3d–4f Metal–Organic Framework with Dual Luminescent Centers That Efficiently Discriminates the Isomer and Homologues of Small Organic Molecules

A 3d–4f luminescent metal–organic
framework (MOF), [Tb2(Cu8I8)­(C12H8NO2)6(H2O)4]·5C4H8O2 (4), and three analogues {[La2(Cu8I8)­(C12H8NO2)6(C4H8O2)2(H2O)2]·3C4H8O2·2H2O (1), [Ce2(Cu8I8)­(C12H8NO2)6(H2O)4]·5C4H8O2 (2), and [Eu2(Cu8I8)­(C12H8NO2)6(H2O)4]·5C4H8O2 (3)},
were self-assembled from copper­(I) halide clusters and lanthanide
metal ions with an organic linker [3-(pyridin-4-yl)­benzoic acid] under
solvothermal conditions. Compound 4 with high quantum
yield (Φ = 68%) exhibits reversible luminescence behavior, accompanying
the removal and recovery of guest molecules (1,4-dioxane). Because
of the unique porous structure and dual luminescent centers of compound 4, it can efficiently differentiate benzene series with different
sizes and provide readouts in corresponding optical signals. Furthermore,
it also can unambiguously discriminate the isomers, homologues, and
other small molecules with similar structural motifs from one another.
The luminescent color of the MOF sensor in different guest solvents
has obvious changes that can be clearly distinguished by the naked
eye. This multicolor luminescence originates from emissions of the
dual luminescent centers, and the emissions have shifted, enhanced,
weakened, or quenched to different degrees.