Stable Porous Organic Polymers Used for Reversible Adsorption and Efficient Separation of Trace SO₂

The development of porous solid adsorbents for selective adsorption and separation of SO₂ has attracted much attention recently. Herein, we design porous organic polymers (POPs) decorated with pyridine ligands as building units (POP-Py) through a radical polymerization of the 2,5-divinylpyridine (v-Py) monomer. Due to its high BET surface area, nanoporosity, and excellent stability, the prepared POP-Py can be used for reversible adsorption and efficient separation of SO₂. The POP-Py possesses a SO₂ capacity of 10.8 mmol g^-1 at 298 K and 1.0 bar, which can be well retained after 6 recycles, showing an excellent reversible adsorption capacity. The POP-Py also shows superior separation performance for SO₂ from a ternary SO₂/CO₂/N₂ mixture (0.17/15/84.83v%), giving a breakthrough time and a saturated SO₂ capacity at 178 min g^-1 and 0.4 mmol g^-1. The retention time was well maintained even under high moisture conditions, confirming its superior water resistance. Furthermore, when other vinyl-functionalized organic ligand monomers (bipyridine, pyrimidine, and pyrazine) were employed for radical polymerization, all of the resultant porous organic ligand polymers (POP-BPy, POP-PyI, and POP-PyA) exhibited superior performance for reversible adsorption and efficient separation of SO₂. The combined features of reversible adsorption, efficient separation, and water resistance are important for the industrial applications of these materials as SO₂ adsorbents.