Preparation Of Nitro/Amino Functionalized Magnetic Covalent Organic Framework Adsorbent And Its Application In The Analysis Of Bisphenols

Magnetic solid phase extraction is a sample pretreatment technique used to enrich and determine trace contaminants.Covalent organic framework（COFs）is considered an ideal material for applications in the field of molecular separation due to its low density,excellent stability,high surface area,easy-to-adjust pore size and chemical environment.In recent years,the combination of the advantages of various functional components to obtain core-shell composite materials has received more and more attention.In this work,Fe₃O₄ was used as the core of magnetic nanoparticles and COFs as the shell,and nitro and amino functionalized core-shell magnetic nanoparticles were prepared.The performance of the two adsorbents was studied.The main content is as follows:1.Using the superparamagnetic nanosphere Fe₃O₄as the core,coated with silica gel and the COFs shell layer was grown in situ using monomer as the medium to obtain core-shell Fe₃O₄@TpBD（NO₂）₂.A large amount of NO₂ was introduced into the hydrophobic COFs network to enhanceπ-πeffect.After reducing the nitro group,the amino-functionalized Fe₃O₄@TpBD（NH₂）₂ was obtained,and the large amount of-NH₂ on the surface could provide hydrogen bonding force.The nitro group was further reduced to obtain the functionalized Fe₃O₄@TpBD（NH₂）₂ with amino groups.The enrichment capacity and adsorption process of the adsorbent were studied.The results showed that the adsorption of bisphenol F and bisphenol A on Fe₃O₄@TpBD（NO₂）₂ was a spontaneous entropy heat-increasing endothermic process,with adsorption capacities of 206 and 239 mg/g.The adsorption capacities of Fe₃O₄@TpBD（NH₂）₂ on bisphenol F and bisphenol A were 286 and233 mg/g,respectively,and the adsorption was a spontaneous entropy reduction exothermic process.The retention mechanisms of the two adsorbents for bisphenols include hydrophobic interaction,p-pinteraction and hydrogen bonding,and the adsorption process of the two adsorbents conforms to the Freundlich adsorption model.2.Fe₃O₄@TpBD（NO₂）₂ and Fe₃O₄@TpBD（NH₂）₂ were used as adsorbents for the adsorption of five kinds of bisphenols,all of which had good reproducibility and reusability.The two adsorbents were used in magnetic solid phase extraction（MSPE）,combined with gas-mass spectrometry（GC-MS）to establish analysis methods for five phenolic substances.These methods had the advantages of wide linear range（0.1-100 ng/mL）and low detection limits（0.017-0.047 ng/mL and 0.013-0.043 ng/mL）.The recovery rates of bisphenols in spiked beverages were 82.6%-109.5%and 80.6%-103.9%,the intraday relative standard deviation（RSD）were less than 7.6%and 6.6%,respectively,and the interday RSD were less than 7.8%and 8.2%.MSPE can reach adsorption equilibrium within 1 minute,which improved the efficiency of rapid sample processing and analysis.Nitro and amino COFs-based adsorbents were applied to beverages,and trace amounts of bisphenol were detected.These results indicated that the detection method established based on the prepared adsorbent can be used for the detection and analysis of bisphenols in actual samples.