Heterometal–organic frameworks as highly sensitive and highly selective luminescent probes to detect I− ions in aqueous solutions

Abstract

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.