UiO-66 metal–organic frameworks in water treatment: A critical review

Metal-organic frameworks (MOFs) have recently achieved much attention to eliminating toxic pollutants because of their attractive attributes, including large specific surface area, ultra-high porosity, abundant active adsorption sites, tunable surface chemistry, well-controlled pore size distribution, and strong host–guest interactions. Among the many developed MOFs, the Zr-based MOFs, particularly the UiO-66 family, are considered extremely attractive for wastewater treatment applications. The fascinating properties of UiO-66 such as high thermal stability, superior chemical resistance towards several solvents, including benzene, acetone, different alcohols, dimethylformamide, acidic and basic solution, excellent chemical stability against various conditions such as air, water, and chloroform, and exceptional resistance to high external pressure, mainly due to strong Zr-O bond and high coordination number between the Zr clusters and organic ligands have led to numerous potential applications in wastewater treatment. This review primarily focuses on the latest efforts in applying UiO-66 MOFs as superior water-stable MOFs for efficient removal (adsorption/separation and degradation/reduction) of various water pollutants, including organic dyes, heavy metal ions, pharmaceuticals and personal care products, phosphate, and fluoride. The possible adsorption/separation and degradation/reduction mechanisms for removing water pollutants by UiO-66 and its modified derivatives are fully addressed. Thus, the review is expected to provide guidance and stimulate researchers to carefully investigate the real applications of UiO-66 MOFs in water and wastewater treatment applications.