Preparation Of Pyrazine-based Hypercrosslinked Porous Polymers And Their Application For Separation Analysis

Hypercrosslinked polymers（HCPs）are a class of emerging porous materials composed of lightweight elements.They are internally connected through Friedel-Crafts reactions,resulting in a highly crosslinked network,rich microporous structure,and stable framework.Compared to other porous materials,HCPs have the advantages of being easily synthesized,functionalized,and selectively tailored,as well as having a broad range of monomer options and low raw material cost.However,the preparation of HCPs is limited using external crosslinking agents such as dimethoxy methane,1,4-Dichlorobenzene and 1,4-Benzenedimethanol.The resulting HCPs are composed only of carbon,which lacks effective active sites,and the self-condensation of 1,4-Dichlorobenzene and 1,4-Benzenedimethanol reduces the purity of the target HCPs.These materials have low adsorption efficiency for polar analytes.To increase retention of polar analytes,hydrophilic groups can be introduced into the hydrophobic material skeleton.Therefore,the development of low-cost,structurally stable,and selectively specific hydrophilic-lipophilic balanced solid phase extraction materials and their combination with modern extraction techniques has become the key to solving the simultaneous extraction and analysis of different analytes in complex samples.This paper,used 2,5-dibromomethylpyrazine（2,5-DBMP）as an external cross-linking agent with high electrophilic activity to prepare a series of hydrophilic-hydrophobic balanced pyrazine-based HCPs,which were applied to capture gaseous iodine.To further evaluate the performance and separation analysis application of these pyrazine-based HCPs,the HCPs materials were applied to extract various samples in pre-treatment techniques and combined with HPLC,GC-MS,and other detection instruments to establish a new method for the separation and detection of various pollutants in environmental water samples and edible oil samples.The main content and relevant conclusions are as follows:1.A series of pyrazine-based HCPs were synthesized by a simple Friedel-Crafts reaction using 2,5-DBMP as an external cross-linking agent with high electrophilic activity.The highest specific surface area of the materials reached 908.23 m²·g^-1,and the materials had a rich microporous structure.The experiment further verified that the structure and pore distribution of HCPs could be regulated by changing the monomer type and the molar ratio of the monomer and crosslinking agent.The pyrazine-based HCPs had a high iodine capture capacity of up to 472 wt%,attributed to the high specific surface area of the materials,and the dual effective adsorption sites provided by the pyrazine and benzene rings in HCPs,which were beneficial for the selective recognition of guest molecules.The prepared HCPs were enhanced in iodine capture capacity by forming a charge transfer complex between the doped N atoms and polyiodide anions.In addition,the iodine-captured HCPs could be regenerated by ethanol immersion,and the reused HCPs still showed excellent iodine capture capacity and recovery rate after four cycles of experiments.2.HCP_Pz-TPB material was synthesized using 2,5-DBMP as an external cross-linking agent,and phenyl-modified Fe₃O₄@SiO₂ as a core to encapsulate HCP_Pz-TPB through continuous Friedel-Crafts reactions on its surface,resulting in a novel core-shell hydrophilic-lipophilic balanced magnetic hypercrosslinked polymers material（Fe₃O₄@SiO₂@Ph-HCP）.This material was used as an adsorbent for magnetic solid phase extraction（MSPE）combined with high-performance liquid chromatography-photodiode array detector（HPLC-PDA）to establish a new method for detecting seven different polar pollutants（4-nitrophenol,2,4-dichlorophenol,bisphenol A,triclocarban,triclosan,dibutyl phthalate and naphthalene）in environmental water samples.The linear ranges of the Fe₃O₄@SiO₂@Ph-HCP-MSPE-HPLC-PDA method were 0.05-2μg·m L^-1 for 4-nitrophenol,bisphenol A,naphthalene,triclocarban and triclosan,and 0.1-2μg·m L^-1 for 2,4-dichlorophenol and dibutyl phthalate,with detection limit detection limit（S/N=3）of 0.0019-0.016μg·m L^-1 and quantification limit（S/N=10）of0.0064-0.054μg·m L^-1.This method was successfully applied to separate and detect seven different polar pollutants in lake water,rainwater,and tap water,with spiked recoveries ranging from 78.91-119.25%,78.77-119.87%,and 83.61-116.46%,respectively.The results showed that the novel extraction agent Fe₃O₄@SiO₂@Ph-HCP had good extraction performance for different polar pollutants,providing a new method for extracting trace multi-target pollutants.3.The novel PDMS/HCP_Pz-TPB coating based on Sol-Gel method was synthesized,and a dumbbell-shaped stir bar sorptive extraction（SBSE）device was made.Compared with conventional PDMS coating,HCP_Pz-TPB has rich microporous structure and high specific surface area,providing multiple extraction sites.Based on this,the PDMS/HCP_Pz-TPB coating was applied to SBSE,and a new method for detecting 15 PAHs in edible oil samples was established by combining solvent desorption（SD）with gas chromatography-mass spectrometry（GC-MS）.The linear ranges of the newly developed PDMS/HCP_Pz-TPB-SBSE-SD-GC-MS method for the determination of the 15 PAHs were 0.6-150 ng·g^-1 and 1.2-150ng·g^-1,with detection limit（S/N=3）of 0.04-0.28 ng·g^-1 and quantification limit（S/N=10）of0.12-0.93 ng·g^-1.This method was successfully applied to the separation and detection of 15PAHs in three actual samples of olive oil,salad oil,and rapeseed oil,with recovery rates ranging from 83.52%to 117.79%,93.85%to 128.01%,and 93.19%to 120.20%,respectively.The results showed that the novel PDMS/HCP stir bar based on HCP_Pz-TPB has good extraction performance for PAHs in edible oils,and further research confirmed that the stir bar has good reproducibility and long service life.This work expands the coating types of SBSE and provides a solution for the application of SBSE in edible oils.