Figure 6.

(a) Diagram of the Ce⁴⁺/Tb³⁺ based Ln-MOF for sensing SO₂ and sulfite via the turn-on of luminescence induced by energy transfer (ET) triggered by redox-reaction. (b) The luminescence of Ln-MOF increases with the concentration (0, 0.05, 0.1, 0.2, 0.5, 0.8, 1, 5, 20, 50, 100, 150, 200, and 300 mM) of SO₃²⁻; the inset shows the linear relationship of the luminescence intensity of Ce-PA-Tb at 545 nm with the concentration of SO₃²⁻. Adapted from [53].