Carbon nanodots anchored onto the metal-organic framework NH2-MIL-88B(Fe) as a novel visible light-driven photocatalyst: Photocatalytic performance and mechanism investigation

A one-pot strategy for the preparation of NH2-MIL-88B(Fe)/CDs composite was successfully developed via a simple solvothermal synthesis method. NH2-MIL-88B(Fe)/CDs composites were characterized by XRD, FT-IR, SEM, TEM, XPS, UV–vis DRS, PL, transient photocurrent response and Mott-Schottky plots. The synthesized NH2-MIL-88B(Fe)/CDs composites exhibit stronger photocatalytic activity than the original NH2-MIL-88B(Fe) in both photoreduction of Cr(VI) and photodegradation of MB. This is mainly because on the one hand, there is an interaction at the interface between CDs and NH2-MIL-88B(Fe), and on the other hand, CDs in the composite as local electron acceptors can effectively enhance charge transfer and inhibit electron-hole recombination. The experimental results show that the pH value greatly affects the reduction efficiency of Cr(VI) over photocatalyst, and the addition of hole trapping agent is beneficial to photocatalytic reduction. Moreover, we have proposed the possible photocatalytic mechanism on composites through trapping experiments of active species. Importantly, cycling experiments have also revealed that NH2-MIL-88B(Fe)/CDs photocatalysts have good chemical stability and reusability, and have broad industrial application prospects.