Preparation And Photocatalytic Performance Of BiOBr/MOF Composite Materials

Bismuth oxybromide?BiOBr?has a tetragonal matlockite?PbFCl-type?structure?space group P4/nmm?which crystallizes into a layered structure semiconductor.Two-dimensional?2D?BiOBr have been found to have excellent photocatalytic performance material under visible light due to its unique electronic structure,crystal structure,the indirect transition mode and induced dipole moment.At present,BiOBr has been the subject of many studies for the efficient photodegradation of organic dyes under visible light illumination.Although pure BiOBr possesses good visible-light photocatalytic activity,there are two main inherent problems associated with the development of photocatalysts.First is the band gap which limits the full use of sunlight,especially in the visible region.Second is that the high rate of photo-generated electron–hole pairs recombination hampers the photocatalytic reaction efficiency.To overcome these problems and improve the performance of BiOBr for photocatalytic application,various effective methods have been applied.Metal–organic frameworks?MOFs?are porous crystalline structures constructed from a large number of metal ions or metal-containing clusters and multifunctional organic linkers through a variety types of coordination bond.Especially in recent years,an increasing researchers interest in MOFs has focused on the field of photocatalysis.In addition,MOFs have been demonstrated to be promising precursors or templates to construct different composition,morphology,size and specific surface area of metal oxides after the thermal treatment.Relative to MOFs,Covalent organic frameworks?COFs?do not contain metal ions.COFs,as promising photocatalysts,are intriguing research topics due to their structural flexibility and tremendous catalytic sites.In addition,polydopamine?PDA?acts as an effective sensitizer in a dye-sensitizer solar cell and theoretical calculations revealed the possible interactions between semiconductor materials and PDA under visible light irradiation,resulting in efficient separation of photo-generated charge carriers.According to the above ideas,this paper offers thoughts and feasible ways so that photocatalytic activity of the BiOBr would be further enhanced by combined with the above materials.The main research results can be summarized as follows.?1?Preparation and photocatalytic performance of BiOBr/NH2-MIL-125?Ti?composite materials.In this work,BiOBr/NH₂-MIL-125?Ti?composite photocatalysts with different NH₂-MIL-125?Ti?content were prepared by incorporating NH₂-MIL-125?Ti?with BiOBr using a co-precipitation method.The enhanced photocatalytic performance under visible light illumination could be attributed to the Ti³⁺–Ti⁴⁺intervalence electron transfer and synergistic effect between NH2-MIL-125?Ti?and BiOBr,and also resulted in a separation efficiency of photo-generated electron–hole pairs during the photocatalytic reaction.?2?Preparation and photocatalytic performance of BiOBr/CAU-17 composite materials.The in situ growth of Bi-based metal-organic framework?MOF??CAU-17?on BiOBr 2D material was prepared for the first time by using a facile solvothermal transformation approach.The BiOBr was applied both as template to support the growth of MOF and as Bi³⁺source of MOF.The BiOBr/CAU-17-2h composite exhibited enhanced photocatalytic activity for degradation of Rhodamine B?RhB?,methylene blue?MB?,and methyl orange?MO?under visible light irradiation.?3?Preparation and photocatalytic performance of BiOBr/Bi24O31Br10/TiO2 composite materials.The BiOBr/Bi₂₄O₃₁Br₁₀/TiO₂?BBT?heterostructures have been achieved for the first time by calcining BiOBr/MIL-125?Ti?composite at 500°C in air.The enhanced photocatalytic activity is attributed to narrower band-gaps and synergistic effect originating from the well-aligned straddling band-structures between BiOBr,Bi₂₄O₃₁Br₁₀ and TiO₂.?4?Preparation and photocatalytic performance of BiOBr/CTF-3D composite materials.2D BiOBr nanoflakes coupling with amorphous CTF-3D composites were synthesized for the first time via a simple coprecipitation method.The photocatalytic activity of the BiOBr/CTF-3D composite was evaluated by the degradation of colorless antibiotic agents,tetracycline hydrochloride?TC?and ciprofloxacin?CIP?under visible light irradiation.?5?Preparation and photocatalytic performance of SiO₂@PDA@BiOBr composite materials.A novel SiO₂@PDA@BiOBr composite photocatalyst with a hierarchical core–shell structure was prepared by a facile solvothermal method.The catalysts show a superior performance on photodegradation of RhB under visible light irradiation.