Franck Millange

Hydrogen adsorption in the nanoporous metal-benzenedicarboxylate M(OH)(O2C–C6H4–CO2)(M = Al3+, Cr3+), MIL-53

Hydrogen adsorption has been studied in the nanoporous metal-benzenedicarboxylate M(OH)(O2C-C6H4-CO2) (M = Al3+, Cr3+); these solids show a hydrogen storage capacity of 3.8 and 3.1 wt.% respectively when loaded at 77 K under 1.6 MPa.

Comparative Study of Hydrogen Sulfide Adsorption in the MIL-53(Al, Cr, Fe), MIL-47(V), MIL-100(Cr), and MIL-101(Cr) Metal−Organic Frameworks at Room Temperature

Hydrogen sulfide gravimetric isotherm adsorption measurements were carried out on MIL-53(Al, Cr, Fe), MIL-47(V), MIL-100(Cr), and MIL-101(Cr) metal-organic frameworks (MOFs). A two-step adsorption mechanism related to a breathing effect was observed for MIL-53 terephthalate-based MOFs. Methane adsorption measurements highlighted the regenerability of MIL-53(Al, Cr) and MIL-47(V) MOFs after H(2)S treatment, whereas MIL-100 and MIL-101 CH(4) adsorption capacities were significantly decreased.

A new isoreticular class of metal-organic-frameworks with the MIL-88 topology

We report here a new family of isoreticular MOFs, comprising three larger analogues of the nanoporous metallocarboxylate MIL-88; these solids were synthesized using a controlled SBU approach and the three crystal structures were solved using an original simulation-assisted structure determination method in direct space.

Effect of the nature of the metal on the breathing steps in MOFs with dynamic frameworks

The thermal behaviour of the nanoporous iron(iii) terephthalate MIL-53 is in stark contrast to its chromium and aluminium analogues which show an expansion of the cell during dehydration; with iron, reversible dehydration occurs via evolution of the structure through a highly distorted metastable anhydrous phase to a more regular phase above 423 K in which pore volume remains approximately constant.

Synthesis, characterisation and luminescent properties of a new three-dimensional lanthanide trimesate: M((C6H3)–(CO2)3)(M = Y, Ln) or MIL-78

A new three-dimensional europium-doped yttrium 1,3,5-benzenetricarboxylate has been obtained under hydrothermal conditions. The structure of MIL-78(Y, Eu) or Y1−xEux((C6H3)–(CO2)3) (x ∼ 0.024) has been solved from X-ray powder diffraction data (a = 6.941(1) A, b = 14.700(2) A, c = 8.488(1) A, β = 107.73(1)°, V = 824.9(4) A3, space group C2/m (no. 12)). Its structure is built up from chains of edged-sharing eight-coordinated monocapped square antiprism polyhedra and trimesate anions, creating a three-dimensional structure. The same structure is formed by replacing yttrium by a rare-earth element. The thermal behaviour of MIL-78(Y, Eu) has been investigated using TGA and X-ray thermodiffractometry and indicates that MIL-78(Y, Eu) is stable up to 450 °C. The study of the optical properties of samples doped with different rare-earths reveals strong fluorescence under VUV radiation.

Synthesis, structure and properties of a three-dimensional porous rare-earth carboxylate MIL-83(Eu): Eu2(O2C-C10H14-CO2)3

A new three-dimensional rare-earth(III) dicarboxylate, MIL-83(Eu) or Eu2(O2C-C10H14-CO2)3, has been obtained under hydrothermal conditions from aqueous mixtures of europium nitrate and 1,3-adamantanedicarboxylic acid. Its three-dimensional structure consists of chains built up from face-sharing nine-coordinated rare-earth(III) polyhedra connected by the 1,3-adamantanedicarboxylate linkers, delimiting anhydrous porous channels. This structure is understood by comparison with the already known hybrid rare-earth(III)carboxylates. The thermal behavior of the solid has been investigated using TGA and X-ray thermodiffractometry and shows that the title solid is stable up to 300 °C. Finally, the study of the luminescence properties of the yttrium(III) form of MIL-83(Y/Eu) doped with europium(III) reveals a significant red-emission upon VUV radiation.

