We report the inaugural experimental investigation of covalent organic frameworks (COFs) to address the formidable challenge of SO2 detection. Specifically, an imineâfunctionalized COF (SonoCOFâ9) demonstrated a modest and reversible SO2 sorption of 3.5 mmol gâ1 at 1 bar and 298 K. At 0.1 bar (and 298 K), the total SO2 uptake reached 0.91 mmol gâ1 with excellent reversibility for at least 50 adsorptionâdesorption cycles. An isosteric enthalpy of adsorption (ÎHads) for SO2 equaled â42.3 kJ molâ1, indicating a relatively strong interaction of SO2 molecules with the COF material. Also, molecular dynamics simulations and MĂžllerâPlesset perturbation theory calculations showed the interaction of SO2 with Ï density of the rings and lone pairs of the N atoms of SonoCOFâ9. The combination of experimental data and theoretical calculations corroborated the potential use of this COF for the selective detection and sensing of SO2 at the subâppm level (0.0064 ppm of SO2).