Metal-Organic Frameworks For Gas Chromatographic Separation And Solid Phase Microextraction Based On Shape And Size Selectivity

In this dissertation, metal-organic frameworks （MOFs） were utilized asadsorbents for solid phase microextraction as well as stationary phases for gaschromatographic separation for extraction and separation of alkanes. The shape andsize selectivity of MOFs was studied during the process of extraction and separation.The novel aspects of this dissertation are summarized as follows:（1） ZIF-8, a zeolitic imidazolate framework which had high thermal andchemical stability was introduced to fabricate capillary column for gaschromatographic separation. The ZIF-8nanocrystal coated capillary was shown notonly to have a strong ability to sieve branched alkanes from linear alkane isomersowing to the narrow pore windows but also to offer excellent features for highresolution gas chromatographic separation of linear alkanes due to van der Waalsinteraction between linear alkanes and the hydrophobic inner surfaces of themicropores. This feature made the ZIF-8coated capillary very promising for thespecific adsorption and separation of alkanes in complicated matrices. The adsorptionof target analytes into the micropores of MOFs was a necessary process in theseparation based on MOFs. ZIF-7, another zeolitic imidazolate framework with thesame topology of ZIF-8, could not separate alkanes because of the too narrow porewindow which inaccessible to alkanes.（2） The fabricated UIO-66coated capillary column had high affinity to branchedalkanes compared to linear alkanes, which exhibited reverse shape selectivity. UIO-66was the first MOF that had been observed to have that reverse shape selectivity.Besides, UIO-66coated capillary column gave high resolution gas chromatographicseparation of alkane isomers and benzene homologues with excellent selectivity andprecision. The adsorption enthalpies and entropies on the interaction betweenhydrocarbons and UIO-66were measured to illustrate the energy effect on theseparation of alkane isomers and benzene homologues. The combination of reverseshape selectivity with molecular sieving effect made the UIO-66coated capillarycolumn promising for the separation of structure isomers. （3） MOFs were employed to design tandem molecular sieve as a dual platformfor selective solid-phase microextraction and high-resolution gas chromatographicseparation of target analytes in complex matrices. Elegant combination of ZIF-8coated fiber for SPME with ZIF-8coated capillary for GC allowed selectiveextraction and separation of n-alkanes from complex matrices such aspetroleum-based fuel and biological fluids. The proposed tandem ZIF-8molecularsieve not only offered good enhancement factors from235（hexane） to1212（nonane）,but also exhibited wide linearity with3orders of magnitude for the tested linearalkanes. The limits of detection for the linear alkanes ranged from0.46ng L^-1（nonane） to1.06ng L^-1（hexane）. The relative standard deviations of retention time,peak area, peak height, and half peak width for five replicate determinations of thetested n-alkanes at30ng L^-1were0.02-0.26%,1.9-8.6%,1.4-6.0%, and1.3-7.2%,respectively. The developed tandem ZIF-8molecular sieve was further used for thedetermination of linear alkanes in petroleum-based fuel and human serum.