Deep eutectic solvents (DESs) are environmentally friendly solvents with excellent affinity to acidic gases and have broad application prospect in the field of SO₂ capture. In this work, four inexpensive DESs comprising of tetraethylammonium chloride (TEACl) and azoles (imidazole, pyrazole and tetrazole) were designed and prepared for highly efficient and reversible absorption of SO₂. Physical properties and chemical structures of the prepared DESs were characterized. High SO₂ capacity ranging from 0.756 to 1.251 g/g (3.610–7.231 mol/mol) were obtained at 20 °C and 1.0 bar. Surprisingly, owing to the accompanying phase transition, available SO₂ capacity of TEACl-Im (1:3) reaches 0.438 g/g (2.532 mol/mol) at 2000 ppm and 20 °C, which is the highest value reported so far. The absorption mechanism and phase transition were further investigated using FTIR, NMR and XRD, revealing the generation and precipitation of SO₂-imdazole adduct. In addition, no significant drop in SO₂ absorption capacity was observed after five successive absorption–desorption cycles. Overall, TEACl-Im (1:3) exhibits good absorption performance especially for low-concentration SO₂, providing potential alternatives for flue gas desulfurization.

深共熔溶剂（DESs）是一种对酸性气体具有优异亲和力的环保溶剂，在SO ₂捕集领域具有广阔的应用前景。在这项工作中，设计和制备了四种廉价的 DES，包括四乙基氯化铵 (TEACl) 和唑类（咪唑、吡唑和四唑），用于高效和可逆地吸收 SO ₂。表征了制备的DES的物理性质和化学结构。在 20 °C 和 1.0 bar 的条件下，获得了范围从 0.756 到 1.251 g/g（3.610–7.231 mol/mol）的高 SO _2容量。令人惊讶的是，由于伴随的相变，可用的 SO ₂在 2000 ppm 和 20 °C 时，TEACl-Im (1:3) 的容量达到 0.438 g/g (2.532 mol/mol)，这是迄今为止报道的最高值。利用FTIR、NMR和XRD进一步研究了吸收机理和相变，揭示了SO ₂ -咪唑加合物的生成和沉淀。此外，在连续五次吸收-解吸循环后，未观察到SO _{2吸收能力显着下降。}总体而言，TEACl-Im（1:3）表现出良好的吸收性能，尤其是对低浓度SO ₂，为烟气脱硫提供了潜在的替代方案。