Preparation,Properties And Applications Of MAPbBr₃@MOFs Composites

With the continuous acceleration of social modernization,industry and agriculture have been developed rapidly,but at the same time,a large amount of industrial and agricultural wastewater is directly discharged into the external environment without treatment,causing serious water pollution,which leads to a harmful impact on human survival and sustainable development.Therefore,water pollution caused by organic dyes and heavy metal ions has become a research hotspot for researchers for a long time due to its high purification difficulty and high biological toxicity.And researchers have proposed many practical and effective strategies to address water pollution.Among them,photocatalytic technology uses solar energy to degrade pollutants,and is one of the ideal strategies to solve the pollution of organic dyes green and friendly.In addition,the photosensitive sensor can detect heavy metal ions in solution clearly,sensitively and rapidly by measuring the change of its optical properties,which is favored by researchers.As an organic-inorganic hybrid porous network crystalline material,metal-organic frameworks have high chemical stability,large specific surface area,tunable structure and excellent physicochemical properties.Porphyrin-based metal-organic frameworks not only have outstanding optoelectronic properties of porphyrins,but also have the advantages of high stability and porosity of metal-organic frameworks,making them ideal host materials.Lead halide perovskite quantum dots have very excellent and unique optoelectronic properties,such as: tunable band gap and emission wavelength,strong visible light absorption,long carrier diffusion length,extremely narrow half width and high carrier mobility,etc.They can be used as a guest material and combined with the host material to realize the functional structural design of the composite material.This paper focuses on the composites of lead halide perovskite quantum dots MAPb Br3 and porphyrin-based metal organic frameworks PCN-221 and PCN-221(Fe),and explores the photoelectric properties and photocatalytic applications of the composites MAPb Br3@PCN-221.The application of the composites MAPb Br3@PCN-221(Fe)in sensing field is also explored.The main research contents are as follows:(1)Lead halide perovskite quantum dots MAPb Br3 were synthesized at room temperature by ligand-assisted reprecipitation method,and their optical properties were characterized.It was found that MAPb Br3 had good light absorption in the visible light region and at the same time showed a narrow half width at 520 nm.Porphyrin-based metal-organic framework PCN-221 was synthesized by solvothermal method and characterized by XRD and other means.It was found that PCN-2221 has strong visible light harvesting ability.Under the combined action of DMF and high temperature,Fe3+ can enter the center of the porphyrin ring,and realize the conversion from PCN-221 to PCN-221(Fe).The size of PCN-221(Fe)can be controlled by the reaction time.(2)The precursor material Pb Br2@PCN-221 was synthesized by solvothermal method,and then the composite material MAPb Br3@PCN-221 was prepared by a in situ growth method.The optoelectronic properties of the composites were explored,and the optoelectronic properties of the composites MAPb Br3@PCN-221 were higher than those of PCN-221.The photodegradation experiment of rhodamine B showed that the degradation efficiency of the composite material MAPb Br3@PCN-221 was higher than that of PCN-221,which verified the previous experimental analysis results.Then,the degradation mechanism was explained and analyzed based on the energy band structure of the composite material.As a result,the degradation mechanism of the composite material MAPb Br3@PCN-221 was Type-Ⅱ heterojunction charge transfer.(3)The porphyrin-based metal-organic framework PCN-221(Fe)was synthesized by a solvothermal method,and then MAPb Br3 was grown in the pores of PCN-221(Fe)by a two-step method.Based on the properties of porphyrin-based metal organic frameworks and lead halide perovskites,the application of composite materials in metal ion detection was explored.It revealed that the composite material had an obvious and rapid selective fluorescence response to Ag+ ions,showing a fluorescence turn-on signal.And the relationship between the fluorescence intensity of the composite and the Ag+ ions concentration in the solution was a linear relationship.The fluorescence intensity of the composite MAPb Br3@PCN-221(Fe)increased with the increase of the Ag+ ions concentration.The lowest detection concentration of the composite MAPb Br3@PCN-221(Fe)was 8.68 μM,and the fluorescence enhancement mechanism of MAPb Br3@PCN-221(Fe)on Ag+ ions as the charge transfer between molecules.