Synthesis and structural characterization of metal-organic frameworks with the mellitate linker M2(OH)2[C12O12H2]•2H2O (M = Al, Ga, In) MIL-116

A new series of isostructural MOF-type carboxylates called MIL-116 (M-2(OH)(2)[C12O12H2]center dot 2H(2)O), was synthesized from the combination of mellitic acid and trivalent p cations M = Al3+, Ga3+ or In3+. Their structures were analyzed either by single-crystal microdiffraction using the synchrotron radiation beamline (ID13 station at ESRF, Grenoble) or solved from powder X-ray diffraction. The 3D hybrid framework is built up from the connection of infinite straight chains of metal-centered octahedra sharing trans corners linked to each other through the mellitate ligands. Here the ligand acts as octadentate linker with four of the carboxylic groups involved in the M-O-C bondings. The two other carboxylate arms remain non-bonded under their protonated form. This represents a rare case of the occurrence of both non-bonding and bonding organic functionalities in a MOF-type solid. Within the tunnels are located water species that interact with the non-coordinated -COOH groups pointing towards the channel. (C) 2013 Elsevier Masson SAS. All rights reserved.