Multifunctional luminescence sensing and white light adjustment of lanthanide metal-organic frameworks constructed from the flexible cyclotriphosphazene-derived hexacarboxylic acid ligand.

Considering that cyclotriphosphazene polycarboxylic acid is a kind of organic ligands with fantastic structures and performances as well as the unique luminescence characteristics of rare earth ions, a series of the porous lanthanide metal-organic frameworks (Ln-MOFs) (CH3)2NH2[Ln3(HCPCP)1.5(CH3COO)]‧6DMA (Ln = Ce (1), Sm (2), Eu (3), Tb (4), HCPCP = hexa (4-carboxy-phenoxy) cyclotriphosphazene, DMA = N,N-dimethylacetamide) were synthesized with novel topological network structures. Compound 4 displayed a sensitive recognition of -NO2, and had fluorescence quenching phenomenon for seven kinds of nitro aromatic compounds (NACs). In particular, it showed the best fluorescence response to 2,4,6-trinitrophenol (TNP) and 2,4-dinitrophenol (DNP), which the KSV were 2.86×105 M-1 and 8.21×104 M-1, and the limit of detection (LOD) were 0.20 μM and 0.71 μM, respectively. At the same time, we successfully doped different concentrations of Eu3+ into compound 4 to obtain a series of doped Ln-MOFs materials x%Eu3+@4 (x = 0.5, 2.5, 5, 7.5, 10, 15 and 20). With the increase of Eu3+ doping ratios, the characteristic peaks of Tb3+ and Eu3+ changed regularly, and the energy transfer from Tb3+ to Eu3+ ions occurred. By changing the excitation wavelength of samples with different Eu3+ doping concentrations, a higher quality white light emitting material 7.5%Eu3+@4 (λex = 340 nm) was finally obtained, with a CIE coordinate of (0.3268, 0.3212).