Synthesis of two new Cd(II)-MOFs based on different secondary building units with highly selective gas sorption for CO2/CH4 and luminescent sensor for Fe3+ and Cr2O72− ions

Two new metal-organic frameworks (MOFs), [Cd4(L1)2(H2O)4]·3(H2O)·DMA (1) and (Me2NH2)2[Cd2(L1)(L2)]·[solvent] (2) (DMA ​= ​N,N-Dimethylacetamide) were successfully synthesized via the solvothermal reaction procedure by a rigid V-shaped N-heterocyclic 2,6-di(2′,5′-dicarboxylatephenyl)pyridine (H4L1) ligand, terephthalic acid (H2L2) and Cd(II) ions in this work. Structural analyses show that the carboxylate groups of L14− adopt different coordination modes with Cd(II) ions in 1 and 2, which form the different secondary building units (SBUs) to yield two new different 3D MOFs. Compared with 1, the introduction of the terephthalic acid (H2L2) produces 2 with potential solvent area volume 51.9% (2608.5 ​Å3, per unit cell volume 5029.2 ​Å3). The gas sorption and luminescent experiments of 2 show the high selectivity of CO2 over CH4 and selective sensitivity for Fe3+ and Cr2O72− ions in aqueous solution. The experiment results offer a facile route for designing and yielding new potential multi-functional MOF materials in gas sorption and detecting Fe3+ and Cr2O72− ions.