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Synthesis and Preparation of Metal Organic Frameworks Based on Metals such as Zinc, Copper, Chromium and Nickel and their Applications in Microextraction Techniques

Javanmardi, Hassan | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53941 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagheri, Habib; Abbasi, Alireza
  7. Abstract:
  8. The main approach of this thesis is the study of metal- organic frameworks (MOFs) performance as extractive phases in sample preparation methods. Hence, various MOFs were synthesized to investigate the roles of sorbent properties such as surface areas, pore sizes and shapes, interaction types, bonds and building units in extraction procedures of analytes. The prepared sorbents in conjugation with gas chromatography- mass spectrometry (GC-MS) were applied to determination of the environmental pollutants like chlorobenzenes, benzene derivatives (BTEX), polyaromatic hydrocarbons (PAHs) and residues of agriculture herbicides.In the first work, considering studying the roles of the sorbent pore size and shapes in extraction efficiency, two MOFs with the same molecular formula, based on nickel metal salt and benzene dicarboxylic acid and 1,4-diaza bicyclo [2.2.2] octane ligands were synthesized by solvothermal and precipitation techniques, which results two distinct structures with different pores. The sorption performance of as-synthesized structures was evaluated toward chlorobenzenes and BTEX in aqueous samples with needle trap extraction. The obtained results show the size and shape effects of pores in extraction properly. Using the more capacitance sorbent, the influencing parameters on extraction procedure such as desorption temperature and time, the ionic strength of solution, sample stirring rate and extraction temperature and time were investigated and optimized. The detection limit of the optimized method for extraction of chlorobenzenes coupling with GC-MS was in the range of 2-10 ng L-1. The linear dynamic range (LDR) and relative standard deviation (RSD) were 6-1000 ng L-1 and 5-12%, respectively. Relative recovery (RR%) amount of the method for Tehran tap water, Persian Gulf, Karoun and Zayandeh Rood rivers samples were obtained in the range of 85-96%.In the second research, for investigating the effect of the functional group on MOF performance in solid phase microextraction (SPME), the stable structure of MIL-101-NH2 based on chromium metal salt and 2-amino benzoic acid ligand was synthesized through solvothermal method. Then, the sorbent surface functionalized with acyl chloride and ethanol by post synthetic modification (PSM) and as the result two modified structures (ethylated and acylated) were obtained. The efficiencies of three sorbents with different functional groups were evaluated in the sorption and extraction of four organophosphorus pesticides (OPPs) in the tomato sample as model analytes. The sol-gel technique with APTES precursor was used for better fix of MOF structures on stainless steel needle as nonfragile metallic substrate. After preparing the tomato sample, the performance of the prepared fibers was compared to each other. The prepared fiber with acylated MOF shows superior performance in solid phase microextraction of model poisons from sample matrix. Afterward the fiber- to- fiber repeatability was examined and the results approve similar efficiencies for different fibers. Influencing parameters in the extraction procedure such as ionic strength, stirring rate and time extraction were investigated. Under optimized condition, the developed method had detection limits in the range of 0.2-1 ng L-1 and LDR of 1-1000 ng L-1 with regression coefficient (R2) more than 0.99. the RSD values at different concentration levels were less than 12%. Recovery percentages of the method in tomato samples spiked with OPPs were in the range of 80-95%.In the third work, to investigate the role of metal and ligand type in extraction efficiency of volatile organic compounds (VOCs) in aqueous samples, a set of sorbents including eleven MOFs based on chromium, zinc and iron metals salts with ligands containing 2,6-naphthalenedicarboxylic acid, benzene dicarboxylic acid and 2-aminobenzene dicarboxylic acid were synthesized. In following, for more investigation of PSM effect, the surfaces of some obtained structures were functionalized with benzyl functional group via the reaction with benzyl alcohol. The performance of each of the synthesized structures were evaluated in headspace needle trap extraction of PAHs, chlorobenzenes and BTEX from aqueous samples. Also, the effect of PSM on the hydrophobicity of sorbents was evaluated. Eventually, one of the structures modified with benzyl alcohol as optimized sorbent was applied to develop an analytical method in the measurement of PAHs in tea, coffee and rivers water samples. Therefore, all effecting parameters on the extraction procedure were optimized. Under optimized condition, the developed method had limitation of detection (LOD) and limit of quantification (LOQ) values less than 0.3 ng L-1 and 0.8 ng L-1, respectively. Furthermore, R2 was more than 0.99, while the RSDs in various concentrations were less than 11%.In the fourth work, to investigate the effect of similar structures in analyte and sorbent, on the extraction and adsorption efficiency, nitrogen-rich bis-tetrazole ligand was synthesized and then, a stable structure based on zinc metal salt and nitrogen-rich ligand were synthesized. To evaluate the role of similar structures presence in the analyte molecule and adsorbent network and their effect on the adsorption efficiency, the synthesized nitrogen-rich structure capability in comparison with other nitrogen-free and commercial adsorbent compounds in the extraction of triazines and BTEX was investigated. The obtained results showed higher efficiency of nitrogen-rich structure in the extraction of triazines. The synthesized sorbent was used in the development of an extraction method based on dispersive micro solid phase extraction in combination with gas chromatography-mass spectrometry to quantify triazine herbicides in paddy, field and river water samples. The obtained analysis results for the developed method showed limits of detection values less than 11 ng L-1 and a linear dynamic range was in the range of 6-1000 ng L-1 with a regression coefficient (R2) greater than 0.99 . Also, the RSD and RR values of the method were less than 8% and 89-98%, respectively
  9. Keywords:
  10. Post-Synthetic Modification ; Solid Phase Microextraction ; Needle Trap Extraction ; Gas Chromatography/Mass Spectrometry (GC/MS) ; Water Samples ; Metal-Organic Framework ; Biological Sample ; Pesticides Residue

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