Hybrid open frameworks (MIL-n). Part 5 Synthesis and crystal structure of MIL-9: a new three-dimensional ferrimagnetic cobalt(II) carboxylate with a two-dimensional array of edge-sharing Co octahedra with 12-membered rings

A Rationale for the Large Breathing of the Porous Aluminum Terephthalate (MIL‐53) Upon Hydration

“…NMR study: The three forms, that is MIL-53 as (Al), the calcined MIL-53 ht (Al), and the monohydrate MIL-53 lt (Al), were subjected to 1 H, 13 C, and 27 Al NMR measurements. For clarity, a 2q offset is applied for each pattern, which were collected at intervals of 20 8C, except for the last two, which were collected 100 8C apart.…”

“…From bottom to top for each series: first and second, spectra recorded after sample preparation according to Procedure 1 at t = 0 (ht form) and 45 min (approximately 30 % hydrated, as can be roughly estimated from the spectra); third and fourth, spectra recorded after sample preparation according to Procedure 2, at ™t = 0∫ (about 50 % hydration has already occurred) and 2 h (lt, fully hydrated form). For the sake of clarity, the 13 C spectra plotted in this figure are simulations. In the 27 Al spectra of both intermediate hydrated states, the simulated component corresponding to the wet averaged structure is shown to indicate the dependence of the average quadrupolar interaction on the water content.…”

“…At room temperature, the solid reversibly absorbs water in its tunnels, causing a very large breathing effect and shrinkage of the pores. Analysis of the hydration process by solid-state NMR ( 1 H, 13 C, 27 Al) has clearly indicated that the trapped water molecules interact with the carboxylate groups through hydrogen bonds, but do not affect the hydroxyl species bridging the aluminum atoms. The hydrogen bonds between water and the oxygen atoms of the framework are responsible for the contraction of the rhombic channels.…”

“…A combination of 27 Al, 13 C, and 1 H NMR spectrometries has allowed analysis of the breathing effect that accompanies the hydration/dehydration processes. This has revealed that hydrogen-bonding interactions between water molecules trapped within the channels and the carboxylate groups of the BDC linkers are responsible for the dynamic switching of the structure.…”

Effect of Mixing of Metal Cations on the Topology of Metal Oxide Networks

“…[18] Comparison of these compounds to known nickel succinates indicates that the phases that occur at lower temperatures tend to be isostructural (consistent with other Co II and Ni II coordination polymers) [19,20] while the hydrothermal phases differ significantly. In particular conditions used for synthesizing the cobalt structure MIL-9, [21][22][23] which exhibits a 2D array of metal octahedra, gave a remarkable 3D inorganic framework when applied to nickel. [12] These observations suggest that a hydrothermal study of the Co/Ni ratio as sole reaction variable may improve our understanding of the relationship between these two systems.…”