Functionalization of Defective Zr Metal–Organic Frameworks for Water Decontamination: Mechanistic Insight into the Competitive Roles of -NH₂ and -SH Sites in Removal of As(III) Species

Abstract

Direct removal of trivalent arsenic, As(III), arsenite, or H 3 AsO 3 , is a great challenge in accessing clean sources of water. Different methodologies and materials were applied in this regard, but among them, direct removal of As(III) species using a metal− organic framework (MOF)-based adsorbent shows a great deal of potential. Although some studies were conducted on As(III) removal using MOFs, studies of functional groups are still quite rare. For this purpose, three novel functionalized defective Zr-MOFs, using UiO-66 [Zr 6 (OH) 4 O 4 (BDC) 6 , where BDC 2− = benzene-1,4-dicarboxylate], were fabricated to investigate the competitive or cooperative roles of the free -NH 2 and/or -SH site in the removal of As(III). UiO-66 was functionalized with monocarboxylate linkers, including glycine (Gly, NH 2 -CH 2 -COOH), cysteine [Cys, SH(CH 2 )-NH 2 (CH)-COOH], and mercaptopropionic acid [Mer, SH-(CH 2 ) 2 -COOH].