Synthesis And Characterization Of MOFs/Bismuth-based Semiconductor Heterostructures And Their Application For Visible-Light-drivened Photocatalysis

Solving energy shortages and environmental pollution are two major challenges for human beings to achieve the sustainable development of human society.With energy efficient,clean non-toxic,no secondary pollution advantages,photocatalytic technology is expected to become an effective way to solve environmental and energy problems and is a highly promising environmental pollution green governance technology.Besides,it can degrade pollutants into CO₂ and H₂O.The core of photocatalytic technology is photocatalyst.At present,the most widely studied catalyst is TiO₂.Unfortunately,the band gap of TiO₂ is too wide to utilize solar energy,it only absorb ultraviolet light and near ultraviolet light?which only account for 5% energy of the solar energy?.In order to make more efficient use Sunlight,the development of efficient visible light response catalyst becomes inevitable.Since last decade,a class of porous materials called Meatal-organic Frameworks?MOFs?materials have attracted much attention.With pecific surface area,tolarial pore,MOFs have been applied as a photocatalytic catalyst.However,MOFs have a low photon production rate,which seriously restricts its practical application.In recent years,bismuth-based semiconductor photocatalyst has been developed,bismuth-based materials have a good absorption of visible light.Therefore,this paper uses MOFs as carrier and supports bismuth-based semiconductor materials to prepare heterojunctions.The main contents are as follows:?1?A novel visible-light-responsive photocatalyst that comprised BiVO₄ together with MIL-125?Ti?,was synthesized by a two-step hydrothermal approach.The characterization of asobtained samples as performed by X-ray diffraction,scanning electron microscopy,high resolution transmission electron microscopy,Fourier transform infrared spectroscope,X-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflection spectra.Rhodamine B was selected being a target for the evaluation of the photocatalytic function of as-developed photocatalyst.The photocatalytic reaction parameters,for example,the content of Bi VO₄ as well as initial concentration of Rhodamine B was researched.The composite photocatalyst possessing Bi:Ti molar ratio of 3:2 brought to light the fact that the greatest photocatalytic activity had the ability to degrade 92% of Rhodamine B in 180 min.In addition to that,The Bi VO₄/MIL-125?Ti?composite could keep its photocatalytic activity during the recycling test.The phenomenon of disintegration of the photo-generated charges in the Bi VO₄/MIL-125?Ti?composite was brought to discussion as well.?2?This study provides the first attempt to combine UiO-66?Zr?with Bi₂MoO₆ for the preparation of composite via electrostatic interaction induced self-assembly process.Synthesized products were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,Fourier transform infrared spectroscope?FT-IR?,X-ray photoelectron spectroscopy?XPS?,Brunauer-Emmett-Teller?BET?surface area analyse and UV-vis diffuse reflectance spectroscopy?UV-vis DRS?.The photocatalytic activities of as-obtained Bi₂MoO₆/UiO-66?Zr?composites were assessed by degradation of Rhodamine B?Rh B?under the visible-light irradiation.Comparing to the pristine materials,the developed Bi₂MoO₆/UiO-66?Zr?composite with Bi:Zr molar ratio 2:1,labelled as BMUO-2,showed the best photocatalytic activity.It was supposed that the participation of Bi₂MoO₆ increased the use of solar energy and the existence of Ui O-66?Zr?restrained the recombination rate of photo-generated electron-hole pairs.Moreover,Bi₂MoO₆/UiO-66?Zr?composite showed excellent stability and recyclability during cycling experiment.The mechanism and plausible pathway of Rh B degradation were also discussed in this paper.The experimental results show that the composite produced by MOFs and bismuth-based semiconductors has a higher catalytic effect than pristine materials.The improvement of the catalytic effect is attributed to the fact that the heterojunction formed by the two forms,which can suppresses the recombination rate of photogenerated electrons and holes,and leading to the improvement of visible-light-driven photocatalytic activity.The photocatalyst prepared in this paper has a good degradation effect on rhodamine B,and the research work provides a new design idea and reference for the application of MOFs in water phase.