Two-dimensional Cd(ii) coordination polymer encapsulated by Tb as a reversible luminescent probe for Fe.

A two-dimensional luminescent cadmium(ii) coordination polymer, [Cd(modbc)] (Cd-P); modbc = 2-methyl-6-oxygen-1,6-dihydro-3,4'-bipyridine-5-carbonitrile, was successfully synthesized by a solvothermal reaction and fully characterized. Cd-P exhibited excellent luminescence emission, and detected Cu, Co, Fe, Hg, Ni and Fe ions with high sensitivity and showed good anti-interference performance. After encapsulation of Tb ions in Cd-P, the as-obtained fluorescent functionalized Tb@Cd-P maintained distinct chemical stabilities in different pHs and metal salt solutions. Subsequently, we explored the potential application of Tb@Cd-P as a probe for Fe ions. A new and convenient method for individual identification of Fe ions by the combination of Cd-P and Tb@Cd-P was successfully established. A possible sensing mechanism is discussed in detail.