Selective Capture of Toxic Selenite Anions by Bismuth-based Metal-Organic Frameworks

Chemically durable and effective absorbent materials for selenite (SeO₃^2- ) remain highly desirable for contamination remediation. Now a bismuth-based metal-organic framework (Bi-MOF, CAU-17) was used as adsorbent to capture SeO₃^2- anions from aqueous solution with ultrahigh adsorption capacity of 255.3 mg g^-1 and fast kinetics. Furthermore, the adsorbent showed excellent selectivity for SeO₃^2- and was able to work steadily in a broad pH range of 4-11. Density functional theory (DFT) calculation, XANES modeling, and EXAFS fitting suggested that SeO₃^2- anions were immobilized by forming Bi-O-Se bonds (T-3 structural model) though splitting the O-Bi-O bond in the crystal structure, leading to a structural transformation of CAU-17 in the solid state.