Application Of Metal-Organic Framworks For Removal And Solid Phase (Micro-) Extraction Of Organic Polltant

Metal-organic frameworks （MOFs） have received great attention due to theirfascinating structures and intriguing potential applications in various fields. Thisdissertation focuses on the utilization of MOFs for the removal and solid-phase（micro）-extraction of organic pollutants. The main results are summarized as follows：The adsorption of malachite green in aqueous solution on a highly porousmetal-organic framework MIL-100（Fe） was studied in view of the adsorptionisotherm, thermodynamics, kinetics, and regeneration of the sorbent. The adsorptionisotherms of malachite green on MIL-100（Fe） followed the Freundlich model, andMIL-100（Fe） possessed heterogeneous surface caused by the presence of differentfunctional groups on the surface. The adsorption of malachite green on MIL-100（Fe）is controlled by an entropy effect rather than an enthalpy change, and obeyed apseudo-second-order kinetics. Analysis of the intraparticle diffusion plots revealedthat more than one process affected the adsorption, and film （boundary layer）diffusion controlled the adsorption rate at the beginning. Evidences from Zetapotential and X-ray photoelectron spectroscopic data showed the adsorption ofmalachite green was also driven by electrostatic attraction and the interaction betweenthe Lewis base-N（CH3）2in malachite green and the water molecule coordinatedmetal sites of MIL-100（Fe）. MIL-100（Fe） gave much higher adsorption capacity formalachite green than other conventional adsorbents such as activated carbon andnatural zeolite. The high adsorption capacity, good solvent stability, and excellentreusability make MIL-100（Fe） attractive for the removal of MG from aqueoussolution.The unusual properties such as high surface area, good thermal stability, uniformstructured nanoscale cavities and the availability of in-pore functionality andouter-surface modification make MOFs attractive for diverse analytical applications.However, integration of MOFs with magnet for magnetic solid-phase extraction foranalytical application has not been touched so far. Here we show a facile magnetization of MOF MIL-101（Cr） for rapid magnetic solid-phase extraction ofpolycyclic aromatic hydrocarbons （PAHs） from environmental water samples.MIL-101is attractive as the sorbent for solid-phase extraction of pollutants inaqueous solution due to its high surface area, large pores, accessible coordinativeunsaturated sites, and excellent chemical and solvent stability. In situ magnetizationof MIL-101microcrystals as well as magnetic solid-phase extraction of PAHs wasachieved simultaneously by simply mixing MIL-101and silica coated Fe₃O₄microparticles in sample solution under sonication. Such MOF-based magneticsolid-phase extraction in combination with high-performance liquid chromatographygave the detection limits of2.8-27.2ng L^-1and quantitation limits of6.3-87.7ngL-1for the PAHs. The relative standard deviations for intra-and inter-day analysiswere in the range of3.1%-8.7%and6.1%-8.5%, respectively. The results showedthat hydrophobic and π-π interactions between the PAHs and the frameworkterephthalic acid molecules, and the π-complexation between PAHs and the Lewisacid sites in the pores of MIL-101play a significant role in the adsorption of PAHs.Bio-MOF-1was employed as the coating for SPME fiber to extract PAHs. TheSPME fiber was fabricated by in situ growth of thin Bio-MOF-1films onhydrofluoric acid etched stainless steel wire. Fe and Cr source on the surface of thestainless steel wire after etching with hydrofluoric acid could give more activated sitefor connection with organic ligands. Zn source must be needed for subsequent growthof Bio-MOF-1film. Metal-π and π-π interaction between PAHs and Bio-MOF-1mayplay a significant role in the adsorption of PAHs. The developed approach offers widelinear range, low detection limits and good reproducibility.