Unsaturated Fe centers of 2D MOFs mediated the efficient Fenton-like reaction for organic pollutant elimination

Abstract

Fe-based metal-organic frameworks (Fe-MOFs) are currently regarded as a promising candidate for heterogeneous Fenton-like reactions to eliminate organic contaminants in wastewater. However, improving the cycling rate of Fe(II)/Fe(III) to create a highly efficient heterogeneous Fenton-like system continues to be a challenge. Here, we prepared 2D MIL-88B(Fe)-NO₂ by a facile approach. 2D MIL-88B(Fe)-NO₂ has a higher capacity to degrade pollutants than 3D MIL-88B(Fe)-NO₂, 2D-M30 showed the best Fenton-like performance in particular, with a phenol removal rate of approximately 97.2 % within 6 min and a kinetic degradation constant of 0.57 min⁻¹. The phosphate addition experiment confirmed that the unsaturated coordination Fe on 2D MIL-88B(Fe)-NO₂ was the main active site for H₂O₂ activation. Additionally, it can be concluded by CO adsorption in-situ infrared spectra and specific surface area measurement that 2D MIL-88B(Fe)-NO₂ has more unsaturated coordinated Fe than MIL-88B(Fe)-NO₂. The outstanding Fenton-like catalytic efficiency was attributed to the defects of metal node coordination sites at the 2D MOFs. Furthermore, the electron cloud density of Fe(III) decreased due to the unsaturation of the coordinated Fe, which encourages the transition of Fe(II)/Fe(III). This approach provides innovative ideas for the logical design and creation of efficient heterogeneous Fenton-like catalysts.