MIL-96, a Porous Aluminum Trimesate 3D Structure Constructed from a Hexagonal Network of 18-Membered Rings and μ₃-Oxo-Centered Trinuclear Units

Abstract

A new aluminum trimesate Al12O(OH)18(H2O)3(Al2(OH)4)[btc]6.24H2O, denominated MIL-96, was synthesized under mild hydrothermal conditions (210 degrees C, 24 h) in the presence of 1,3,5-benzenetricarboxylic acid (trimesic acid or H3btc) in water. Hexagonal crystals, allowing a single-crystal XRD analysis, are grown from a mixture of trimethyl 1,3,5-benzenetricarboxylate (Me3btc), HF, and TEOS. The MIL-96 structure exhibits a three-dimensional (3D) framework containing isolated trinuclear mu3-oxo-bridged aluminum clusters and infinite chains of AlO4(OH)2 and AlO2(OH)4 octahedra forming a honeycomb lattice based on 18-membered rings. The two types of aluminum groups are connected to each other through the trimesate species, which induce corrugated chains of aluminum octahedra, linked via mu2-hydroxo bonds with the specific -cis-cis-trans- sequence. The 3D framework of MIL-96 reveals three types of cages. Two of them, centered at the special positions 0 0 0 and 2/3 1/3 1/4, have estimated pore volumes of 417 and 635 A3, respectively, and encapsulate free water molecules. The third one has a smaller pore volume and contains disordered aluminum octahedral species (Al(OH)6). The solid-state NMR characterization is consistent with crystal structure and elemental and thermal analyses. The four aluminum crystallographic sites are resolved by means of 27Al 3QMAS technique. This product is able to sorb both carbon dioxide and methane at room temperature (4.4 mmol.g(-1) for CO2 and 1.95 mmol.g(-1) for CH4 at 10 bar) and hydrogen at 77 K (1.91 wt % under 3 bar).

Multifunctional metal–organic frameworks: from academia to industrial applications

“…Hydrogen storage requires specific conditions: i) very high pressure gas; ii) liquid hydrogen; iii) intercalating of H 2 in metals; iv) porous materials. 75 The hydrogen storage capacity of several known families of MOFs as, for instance, IRMOFs, 76 MILs, 77 ZIFs, 78 NOTTs, 79 PCNs 80 and SNUs 81 have been extensively studied. Both small pore sizes (in order to allow the interaction of H 2 with the wall of the MOF) and the incorporation of coordinatively unsaturated metal centres (to bind H 2 ) are two important requirements to retain H 2 molecules.…”

On the Nature of the Adsorbed Hydrogen Phase in Microporous Metal−Organic Frameworks at Supercritical Temperatures

“…The first group of materials we studied is first-generation MOFs based on aromatic carboxylate ligands such as BDC (1, 26,27 and DOBDC (2,5-dihydroxy-1,4-benzenedicarboxylate). 28 We also have examined microporous coordination solids analogous to the MOFs where carboxylate ligands are replaced by structurally analogous functional nitrogen-based bridging ligands while essentially keeping the same specific surface area.…”

Poröse Materialien zur CO2‐Abtrennung und ‐Abscheidung – Entwicklung und Bewertung

“…[10,11,23] Einige MOFs zeigten eine gute selektive Adsorption von CO 2 gegenüber N 2 oder CH 4 aufgrund der Molekularsiebwirkung, [26][27][28][29] während die selektive CO 2 -Adsorption anderer MOFs auf der kinetischen Trennwirkung beruhte. [30,31] Die meisten weiteren Berichte über die selektive CO 2 -Adsorption von MOFs beziehen sich auf die Gleichgewichtsadsorption, bei der es auf unterschiedliche relative Wechselwirkungen zwischen den Adsorbaten (CO 2 , CH 4 oder N 2 ) und den Atomen des MOF ankommt.…”