Synthesis And Humidity Sensing Properties Of CdL And MOF-808 Complex Materials

With the increasing requirements of the society for humidity sensors,it is extremely urgent to develop new materials for higher humidity sensing requirement.In this paper,the CdL were prepared by solvent evaporation method and MOF-808 were prepared by Condensation reflux method.MOF-808 was heated by different temperature and mixing KCl.The material mentioned above is used as humidity sensitive material to make humidity sensor,and its humidity performance is tested,and corresponding humidity sensitive mechanism is analyzed.The main research contents include the following three parts:1.A new coordination compound CDL was prepared by simple solvent evaporation at room temperature.It contains zero-dimensional binuclear spatial structure cells and many S,O and N active sites.The crystal structure of the material was characterized by single crystal diffraction,XRD and FT-IR,and the humidity sensing property was measured.The results show that due to the novel material structure,the response time of the sensor is as short as 5s,and the wet hysteresis is 0.94%RH.Finally,through complex impedance analysis,the moisture sensing mechanism of CdL sensor is discussed,and the interaction between water molecules and CdL active layer is visually demonstrated through a schematic diagram.2.The composite system was prepared by physical mixing method of MOF-808 and trace KCl.The materials were characterized by XRD,SEM,XPS and BET,and the humidity sensor was prepared from this material.The results showed that the sensitivity of 0.2 wt% KCl/MOF-808 was up to four orders of magnitude,with low wet lag(only0.97% RH),50 s response time and 48 s recovery time.It is proved that loaded KCl can improve the humidity sensitivity.The results of reproducibility and long-term stability confirmed that 0.2wt % KCl/MOF-808 had good stability under both high and low RH conditions.By complex impedance analysis,the load KCl changed the carrier type of MOF-808 in high humidity environment.3.The MOF-808 samples with different degrees of defects are prepared by treating them at different temperatures.The formation of defects is accompanied by the appearance of many active sites.The material was characterized by XRD,SEM,BET,TGA and 1HNMR,and the humidity sensor was fabricated from this material.The MOF-808 treated at 250? has a sensitivity of three orders of magnitude,a low wet hysteretic rate(only 0.11%RH),a response time of 54 s and a recovery time of 74 s.It is proved that after high temperature treatment,the overflow of formic acid molecules will lead to the enlargement of pore size and the increase of active sites,which will lead to better moisture sensing performance of the material.Through complex impedance analysis,the defects changed the carrier type of MOF-808 in high humidity environment.