An “off-on” Zn²⁺ and “on-off” Cu²⁺ fluorescent chemosensor C was designed and synthesized. The binding of C and Zn²⁺/Cu²⁺ is chemically reversible by the addition of EDTA disodium solution; moreover, the fluorescence emission signal of ZnC decreased with the addition of Cu²⁺, demonstrating that ZnC could detect Cu²⁺via metal displacement.