限进磁性金属有机骨架材料的研制及其在微耗损磁固相萃取自由溶解态污染物中的应用

The freely dissolved concentration (Cfree) of pollutants in environmental matrix is a key parameter to interpret the environmental processes and to evaluate environmental and biological effects of pollutants. Although negligible depletion extraction can be used to determine Cfree of organic pollutants accurately, most methods based on this technique suffered from the long time required to reach the extraction equilibration of analytes, which can be overcome by using nanomaterials of metal-organic frameworks (MOFs) for its unique structure and composition. The project aims to study the synthesis restricted-access magnetic MOF composites and their application as adsorbents of negligible depletion-magnetic solid phase extraction, for the achievement of fast extraction and measurement of freely dissolved pollutants. Using polycyclic aromatic hydrocarbons (PAHs) as the model of low molecule weight pollutants, the pore size of MOFs will be adjusted to selectively (“restricted-access”) extract the freely dissolved low molecule weight pollutants, and the composition of MOFs will be manipulated to ensure that the pollutants are extracted based on the partitioning equilibration for eliminating the competitive adsorption of coexisting substances in environmental samples. Additionally, the magnetic functionalization of MOFs materials will be performed to facilitate separation operation during extraction. Finally, the factors influencing negligible depletion-magnetic solid phase extraction will be optimized. The implement of this project will provide a rapid and efficient method for the measurement of Cfree of environmental pollutants, and provide technical support for studying the environmental risk of pollutants, which has important academic significance and great potential in applications.

环境基质中污染物的自由溶解态浓度(Cfree)是解释污染物的环境过程和评估其环境和生物效应的关键参数。微耗损萃取技术可准确测定Cfree，但现有方法普遍存在萃取平衡慢等不足。金属有机骨架(MOFs)因其独特的结构和组成，可在短时间内达到对目标物的萃取平衡，为解决此难题提供了可能。本项目旨在研制限进磁性MOFs作为微耗损磁固相萃取的吸附材料，实现对自由溶解态污染物的快速萃取测定。拟以多环芳烃为模型污染物，通过调控MOFs的孔径，实现对自由溶解态小分子污染物的选择性（“限进性”）萃取；同时调控MOFs的组成以确保对目标物按分配平衡机制进行萃取，消除环境样品中共存物竞争吸附的干扰；再将MOFs磁功能化，以便萃取分离操作；最后，对萃取条件进行优化。项目的实施，可望发展出一种快速、高灵敏测定环境污染物Cfree的新方法，为科学评估污染物的环境风险提供新的技术手段，具有重要的学术意义和良好的应用前景。

环境污染物的自由溶解态浓度（Cfree）控制其蒸发、吸附、生物降解等多个过程，但现有Cfree测定方法普遍存在萃取平衡慢等不足。本研究研制限进磁性金属有机骨架（MOFs）并将其作为微耗损磁固相萃取的吸附材料，发展了一种适用于自由溶解态污染物的高效萃取测定方法。主要结论如下：通过调控反应物浓度和反应时间，成功制备了适用于自由溶解态浓度的限进磁性MOFs材料—Fe3O4@MIL-101(Cr)。采用X射线粉末衍射（PXRD），扫描电镜（SEM）、透射电镜（TEM）、X射线光电子能谱（XPS）和红外光谱（IR）等手段对此材料进行了表征。测试结果显示：制备的Fe3O4@MIL-101(Cr)复合材料同时具有MIL-101(Cr)的多孔性质和磁性纳米粒子的超顺磁性；Fe3O4@MIL-101(Cr)为花朵状的球形核-壳结构。以多环芳烃（PAHs）为模型化合物，发展了以限进磁性MOFs材料为微耗损萃取吸附剂的PAHs Cfree测定新方法。MIL-101(Cr)的孔窗结构可有效排阻与环境基质结合的PAHs，因而限进磁性MOFs仅选择性萃取自由溶解态的PAHs。磁性MOFs大的比表面积和孔体积，极大地增加了材料与PAHs的接触面积；并且，多环芳烃和磁性MOFs之间存在疏水性、π-π和π-金属离子等多种相互作用。上述性质使得磁性MOFs能够快速高效地萃取水中的自由溶解态PAHs，萃取平衡时间仅为传统nd-SPME的1/200。本研究建立了简便、快速、高效的自由溶解态浓度测定方法，已成功应用于实际天然水样中PAHs的Cfree测定。