Evaluation of the catalytic activity of Zn-MOF-74 for the alcoholysis of cyclohexene oxide.

In the present work, nanocrystalline Zn-MOF-74 is shown to be a heterogeneous catalyst for the acid-catalyzed ring-opening alcoholysis of cyclohexene oxide. The results corroborated that accessible open metal sites within the material are critical conditions (Zn(ii) Lewis acid sites) for this reaction. Zn-MOF-74 was tested at three different temperatures (30, 40, and 50 °C) for the alcoholysis reaction. Furthermore, the cyclohexene oxide conversion was 94% in less than two days. A comparison of the catalytic activity with different crystal sizes of Zn-MOF-74 and the homogenous phase, zinc acetate, was conducted. Zn-MOF-74 exhibited excellent catalytic cyclability for three cycles without losing its activity. The material showed chemical stability by retaining its crystalline structure after the reaction and cyclability process.

MOF-based catalysts: insights into the chemical transformation of greenhouse and toxic gases.

Metal-organic framework (MOF)-based catalysts are outstanding alternative materials for the chemical transformation of greenhouse and toxic gases into high-add-value products. MOF catalysts exhibit remarkable properties to host different active sites. The combination of catalytic properties of MOFs is mentioned in order to understand their application. Furthermore, the main catalytic reactions, which involve the chemical transformation of CH4, CO2, NOx, fluorinated gases, O3, CO, VOCs, and H2S, are highlighted. The main active centers and reaction conditions for these reactions are presented and discussed to understand the reaction mechanisms. Interestingly, implementing MOF materials as catalysts for toxic gas-phase reactions is a great opportunity to provide new alternatives to enhance the air quality of our planet.

SU-101: a Bi(III)-based metal-organic framework as an efficient heterogeneous catalyst for the CO2 cycloaddition reaction.

A non-porous version of SU-101 (herein n-SU-101) was evaluated for the CO2 cycloaddition reaction. The findings revealed that open metal sites (Bi3+) are necessary for the reaction. n-SU-101 displays a high styrene oxide conversion of 96.6% under mild conditions (3 bar and 80 °C). The catalytic activity of n-SU-101 demonstrated its potential application for the cycloaddition of CO2 using styrene oxide.

Mn-CUK-1: A Flexible MOF for SO2, H2O, and H2S Capture.

The environmentally benign metal-organic framework (MOF) CUK-1 based on 2,4-pyridine dicarboxylate has been prepared for the first time using Mn(II) as the inorganic node and water as the only solvent. Mn-CUK-1 shows reversible and efficient capture of H2O, SO2, and H2S. Compared to previously studied Co(II) and Mg(II) versions of the same MOF, Mn-CUK-1 also exhibited unique temperature-induced structural flexibility due to organic linker torsion, as detailed by variable-temperature single-crystal X-ray diffraction studies. Owing to this inherent solid-state flexibility, Mn-CUK-1 showed stepwise adsorption for polar gases, which induce structural deformations upon adsorption, while the nonpolar guest adsorbates were reversibly sorbed in a more classical manner. Notably, Mn-CUK-1 demonstrates the highest reported H2S capacity-to-surface area ratio among MOFs that are chemically stable toward this reactive acidic molecule. Moreover, Mn-CUK-1 displays exceptional structural stability in the presence of high relative humidity and corrosive gases and shows soft crystalline behavior triggered by changes in both the adsorption temperature and guest molecule identity.

A Robust and Biocompatible Bismuth Ellagate MOF Synthesized Under Green Ambient Conditions.

The first bioinspired microporous metal-organic framework (MOF) synthesized using ellagic acid, a common natural antioxidant and polyphenol building unit, is presented. Bi2O(H2O)2(C14H2O8)·nH2O (SU-101) was inspired by bismuth phenolate metallodrugs, and could be synthesized entirely from nonhazardous or edible reagents under ambient aqueous conditions, enabling simple scale-up. Reagent-grade and affordable dietary supplement-grade ellagic acid was sourced from tree bark and pomegranate hulls, respectively. Biocompatibility and colloidal stability were confirmed by in vitro assays. The material exhibits remarkable chemical stability for a bioinspired MOF (pH = 2-14, hydrothermal conditions, heated organic solvents, biological media, SO2 and H2S), attributed to the strongly chelating phenolates. A total H2S uptake of 15.95 mmol g-1 was recorded, representing one of the highest H2S capacities for a MOF, where polysulfides are formed inside the pores of the material. Phenolic phytochemicals remain largely unexplored as linkers for MOF synthesis, opening new avenues to design stable, eco-friendly, scalable, and low-cost MOFs for diverse applications, including drug delivery.

Partially Reversible H2S Adsorption by MFM-300(Sc): Formation of Polysulfides.

The metal-organic framework (MOF)-type MFM-300(Sc) exhibits a combined physisorption and chemisorption capture of H2S, leading to a high uptake (16.55 mmol g-1) associated with high structural stability. The irreversible chemisorbed sulfur species were identified as low-order polysulfide (n = 2) species. The isostructural MFM-300(In) was demonstrated to promote the formation of different polysulfide species, paving the way toward a new methodology to incorporate polysulfides within MOFs for the generation of novel MOF-lithium/sulfur batteries.

Bottleneck Effect Explained by Le Bail Refinements: Structure Transformation of Mg-CUK-1 by Confining H2O Molecules.

The structure transformation of Mg-CUK-1 due to the confinement of H2O molecules was investigated. Powder X-ray diffraction (PXRD) patterns were collected at different H2O loadings and the cell parameters of the H2O-loaded Mg-CUK-1 material were determined by the Le Bail strategy refinements. A bottleneck effect was observed when one hydrogen-bonded H2O molecule per unit cell (18% relative humidity (RH)) was confined within Mg-CUK-1, confirming the increase in the CO2 capture for Mg-CUK-1.

Greener synthesis of Cu-MOF-74 and its catalytic use for the generation of vanillin.

A greener synthesis of Cu-MOF-74 was obtained, for the first time, in methanol as the unique solvent and at room temperature. Full characterisation of the MOF material showed its purity and also its nanocrystalline nature. Complete activation (150 °C for 1 h and 10-3 bar) of Cu-MOF-74 afforded unsaturated Cu metal sites and this was corroborated by in situ DRIFT spectroscopy. The access to these Cu open metal sites was tested for the catalytic transformation of trans-ferulic acid to vanillin (yield of 71% and 97% selectivity) and a plausible catalytic reaction mechanism was postulated based on quantum chemical calculations.