Owing to their structural designability and tuneable properties, supramolecular metal–organic complexes have recently emerged as promising candidates for the sensing and detection of molecules and anions. Herein, we synthesised three tripyrazolate-linked [M₆L₂] metallocages with the formulas [(bpyPd)₆L₂](NO₃)₆ (1), [(dmbpyPd)₆L₂](NO₃)₆ (2), and [(phenPd)₆L₂](NO₃)₆ (3) (H₃L = tris(4-(5-(trifluoromethyl)-1H-pyrazol-3-yl)phenyl)amine, bpy = 2,2′-bipyridine, dmbpy = 4,4′-dimethylbipyridine, phen = 1,10-phenanthroline). Crystallography revealed that metal-directed coordination and the bidentate chelate behaviour of the ligand induced the self-assembly of supramolecular metal–organic cages. Notably, these cages were employed as turn-on fluorescence sensors for SO₂ and its derivative (HSO₃⁻) through a disassembly mechanism. Cages 1, 2, and 3 showed a highly selective and sensitive detection of HSO₃⁻ over other common anions in aqueous solutions and of SO₂ gas over other common gasses, with an excellent anti-interference ability. These metallocages were subsequently applied as sensors in environmental and biological samples. This study not only enriches the ongoing research on metal–organic supramolecular materials but also facilitates the future preparation of stimuli-responsive supramolecular coordination complexes.