A novel fluorescence phenomenon caused by amine induced ion-exchange between Cd²⁺ and Fe³⁺ ions

A 3D metal–organic framework {[Cd(5-Brp)(dpa)]·0.5DMF·H₂O}_n (1) was successfully synthesized and characterized, which markedly recognized iron ions under the induction of an amino group. With the concentration of Fe³⁺ increasing, the emission of 1 first declined, then enhanced with a red shift and was finally quenched, which was different from the reference compound [Cd(5-Brp)(bpp)(H₂O)]_n (2). This result drew our attention to amine induced ion-exchange. This peculiar phenomenon inspired us to construct an effective ion detector.