Two cationic heterometal-organic frameworks (Eu-Zn (1·NO₃⁻) and Tb-Zn (2·NO₃⁻)) with NO3(-) counter-anions in the channels are structurally and luminously characterized. Both of them can serve as highly sensitive and highly selective luminescent probes for detecting I(-) ions in aqueous solutions. In particular, 2·NO₃⁻ can selectively and reversibly detect I(-) with a fast response time of just 10 s and an extremely low detection limit of 0.001 ppm. Mechanism studies reveal that I(-) is quickly oxidized to form I₃⁻with the help of 1·NO₃⁻ or 2·NO₃⁻, leading to luminescence quenching. This represents the first report of MOF-based luminescent probes for the detection of I(-) in aqueous solutions.

Two novel Dy-Cu MOFs were structurally and magnetically characterized. The results reveal that it is the first example of anion-induced change of structure interpenetration and magnetic properties in 3d-4f MOFs.

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