Synthesis,Structure And Adsorption/Separation Properties Of Metal-Organic Frameworks Constructed By Multicarboxylate Ligands

Metal-organic frameworks?MOFs?,also known as porous coordination polymers,are formed by the self-assembly of metal ions or clusters and multitopic bridging ligands linked through metal coordination bonds,which are a new kind of organic-inorganic hybrid materials.Compared to traditional porous materials,MOFs have high specific surface areas and pore volumes,tuneable pore sizes/shapes,and modifiable pore surfaces,thus offering MOFs promising applications in various fileds including but not limited to molecular sensing,heterogeneous catalysis,drug delivery and gas storage and separation.The dissertation has been mainly focused on design and synthesis of aromatic multicarboxylate ligands and solvothermal construction of their corresponding copper-based MOFs.their structures were determined by single-crystal X-ray diffraction,and gas adsorption properties with respect to acetylene?C2H2?,carbon dioxide?CO2?,and methane?CH₄?were systematically investigated.1.Five linear diisophthalate ligands with the same length but different organic functionalities?-NH2,-CH3,-NO2,-F,and-CF3?,termed H₄L1,H₄L2,H₄L3,H₄L4,and H₄L5,were synthesized and successfully incorporated into MOFs with NbO-type topology.The resulting MOFs are termed ZJNU-34?NH2?,ZJNU-35?CH3?,ZJNU-36?NO2?,ZJNU-37?F?,and ZJNU-38?CF3?,respectively.Their gas adsorption properties with respect to C2H2 were systematically investigated.The results show that compared to the parent compound,the electron-donating functional group functionalized MOF compounds exhibit comparable and even higher C2H2 uptakes,while those functionalized with electron-withdrawing groups do not exhibit better C2H2 uptakes.Specifically,the amine group-functionalized compound ZJNU-34?NH2?exhibits the highest C2H2 uptake capacity of the five MOF compounds investigated,reaching as high as 193.8 cm3?STP?g-1 at 298 K and 1 atm.This work provides a basic understanding of the effect of functional groups on C2H2 adsorption,which is useful for future design of porous MOFs with enhanced acetylene-storage capacities.2.Six naphthalene-based diisophthalate ligand isomers,termed H₄L6,H₄L7,H₄L8,H₄L9,H₄L10 and H₄L11,were designed and synthesized.Subsequently,seven copper-based MOF isomers derived from these lgiands were successfully constructed under the appropriate solvothermal conditions,termed ZJNU-71,ZJNU-72,ZJNU-73,ZJNU-74,NOTT-103,ZJNU-77 and ZJNU-78,respectively.According to the single crystal X-ray structure analyses,those MOFs can be divided into two categories:ZJNU-71,ZJNU-72,ZJNU-73,ZJNU-74 and NOTT-103 are considered as ligand-orginated MOFs isomers,while ZJNU-77 and ZJNU-78 belong to supramolecular isomers.Accordingly,the effects of ligand-orginated MOFs isomerism and supramolecular isomerization on C2H2 storage and separation/purification performance were systematically studied.This work provides a fundamental understanding of the effect of ligand-originated MOF isomerism and MOF polymorphism on gas adsorption properties,which provides valuable guidance for further design and synthesis of MOF materials with better performance.3.We designed and synthesized six unsymmetrical diisophthalate ligands consisting of two terminal isophthalate units bridged by the central naphthyl moiety,termed H₄L6,H₄L12,H₄L13,H₄L9,H₄L14 and H₄L15,respectively,and successfully constructed their corresponding copper-based MOFs,termed ZJNU-71,ZJNU-70,ZJNU-69,ZJNU-74,ZJNU-75 and ZJNU-76,respectively.Their gas adsorption properties with respect to C2H2,CO2,and CH₄ were systematically investigated.This work not only demonstrates that the six MOFs are promising materials for C2H2/CH₄ and CO2/CH₄ separations,but also reveals the effect of alkoxy group on gas adsorption properties,which is dependent on the parent compounds.