Recognition-enrichment-in-situ degradation of p-chlorophenol by Fe-IL@UIO-66

Abstract

Persistent organic pollutants (POPs) represent a significant environmental and health risk due to their high toxicity, persistence, strong accumulation potential, and adverse effects on human health. 4-Chlorophenol (4-CP), a type of POP, has low catalytic efficiency at low concentrations and is easily interfered with by other pollutants, making its degradation challenging. A new “recognition-enrichment-in-situ degradation” strategy is introduced to selectively remove chlorophenols from contaminated aqueous environments. In this study, ionic liquids were incorporated into the UIO-66 framework as active sites for selective adsorption. 4-CP contains phenolic hydroxyl groups and exhibits high polarity. The dispersive interactions between 4-CP and ionic liquids, along with hydrogen-bonding interactions between the Tf₂N anion and the hydroxyl groups of 4-CP, enhance the selective enrichment of 4-CP within the nanocavities of the metal–organic frameworks (MOFs). Fe³⁺ was then introduced, enabling in-situ degradation of 4-CP through photo-induced generation of free radicals and cavities from H₂O₂ catalyzed by Fe-IL@UIO-66. The results indicated that the adsorption capacity of IL@UIO-66 for 4-CP reached 53 %, significantly higher than that for five other organic pollutants. The adsorption capacity of IL@UIO-66 for 4-CP reached 509.5 mg g⁻¹, 49.9 % greater than that of the original UIO-66. The degradation efficiency of 4-CP by Fe-IL@UIO-66 increased from 61 % to 81 %, and after four cycles, the material retained a catalytic activity with a degradation efficiency of 64.2 %. This study provides valuable insights into the recognition-enrichment-in-situ catalytic strategy for treating low-concentration, highly toxic wastewater.