A Flexible and Porous Ferrocene-Based Gallium MOF with MIL-53 Architecture

Abstract

A new gallium based metal-organic framework, denoted as Ga-MIL-53-FcDC, with the chemical formula [Ga(OH)(FeC12H8O4)] was synthesized using the ferrocene containing linker molecule 1,1’-ferrocenedicarboxylic acid (H2FcDC, FeC12H10O4). The porous nature of the compound could be confirmed by nitrogen sorption and a specific surface area of 270 m2/g was determined. The persistence of the ferrocene complex inside the structure was confirmed by Mössbauer-, EPR and UV/VIS-spectroscopy. Ga-MIL-53-FcDC shows structural flexibility depending on which guest molecule is located in the pores of the compound. The mechanism of structural flexibility was analyzed by means of powder X-ray diffraction adsorbing pyrazine or iodine. The flexibility of the crystal structure can be attributed to the torsion of the GaO6 octahedra in the IBU respective to each other and the torsion of the carboxylate groups of FcDC2− relative to the aromatic ring.