Multifunctional Zn-Ln (Ln = Eu and Tb) heterometallic metal-organic frameworks with highly efficient I2 capture, dye adsorption, luminescence sensing and white-light emission

A new family of isostructural 3d-4f heterometallic metal-organic frameworks (HMOFs), [Zn3EuxTb2-x(TZI)(4)(DMA)(5)(H2O)(3)]center dot 4DMA [x = 0 (1), 0.3 (2), 0.6 (3), 0.9 (4), 1 (5), 1.2 (6), 1.5 (7), 1.8 (8), 2 (9)], has been synthesized using the 5-(4-(tetrazol-5-yl) phenyl)isophthalic acid (H(3)TZI) ligand, LnIII ions and Zn-II ions under solvothermal conditions. All HMOFs exhibit a (3,3,4,5,5)-connected 6(3).6(3)(4(2).6(2).8(2))(4.6(5).8) (4.6(6).8(3)) topology, which features three different types of motifs: one is a mononuclear ZnII ion and the other two motifs are binuclear [Zn(COO)(3)Ln] clusters. The adsorption experiments indicate that Zn3Tb2 (1) could efficiently remove almost all I-2 from cyclohexane solution after 12 h and also showed better adsorption towards neutral red (NR) dye (adsorption: only the Zn3Tb2 (1) was taken as one representative). Simultaneously, the luminescence sensing showed that Zn3Tb2 (1) and Zn3Eu2 (9) have excellent response and sensitivity towards pollutants such as Fe3+ ions and 2,4,6-trinitrophenol (TNP) with high selectivity and a fairly low limit of detection through luminescence quenching effect. Moreover, seven trimetallicdoped HMOFs 2-8 analogues of Zn(3)Ln(2) (single) HMOFs were designed and prepared, showing different changes of luminescent color. More interestingly, Zn3Eu1.5Tb0.5 (7) with white-light emission was fabricated by doping relative concentrations of Eu3+ and Tb3+ ions. To the best of our knowledge, Zn(3)Eu(1.5)Tb(0.)5 (7) represents a novel kind of heterometallic Zn(3)Ln(2) HMOFs with white-light emission. It could be deduced that the excellent characteristics, namely strong typical luminescence emission of ZnII and LnIII ions, microporous channels, active open metal sites (tetra-coordinated Zn-II- metal sites), and uncoordinated carboxylate O atoms and uncoordinated tetrazolate N atoms, made the above HMOFs an ideal platform for adsorption, luminescence sensing, and white-light emission. More significantly, these HMOFs are the first reported Zn-Ln heterometallic materials with the H(3)TZI ligand.

Automated summary

A new family of isostructural 3d-4f heterometallic metal-organic frameworks has been synthesized, showing excellent adsorption and luminescence sensing properties. Among them, Zn3Eu1.5Tb0.5 HMOFs exhibit white-light emission.