Continuous‐Flow Adsorption With Imidazolium‐Based Porous Organic Polymers Capable of Selective Removal of Chromate Contaminants From Water

Abstract N ‐rich triazine core functionalized imidazolium‐based porous organic polymers (iPOPs) are developed with exceptional oxoanions sequestration capabilities. Two iPOPs, iPOP‐1 and iPOP‐2, are synthesized via a facile Radziszewski multicomponent reaction and designed with multiple interaction sites for the electrostatically driven adsorption of toxic oxoanion, chromate (CrO ₄ ²⁻ ). The strategic incorporation of methylene spacers in iPOP‐1 resulted in a structurally flexible framework, enabling ultrafast capture kinetics with 99% removal of CrO ₄ ²⁻ from a 40 ppm aqueous solution within just 15 sec. In contrast, the structurally rigid iPOP‐2, lacking methylene spacer units, exhibits significantly reduced performance, achieving only 25% removal even after 300 seconds of contact time. Notably, iPOP‐1 maintained remarkable selectivity, effectively capturing CrO ₄ ²⁻ even in the presence of a 200‐fold excess of competing anions (Cl ⁻ , Br ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , H ₂ PO ₄ ⁻ ). To evaluate the practical application potential of iPOP‐1, continuous‐flow CrO ₄ ²⁻ sequestration experiments are conducted using both glass‐column chromatography and packed‐bed reactor configurations, successfully reducing CrO ₄ ²⁻ concentrations to below 40 ppb, well within World Health Organization (WHO) drinking water safety thresholds. Additionally, iPOP‐1 demonstrate excellent recyclability, maintaining high sequestration efficiency through five regeneration cycles. These results offer a robust, selective, and reusable approach for the efficient removal of hazardous oxoanions from industrial wastewater.