A new three-dimensional twofold interpenetrated cadmium(II) metal-organic framework: synthesis, structure and photoluminescence properties.

Abstract

The design and synthesis of metal-organic frameworks (MOFs) have attracted much interest due to the aesthetics of their crystalline architectures and their potential applications as new functional materials. A new twofold interpenetrated three-dimensional (3D) MOF, namely, poly[[triaqua(μ4-(2R,2'R)-2,2'-{[1,4-phenylenebis(carbonyl)]bis(azanediyl)}dipropionato-κ7O1:O1,O1':O4:O4,O4',O4'')(μ3-(2R,2'R)-2,2'-{[1,4-phenylenebis(carbonyl)]bis(azanediyl)}dipropionato-κ3O1:O4:O4)dicadmium(II)] dihydrate], {[Cd2(C14H14N2O6)2(H2O)3]·2H2O}n, (I), has been synthesized by the reaction of Cd(CH3COO)2·2H2O with the synthesized ligand (2R,2'R)-2,2'-{[1,4-phenylenebis(carbonyl)]bis(azanediyl)}dipropionic acid (H2L). Single-crystal X-ray diffraction analysis reveals that the carboxylate groups from two crystallographically independent L2- dianions link the cadmium cations into a one-dimensional helical secondary building unit (SBU). The resulting SBUs are extended into a 3D metal-organic framework via the terephthalamide moiety of the ligand as a spacer. In the crystal, two independent MOFs interpenetrate each other, thus producing a twofold interpenetrated 3D architecture, which shows an unprecedented 2-nodal (7,9)-connected net with the point (Schläfli) symbol (37·46·58)(38·411·516·6). MOF (I) was further characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction and thermogravimetric analysis. The photoluminescence properties and UV-Vis absorption spectrum of (I) have also been investigated. The MOF exhibits enhanced fluorescence emission with a high photoluminescence quantum yield of 31.55% and a longer lifetime compared with free H2L.