Construction of 3D N-CQD/MOF-5 photocatalyst to improve the photocatalytic performance of MOF-5 by changing the electron transfer path

MOF-5 is an emerging semiconductor material with a great potential in photocatalytic wastewater treatment. However, its inherent deficiencies, such as the narrow range of photo-response, the fast recombination of photoinduced carriers and the unstable structure, largely limit its further application. In this work, super biocompatible N-doped carbon quantum dots (N-CQD) derived from the green precursor, coconut shells, were in situ grown on MOF-5 via a facile solvothermal method to construction of 0D/3D N-CQD/MOF-5 photocatalyst with an enhanced photoreduction ability. A sustainable and pollution-free preparation process of N-CQD/MOF-5 photocatalyst was delivered and biomass waste resource was effectively utilized via this method. This well-designed photocatalyst with the optimized 1% N-CQD loading presented a considerable photoreduction rate of Cr (VI), which was 2.5 times higher that of pure MOF-5. It also possessed a strong structural stability and reusability even after multiple tests. The boosting photocatalysis activity could be attributed to the doping of N-CQD, who not only act as an electron acceptor to separate the photoexcited electrons and holes effectively, but also play a vital role as a photosensitizer to improve the visible-light absorption. Furthermore, the influence of activation methods on the photocatalytic activity of MOF-5 were also investigated theoretically. For the purpose of clarifying the potentially photocatalytic mechanism of N-CQD/MOF-5 in photoreduction Cr (VI), a series of tests involving photoelectrical characterizations and fluorescence spectroscopy were executed. Therefore, this study provides an innovative photocatalytic system for an enhanced photoreduction performance of Cr (VI) of MOF-5.