Biomimetic 1-Aminocyclopropane-1-Carboxylic Acid Oxidase Ethylene Production by MIL-100(Fe)-Based Materials

A novel core@shell hybrid material based on biocompatible hydroxyapatite nanoparticles (HA) and the well-known MIL-100(Fe) (Fe₃O(H₂O)₂F(BTC)₂·nH₂O, BTC: 1,3,5-benzenetricarboxylate) has been prepared following a layer-by-layer strategy. The core@shell nature of the studied system has been confirmed by infrared, X-ray powder diffraction, N₂ adsorption, transmission electron microscopy imaging, and EDS analyses revealing the homogeneous deposition of MIL-100(Fe) on HA, leading to HA@MIL-100(Fe) rod-shaped nanoparticles with a 7 nm shell thickness. Moreover, both MIL-100(Fe) and HA@MIL-100(Fe) have demonstrated to act as efficient heterogeneous catalysts toward the biomimetic oxidation of 1-aminocyclopropane-1-carboxylic acid into ethylene gas, a stimulator that regulates fruit ripening. Indeed, the hybrid material maintains the catalytic properties of pristine MIL-100(Fe) reaching 40% of conversion after only 20 min. Finally, the chemical stability of the catalyst in water has also been monitored for 21 days by inductively coupled plasma-mass spectrometry confirming that only ca. 3% of Ca is leached.

Magnesium Exchanged Zirconium Metal-Organic Frameworks with Improved Detoxification Properties of Nerve Agents

UiO-66, MOF-808 and NU-1000 metal-organic frameworks exhibit a differentiated reactivity toward [Mg(OMe)₂(MeOH)₂]₄ related to their pore accessibility. Microporous UiO-66 remains unchanged while mesoporous MOF-808 and hierarchical micro/mesoporous NU-1000 materials yield doped systems containing exposed MgZr₅O₂(OH)₆ clusters in the mesoporous cavities. This modification is responsible for a remarkable enhancement of the catalytic activity toward the hydrolytic degradation of P-F and P-S bonds of toxic nerve agents, at room temperature, in unbuffered aqueous solutions.

Biporous Metal-Organic Framework with Tunable CO2/CH4 Separation Performance Facilitated by Intrinsic Flexibility

In this work, we report the synthesis of SION-8, a novel metal-organic framework (MOF) based on Ca(II) and a tetracarboxylate ligand TBAPy^4- endowed with two chemically distinct types of pores characterized by their hydrophobic and hydrophilic properties. By altering the activation conditions, we gained access to two bulk materials: the fully activated SION-8F and the partially activated SION-8P with exclusively the hydrophobic pores activated. SION-8P shows high affinity for both CO₂ ( Q_st = 28.4 kJ/mol) and CH₄ ( Q_st = 21.4 kJ/mol), while upon full activation, the difference in affinity for CO₂ ( Q_st = 23.4 kJ/mol) and CH₄ ( Q_st = 16.0 kJ/mol) is more pronounced. The intrinsic flexibility of both materials results in complex adsorption behavior and greater adsorption of gas molecules than if the materials were rigid. Their CO₂/CH₄ separation performance was tested in fixed-bed breakthrough experiments using binary gas mixtures of different compositions and rationalized in terms of molecular interactions. SION-8F showed a 40-160% increase (depending on the temperature and the gas mixture composition probed) of the CO₂/CH₄ dynamic breakthrough selectivity compared to SION-8P, demonstrating the possibility to rationally tune the separation performance of a single MOF by manipulating the stepwise activation made possible by the MOF's biporous nature.

A post-synthetic approach triggers selective and reversible sulphur dioxide adsorption on a metal-organic framework

We report the application of a post-synthetic solid-state cation-exchange process to afford a novel 3D MOF with hydrated barium cations hosted at pores able to trigger selective and reversible SO₂ adsorption. Computational modelling supports the full reversibility of the adsorption process on the basis of weak supramolecular interactions between SO₂ and coordinated water molecules.

