Disclosing the role of defective UiO-66 over Sb(V) removal: A joint experimental and theoretical study

Metal-organic frameworks (MOFs) with ability to create rich defects in the structures for exposed binding sites are beneficial for wastewater treatment. However, the inter-relation between the defect concentration and heavy metal removal performance still deserves the exploration. Herein, UiO-66-X crystal materials are successfully synthesized in the presence of monocarboxylic acid of acetic, benzoic, and trifluoroacetic acid, and the effect of defect concentration on Sb(V) removal performance is systematically studied. XRD, TG, EPR and XPS characterizations reveal that the addition of modulators increases the content of defects in the UiO-66-X, which is beneficial to improve the sites utilization. As expected, the Sb(V) adsorption properties of UiO-66-AA, UiO-66-BA and UiO-66-TFA are boosted by 54.1%, 140.0% and 197.7% compared to that of pristine UiO-66. Density functional theory (DFT) calculations further confirm that UiO-66-TFA with the most defects exhibits lower adsorption energy and higher charge transfer, significantly improving the uptake performance of Sb(V). Additionally, the UiO-66-TFA successfully removes antimony in actual water from the Tianyi Lake and Ganjiang River with residual concentrations below 5 μg L−1, meeting the drinking water standard. This work provides guidance for the rational selection of modulators for efficient heavy metal removal from wastewater.