Defect-induced in situ electron-metal-support interactions on MOFs accelerating Fe(III) reduction for high-efficiency Fenton reactions

The inefficient reduction of Fe³⁺ and activation of H₂O₂ in the Fenton reaction severely limit its application in practical water treatment. In this study, we developed defective NH₂-UiO-66 (d-NU) with coordinated unsaturated metal sites by adjusting the coordination configuration of Zr, creating a solid-liquid interface to facilitate Fe³⁺ reduction and the sustainable generation of •OH from H₂O₂ activation. The d-NU/Fe³⁺/H₂O₂/Vis system demonstrated highly efficient removal of various organic pollutants, with a rapid Fe²⁺ regeneration rate and exceptional stability over ten cycles. The degradation rate constant of d-NU (0.16112 min^–1) was 11 times higher than that of NH₂-UiO-66 (NU) (0.01466 min^–1) without defects. Characterization combined with density functional calculations revealed that defects induced coordination unsaturation of the Zr sites, leading to in situ electron-metal-support interactions between Fe³⁺ and the support via Zr–O–Fe bridges. This accumulation of electrons from the unsaturated Zr sites enabled the adsorption of Fe³⁺ at the solid-liquid interface, promoting the formation of Fe²⁺ across a wide pH range with a reduced energy barrier. This study introduces a promising strategy for accelerating Fe³⁺ reduction in the solid-liquid interfacial Fenton process for the degradation of organic pollutants.