Search results for "frameworks"
showing 10 items of 120 documents
Stimuli-responsive hybrid materials: breathing in magnetic layered double hydroxides induced by a thermoresponsive molecule
2014
[EN] A hybrid magnetic multilayer material of micrometric size, with highly crystalline hexagonal crystals consisting of CoAl-LDH ferromagnetic layers intercalated with thermoresponsive 4-(4-anilinophenylazo)benzenesulfonate (AO5) molecules diluted (ratio 9 : 1) with a flexible sodium dodecylsulphate (SDS) surfactant has been obtained. The resulting material exhibits thermochromism attributable to the isomerization between the azo (prevalent at room temperature) and the hydrazone (favoured at higher temperatures) tautomers, leading to a thermomechanical response. In fact, these crystals exhibited thermally induced motion triggering remarkable changes in the crystal morphology and volume. In…
Effect of modulator connectivity on promoting defectivity in titanium–organic frameworks
2020
The recognition of defect chemistry as a true synthetic tool for targeted creation of defects and controllable performance remains limited by the pool of frameworks explored. The value of defect engineering in controlling the properties of defective frameworks has been beautifully exemplified and largely demonstrated with UiO-type materials based on Zr(iv) nodes. However, titanium–organic frameworks remain largely unexplored in this context arguably due to the complex chemistry in solution of Ti(iv) and the difficulties in growing crystalline solids. We report a systematic study on the ability of mono- and dicarboxylic modulators (benzoic and isophthalic acid) to promote defect creation in …
Synthesis of Densely Packaged, Ultrasmall Pt02Clusters within a Thioether-Functionalized MOF: Catalytic Activity in Industrial Reactions at Low Tempe…
2018
The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt02 clusters, homogenously distributed and densely packaged within the channels of a metal-organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO2 methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal c…
Studies on atomic layer deposition of MOF-5 thin films
2013
International audience; Deposition of MOF-5 thin films from vapor phase by atomic layer deposition (ALD) was studied at 225-350 degrees C. Zinc acetate (ZnAc2) and 1,4-benzenedicarboxylic acid (1,4-BDC) were used as the precursors. The resulting films were characterized by UV-Vis spectrophotometry, Fourier transform infrared spectroscopy (FTIR), optical microscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), time-of-flight elastic recoil detection analysis (TOF-ERDA), isopropanol adsorption tests, and nanoindentation. It was found out that the as-deposited films were amorphous but crystallized in humid conditions at room temperature. The crystalline films h…
Metal-organic framework-activated carbon composite materials for the removal of ammonia from contaminated airstreams
2019
L.N.M and R.E.M wish to acknowledge the financial support from the EPSRC industrial CASE award (grant EP/N50936X/1). A.T and G.B would like to thank the financial support from the Fondo per il finanziamento delle attività base di ricerca (grant PJ-RIC-FFABR_2017). Metal-organic frameworks (MOFs) are a class of porous materials that show promise in the removal of Toxic Industrial Chemicals (TICs) from contaminated airstreams, though their development for this application has so far been hindered by issues of water stability and the wide availability and low cost of traditionally used activated carbons. Here a series of three MOF-activated carbon composite materials with different MOF to carb…
Origin of the Chemiresistive Response of Ultrathin Films of Conductive Metal–Organic Frameworks
2018
Conductive metal-organic frameworks are opening new perspectives for the use of these porous materials for applications traditionally limited to more classical inorganic materials, such as their integration into electronic devices. This has enabled the development of chemiresistive sensors capable of transducing the presence of specific guests into an electrical response with good selectivity and sensitivity. By combining experimental data with computational modelling, a possible origin for the underlying mechanism of this phenomenon in ultrathin films (ca. 30 nm) of Cu-CAT-1 is described. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:57 issue:46 pages:15086-15090 ispartof: location…
A [Cr2Ni] coordination polymer: slow relaxation of magnetization in quasi-one-dimensional ferromagnetic chains
2018
The reaction of [Cr3IIIO(OAc)6(H2O)3]NO3·AcOH with 2-hydroxynaphthaldehyde, 2-amino-isobutyric acid and NiCl2·6H2O in MeOH, under basic and solvothermal conditions, led to the formation of the quasi-1D coordination polymer {[CrIII2NiII(L)4(MeOH)2]}n (where L = the dianion of the Schiff base between 2-hydroxynaphthaldehyde and 2-amino-isobutyric acid), which behaves as a ferromagnetic chain, displaying slow relaxation of magnetization.
Charge-transfer interactions between fullerenes and a mesoporous tetrathiafulvalene-based metal–organic framework
2019
The design of metal–organic frameworks (MOFs) incorporating electroactive guest molecules in the pores has become a subject of great interest in order to obtain additional electrical functionalities within the framework while maintaining porosity. Understanding the charge-transfer (CT) process between the framework and the guest molecules is a crucial step towards the design of new electroactive MOFs. Herein, we present the encapsulation of fullerenes (C60) in a mesoporous tetrathiafulvalene (TTF)-based MOF. The CT process between the electron-acceptor C60 guest and the electron-donor TTF ligand is studied in detail by means of different spectroscopic techniques and density functional theor…
Surface Functionalization of Metal–Organic Framework Crystals with Catechol Coatings for Enhanced Moisture Tolerance
2021
Robust catechol coatings for enhanced moisture tolerance were produced in one step by direct reaction of Hong Kong University of Science and Technology (HKUST) with synthetic catechols. We ascribe the rapid formation of homogeneous coatings around the metal–organic framework particles to the biomimetic catalytic activity of Cu(II) dimers in the external surface of the crystals. Use of fluorinated catechols results in hydrophobic, permeable coatings that protect HKUST from water degradation while retaining close to 100% of its original sorption capacity.
MOF-Mediated Synthesis of Supported Fe-Doped Pd Nanoparticles under Mild Conditions for Magnetically Recoverable Catalysis**
2020
Metal–organic framework (MOF)-driven synthesis is considered as a promising alternative for the development of new catalytic materials with well-designed active sites. This synthetic approach is used here to gradually transform a new bimetallic MOF, with Pd and Fe as the metal components, by the in situ generation of aniline under mild conditions. This methodology results in a compositionally homogeneous nanocomposite formed by Fe-doped Pd nanoparticles that, in turn, are supported on iron oxide-doped carbon. The nanocomposite has been fully characterized by several techniques such as IR and Raman spectroscopy, TEM, XPS, and XAS. The performance of this nanocomposite as an heterogeneous cat…