The Influence of Carbon Nitride Nanosheets Doping on the Crystalline Formation of MIL-88B(Fe) and the Photocatalytic Activities

In this research, bulk graphitic carbon nitride (g-C3N4) is exfoliated and transferred to the carbon nitride nanosheets (CNNSs), which are then coupled with MIL-88B(Fe) to form the hybrid. From the results of the powder X-ray diffraction, scanning electronic microscopy and thermogravimetric analysis, it is found that the doping of CNNSs on the surface of MIL-88(Fe) could maintain the basic structure of MIL-88B(Fe), and the smaller dimension of CNNSs might influence the crystallization process of metal-organic frameworks (MOFs) compared to bulk g-C3N4. Besides, the effects of the CNNSs incorporation on photocatalysis are also investigated. Through the photoluminescence spectra, electrochemical measurements, and photocatalytic experiments, the hybrid containing 6% CNNSs is certified to possess the highest catalytic activity to degrade methylene blue and reduce Cr(VI) under visible light. The improvement of the photocatalytic performance can be attributed to the matched energy level which favors the formation of the heterojunctions. Besides, it promotes the charge migration such that the contact between MOFs and CNNSs is more intimate, which can be inferred from the electronic microscopy images. Finally, a possible photocatalytic mechanism is put forward by the relative calculation and the employment of the scavengers to trap the active species.