Tailoring the Pore Size and Chemistry of Ionic Ultramicroporous Polymers for Trace Sulfur Dioxide Capture with High Capacity and Selectivity

Here we demonstrate the deep removal of SO 2 with high uptake capacity (1.55 mmol g −1 ) and record SO 2 /CO 2 selectivity (>5000) at ultra‐low pressure of 0.002 bar, using ionic ultramicroporous polymers (IUPs) with high density of basic anions. The successful construction of uniform ultramicropores via polymerizing ionic monomers into IUPs enables the fully exploitation of the selective anionic sites. Notably, the aperture size and surface chemistry of IUPs can be finely tuned by adjusting the branched structure of ionic monomers, which play critical roles in excluding CH 4 and N 2 , as well as reducing the coadsorption of CO 2 . The swelling property of IUPs with adsorption of SO 2 contributed to the high SO 2 uptake capacity and high separation selectivity. Systematic investigations including static gas adsorption, dynamic breakthrough experiments, stability tests and modeling studies confirmed the efficient performance of IUPs for trace SO 2 capture.