The Synthesis And Applications Of Functionalized Magnetic Covalent Organic Frameworks

Covalent organic frameworks?COFs?are a series of crystalline porous framework materials formed from organic building blocks,which have large surface area,good stability and facilely functionalization.Combining the merits of COFs and magnetic nanoparticles with good superparamagnetism and biocompatibility to prepare novel magnetic COFs composites is of great significance.In recent years,magnetic COFs have been widely used in the field of separation science.In this study,the specific functional groups were introduced into the magnetic COFs by postsynthetic modification to prepare functionalized adsorbents.And the adsorption properties of the adsorbents were studied.The main contents includes:?1?Firstly,the amino-functionalized COFs were coated on the surface of Fe₃O₄nanoparticles.Then three phenylboronic acid derivatives?2-formylphenylboronic acid,3-pyridylboronic acid and 4-formylphenylboronic acid?were incorporated to magnetic COFs by postsynthetic modification to obtain three magnetic COFs-based boronate affinity adsorbents.The adsorbents were characterized by scanning electron microscope?SEM?,thermogravimetric analysis and so on.The adsorption properties of the prepared adsorbents were evaluated by extraction of cis-diol containing compounds.Compared the extraction efficiency of three adsorbents,it was found that the 2-formylphenylboronic acid modified magnetic COFs?Fe₃O₄@COF@2-FPBA?had the best extraction efficiency for dopamine and catechol,and the adsorption capacities were 1037 and 693.5?mol g^-1,respectively.Thus,we choose the Fe₃O₄@COF@2-FPBA as the adsorbent to extraction monoamine neurotransmitters?MNTs?in urine samples.Under the optimal adsorption conditions,the linear range of the adsorbent for five MNTs were between 2-200 ng mL^-1,the recoveries were in the range of 86.3-115%,the intra-and inter-day relative standard deviations?RSDs?were lower than 14%.The result showed that the established method has high recoveries and good sensitivity,and it can be successfully used for the detection of MNTs in urine samples.?2?Based on the magnetic COFs,the different molecular weight polyethyleneimine?PEI?were grafted onto the surface of magnetic COFs by postsynthetic modification to obtain magnetic COFs-based hydrophilic adsorbents.The prepared adsorbents were characterized by scanning electron microscopy?SEM?,fourier transform infrared spectrometer?FT-IR?and elemental analyzer and so on.The adsorbents have good magnetic response and hydrophilicity.The adsorption properties of the adsorbents were studied for polar analytes including nucleosides,monoamine neurotransmitters and amino acids at the different ratios of acetonitrile.When the ratio of acetonitrile was 99%,PEI?Mw=600?grafted magnetic COFs?Fe₃O₄@COF@PEI-600?have better extraction efficiency for polar analytes.