A New Gas Chromatographic Separation Method Based On Metal Organic Framework Nanosheets And Ultra-microporous Metal Organic Framework

Capillary gas chromatography is an efficient separation technique,which has significant applications in environmental monitoring,petrochemical analysis,and food detection.However,current commercialized column has limitations on the separation of structural isomers.To resolve this problem,metal-rganic frameworks(MOFs)have unique advantages in separation science due to their rich structure and easily tuning.In this dissertation,effects of stacking mode of two-dimensional MOFs nanosheets and pore size of three-dimensional MOFs on the separation of alkane and substituted benzene isomers were investgated.The separation and adsorption mechanism were studied in order to promote progress of chromatographic separation technology.The detailed research contents and mainly results in ths dissertation are as follows:1.Untwisted Restacking of 2-D Metal-Organic Framework Nanosheets for Highly Selective Isomer SeparationsThe stacking between nanosheets is an intriguing and inevitable phenomenon in the chemistry of nano-interfaces.Two-dimensional(2-D)metal-organic framework(MOF)nanosheets as emerging new type of 2-D materials with ultrathin and porous features,which are high potential in the separation applications.The stacking between single-layer 2-D MOF nanosheets with precise positions are revealed for Zr-1,3,5-(4-carboxylphenyl)-benzene(BTB)framework as an example.Three thermodynamic-favored conformations were observed with the tilted angles of 8°,14° and 30°between adjacent nanolayers.Efficient untwisted stacking strategy of simple heating was proposed.A detailed structural analysis of stacking modes revealed the creation of highly ordered sub-nanometer micropores in the interspacing of untwisted Zr-BTB-FA nanosheets,yielding a high-resolution separator for the pair of para-/meta-isomers over the twisted stacking precursors and commercial column.This general method is proven by the additional MOF nanosheet examples and supported by Grand Canonical Monte Carlo(GCMC)simulation.This new finding will provide a synthetic route in the rational design of desirable functionalities in 2-D MOF nanosheet.2.Ultramicroporous Metal-Organic Framework for Capillary Gas Chromatography SeparationSynthesis of ion hybrid metal organic framework SIFSIX series materials,by changing the length of organic ligands to control pore size of MOFs from microporous to ultramicroporous scale.The channel of SIFSIX presents a one-dimensional square straight channel with large porosity.Compared with microporous SIFSIX-1-Zn column,the capillary column coated with ultramicroporous SIFSIX-3-Zn can efficiently separate alkane isomer and substituted benzene isomer.The elution order of analyte is based on the boiling point,which the alkane isomers separation can be achieved at relative lower temperatures.The measurements of column efficiency and McReynolds constant also confirmed the difference between SIFSIX-3-1-Zn and SIFSIX-1-Zn coated columns,and further interpretateing effect of MOFs pore structure on the separation performance.