Metal –Organic Frameworks as Promising Adsorbents for Hexavalent Chromium Removal

Among the various waterborne contaminants, heavy metals are of particular concern due to their toxicity, environmental persistence, and potential for bioaccumulation. Although certain heavy metals are essential micronutrients at trace levels, their accumulation at higher concentrations poses severe health hazards. Hexavalent chromium (Cr(VI)) is a prominent example of such pollutants, frequently detected in industrial wastewater streams generated by leather tanning, electroplating, and pigment production. Its high mobility and solubility make it particularly hazardous. In contrast, trivalent chromium (Cr(III)), although less toxic, is only beneficial to human health in minimal quantities. To mitigate the environmental and health risks associated with Cr(VI), considerable attention has been directed toward the development of efficient removal strategies. Among them, Metal-Organic Frameworks (MOFs), as crystalline porous materials constructed from metal ions/clusters and organic linkers, have garnered increasing interest due to their high surface areas, tunable pore structures, and chemical versatility. These features render them highly suitable for targeted adsorption of Cr(VI) from aqueous environments. This study aims to provide a comprehensive overview of MOF structures and their physicochemical properties relevant to Cr(VI) adsorption performance, and mechanisms. Moreover, we investigate the adsorption properties of pristine MOFs (MIL-۱۰۰(Fe), GO-CS@MOF, Zr-MOF@polypyrrole, UiO-۶۶, Amino-functionalized MIL-۱۰۱ (Cr), ZIF-۸, ZIF-۸@ZIF-۸/polyacrylonitrile nanofibers), functionalized MOFs, and MOF-based composites for hexavalent chromium removal. MOFs, with their high surface area and adjustable porosity, show greater Cr(VI) adsorption than zeolites. However, zeolites, despite their structural stability, are less efficient due to the limited tunability of pore size and functional groups. Furthermore, this review investigates the adsorption performance of MOF materials compared with the other porous sorbents, especially zeolites. Finally, this review summarizes the challenges of the practical application of MOF-based adsorbents for chromium removal and future perspectives.

کلیدواژه ها:

Hexavalent Chromium (Cr(VI)) ، Metal –Organic Frameworks (MOFs) ، Water Purification ، Adsorptive Removal ، Industrial Wastewater