)(C(4)H(4)N(2))(4)]·2C(4)H(4)N(2), which is isotypic with its nickel(II) thio-cyanate analogue. The Co(2+) cations are coordinated by two N-bonded seleno-cyanate ligands and four N atoms from four pyridazine ligands into discrete complexes. The complexes are arranged into layers parallel to (001).

Tetra-kis(pyridazine-κN)bis-(thio-cyanato-κN)nickel(II) pyridazine disolvate.

The reaction of nickel(II) thio-cyanate with an excess of pyridazine leads to single crystals of the title compound, [Ni(NCS)(2)(C(4)H(4)N(2))(4)]·2C(4)H(4)N(2). The Ni(II) cations are coordinated by two terminal N-bonded thio-cyanate anions (trans) and four pyridazine ligands in a slightly distorted octa-hedral geometry. The discrete complexes are arranged into layers parallel to the ab plane which are separated by additional non-coordinated pyridazine ligands.

Bis(dicyanamido-κN)tetra-kis-(pyridine-κN)nickel(II).

In the crystal structure of the title compound, [Ni(C(2)N(3))(2)(C(5)H(5)N)(4)], the Ni(II) cations are coordinated by four pyridine ligands and two dicyanamide anions into discrete complexes. The shortest Ni⋯Ni separation is 8.1068 (10) Å.

Bis(dicyanamido-κN)tetra-kis-(pyridazine-κN)nickel(II).

Reaction of nickel(II) chloride with sodium dicyanamide and pyridazine leads to single crystals of the title compound, [Ni{N(CN)(2)}(2)(C(4)H(4)N(2))(4)], in which the Ni(II) cation is octa-hedrally coordinated by two dicyanamide anions and four pyridazine ligands into a discrete complex that is located on a center of inversion.

Metamagnetism and single-chain magnetic behavior in a homospin one-dimensional iron(II) coordination polymer.

Reaction of FeCl(2)·4H(2)O with KNCSe and pyridine in ethanol leads to the formation of the discrete complex [Fe(NCSe)(2)(pyridine)(4)] (1) in which the Fe(II) cations are coordinated by two N-terminal-bonded selenocyanato anions and four pyridine co-ligands. Thermal treatment of compound 1 enforces the removal of half of the co-ligands leading to the formation of a ligand-deficient (lacking on neutral co-ligands) intermediate of composition [Fe(NCSe)(2)(pyridine)(2)](n) (2) to which we have found no access in the liquid phase. Compound 2 is obtained only as a microcrystalline powder, but it is isotypic to [Cd(NCSe)(2)(pyridine)(2)](n) and therefore, its structure was determined by Rietveld refinement.

Systematic investigations on magneto-structural correlations of copper(II) coordination polymers based on organic ligands with mixed carboxylic and nitrogen-based moieties.

Reaction of copper(II) tetrazolate-5-carboxylate with different neutral N-donor spacer ligands under hydrothermal conditions leads to the formation of five new coordination polymers, [Cu(tzc)(pyz)(0.5)(H(2)O)(2)](n)·H(2)O (1), [Cu(tzc)(pyz)](n) (2), [Cu(tzc)(pym)(H(2)O)](n) (3), [Cu(tzc)(dpe)(0.5)(H(2)O)](n) (4) and [Cu(tzc)(azpy)(0.