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

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-κ7 O 1:O 1,O 1′:O 4:O 4,O 4′,O 4′′)(μ3-(2R,2′R)-2,2′-{[1,4-phenylenebis(carbonyl)]bis(azanediyl)}dipropionato-κ3 O 1:O 4:O 4)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 (H2 L). Single-crystal X-ray diffraction analysis reveals that the carboxylate groups from two crystallographically independent L 2− 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 H2 L.