Sabine Devautour-Vinot

Influence of framework metal ions on the dye capture behavior of MIL-100 (Fe, Cr) MOF type solids

MIL-100(Fe) shows large adsorption uptakes for both MO and MB, while MIL-100(Cr) can selectively adsorb MB from a MO–MB mixture. This work demonstrates that MOFs are promising adsorbents for dye capture and highlights that framework metal ion replacement is an efficient way to tailor MOFs for different applications in liquid separation.

Proton Transport in a Highly Conductive Porous Zirconium-Based Metal-Organic Framework: Molecular Insight.

The water stable UiO-66(Zr)-(CO2H)2 MOF exhibits a superprotonic conductivity of 2.3×10(-3) u2005Su2009cm(-1) at 90u2009°C and 95u2009% relative humidity. Quasi-elastic neutron scattering measurements combined with aMS-EVB3 molecular dynamics simulations were able to probe individually the dynamics of both confined protons and water molecules and to further reveal that the proton transport is assisted by the formation of a hydrogen-bonded water network that spans from the tetrahedral to the octahedral cages of this MOF. This is the first joint experimental/modeling study that unambiguously elucidates the proton-conduction mechanism at the molecular level in a highly conductive MOF.

Molecular iodine adsorption within Hofmann-type structures M(L)[M'(CN)4] (M = Ni, Co; M' = Ni, Pd, Pt): impact of their composition.

A series of thermally stable Hofmann-type clathrate structures with the general formula M(pz)[M(CN)4], where M and M are bivalent metal ions M(II) = Ni(II), Co(II), M(II) = Ni(II), Pd(II), Pt(II), and pz is the pyrazine bidentate ligand, was synthesized and investigated for the efficient entrapment of iodine (I2) in solution and in the gas phase. Iodine-containing clathrates thus prepared were analysed to determine the saturation capacity, thermal stability, guest-induced structural changes of the clathrates lattice and the nature of the confined iodine according to the chemical composition of the host structure. An efficient confinement of about 1 I2 per unit cell is observed for the series of clathrates with the Ni(II) and Pd(II) ions in the square planar position whatever the bivalent metal ion in the octahedral position. Specific responses in the lattice adjustment are detected for Co(II) in the octahedral and Pd(II) in the square planar positions.

Ultra stable oscillators dedicated for space applications: oscillator and quartz material behaviors vs radiation

This paper presents the first results obtained in the R&D study initiated by the CNES at the end of 2004. Numerous French experts have been gathered to determine and to tentatively understand the mechanisms responsible for the radiation sensitivity of quartz resonators and to correlate the results of various analyses in order to reduce or to anneal their susceptibilities

Characterization of unswept and swept quartz crystals for space applications

Unswept and vacuum-swept synthetic quartz crystals were investigated in order to determine the mechanisms responsible for the radiation sensitivity of this material. Results were obtained by means of infrared (IR) spectroscopy, dielectric relaxation spectroscopy (DRS), and thermoluminescence (TL). First, the effect of vacuum sweeping was clearly demonstrated in IR absorption by a significant decrease in the amount of hydroxyl ions and in DRS by the disappearance of the dielectric loss peak arising from the relaxation of alkali ions. Second, it was shown that swept quartz is less sensitive to irradiation than the unswept crystal. A sharp decrease in the TL sensitivity of the electrolyzed material was observed in the energy range corresponding to the recombination of alkaline-electronic defects. DRS results indicated that the dielectric signal is shifted toward a lower energy range for both types of crystals, suggesting that the irradiation greatly facilitates the relaxation of alkaline species by creating ...

A promising metal–organic framework (MOF), MIL-96(Al), for CO2 separation under humid conditions

The CO2 adsorption uptake and enthalpies with MIL-96(Al) were assessed in the presence of up to 40% relative humidity via both experiment and simulation. Interestingly at 10% relative humidity, the water equilibrated in the pores of this MOF proffers a significant increase in affinity for CO2 at 0.2 bar, which is associated with a limited decrease in capacity. This study suggests that at medium RH, water and CO2 are able to adsorb in different regions of the structure. Indeed, such behaviour is explained by the preferential adsorption of H2O in cavities containing more hydrophilic groups including Al(1)–H2Oterminal, Al(3′)–OHterminal and Al(3)–H2Oterminal while CO2 adsorbs in the remaining, less hydrophilic cavities containing μ2-OH groups. This highlights the interest of using materials with this variety in pore chemistry as one way forward for CO2 capture in the presence of contaminants such as water.

