Design And Fabrication Of MOFs Derived Zinc-cobalt Based Metal Oxide Gas Sensing Material

With the development of society and improvement of living quality,people pay more and more attention to their own health problems.Acetone is a common toxic and harmful gas.When its concentration exceeds a certain degree,it will cause irreversible effects on human health.In addition,the detection of acetone occupies an important position in the medical field,because it can be used to diagnose diabetes according to its concentration.Based on the important role of acetone detection,the development of high-performance acetone gas sensors is crucial.Based on the characteristics of large specific surface area and abundant pore structure of metal-organic framework（MOFs）materials,the metal oxides derived from MOFs templates are very promising gas sensing materials because it can retain the advantages of MOFs materials.In this paper,we designed and prepared flower-like Zn O/Co₃O₄ heterojunctions sensing material and Zn-doped Co₃O₄ sensing material derived from Zn/Co-MOF by chosing the way of constructing heterostructure and doping,which effectively improved the sensing properties of intrinsic metal oxide to acetone.The specific research contents are as follows:Firstly,ZIF-L nanosheets were synthesized by solution mixing method,and then Zn/Co-MOF structures were obtained by modifying Co-MOF nanoparticles on the surface of ZIF-L nanosheets.After annealing,Zn/Co-MOF derived hierarchical flower-like Zn O/Co₃O₄heterojunctions were obtained.The characterization results showed that Co₃O₄ nanoparticles were successfully modified on Zn O nanosheets to form flower-like heterostructures through self-assembly process.According to the measurement of acetone sensing properties,the Zn O/Co₃O₄ heterojunctions had an excellent ability to detect ppb-level acetone.At 300℃,the response value of Zn O/Co₃O₄ heterojunctions sensing material was up to 120%towards 500ppb acetone,which was about 30-fold enhancement than that of intrinsic Zn O and Co₃O₄.In addition,the Zn O/Co₃O₄ heterojunctions sensing material had excellent selectivity and stability,and its response/recovery time was only 22 s/27 s.We systematically studied the acetone sensing mechanism of the flower-like Zn O/Co₃O₄ heterojunctions.The enhanced acetone sensing properties were attributed to the construction of p-n heterojunction and transport channel provided by Zn O nanosheets.This finding provides important insights and useful guidance for the detection of ppb-level acetone.Secondly,the flower-like structure of Zn/Co-MOF composed of ultrathin nanosheets was prepared by solvothermal method.After annealing,the Zn-doped Co₃O₄ flower-like structure was obtained and its acetone sensing properties were studied.The results showed that the doping of Zn effectively reduced the operating temperature of Co₃O₄ sensing material and significantly improved its sensing properties to acetone.Among them,3 mol%Zn-doped Co₃O₄exhibited the highest response of 52.3 toward 100 ppm acetone at 200℃,which was nearly 20times higher than that of pure Co₃O₄.Its response/recovery time was 12 s/54 s.In addition,3mol%Zn-doped Co₃O₄ also had the ability to detect ppb-level acetone,and it had a stable response to 250 ppb acetone.In detail,we studied the acetone sensing mechanism caused by Zn doping,and comprehensively described the enhanced gas-sensing mechanism.The changes of carrier concentration,specific surface area and chemisorbed oxygen amount of the Co₃O₄semiconductor caused by Zn doping lead to the improvement of acetone sensing properties,which provides a new idea for the development of high-performance acetone sensors.