Two entangled Cd(II) MOFs of sebacic acid and bis(2-methyl-imidazole) ligands for selective sensing of Fe3+

Two new entangled Cd(II) MOFs, [Cd(Seb)(1,2-mbix)]center dot H2O (1) and [Cd(Seb)(1,4-mbix)] (2), based on sebacic acid (Seb) mixed with 1,2-bis(2-methyl-imidazol-1-ylmethyl)benzene (1,2-mbix) and 1,4-bis(2-methyl-imidazol-1-ylmethyl)benzene (1,4-mbix) ligands, have been hydrothermally prepared and characterized by single-crystal X-ray diffraction, IR and UV-Vis spectra, thermogravimetric and photoluminescent analyses. In 1, the Cd(II) centers are connected by Seb(2-) and 1,2-mbix into a 3D framework with a 4-fold interpenetrating dia topology. When 1,2-mbix was replaced by 1,4-mbix, a distinct structure for 2 was constructed, which is a 2D interpenetrating network containing both polyrotaxane and polycatenane features. This result demonstrates the important role of the two position isomeric bis(2-methyl-imidazole) ligands to their structural diversity. 1 and 2 dispay photoluminescence at 368 nm (lambda(ex)= 247 nm) and 401 nm (lambda(ex) = 306 nm), respectively. And both MOFs exhibit selective sensing toward Fe3+ through the luminescent quenching experiments.