Series of Cadmium(II) Coordination Polymers Based on a Versatile Multi-N-Donor Tecton or Mixed Carboxylate Ligands: Synthesis, Structure, and Selectively Sensing Property.

Five Cd(II) metal-organic frameworks (MOFs), [Cd(HL)] (), [Cd(HL)(HO)] (), [Cd(HL)(obda)] (), [Cd(HL)(ohmbda)(DMA)(HO)] (), and [Cd(HL)(btc)(HO)]·3HO (), were prepared by reactions of Cd(NO)·4HO with 1-(1-imidazol-4-yl)-4-(4-tetrazol-5-yl)benzene (HL) or mixed carboxylate ancillary ligands of 1,2-benzenedicarboxylic acid (Hobda), 5-hydroxy-1,3-benzenedicarboxylic acid (Hohmbda), and 1,3,5-benzenetricarboxylic acid (Hbtc), respectively. Their structures have been characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy (IR), thermogravimetric analysis, and powder X-ray diffraction. Compounds and are supramolecular isomeric frameworks without consideration of the solvent molecules. Complex exhibits a binodal (3, 5)-connected two-dimensional (2D) layer structure with the point (Schläfli) symbol of (5·6)(5·6·7), while complex shows a 2D + 2D → 3D (three-dimensional) framework. Complex is a (3, 5, 6)-connected tetranodal 3D net with the point (Schläfli) symbol of (4·8)(4·6·8)(4·6)(4·6·8). Compound is a (3, 3, 8)-connected trinodal 3D net with the point (Schläfli) symbol based on a binuclear [CdNO] subunit, while is a 2-nodal (3, 4)-connected 2D VO-type network based on [CdN(COO)] SBU. The studies of molecular sensing properties show that the luminescent MOFs can be employed as fluorescent sensors for the detection of Fe and nitro compounds. Compound and exhibit quenching responses for Fe in dimethylformamide solution with detection limits of 2.3 × 10 and 8.6 × 10 M, respectively. Meanwhile, compound can sense 4-nitrophenol with a detection limit as low as 5.75 × 10 M.