Functionalization of UiO-66-NH2 with rhodanine via amidation: Towarding a robust adsorbent with dual coordination sites for selective capture of Ag(I) from wastewater.

• UiO-66-NH 2 -Rd adsorbent with dual coordination sites was designed and synthesized. • UiO-66-NH 2 -Rd exhibited high capacity and outstanding selectivity for Ag(I) capture. • Amide bonds endowed UiO-66-NH 2 -Rd with excellent recyclability and durability. • Specific adsorption site was identified by theoretical and experimental studies. Selective capture and maximum recovery of Ag(I) from wastewater is of great significance for a sustainable future. In this work, novel rhodanine (Rd)-functionalized UiO-66 adsorbents (i.e., UiO-66-Rd and UiO-66-NH 2 -Rd) were designed and synthesized. Different from previously reported UiO-66 derivatives with single metal coordination sites, the as-synthesized UiO-66-Rd and UiO-66-NH 2 -Rd have dual coordination sites, resulting in higher capacity and outstanding selectivity. The maximum capacities of UiO-66-Rd and UiO-66-NH 2 -Rd are 112 and 163 mg·g−1, nearly 5.6 and 8.2 times higher than that of UiO-66, respectively. Impressively, the maximum selectivity coefficient of UiO-66-NH 2 -Rd is approximately 1795 and 1173 folds higher than that of UiO-66 and UiO-66-NH 2. The experimental characterizations and theoretical calculations indicate that the Rd-induced enhancement in the adsorptivity and selectivity are mainly attributed to the dual coordination sites (i.e., C S and C S bonds), which collectively coordinate with Ag(I) in the form of Ag mono-coordinated with S. Compared with the UiO-66-Rd, UiO-66-NH 2 -Rd possesses excellent recyclability and durability due to the vital role of amide bonds generated from NH 2 group in the functionalization of UiO-66 with Rd. Furthermore, UiO-66-NH 2 -Rd can almost completely remove Ag(I) from the actual wastewater with complex matrix, satisfying the national integrated wastewater discharge standard and industrial wastewater emission standard, highlighting a great potential of practical application. [ABSTRACT FROM AUTHOR]