Removing sulfur dioxide (SO₂) from exhaust flue gases of fossil fuel power plants is an important issue given the toxicity of SO₂ and subsequent environmental problems. To address this issue, we successfully developed a new series of imide-linked covalent organic frameworks (COFs) that have high mesoporosity with large surface areas to support gas flowing through channels; furthermore, we incorporated 4-[(dimethylamino)methyl]aniline (DMMA) as the modulator to the imide-linked COF. We observed that the functionalized COFs serving as SO₂ adsorbents exhibit outstanding molar SO₂ sorption capacity, i.e., PI-COF-m10 record 6.30 mmol SO₂ g⁻¹ (40 wt%). To our knowledge, it is firstly reported COF as SO₂ sorbent to date. We also observed that the adsorbed SO₂ is completely desorbed in a short time period with remarkable reversibility. These results suggest that channel-wall functional engineering could be a facile and powerful strategy for developing mesoporous COFs for high-performance reproducible gas storage and separation.