Thermally stable and robust gadolinium-based metal-organic framework: Synthesis, structure and heterogeneous catalytic O-arylation reaction

Abstract

Hydrothermal treatment of gadolinium nitrate and 2,6-naphthalenedicarboxylic acid (H2NDC) afforded a new metal-organic framework compound, {[Gd4(NDC)6(H2O)6]·2H2O}n(1). Compound 1 has been characterized by single-crystal X-ray crystallography, elemental analysis, FT-IR spectroscopy, therrmogravimetric analysis (TGA) and powder X-ray diffraction analysis. It is crystallized in the monoclinic system with the P21/n space group. Four crystallographically distinct Gd (III) centres are interconnected with each other through bridged carboxylato oxygen atoms and water molecules to form tetranuclear secondary building units, which are further connected through the carboxylato ligand and the network propagates along the crystallographic ac plane to form a 2D structure. Subsequent reinforcement from the remaining carboxylato oxygen atoms gives rise to a robust 3D framework structure. Thermogravimetric analysis demonstrates that compound 1 is fairly stable after dehydration under a nitrogen atmosphere.Notably, compound 1 is capable of catalyzing the O-arylation reaction efficiently between substituted phenols and bromoarene under heterogeneous conditions at 80 °C to afford unsymmetrical diarylethers.