A Zr-based metal-organic framework (Zr-MOF) which has free carbonyl groups is synthesized successfully through mix-ligand strategy. Subsequently, Tb is encapsulated into a Zr-MOF by postcoordinated modification. The Tb@Zr-MOF exhibits the characteristic emission of Tb because of efficient sensitization through antenna effects. The Tb@Zr-MOF is further developed as a novel "turn-on" fluorescent probe to detect fluoride ions in aqueous solution. The results show that Tb@Zr-MOF exhibits excellent selectivity, high stability, low detection limits, and good anti-interference for sensitizing fluoride ions. In addition, the possible sensing mechanism that the induced luminescence properties may be attributed to Lewis acid-base interactions is discussed.