Synthetic Structures And Adsorption And Separation Properties Of Several Examples Of Zr/Ce(IV)-MOFs

The technology of methane storage and hydrocarbon separation and purification using porous materials as a medium has attracted great attention from scientists around the world.Metal-organic frameworks(MOFs),as a new class of porous solid materials,have shown potential applications in this field.However,for real applications,many MOFs still suffer from poor material stability,low storage capacity and low separation efficiency.In my thesis,two linear dicarboxylate and semi-rigid tricarboxylate ligands have been chosen to construct five new types of Zr/Ce(?)-MOFs,and further systematically explored their properties as methane storage and ethylene/propylene(C2H4/C3H6),ethane/ethylene(C2H6/C2H4),acetylene/ethylene(C2H2/C2H4)and acetylene/carbon dioxide(C2H2/CO2)separation materials.1.Synthesis,structure,methane storage and C3H6/C2H4 separation properties of two Zr(IV)-MOFs based on semi-rigid tricarboxylate ligandsWe selected semi-rigid ligand,4,4',4”-s-triazine-1,3,5-triyltri-p-aminobenzoic acid(H3TATAB),and ZrCl4 in the presence of dual modulators of trifluoroacetic acid and acetic acid to obtain two cases of Zr-MOF with new topological structures,namely srlMOF and spe-MOF.Further structural analyses reveal that both topologies are merged from 3-periodic edge-transitive nets with scarce ones,i.e.,3-c srs and 6-c Icy;(3,6)-c spn and(3,6,12)-c epw,respectively.They were fully characterized by single crystal X-ray diffraction(SCXRD),powder X-ray diffraction(PXRD),Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TG)and elemental analysis(EA).Then,the permanent porosity of both was tested respectively,and the results showed that the narrow window and channel sizes in the srl-MOF hindered the entry of guest molecules,which made its pores unable to be effectively used and prevented the subsequent study of srl-MOF in host-guest chemistry.Specifically,the spe-MOF exhibits structurally higher complexity,hierarchical micropores,open metal sites free and rich electronegative groups on the pore surfaces,leading to relatively high methane storage capacity without considering the missing-linker defects and efficient MTO product(C3H6/C2H4)separation performance.2.Synthesis,structure and dynamic transformation of a cerium(?)oxygen chainbased MOF and its derivatives' separation properties of C2H6/C2H4,C2H2/C2H4 and C2H2/CO2Cationic Ce(?)-MOF-0 with triangular one-dimensional channels was synthesized by the solvothermal reaction of azobenzene-4,4'-dicarboxylic acid linear ligand(H2L1)and(NH4)2Ce(NO3)6.Two new compounds,namely Ce(?)-MOF-1 and Ce(?)-MOF2,were formed by single crystal to single crystal transformation under solvent acetone exchange and vacuum heating at 60?,respectively.Three structures were characterized by SCXRD,PXRD,TG and EA.The low pressure adsorption and separation experiments show that both Ce(?)-MOF-1 and Ce(?)-MOF-2 are permanent microporous materials.Due to the difference in pore volume,triangular pore size and pore microenvironment between the two,Ce(?)-MOF-1 shows the ability of selective adsorption of C2H6,which can achieve one-step purification and separation of the C2H6/C2H4 mixed gas.Ce(?)-MOF-2 has the ability to selectively adsorb C2H2,so it can be used for efficient separation of C2H2/C2H4 and C2H2/CO2 mixtures,respectively.These separation results are not only supported by the ideal adsorption solution theory(IAST),but also further verified by penetration experiments.