Chemical Warfare Agents Detoxification Properties of Zirconium Metal-Organic Frameworks by Synergistic Incorporation of Nucleophilic and Basic Sites

The development of protective self-detoxifying materials is an important societal challenge to counteract risk of attacks employing highly toxic chemical warfare agents (CWAs). In this work, we have developed bifunctional zirconium metal-organic frameworks (MOFs) incorporating variable amounts of nucleophilic amino residues by means of formation of the mixed ligand [Zr₆O₄(OH)₄(bdc)_6(1-x)(bdc-NH₂)_6x] (UiO-66-xNH₂) and [Zr₆O₄(OH)₄(bpdc)_6(1-x)(bpdc-(NH₂)₂)_6x] (UiO-67-x(NH₂)₂) systems where bdc = benzene-1,4-dicarboxylate; bdc-NH₂= benzene-2-amino-1,4-dicarboxylate; bpdc = 4,4'-biphenyldicarboxylate; bpdc-(NH₂)₂ = 2,2'-diamino-4,4'-biphenyldicarboxylate and x = 0, 0.25, 0.5, 0.75, 1. In a second step, the UiO-66-xNH₂ and UiO-67-x(NH₂)₂ systems have been postsynthetically modified by introduction of highly basic lithium tert-butoxide (LiO^tBu) on the oxohydroxometallic clusters of the mixed ligand MOFs to yield UiO-66-xNH₂@LiO^tBu and UiO-67-x(NH₂)₂@LiO^tBu materials. The results show that the combination of pre and postsynthetic modifications on these MOF series gives rise to fine-tuning of the catalytic activity toward the hydrolytic degradation of both simulants and real CWAs in unbuffered aqueous solutions. Indeed, UiO-66-0.25NH₂@LiO^tBu is able to hydrolyze both CWAs simulants (diisopropylfluorophosphate (DIFP), 2-chloroethylethylsulfide (CEES), and real CWAs (soman (GD), sulfur mustard (HD)) quickly in aqueous solution. These results are related to a suitable combination of robustness, nucleophilicity, basicity, and accessibility to the porous framework.

Selective sulfur dioxide adsorption on crystal defect sites on an isoreticular metal organic framework series

The widespread emissions of toxic gases from fossil fuel combustion represent major welfare risks. Here we report the improvement of the selective sulfur dioxide capture from flue gas emissions of isoreticular nickel pyrazolate metal organic frameworks through the sequential introduction of missing-linker defects and extra-framework barium cations. The results and feasibility of the defect pore engineering carried out are quantified through a combination of dynamic adsorption experiments, X-ray diffraction, electron microscopy and density functional theory calculations. The increased sulfur dioxide adsorption capacities and energies as well as the sulfur dioxide/carbon dioxide partition coefficients values of defective materials compared to original non-defective ones are related to the missing linkers enhanced pore accessibility and to the specificity of sulfur dioxide interactions with crystal defect sites. The selective sulfur dioxide adsorption on defects indicates the potential of fine-tuning the functional properties of metal organic frameworks through the deliberate creation of defects.

The widespread emission of sulfur oxide gases from fossil fuel combustion presents major health risks. Here, the authors show that the selective sulfur dioxide capture performance of a metal organic framework is improved by the introduction of missing linker defects and extra-framework barium cations.

RAPTA-C incorporation and controlled delivery from MIL-100(Fe) nanoparticles

The properties of MIL-100(Fe) nanoparticles as vehicles of a non-conventional half-sandwich ruthenium(ii) metallodrug in simulated intravenous conditions have been investigated.

Crystalline fibres of a covalent organic framework through bottom-up microfluidic synthesis

This work describes the formation of high quality fibres of a covalent organic framework (COF) under microfluidic conditions.

A vanadium(IV) pyrazolate metal-organic polyhedron with permanent porosity and adsorption selectivity

A vanadium(IV) pyrazolate-based open metal-organic polyhedron of [V3(μ3-O)O(OH)2(μ4-BPD)1.5(μ-HCOO)3] (BDP = benzene-1,4-bipyrazolate) formulation gives rise to a porous crystal structure exhibiting micro and mesoporosity which is useful for selective adsorption of gases.