Hajjar R.,French National Center for Scientific Research |
Volkringer C.,Porous Solids Group and Tectospin Group |
Loiseau T.,Porous Solids Group and Tectospin Group |
Guillou N.,Porous Solids Group and Tectospin Group |
And 7 more authors.
Chemistry of Materials | Year: 2011
Two gallium carboxylates of MOF-type have been hydrothermally synthesized (210 'C) by using 1,2,4,5-benzenetetracarboxylate (Ga4(OH) 8[C10O8H2]'5-5.6H2O or MIL-120) or 1,2,4-benzenetricarboxylate (Ga2(OH)4[C 9O6H4] or MIL-124) as linkers. The structures of both compounds solved from XRD analysis, revealed two independent crystallographic sites for the gallium atoms, which are connected to each other through -2-hydroxo edge, generating zigzag chains with a cis?trans mode. The inorganic ribbons are linked to each other via all the carboxylate functions of the pyromellitate ligand to form a 3D framework (MIL-120) or two of the carboxylate arms of the trimellitate ligand to form a 2D structure (MIL-124). For the latter, one of the carboxylate arms is not bonded to the gallium centers, resulting in the layered aspect of the final structure. Solid-state NMR using the slow-CTMAS method has been successfully implemented for the determination of the gallium site parameters for MIL-120, allowing more resolved spectra at moderate magnetic fileds than at very high field. Only one gallium site is visible for MIL-124, indicating a dynamic disorder resulting from the nonfully connected carboxylate species of the trimellitate ligand. © 2010 American Chemical Society. Source