Quinone-modified NH₂-MIL-101(Fe) composite as a redox mediator for improved degradation of bisphenol A

A novel quinone-modified metal-organic frameworks NH₂-MIL-101(Fe) was synthesized using a simple chemical method under mild condition. The introduced 2-anthraquinone sulfonate (AQS) can be covalently modified with NH₂-MIL-101(Fe) and acts as a redox mediator to enhance the degradation of bisphenol A (BPA) via persulfate activation. The obtained AQS-NH-MIL-101(Fe) was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectra, cyclic voltammetry and electrochemical impedance spectroscopy. AQS-NH-MIL-101(Fe) exhibited better catalytic performance compared with NH₂-MIL-101(Fe) and NH₂-MIL-101(Fe) with free AQS (NH₂-MIL-101(Fe)/AQS). That is, AQS-NH-MIL-101(Fe) was proved to be the most effective in that more than 97.7% of BPA was removed. The degradation rate constants (k) of AQS-NH-MIL-101(Fe) was 9-fold higher than that of NH₂-MIL-101(Fe) and 7-fold higher than NH₂-MIL-101(Fe)/AQS, indicating that AQS is a great electron-transfer mediator when modified with NH₂-MIL-101(Fe). Based on the above results, the possible mechanism of catalytic reaction has been investigated in view of the trapping experiments. In addition, the AQS-NH-MIL-101(Fe) catalyst exhibited excellent stability and can be used several times without significant deterioration in performance.