Preparation Of CuO-based Micro-nanomaterials Based On Metal-organic Frameworks And Their NO₂ Gas Sensing Properties

NO2 is a pollution gas,mainly from automobile exhaust and industrial production.With the progress of science and technology,more and more NO2 is discharged into atmosphere,which will not only harm the environment but also cause damage to human body.Therefore,it is important for us to control and detect the content of NO2.It is very urgent to develop sensors with good gas-sensing performance.Metal oxide semiconductor sensors have many advantages,such as excellent performance,simple preparation,etc,showing potential in commercialization.At present,only a few p-type metal oxides have been used to detect NO2,and most of the reported p-type metal oxides exhibit some problems of low response value and high operating temperature.Metal-organic frameworks（MOFs）,as a new type of porous materials,show the advantages of structural plasticity and stability,which can be used as the structural framework for sensing materials.By using MOFs as precursors,the specific surface area and oxygen adsorption site of the sensing material can be increased.In this dissertation,MOFs were used as the framework to construct the p-p heterojunctions to enhance the resistance modulation ability,so as to improve the gas sensing performance.In addition,in order to further inprove the specific surface area and oxygen species adsorbing capability of MOFs-based CuO material,MOFs-based CuO tubular nanofibers were constructed using Cu-MOFs as precursor.The main research contents of this dissertation are as follow:Cu2O-CuO composite octahedral were fabricated by calcining hydrothermal prepared Cu-MOFs at 400℃.This method displays the advantages of simple operation,easy preparation,high repetition rate,and low cost.Gas-sensing results confirmed that the Cu2O-CuO octahedral microstructures exhibited obviously enhanced sensing properties to NO2 at room temperature.The response value of Cu2O-CuO octahedrons to 500 ppb NO2 was 8.25,which was obviously better than the values of reported CuO-based gas sensors.In addition,the prepared Cu2O-CuO sensor not only showed the advantages of excellent selectivity and good stability,but also exhibited a very low detection limit（10 ppb）and operating temperature（25 ℃）.The main reason of the excellent sensing properties of Cu2O-CuO sensor to NO2 can be attributed to the formation of p-p heterojunctions,which was beneficial to enhance the modulation ability of sensor resistance.Cu-MOFs with small size were prepared by a solvothermal method at room temperature.A new kind of MOFs-based porous CuO tubular nanofibers were then constructed by combining MOFs method and electro spinning technique.Gas-sensing results indicated that the response value of CuO tubular nanofiber sensor to 500 ppb NO2 at room temperature can up to 16.00.CuO tubular nanofiber sensor showed excellent stability and selectivity.The better sensing properties of the CuO tubular nanofibers were mainly attributed to their special tubular fiber structure,which enhanced the anti-aggregation property,specific surface area,and oxygen species absorbing capability of the CuO material.This study provides an effective strategy for the construction of MOFs-based porous network nanofibers for high-performance gas sensing application.