MOF-5/Graphene Oxide Composite Photocatalyst for Enhanced Photocatalytic Activity of Methylene Blue Degradation Under Solar Light

This work focuses on the degradation of methylene blue dye using graphene oxide and metal-organic frameworks (MOFs). In particular, the performance of these materials towards the photocatalytic of methylene blue dye (MB) under sun irradiation was investigated. To this aim, graphene oxide (GO) and metal-organic framework (MOF-5) were synthesized using the modified Hummer's method and room temperature method respectively. Our resulting composites MOF-5/GO contain 5 and 10 wt% of GO. X-Ray Diffraction (XRD), FTIR spectroscopy, Thermogravimetric Analysis (TGA), and UV-Vis spectroscopy were used to characterize the structure and the thermal stability of the synthesized materials. The degradation of methylene blue was performed under varying conditions of pH and mass ratio. Our results indicate that, for the degradation of methylene blue dye under 390 min of solar exposure, the hybrid materials MOF-5/GO exhibit a remarkable photocatalytic efficiency when compared to the pure MOF-5. MOF-5/GO achieved 92% degradation at pH = 6.8 of MB. The reduced band gap, various functional groups and an adequate supply of active sites also are additional advantages in this design. The kinetic indicates that the Langmuir-Hinshelwood (L-H) model is well adapted to the experimental data. We demonstrated, using a linear fit that the degradation obeys a pseudo-first-order kinetic with apparent constants of 0.0369 and 0.0396 min(-1) for MOF-5/GO5 and MOF-5/GO10 respectively. In contrast, in the case of a reaction with the highest activity, a nonlinear technique method was used to obtain the apparent reaction rate constants. Finally, the improved photocatalytic mechanism over MOF-5/GO was also suggested. The hybrid combination of MOF-5 and GO confers a synergistic effect that is crucial for delaying the rate of photogenerated electron-hole recombination and maximizing charge transfer throughout the entire hybrid system structure, leading to a high efficiency photocatalytic performance.