UiO-66-NH₂: Sourcing amino groups from natural material and their application in membranes for water contaminants removal

UiO-66-NH₂ is a type of metal–organic framework (MOF) widely utilized across various applications, particularly in membrane-based processes, owing to its excellent chemical and thermal stability. The synthesis of UiO-66-NH₂ can be accomplished through direct synthesis (including hydrothermal or solvothermal, microwave assisted, electrochemical, mechanochemical, sonochemical, or spray-drying techniques) and indirect synthesis (via post-synthesis modification). Amine functionalization on UiO-66, typically achieved using organic ligand 2-aminoterephthalic acid, can enhance its selectivity. Nevertheless, natural materials containing amino groups, such as keratin, chitosan, collagen, quinoa, and sunflower seed husks, also hold potential for functionalizing UiO-66 into UiO-66-NH₂. The incorporation of UiO-66-NH₂ onto membranes can influence membrane hydrophilicity, resulting in increased water permeability, and surface charge, resulting in enhanced rejection due to strong electrostatic interactions between the UiO-66-NH₂-incorporated membrane and charged contaminants. Previous studies have demonstrated that membranes modified with UiO-66-NH₂ exhibit excellent performance in separating heavy metal ions, dyes, and salts from water, achieving solute rejection of above 90 %. Our review aims to introduce readers and active researches in the field of MOFs, especially UiO-66, to the functionalization of UiO-66 with amine groups sourced from natural and synthetic materials, to provide valuable insights into the development of membranes that can be further evolved for water and wastewater treatment. In addition, we dispense the continuing challenges and areas of future study in this field.