Studied On Photocatalytic Performance Of Modified Porous Carbon Derived From MOFs

Metal-Organic frameworks?MOFs?and porous carbon materials derived from MOFs through a calcination method,bearing the advantages of uniform distribution of metal active sites,high specific surface area and good electronic transport properties,have attracted wide attention in the field of photocatalysis.MOFs and porous carbon materials to be used as photocatalysts alone,however,have low photocatalytic performances.An effective strategy of combining these materials with semiconductor materials was generally adopted to solve the problem.Therefore,in order to obtain high photocatalytic performances,MOFs and porous carbon materials were combined with CdS or TiO₂ in this paper.Firstly,a series of ZnO-rich CdS-ZIF-8-n photocatalysts were innovatively synthesized by a solvothermal method.Scanning electron microscopy?SEM?and transmission electron microscopy?TEM?results showed that CdS nanoparticles were well dispersed on the surface of ZIF-8.Furthermore,Energy dispersive X-ray spectroscopy?EDX?,Fourier transform infrared spectroscopy?FI-IR?and X-ray photoelectron spectroscope?XPS?results suggested that a CdS/ZnO heterostructure and a Z-scheme behavior were formed.The co-effect of both structures effectively accelerated the separation rate of photogenerated electron-hole pairs.In addition,a CdS-ZIF-8-30obtained higher surface area?77.3 m²/g?and pore volume?0.103 cm³/g?,which were benefit to improve photodegradation performance.In the photodegradation evaluation of methylene blue?MB?under visible light irradiation,the photocatalyst CdS-ZIF-8-30realized the complete degradation of the MB within 60 min and exhibited an optimal photodegradation performance.Secondly,a porous carbon material ZC derived from ZnO-rich ZIF-8 was prepared by a calcinations strategy.Further,CdS-ZCx-n catalysts were creatively obtained by a solvothermal method.The catalysts were characterized by some technologies including XRD?SEM?EDX and XPS.The results proved that the CdS-ZCx-n simultaneously possessed C,CdS and ZnO phases and a CdS/ZnO heterostructure was formed.Moreover,forming mesoporous structures in CdS-ZCx-n were helpful for the diffusion of MB molecules in the channel and adsorption on active sites.PL spectra illustrated that a CdS-ZC600-30 was provided with weaker intensity compared to that of a pure CdS and CdS-ZIF-8-30,respectively.The phenomenon was attributed to the CdS/ZnO heterostructure formation in CdS-ZC600-30 and the good electron transport properties of graphite phase ZC.In same photodegradation conditions,the degradation efficiency of CdS-ZC600-30 was 1.2 times than that of CdS-ZIF-8-30.Finally,TiO₂/ZC600-n catalysts were innovatively prepared by a sol-solvothermal method.XPS and FT-IR results demonstrated that the surface element carbon of ZC was doped into the crystal lattice of TiO₂.UV-DRS results exhibited that the band gap of TiO₂/ZC600-8?2.75 eV?was obviously narrowed.Furthermore,TiO₂/ZC600-8 had a larger specific surface area?185.26 m²/g?and a pore volume?0.179 cm³/g?.In the degradation investigation of MB under visible light irradiation,TiO₂/ZC600-8 realized the complete degradation of methyl orange?MO?within 50 min.