A phase transformable ultrastable titanium-carboxylate framework for photoconduction

Porous titanium oxide materials are attractive for energy-related applications. However, many suffer from poor stability and crystallinity. Here we present a robust nanoporous metal–organic framework (MOF), comprising a Ti12O15 oxocluster and a tetracarboxylate ligand, achieved through a scalable synthesis. This material undergoes an unusual irreversible thermally induced phase transformation that generates a highly crystalline porous product with an infinite inorganic moiety of a very high condensation degree. Preliminary photophysical experiments indicate that the product after phase transformation exhibits photoconductive behavior, highlighting the impact of inorganic unit dimensionality on the alteration of physical properties. Introduction of a conductive polymer into its pores leads to a significant increase of the charge separation lifetime under irradiation. Additionally, the inorganic unit of this Ti-MOF can be easily modified via doping with other metal elements. The combined advantages of this compound make it a promising functional scaffold for practical applications.Porous TiO2 materials are attractive for energy-related applications owing to their accessible active sites, but suffer from poor stability. Here the authors synthesize a highly stable and porous metal–organic framework containing polymeric 1D Ti–O subunits, which displays a high condensation degree and high photoconductivity.

Measurements of radiation induced defects in quartz material by Dielectric Relaxation Spectroscopy

This paper presents the continuation of the results obtained in the R&D study initiated by the Centre National dEtudes Spatiales (CNES) and presented during the last Frequency Control Symposium in 2006. This concerns more particularly the characterization of the defects in quartz material by using the Dielectric Relaxation Spectroscopy technique. Five different kinds (4 synthetic and one natural) of quartz material have been investigated. DRS measurements have been performed before and after three different irradiation doses (100 krad, 1 Mrad and 10 Mrad). The irradiation exposure yields in all cases the defects in the materials more instable. No dose level effect has been established. An annealing process (450degC during 24 hours) after irradiation cures to the damages produced in the quartz material by the irradiation dose.

Achieving Superprotonic Conduction with a 2D Fluorinated MOF

A hydrolytically stable metal-organic framework (MOF) material, named KAUST-7, was derived from a structural phase change of KAUST-7 upon exposure to conditions akin to protonic conduction (363 K/95% relative humidity). KAUST 7 exhibited a superprotonic conductivity as evidenced by the impedance spectroscopic measurement revealing an exceptional conductivity up to 2.0 × 10-2 S cm-1 at 363 K and under 95% RH, a performance maintained over 7 days. Ab initio molecular dynamics simulations suggested that the water-mediated proton transport mechanism is governed by water assisted reorganization of the H-bond network involving the fluorine moieties in KAUST-7 and the guest water molecules. The notable level of performances combined with a very good hydrolytic stability positions KAUST-7 as a prospective proton-exchange membrane alternative to the commercial benchmark Nafion. Furthermore, the remarkable RH sensitivity of KAUST-7 conductivity, substantially higher than previously reported MOFs, offers great opportunities for deployment as a humidity sensor.

Assessing the Potential of Sodium 1-Oxa-nido-dodecaborate NaB11H12O for Energy Storage

In the recent years, polyborate anions have been considered as possible candidates for energy. In aqueous solutions, they have been studied as either hydrogen carriers or anodic fuels. In the solid state (as an alkali salt), they have been seen as solid electrolytes. Herein, we focus on sodium 1-oxa-nido-dodecaborate NaB11H12O, a novel possible candidate for the aforementioned applications. The compound is soluble in water, and its stability depends on pH: under acidic conditions, it readily hydrolyzes while liberating hydrogen, and under alkaline conditions, it is stable, which is a feature searched for an anodic fuel. Over bulk platinum, gold, or silver electrode, oxidation takes place. The best performance has been noticed for the silver electrode. In the solid state, NaB11H12O shows Na+ conductivity at a high temperature of up to 150 °C. All of these properties are presented in detail, and hereafter they are discussed while giving indications of what have to be developed to open up more realistic prospectives for NaB11H12O in energy.