Rational design of a MOF@Au@COF catalyst with electron synergy for the reduction of 4-nitrophenol

Abstract

4-Nitrophenol (4-NP) usually exists in soil and groundwater, which causes great harm to the environment and human health. Removal of 4-nitrophenol has become the focus of research. Herein, a smart synthetic strategy of NH2-MIL-88B(Fe)@Au@Covalent Organic Frameworks (COFs) is proposed for the first time. NH₂-MIL-88B(Fe)@Au@COFs are composed of NH₂-MIL-88B(Fe) as the core and COFs as the shell with Au nanoparticles. Au nanoparticles in NH₂-MIL-88B(Fe)@Au@COFs exhibit good dispersion and thermal stability due to amino group immobilization on NH₂-MIL-88B(Fe). The core–shell structure, high thermal stability and highly dispersed active sites of NH₂-MIL-88B(Fe)@Au@COFs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and so on. To the best of our knowledge, 4-nitrophenol was reduced to 4-aminophenol using NH₂-MIL-88B(Fe)@Au@COFs as the catalyst, NaBH₄ as the reductant and 4-nitrophenol as the raw material at room temperature. The catalyst has high catalytic activity and can be used repeatedly for the reduction of 4-nitrophenol under the cooperation of Fe and Au electrons. In addition, the kinetics and mechanism of catalytic reduction were discussed in detail. Multi-functional materials constructed using metal organic frameworks (MOFs) and COFs provide a basis for the application and expansion of new porous materials.