Series d-f Heteronuclear Metal-Organic Frameworks: Color Tunability and Luminescent Probe with Switchable Properties

A series of five unique df heteronuclear luminescent metal-organic frameworks (MOFs) in an entangled polyrotaxane array and the light-harvesting block homonuclear zinc compound have been isolated successfully and characterized. The series of isostructural polymers feature 3,4-connected (4.8(2))(4.8(3).9(2))(6.8.9)(2)(6.9(2))(8(3)) topology and high stability, exhibiting diverse void spaces. By taking advantage of the isostructural MOFs 2 and 3, the intensities of red and green emissions can be modulated by adjusting the ratios of Eu-III and Tb-III ions correspondingly, and white-light emission can be generated by a combination of different doped Tb-III and Eu-III concentrations. The Tb-Zn-based framework {[Tb3Zn6(bipy(2))(2)(Hmimda)(7) (H2O)(3)]center dot 5H(2)O}(n) (3; H(3)mimda = 2-methyl-1-H-imidazole-4,5-dicarboxylic acid and bipy = 4,4'-bipyridine) can detect trace Mg-II ion with relatively high sensitivity and selectivity. Dehydrated MOF 3a shows a remarkable emission quenching effect through the introduction of I-2 solids. Further investigation indicates that it exhibits turn on/off switchable properties for small solvent molecules or heavy-metal ions. Steady/transient-state near-IR luminescence properties for MOFs 1, 4, and 5 were investigated under visible-light excitation.