Achieving Sub‐ppm Sensitivity in SO2 Detection with a Chemically Stable Covalent Organic Framework

We report the inaugural experimental investigation of covalent organic frameworks (COFs) to address the formidable challenge of SO₂ detection. Specifically, an imine-functionalized COF (SonoCOF-9) demonstrated a modest and reversible SO₂ sorption of 3.5 mmol g^-1 at 1 bar and 298 K. At 0.1 bar (and 298 K), the total SO₂ uptake reached 0.91 mmol g^-1 with excellent reversibility for at least 50 adsorption-desorption cycles. An isosteric enthalpy of adsorption (ΔH_ads) for SO₂ equaled -42.3 kJ mol^-1, indicating a relatively strong interaction of SO₂ molecules with the COF material. Also, molecular dynamics simulations and Møller-Plesset perturbation theory calculations showed the interaction of SO₂ with π density of the rings and lone pairs of the N atoms of SonoCOF-9. 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 sub-ppm level (0.0064 ppm of SO₂).