Manuela E. Medina

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.

One teflon®-like channelled nanoporous polymer with a chiral and new uninodal 4-connected net: sorption and catalytic properties

Zn(C17H8F6O4) is the first example of a fluoro-lined nanotube organo-inorganic 3D polymeric chiral structure, which possesses two different types of isolated channels, one of them being laid out with a double spiral of CF3-groups from the ligand molecule; the structure is a new uninodal 4-connected net that only exists when bent ligands connect the centres, and the compound exhibits selective sorption and catalytic chiral recognition properties.

A germanium zeotype with a three-dimensional net of interconnected 14-, 12- and 12-ring channels. Ge13O26(OH)4[C6N2H16]2(H2O)1.5

Ge(13)O(26)(OH)(4)[C(6)N(2)H(16)](2)(H(2)O)(1.5) is a novel germanium zeotype built up from a new type of SBU; the SBU-13 is formed from polyhedra distributed in three shells. Its open 3D framework has a three-dimensional system of intersecting channels, where the 14-ring channels are lined with OH(-) anions.

Ligand dependent topology changes in six zinc coordination polymers

Using 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb) and different pyridyl-containing additional ligands, six novel zinc coordination polymers have been obtained under hydrothermal conditions, and structurally characterized. The frame topology of the obtained compounds is discussed.

Two-Dimensional Hybrid Germanium Zeotype Formed by Selective Coordination of the trans-1,2-Diaminocyclohexane Isomer to the Ge Atom : Heterogeneous Acid-Base Bifunctional Catalyst

[C 6H 10(NH 2) 2Ge 3O 6] ICMM9 is a two-dimensional germanate in which the metallic atoms are covalently bonded to chelating diamines. Its layered structure having some similitude with that of the pyroxene mineral, presents a totally new topology with two 4-c nodes. The solvothermal synthesis reaction allows the separation in situ of the two 1,2-diaminocyclohexane isomers by selective coordination of the trans isomer to octahedral Ge atoms of the ICMM9 framework. This material behaves as an active and selective heterogeneous acid-base bifunctional catalyst.

Three novel indium MOFs derived from diphenic acid: synthesis, crystal structures and supramolecular chemistry†

Three In(III) MOFs based on diphenic acid and nitrogen-donor ancillary ligands were obtained as pure phases. Two of them have 1D chain structures, and the third forms 2D zig-zag layers. The different torsion angles adopted by the diphenic ligand along with the existence of several non-covalent interactions govern the crystal packing and determine the formation of a centrosymmetric one-dimensional compound (1) or a non-centrosymmetric helical chain-based compound (3). Reaction with 2,2′-bipyridyl under certain conditions leads also to the formation of two dimeric precursors (compounds 4 and 5). The topological study of all their nets is reported.

Cooperative directing effect of OH anions and polymerized DABCO cations in the formation of the Ge16O32(OH)−(C6H12N2H)+(C6H12N2)·1.125H2O zeotype

Ge16O32(OH)−(C6 H12N2H)+(C6H12 N2)·1.125H2O results from a simultaneous cation and anion templating effect during the zeotype formation; the structure shows a linear arrangement of the organic species along the channels as well as the existence of Ge4O8 tetramers with confined OH− anions in the middle of large germanium cages.

A new 2D germanate formed by selective coordination of the trans 1,2-diaminocyclohexane to Ge atoms

The disulfonate anions can be used as versatile ligands in the design of metallorganic frameworks, when they are used in combination with metals with variable coordination number. In this way, by using anthraquinone-2,6-disulfonate (AQDS) anions and rare-earth cations, ytterbium in this case, two different structural types have been obtained. The first of them, named layered rare-earth hydroxide, is a new type of crystalline material, very related to the LDH family of compounds. In the compound, cationic layers of ytterbium hydroxides are created, with molecular formula [Yb4 (OH)10(H2O)4]. These layers are separated by the AQDS anions, which are not coordinated to the rare-earth cations and neutralize the charge. The SO3 groups of the ligand are directed towards the sheets, being connected to them by H bonds. The second type is a 3D polymeric structure. Its molecular formula is [Yb(OH)(H2O)AQDS], with the sulfonate groups covalently coordinated to the metallic atoms. In this structure, a completely inorganic layer is formed, with the ytterbium atoms connected between them through hydroxyl groups, or by OSO bridges, giving rise to a (6,3) honeycomb layer. The layers are joined through the whole ligand molecules, giving rise to a binodal three dimensional network, threeand pentaconnected. The two types of materials have been tested as heterogeneous catalysts, showing excellent results in the reactions of oxidation of sulphides and hydrodesulphurization of tiophene.