A time-resolved diffraction study of a window of stability in the synthesis of a copper carboxylate metal–organic framework

An in situ, time-resolved energy dispersive powder X-ray diffraction study of the solvothermal crystallisation of the copper(II) 4,4′,4″-benzene-1,3,5-triyl-tris(benzoate) metal–organic framework MOF-14 shows how reaction conditions must be carefully chosen to allow successful preparation of the material, since on prolonged heating at ≥120 °C the material irreversibly collapses into Cu2O under solvothermal conditions in less than 2 hours. This situation is in contrast to the related Cu(II)-containing metal–organic framework HKUST-1, which shows solvothermal stability over similar temperatures and reaction times. The kinetics of crystallisation of both MOFs are examined using a mathematical model proposed by Gualtieri for zeolite crystallisation: this allows separation of the nucleation and growth regimes to yield two rate constants. Arrhenius analysis gives activation energies that reveal in both cases the crystallisations are nucleation controlled. For MOF-14 we can additionally simulate its decomposition as dissolution of the first-formed interpenetrating structure: this produces a complete picture of the solvothermal stability of MOF-14 as nucleation-growth crystallisation, with some evidence of secondary nucleation, followed by dissolution.

A study of the manganites La0.5M0.5MnO3(M = Ca, Sr, Ba) prepared by hydrothermal synthesis

We present results of the first systematic study of the hydrothermal synthesis of the manganites La0.5M0.5MnO3 (M = Ca, Sr, Ba), and a detailed characterisation of the products using a number of experimental methods. All three materials can be produced as phase-pure, polycrystalline powders in one step from solutions of metal salts in aqueous potassium hydroxide solution at temperatures of 240 °C for M = Sr or Ba and 270 °C for M = Ca. Iodometric titration and Mn K-edge X-ray absorption near edge spectroscopy (XANES) combined with elemental analysis for metals confirms the average manganese oxidation state as 3.5 in each of the materials. Scanning electron microscopy shows that the materials are made up of cube-shaped particles 1 µm in dimension for La0.5Ba0.5MnO3, 10 µm on average for La0.5Sr0.5MnO3 and 20 µm for La0.5Ca0.5MnO3. La0.5Ba0.5MnO3 is shown to adopt an A-site ordered perovskite structure (tetragonal, P4/mmm, a = 3.9160(1) A, c = 7.8054(2) A); this is determined using powder neutron diffraction, thermogravimetric analysis and magnetisation measurements. High-resolution powder neutron diffraction data from La0.5Sr0.5MnO3 show that the material adopts a distorted perovskite structure (tetragonal, I4/mcm, a = 5.44778(40) A, c = 7.7353(10) A) similar to that previously reported for materials of the same composition prepared by a solid-state route. Hydrothermal La0.5Ca0.5MnO3 adopts an orthorhombic perovskite structure (Pnma, a = 5.410(1) A, b = 7.604(1) A, c = 5.443(2) A). Finally, we examine poorly ordered precursors of La0.5Ba0.5MnO3, formed prior to the crystallisation of the perovskite, using Mn K-edge X-ray absorption fine structure spectroscopy. This shows that at the earliest stage of the reaction the manganese is found in an oxidation state of 3.5 in edge-shared octahedral sites, consistent with the formation of a K0.5MnO2·nH2O, birnessite-like phase before the formation of the perovskite.

Synthesis, structure determination and magnetic behaviour of the first porous hybrid oxyfluorinated vanado(III)carboxylate: MIL-71 or VIII2(OH)2F2{O2C-C6H4-CO2}·H2O

A new type of three-dimensional vanadium(III) dicarboxylate, MIL-71 or VIII2(OH)2F2{O2C-C6H4-CO2}·H2O, has been obtained under hydrothermal conditions from aqueous mixtures of vanadium, 1,4-benzenedicarboxylic acid, and HF. MIL-71cal or VIV2O2F2{O2C-C6H4-CO2} is obtained by calcination of the parent compound in air at 250 °C. The three-dimensional structure of MIL-71 (S.G.: Cmmm; a = 21.4477(8) A, b = 7.1449(2) A, c = 3.8246(2) A, and Z = 2) consists of layers built from corner-sharing {VIIIO2(OH)2F2} octahedra connected by the terephthalate linkers. The role of fluorine in this structure is understood by comparison with the already known hybrid vanado(III)carboxylates. The thermal behavior of the two solids has been investigated using TGA and X-ray thermodiffractometry. Finally, magnetic measurements performed on both MIL-71 and MIL-71cal reveal a canted antiferromagnetic behavior with Neel temperatures below 20 K.

Separation of nucleoside monophosphates using preferential anion exchange intercalation in layered double hydroxides

We report the first example of selective intercalation of nucleoside monophosphates in a layered host material. The intercalated nucleoside monophosphates can then be quantitatively recovered from the inorganic host and so this opens up the possibility of using simple layered inorganic hosts as rapid, cost effective and recyclable materials for the purification and separation of complex biomolecules.