Construction And Properties Of Porous Coordination Polymers Based On Imidazole Derivative Ligands

As one of the most attractive porous materials in the 21st century,porous coordination polymers（PCPs）,also known as metal-organic frameworks（MOFs）,have drawn widespread attention in the fields of chemistry,biology,physics and materials science,due to their variable structures and adjustable pore properties.Over the past two decades,tens of thousands of PCPs have been reported.People are not only fascinated by their beautiful microstructures,but also constantly explore the relationship between structure and property,in the hope of reaching the ultimate goal of targeted synthesis at an early date.Therefore,in order to understand the relationship between ligand,metal,structure and property in more depth,this thesis selects six imidazole derivative ligands and in-depth researches into their performance in construction of PCPs materials.The main results of this thesis include the following three aspects:（1）Based on the direction-oriented strategy,by adjusting the ratio of water to organic solvent in the synthesis system,a type of brand-new 4-membered ring（4MR）metal-organic squares（MOSs）with both trans-and cis-coordinated nodes was prepared under solvothermal conditions and three novel zeolite-like supramolecular assemblies（ZSAs）,[Co4（ImDC）4（En）4]·9H2O·1.5DMF（compound1）,[Co4（ImDC）4（En）4]·7H2O（compound 2）,[Cd4（HImDC）4（1,2-DACH）4]·3H2O·DMF（compound 4）,and a non-zeolite-like material,[Co4（ImDC）4（En）4]·xGuest（compound3）,had been synthesized with 4,5-imidazoledicarboxylic acid（H3ImDC）ligand.Compound 1 possesses underling zeolite MER topology and is the only pure MER framework material（without any supporting templates）exhibiting permanent porosity and also exhibits excellent CO2 adsorption capacity and CO2/CH4 selectivity.Compound 2 owns zeolite ABW topology and shows a highly selective adsorption capacity for water vapor.Compound 2 also exhibits single-crystal to single-crystal（SC-SC）transformation phenomenon in water,and transfers to compound 3.Compound 4 is composed of a type of cis-MOS and exhibits zeolite RHO topology.（2）Based on the functional modification strategy,three different functionalized ligands were obtained by introducing three functional groups to the 2-position of H3ImDC ligand:2-hydroxymethyl-4,5-imidazoledicarboxylic acid（CH2OH-ImDC）,2-Amino-4,5-imidazoledicarboxylicacid（NH2-ImDC）,2-propyl-4,5-imidazoledicarboxylic acid（Pr-ImDC）.In addition,we additionally introduced another large organic diamine,1,2-cyclohexanediamine（1,2-DACH）,to study the relationship between capping ligands and properties.Therefore,we successfully synthesized three new ZSAs,namely[Co4（CH2OH-ImDC）4（1,2-PDA）4]·8H2O（compound 5）,[Co4（Pr-ImDC）4（1,2-PDA）4]·9H2O（Compound 6）and[Co4（ImDC）4（1,2-DACH）4]·xGuest（Compound 8）,and further researched into[Co4（NH2-ImDC）4（1,2-PDA）4]·8H2O（Compound 7）which was partially studied in the previous work.These four ZSAs exhibit same GIS topologies.Compared to ZSA-1,the introduction of functional groups reduces the porosity of the material,resulting in a decrease in the BET surface area.Among them,Lewis base sites（LBSs）functionalized Compound 5 and Compound 7 exhibit excellent CO2 adsorption ability and high CO2/CH4 selective separation ability than alkyl groups modified compound 6due to the strong interaction between LBSs and CO2 molecules.Although compound8 does not additionally introduce functional groups,the large 1,2-DACH molecules greatly reduces the porosity,which reduces the CO2 adsorption,but improves the separation ability of CO2/CH4 due to the pore size effect.（3）Based on the desymmetrization strategy,two low-symmetry imidazole derivativeligandsweredesigned:2,4,5-tri（4-pyridyl）imidazole（Htpim）,2-（3,5-dicarboxyphenyl）-1H-imidazole-4,5-dicarboxylic acid（H5DpImDC）.Two isoreticularPCPswereconstructedbyHtpimligand:[Co2（μ2-OH）（bpdc）（Htpim）2·SiF6]^-·H3O⁺·3.5DMA·2CH3OH（Compound9）,[Ni2（μ2-OH）（bpdc）（Htpim）2·SiF6]^-·H3O⁺·7.5DMA·5.5CH3OH（Compound 10）.Two compounds with cis-trans isomerism were constructed under solvothermal conditions using H5DpImDC ligand:[Zn5（DpImDC）2（DMF）4（H2O）3]·H2O·DMF（Compound 11）and[Co5（DpImDC）2（DMF）4（H2O）6]·DMF（Compound 12）.In addition,a type of novel ZMOFs[Cd3（HImDC）3（DMF）]·xGuest（compound 13）was constructed using H3ImDC ligand.Compound 9 and Compound 10 are isoreticular to each other except for the metal ions.Both of the compounds possess finite binuclear[M2（μ₂-OH）（COO）2]secondary building units（SBUs）which formed with a polar functional groupμ2-OH.Both Compound 9 and Compound 10 have a high BET surface area and good CO2adsorption capacity.IAST calculations show that Compound 9 has excellent selective separation ability of C3H8/CH4.Compound 11 and Compound 12 are a pair of structurally and topologically similar compounds.However,due to the cis-trans isomerism in a mononuclear metal node,the symmetries of the two structures are quite different.In addition,compound 11 exhibits excellent detection performance for the nitroaromatic explosives.Compound 13 is a type of novel ZMOFs based on classical MOC SBBs connected by single metal ion and owns LTA zeolitic topology.