Studies On The Assembly And Properties Of Stable Metal Azolate/Carboxylate Frameworks

Due to the excellent properties such as high porosity and surface area,metal-organic frameworks(MOFs)with diversities and regulation as a class of crystalline porous materials have a great potential application in many fields to be one of the most promising materials in the 21 st century,constructed by organic linkers and metal nodes(metal ions or clusters),possessing the unique properties of the organic molecule and the inorganic metal.With the increasing stringent requirements for the properties of MOFs,the hot topic of MOFs is gradually developing towards its multi-functionality rather than the novelty of structures,improving the development of MOFs with more practical value and low cost.Therefore,the stability of MOFs is the key factor in its functional research.Carboxylic acid ligands and azole ligands are the most commonly used in the synthesis of MOFs.The coordination bonds between transition metal ions and azolates are stronger than that between transition metal ions and carboxylates.The metal-azolate frameworks are more stable and can meet the actual application conditions;however,the structures of metal-carboxylate frameworks are more diverse.Therefore,combining their advantages,novel MOFs simultaneously containing azolyl groups and carboxyl groups usually show stable.The dissertation mainly focuses on building the new metal-carboxylate-azolate systems,preparing ten complexes with the excellent properties in gas adsorption and luminescence solvothermally constructed by employing azolate/carboxylate ligands and Co2+,Cd2+ and Zn2+.The full text is divided into six chapters for discussion:In the first chapter,the concept,synthesis methods,stability and functional applications of MOFs are briefly expounded.Refering to several examples of stable MOFs,the research basis of the dissertation is proposed and the main research results are summarized.In the second chapter,employing 4,4'-biphenyldicarboxylic acid(H2bpdc),methyl-functionalized 3,3',5,5'-tetramethyl-4,4'-bipyrazole(H2bpz)as the coligand and Co(Cl O4)2,a stable framework [Co8.5(?4-O)(bpdc)3(bpz)3(Hbpz)3](1)was constructed,revealing two extremely rare trinuclear and tetranuclear metal-carboxylate-pyrazolate clusters extended by the ligand to form porous framework.Hydrophobic groups such as methyl and phenyl groups effectively enhance the stability of 1 towards water.In addition,the methyl group as the electron-donating group makes H2 bpz negatively,and enhances the interaction between the pyrazolate ring and CO2.The hydrogen atoms hanging on the polar pore surface react with the oxygen atoms of CO2.Thence,the framework displays remarkable CO2/N2 selectivity.In the third chapter,by reacting a rich-N carboxylate-triazolate ligand 3-(4-carboxylbenzene)-5-(2-pyrazinyl)-1H-1,2,4-triazole(H2cbptz)with Mn Cl2,a 3D cationic framework [Mn2(Hcbptz)2(Cl)(H2O)](Cl)·(DMF)·(CH3CN)0.5(2)was obtained,which reveals a very polar framework that contains the exposed metal sites,uncoordinated N atoms and Clbasic sites,leading to not only high CO2 uptakes but also remarkable selective adsorptions for CO2 over N2 and CH4 in 298-333 K.Grand canonical Monte Carlo(GCMC)simulations explored the multiple CO2-philic sites.Meanwhile,2 also shows excellent stability in the air.In the fourth chapter,the capture and conversion of CO2 is urgent and important.A new Co(II)-based MOF,{[Co2(tzpa)(OH)(H2O)2]·DMF}n(3)(H3tzpa =5-(4-(tetrazol-5-yl)phenyl)isophthalic acid)was constructed by employing a carboxylatetetrazolate ligand H3 tzpa and Co(NO3)2.The rigid coordination bonds between the tetrazolate ring and Co2+ make 3 exceptionally stable in acidic and basic aqueous solutions.More importantly,high-density open metal centers and ?3-OH groups in activated 3 lead to high CO2 adsorption capacity and siginficantly selective capture for CO2 over CH4 and CO,as well as the heterogeneous Lewis&Br?nsted acid bifunctional catalyst facilitating the chemical fixation of CO2 coupling with epoxides into cyclic carbonates under the ambient condition.The research is conducted through simulation calculations for the multiple CO2-philic sites and the cyclization reaction mechanism.In the fifth chapter,in order to further enhance the luminescence intensity of 4,4-(5-tetrazolyl)-benzoic acid(H2tzba)was modified by the F atom to give 2-fluoro-4-(5-tetrazolyl)-Benzoic acid(F-H2tzba),using similar synthetic methods to prepare isostructural complexes {[Zn3(tzba)3(dabco)]·5DMF·3H2O}(4)and {[Zn3(F-tzba)3(dabco)]·5DMA·3H2O}(5).The coligand dabco increases the size of the pore,while the F atoms dangling on the pore surface of 5,which can serve as CO2-philic sites and can be further enhance the interactions between 5 and metal ions or organic solvent molecules.Therefore,compared to 4,5 exhibits more efficient luminescent quenches for Cu2+ and NB,and more CO2 adsorption amounts and higher CO2/CH4 adsorption selectivities.MOFs were directionally regulated by the modification of substituents so as to optimize their properties.In the sixth chapter,five new Cd(II)complexes were assembled employing a carboxylate-tetrazolate ligand H3tzia(H3tzia = 5-(1H-tetrazol-5-yl)isophthalic acid)with Cd(II)ions,revealing versatile structures from zero-dimensional(0D)mononuclear molecule,2D layer to 3D framework.6-10 exhibit strong luminescence with different energies resulted from the various coordination modes of H3 tzia.The mechanism of luminescence for Cd(II)complexes was further investigated by density functional theory(DFT)calculations.