A novel strategy for SO2 capture through multiple-site absorption in the anion of several azole-based ionic liquids is reported. An extremely high capacity of SO2 (> 3.5 mol/mol) and excellent reversibility (28 recycles) were achieved by tuning the interaction between the basic anion and acidic SO2. Spectroscopic investigations and quantum-mechanical calculations showed that such high SO2 capacity originates from the multiple sites of interaction between the anion and SO2. These tunable azole-based ionic liquids with multiple sites offer significant improvements over commonly used absorbents, indicating the promise for industrial applications in acid gas separation.