A highly phosphorescent Ir(III) complex, containing a dimesitylboryl group in its coordinative phenylpyridine ligand, exhibited a phosphorescence colorimetric and ratiometric fluoride ion-selective sensing behavior and enabled facile signal purification through time-gated acquisition. Poly(methylmethacrylate) films doped with the Ir(III) complex were used to successfully detect fluoride ion in aqueous media.