| Bisphenol A（BPA）and Bisphenol S（BPS）are two typical bisphenol compounds,which are widely used in industrial production and daily life products as they can impart colorless transparency,extrusion resistance and corrosion resistance to products.Large-scale production and application make them detectable in different environmental media such as water and soil.In addition,due to theirs similar structure to estrogen,through direct exposure or indirect enriched contact,they often affect the reproduction and development of organisms to a certain extent,and they still have acute toxicity and genotoxicity even at low concentrations.Therefore,it is of great significance to study the adsorption process of BPA and BPS and to establish a sensitive and efficient detection method for BPA and BPS.Covalent organic frameworks（COFs）are a new type of nanomaterials with porous structures,which have excellent properties such as tunable pore size and structure,high porosity and specific surface area,characteristicπ-πconjugated system,thermal and chemical stability.At the same time,due to the possibility of introducing functional groups in the synthesis process,COFs have great potential in the fields of adsorption and sensing of aromatic compounds.In this paper,the adsorption performance of COFs with different pore sizes（Tp Pa-2、Tp BD、TFPB-BD）after magnetization was studied,and the adsorption method for BPA and BPS was established;the COF-LZU1 with better conductivity was selected,and a ratiometric electrochemical sensing method for simultaneous detection of BPA and BPS was constructed.The main studies and results are as follows:（1）COFs with different pore sizes（Tp Pa-2、Tp BD、TFPB-BD）were synthesized by solvothermal reaction.The corresponding magnetic COFs（Fe3O4/COFs）were conveniently prepared by co-precipitation method of highly ground COFs materials with Fe Cl3·6H2O and Fe SO4·7H2O,which were used for adsorption of BPA and BPS.The adsorption capacity of Fe3O4/Tp Pa-2,Fe3O4/Tp BD,Fe3O4/TFPB-BD for BPA and BPS were reached 44.85,24.14,2.61 mg/g and 49.82,18.35,8.66 mg/g respectively,so Fe3O4/Tp Pa-2 was the best adsorbent,and the adsorption process of BPA and BPS on Fe3O4/COF was further studied.The adsorption kinetic fitted the pseudo-second-order kinetic model and the adsorption isotherm fitted the Freundlich isothermal model.Both models demonstrated that the adsorption of BPA and BPS were based on multilayer adsorption on heterogeneous surfaces.In order to investigate the reusability of the material,the recycling experiment was carried out.The results showed that after five adsorption/desorption,the adsorption capacity of Fe3O4/Tp Pa-2for BPA and BPS could still reach 76.82%and 80.10%of first use,indicating that Fe3O4/Tp Pa-2 was a potential good adsorbent.（2）A carbon cloth（CC）electrodeposited with silver nanoparticles（Ag NPs）and drop-coated by covalent organic framework（COF-LZU1）was prepared,and a novel ratiometric electrochemical sensor was developed for simultaneous determination of BPA and BPS.SEM,FT-IR,thermogravimetric analysis（TGA）,and nitrogen adsorption analysis characterized the successful synthesis of COF-LZU1 and the modification of composite electrodes.The electrochemical properties of the composite electrodes were characterized by cyclic voltammetry（CV）,differential pulse voltammetry（DPV）,and electrochemical impedance spectroscopy（EIS）.The electrochemical activity of BPA and BPS and the adsorption mechanism on the electrode surface were investigated.The experimental parameters such as p H,COF concentration,and enrichment voltage were optimized,and a ratiometric electrochemical sensor for detecting BPA and BPS individually or simultaneously was established.Under optimized conditions,the sensor exhibited a linear range for BPA and BPS from 0.5μmol/L to 100μmol/L with a limit of detection of 0.15μmol/L（S/N=3）.In addition,the constructed ratiometric electrochemical sensor exhibited good reproducibility and stability,as well as excellent anti-interference ability,and has been successfully applied to the detection of BPA and BPS in beverage samples with recoveries of 95.9%～98.3%and88.3%～111.7%respectively. |
