With the increase of population and the rapid development of industry,the rapid economic development also brings many environmental issues.Environmental issues have always been a major topic related to human development,especiallythe air pollution.The random emission of automobile exhaust and industrial exhaust gas are causing the air pollution more serious.Hydrogen sulfide is a flammable gas,at low concentrations,it is colorless,smelly eggs,and highly toxic.Therefore,it remain great requirement to synthesize gas sensing materials with high sensitivity and low cost Metal-organic framework materials are widely used in the preparation of gas sensing materials due to their unique structural advantages.In this dissertation,copper-based metal-organic framework compounds are selected and a bimetallic MOF was prepared by compounding other metal ions.Utilizing MOF as a self-sacrifice template,the ZnO/CuO composite based metal oxide was prepared.The reasons for the enhanced gas-sensitive properties of such composite were thoroughly analyzed.The main research results are conclued as follows:(1)A copper-based MOF(HKUST-1)with octahedral morphology was prepared by a solvothermal method,and CuO was prepared from the sacrificial stencil with octahedral morphology.The morphology and structure of the samples were characterized by XRD and SEM.In order to obtain the best reaction conditions,different samples were prepared by changing the reaction temperature and the calcination temperature,and different samples were prepared as gas sensors.The results show that the gas sensitivity of the obtained sample is the best when the reaction temperature is 85℃and the calcination temperature is 500 oC.The sensitivity to 10 ppm H2S can reach 22.5,and the minimum detection limit is 800 ppb at 40oC.(2)A simple solvothermal method was used to prepare a bimetallic metal organic framework Zn/Cu-BTC in one step and used as a self-sacrifice template to obtain a ZnO/CuO composite material.The morphology and characteristics of composites were characterized by XRD,SEM and XPS.The ZnO/CuO composite maintains an octahedral structure,and a p-n heterojunction can be formed between p-type CuO and n-type ZnO.In order to prove its functional characteristics,ZnO/CuO composites were used as sensing materials to test their gas sensitivity.The effect of the molar ratio of Zn2+to Cu2+was studied.The results show that the gas sensor based on ZnO/CuO composite has the best gas sensing performance when n(Cu):n(Zn)=1:0.33.It exhibits good selectivity for 10 ppm H2S at an optimal operating temperature of 40 oC,with 17.1 and 327.8 times the sensitivity of pristine CuO and pristine ZnO gas sensors,respectively.In addition,the detection limit of such sensors for H2S can be reduced to 300 ppb,and they have good repeatability and long-term stability.At the same time,the gas sensing mechanism of enhanced ZnO/CuO composite gas sensing performance was thoroughly analyzed.(3)Co/Cu-BTC was prepared by solvothermal method and calcined to obtain Co3O4/CuO composite.The composite was characterized by XRD and SEM.The molar ratio of Co ions to Cu ions was changed to prepare the Co3O4/CuO composite with the best gas-sensing performance.The obtained sample was made into a gas-sensing element and subjected to a gas-sensing test.The results show that the gas sensing(n(Cu):n(Co)=1:1)performance is the best.At the optimal operating temperature of 40℃,the sensitivity to 10ppm H2S reaches 196.3,and the minimum detection limit can reach 300 ppb.A p-p heterojunction is formed between the p-type semiconductor CuO and the p-type semiconductor ZnO between the Co3O4/CuO composites,and the reason for the enhanced gas sensing performance can be attributed to the formation of p-p heterojunction. |