Preparation And Electrochemical Performance Of UiO-66 Composite Materials

Electrochemical enzyme-free sensors play the significient role in the fields of environmental detection,medical hygiene and industrial production.It has attracted increasing attention owing to its advantages of high stability and low cost.However,electrochemical enzyme-free sensors suffered many shortcomings such as low sensitivity,insufficient anti-interference ability and low reusability,which greatly limited their application,thus it is necessary to develop the new effective electrochemical enzyme-free sensor.Metal-organic framework（MOF）is widely applied in the field of heterogeneous catalysis attributes to its structural characteristics such as large specific surface area and high porosity,regular pores,abundant active centers and active sites.Through modification of different functional groups,Metal-organic framework compounds have been given different chemical environments,improving the selectivity and yield in some catalytic reactions.At present,various composite materials,which constructed by metal nanoparticles and MOF,have been applied in many catalytic reactions and achieved satisfactory catalytic effects.Researchers are committed to reducing the size of metal nanoparticles to the atomic level to improve the chemical activity.However,there are few studies on the mechanism of functional group effects and single-atom composite MOF materials in the field of electrochemical sensors,unfortunately,the sensitivity of the sensor is low.Based on the above reasons,we carried out two works.One was to prepare three different functional groups modified Pt@UiO-66-X（X=H,NH₂,SO₃H）materials,through detecting ascorbic acid,we explored the difference of functional group effects on nonenzyme electrochemical sensors.The second is to synthesize a single-atom composite material of Cu@UiO-66 to explore the electrochemical performance during the detection of nitrite.The specific research contents are as follows:1.One-pot method was used to encapsulate the prepared Pt nanoparticles into UiO-66,forming Pt@UiO-66-X（X=H,NH₂,SO₃H）composite materials,which is used for exploring the functional groups effects in the oxidation of ascorbic acid.The results showed,among the three materials,the Pt@UiO-66-NH₂ electrode material exhibits the excellent performance in detecting ascorbic acid:the detection range between 0.01 to26 mM,excellent anti-interference ability,and its high applicability in actual samples.We explore the great detection mechanism as follows:（1）In Pt@UiO-66-NH₂ material,the presence of electron-donating group-NH₂ creates an electron-rich environment,promotes the transmission of electrons,which is beneficial to the oxidation of ascorbic acid;（2）According to the density functional theory（DFT）calculation,the benzene ring part of the BDC-NH₂ ligand has a lower electrostatic potential energy（ESP）,which is favor to ascorbic acid oxidation reaction;（3）The simulated hydrogen bonding experiments exhibits hydrogen bonding could exist between BDC-NH₂ ligand and ascorbic acid,promoting the adsorption of ascorbic acid.This idea of using functional group effects to modify and select electrode materials would provide a new direction for the expansion of enzyme-free sensors2.A highly dispersed composite material Cu@UiO-66 was synthesized by hydrothermal method.The composite material retained the structural characteristics of the MOF substrate,and its larger surface area and porosity made it easier to adsorb the substrate.As for the matrial,it would be greatly increase the electrical conductivity and catalytic activity,in addition,Cu coordinated with Zr-O of UiO-66 defect sitesstructurally,resulting in electron transform,which could greatly promote the oxidation reaction.Based on above,we applied the material as a nitrite electrochemical sensor.The experimental results showed that the material has excellent sensing performance:linear concentration range（0.01-44 mM）,lower detection limit（0.885μM）,very short response time（<2s）,strong anti-interference ability,good stability（1000 s）and high recovery（94%-106%）,and high measurability in actual samples.This application of highly dispersed materials in electrochemical sensors broadens the range of materials and provides new ideas for the development of new high-efficiency enzyme-free electrochemical sensors.