Preparation And Performance Study Of Covalent Organic Framework-based Sensors

Based on the reason that Schiff base ligands with electron acceptor properties can be used as charge transfer exchange media between ions and electrodes,and in order to enhance the comprehensive performance of electrochemical sensors,this work mainly uses Schiff base and metal nanoparticles to prepare chemically modified electrodes,which are extremely effective in improving the selectivity and sensitivity of sensors.In this paper,we first give a brief overview of COFs materials and investigate and analyze the main synthetic methods,modification means,and practical applications of COFs materials.Subsequently,the main application studies of COFs in the field of electrochemical sensors are described,based on which the following work is carried out.（1）TT-COF（Zn）materials prepared with 2,3,6,7-tetra（4-formylphenyl）tetraaz acyclopentene（TTF）and 5,10,15,20-tetra（p-aminophenyl）porphyrin zinc（II）（TPZ）as building blocks were directly designed as electrode modifiers for the sensiti ve and selective determination of I^-and Hg²⁺.Notably,the dithioether-sulfur ca talytic site and pyrrole-nitrogen catalytic site of TT-COF（Zn）can effectively cat alyze halide ions due to their inherent electrocatalytic oxidation activity and the synergistic coordination effect between the porphyrin center Zn²⁺and I^-,and make it a sensitive sensing platform for the electrochemical quantification of I^-.DFT calculations show that TT-COF（Zn）/GCE for I^-with the best catalytic pe rformance.A linear range of 0.02-15 m M and LOD of 3.15μM was obtain ed for I^-.The linear range for Hg²⁺detection was 0.5-100μM and LOD of0.115μM.The proposed sensor also performed well in the determination of I^-and Hg²⁺in real river samples.This work not only provides a simple method for the effective determination of I^-and Hg²⁺but also paves the way for the strategic design and synthesis of COFs for electrochemical sensing application s.（2）We successfully synthesized a novel unitary copper-based covalent organic framework by condensing pre-metallated 5,10,15,20-tetra（p-aminophenyl）porphyrin copper（II）（TPC）with 2,3,6,7-tetra（4-formylphenyl）tetraazacyclopentene ligands,and designed and synthesized a crystalline copper-based COF with a unique single-site electrocatalyst having a porous channel structure for GA showed great advantage and high catalytic activity with the obtained linear range of 0.01-1000μM and LOD of2.81 n M under the optimal conditions of square wave voltammetry（SWV）.In addition,the method was successfully used to detect GA in real tea samples with good recovery.This novel sensor can provide ideas for the sensing of COF-based crystalline materials in the quantification of other living analytes.（3）The rational design of Schiff-base structured COFs can improve the selectivity for specific drug molecules and become an excellent carrier for enhancing the electrochemical response of electrodes.We have attempted to use the synthesis of Schiff bases in the form of 5,10,15,20-tetra（p-aminophenyl）porphyrin nickel（II）（TPN）and 2,3,6,7-tetra（4-formylphenyl）tetraazacyclopentene（TTF）to enhance the ability of the material to act as an electron acceptor on the surface of the electrode in the role of exchange and transfer of electrons between the linking ion and the electrode.The folded rectangular sheet array structure on the surface of the TTCOF（Ni）material synthesized this time has the advantage of effectively enhancing the specific surface area of the material itself to promote the mass transfer and reaction of ACOP at the electrode surface area,thus TTCOF（Ni）/GCE has the best catalytic performance for ACOP with a more excellent interference resistance,which is well applied to the actual samples.We finally obtained the linear range of ACOP from 1-1500μM and LOD of 47.6 n M,which will provide a possible selectivity for the application of COFs materials to food and drug sensors.