Photocatalytic Properties Of MOF-Graphene Hybrid Materials

Water pollution, especially the dye wastewater does harm to the environment and human health seriously. So, we should deal with the dye wastewater. Photocatalytic technology has been widely used to deal with wastewater recent years, because of its advantages of low energy consumption, mild operating condition and wide application range. Metal-organic frameworks (MOFs) are a new type of porous coordination compounds, which are made of metal centers and organic ligands by coordination bond. Since they have huge specific surface area and regulated structure etc, they have been applied in the fields of adsorption, hydrogen storage, catalysis and so on. Recent several years, MOFs are begun to use in the photocatalysis field and they can be used to degrade organic compounds in wastewater. However, fast electron-hole recombination leads to low efficiency of MOFs, which limits their application in photocatalysis. Graphene is a new material with2D structure, which is formed by the tightly packed monolayer carbon atoms. It has good electrical conductivity and can promote electron transfer. Therefore, graphene is often made into composites with semiconductors and used for photocatalytic degradation of waste water. The composites usually have better photocatalysis performance.The main research content of this paper is as following:1. Graphene Oxide (GO) was put into the synthesis system of MIL-125(Ti) and MIL-125(Ti)-reduced graphene oxide (rGO) hybrid materials with different rGO contents were prepared through solvothermal method. The products were characterized by some methods. The photocatalytic activities of MIL-125(Ti) and the hybrids in the degradation of Rhodamine B (RhB) under UV light irradiation were investigated. The reaction kinetics and possible photocatalytic mechanism of degradation of RhB were also studied. It demonstrated that the hybride with1.9wt%of graphene had the best photocatalytic performance. It degraded93.1%of RhB after60min of irradiation and its average rate constant was2.05times of that of MIL-125(Ti).2. GO, FeCl36H2O and terephthalic acid were used as raw materials and MIL-53(Fe)-rGO hybrid materials with different rGO contents were prepared through solvothermal method. The catalysts were characterized by some methods. The photocatalytic activities of MIL-53(Fe)[H2O] and the hybrids in the degradation of Methylene Blue (MB) under UV and visible light irradiation were investigated. The reaction kinetics and photocatalytic mechanism of degradation of MB were studied. Under UV light irradiation, the hybride with2.5wt%of graphene had the best photocatalytic performance. It decomposed94.5%of MB after80min of irradiation and its average rate constant was1.34times of that of MIL-53(Fe)[H2O]. Under visible light irradiation, the hybride with2.5wt%of graphene also had the best photocatalytic performance. It degraded48.4%of MB after420min of irradiation and its average rate constant was1.63and1.57times of that of P25and MIL-53(Fe)[H2O] respectively.3. The considerable promotion in photoactivities can be attributed that rGO can separate the photogenerated electrons and suppress electron-hole recombination In addition, the hybrids have smaller band gap and bigger absorbance than MOF.