Influence of Extra-framework Cations on SO2 Adsorption and Fluorescence Detection in SSZ-13 Zeolites

Herein, SSZ-13 zeolites exchanged with Na+-, K+-, and Ce3+ were investigated to determine how cation identity regulates sulfur dioxide adsorption (SO2) and optical response. The three materials exhibited reversible SO2 adsorption, with similar capacities of 5.48–5.59 mmol g–1 at 25 °C and 1 bar, indicating that the total uptake is mainly governed by micropore filling. In contrast, their fluorescence responses were strongly cation dependent. Na-SSZ-13 and K-SSZ-13 showed substantial SO2-induced quenching, whereas Ce-SSZ-13 displayed almost complete quenching of its Ce3+-centered near-UV emission. Ce-SSZ-13 also showed SO2-induced quenching with partial fluorescence recovery, a response under SO2/CO2 co-exposure, and LODs estimated from suspension-phase titrations of 9.26 mg L–1 in THF and 10.37 mg L–1 in toluene, identifying it as a proof-of-concept fluorescent SO2-responsive material.