Insights into the adsorption mechanism of the selenite ion in a cationic metal-organic - organic framework

The selenite ion widely exists in water streams and can impose significant impact on human health owing to its high toxicity at higher concentrations. Selective and efficient removal of the selenite ion is a highly desirable and challenging task because of the weak interaction of the selenite ion with general adsorbents. Herein, we report a cationic metal-organic framework (HIT-100) possessing triangular channels with excellent selectivity and reusability for selenite removal from water. The constructed HIT-100 exhibited a high adsorption capacity of 223 mg(-1) and ultrafast removal kinetics of similar to 91 % for the selenite ions within 10 min. An insightful adsorption mechanism was scrutinized and presented through the single-crystal structure of selenite-loaded HIT-100 and density functional theory (DFT) calculations to visualize the ion-capture site for accommodating selenite ion in the framework of HIT-100. Moreover, DFT calculations further shed light on the removal mechanism of selenite by revealing the stronger interactions between the selenite ion and HIT-100. In nutshell, this study provides a comprehensive molecular-level understanding of designing advanced porous materials for removing anionic pollutants from water.