Precise Construction of Nitrogen-Enriched Porous Ionic Polymers as Highly Efficient Sulfur Dioxide Adsorbent.

Porous ionic polymers with unique features have exhibited high performance in various applications. However, the fabrication of functional porous ionic polymers with custom functionality and porosity for efficient removal of low-concentration SO2 remains challenging. Herein, a novel nitrogen-enriched porous ionic polymer NH2Py-PIP is prepared featuring high-content nitrogen sites (15.9 wt.%), adequate ionic sites (1.22 mmol g-1), and a hierarchical porous structure. The proposed construction pathway relies on a tailored nitrogen-functionalized cross-linker NH2Py, which effectively introduces abundant functional sites and improves the porosity of porous ionic polymers. NH2Py-PIP with a well-engineered SO2-affinity environment achieves excellent SO2/CO2 selectivity (1165) and high SO2 adsorption capacity (1.13 mmol g-1 at 0.002 bar), as well as enables highly efficient and reversible dynamic separation performance. Modeling studies further elucidate that the nitrogen sites and bromide anions collaboratively promote preferential adsorption of SO2. The unique design in this work provides new insights into constructing functional porous ionic polymers for high-efficiency separations.