Synthesis And Properties Of Homochiral Metal-Organic Framework Materials Functionalized With Amino Acids

Homochiral metal-organic frameworks(HMOFs),not only possess attractive topological structures,but also have potential applications in chiral recognition,chiral resolution,asymmetric catalysis and nonlinear optical materials.The most direct and effective strategy for the synthesis of HMOF materials is the self-assemblies of enantiomatically pure chiral organic ligands with metal ions so that the chirality of the used ligands can be transmitted to the whole frameworks of materials.Therefore,the design and synthesis of novel enantiomatically pure chiral organic ligands is the key to the construction of HMOF materials with novel structures and unique properties.In this thesis,based on the strategy of modifying aromatic polycarboxylic acids with natural chiral amino acids,we designed and synthesized enantiomatically pure chiral aromatic polycarboxylic acid ligands with large skeletons,constructed HMOF materials,and carried out the structure and related property research.Under hydrothermal/solvothermal conditions,the use of a enantiomatically pure chiral ligand of aromatic polycarboxylic acid modified by L-pyroglutamate,namely H3L[(S)-5-((2-carboxy-5-oxopyrrolidin-1-yl)methyl)isophthalic acid],to assemble with transition metal ions such as Zn(?),Cd(?)and Cu(?)resulted in five HMOFs with novel structures,namely ?[Zn4(L)2(OH)2(H2O)3]·3H2O}n(1),{[Zn4(L)2(dpe)2(OH)2(H2O)2]6H2O}n(2),[Cu(HL)2(H2O)2]n(3),{[Cu3(L)2(dpe)3]·2H2O}n(4),and {[Cd3(L)2(H2O)4]·4H2O}n(5)(dpe=1,2-bis(4-pyridinyl)ethylene).The structures and related properties of the complexes were characterized by single crystal X-ray diffraction analysis,powder X-ray diffraction analysis,circular dichroism(CD)spectra,infrared spectra,thermal analysis,fluorescence and nonlinear optics(NLO)measurements.The crystal structure analysis shows that the complexes 1,2 and 4 are three-dimensional(3D)homochiral coordination polymers with helical substructural units and complicated novel structures.Complex 1 is a 3D HMOF constructed from a seven-fold helical-chained substructural unit based on a quad-nucleated Zn cluster.Complex 2 is a 3D HMOF consisted of a meso racemic helical-chained substructural unit based on binuclear Zn.Complex 4 is a 3D HMOF based on a right-handed double-stranded helical substructural unit.Complexes 3 and 5 are two dimensional(2D)coordination polymers.Complex 5 is a 2D bilayer HMOF contained a 4-fold meso racemic helical-chained substructural unit based on a trinuclear Cd.In the construction of these complexes,the ligands H3L display six coordination modes.In particular,the introduction of amino acid groups on the ligands not only endows the homochiral characteristics of the synthetic framework materials,but also facilitates the construction of novel HMOFs with varied coordination patterns.The results of CD analysis further confirmed the homochirality of the complex 1-5.In addition,1 and 5 have good thermal stability and second-harmonic generation activity,and their second-harmonic efficiency is 1.15 and 0.95 times that of inorganic nonlinear optical crystal potassium dihydrogen phosphate,respectively.They may have potential applications in nonlinear optical materials.In this thesis,three amino acid-functionalized HMOFs synthesized and characterized by our group,namely Eu-HMOF-1({[Eu2(HL1)2(H2O)6]-2C1-2H2O}n,H3L1=(S)-5-(((1-carboxy-3-methylbutyl)amino)methy l)isophthalic acid),Cu-HMOF-1({[Cu2(HL2)2(bpy)]-2H2O}n,H3L2=((S)-5-(((1-carboxy-2-phenylethyl)amino)methyl)isophthalic acid,bpy=4,4'-bipyridine)and Cu-HMOF-2({[Cu2(HL2)2(dpe)]·H2O}n dpe=1,2-bis(4-pyridyl)ethylene),which have high stability,large cavity size,and hydrogen-bonding and aromatic ring action sites,were selected as solid phase chiral adsorbents,and the enantioselective adsorption of Rand S-phenylethanamine or R-and S-phenylethanol by three HMOF materials was systematically studied,using homochiral phenylethanamine and phenylethanol as adsorbent target molecules.The results show that Eu-HMOF has higher adsorption capacity and better enantioselective adsorption performance for S-phenylethanamine and S-phenylethanol,and the enantioselective adsorption ratio ra was about 2.0 and 4.1,respectively.Both Cu-HMOF-1 and Cu-HMOF-2 have higher adsorption capacity and better enantioselective adsorption performance for R-phenylethanol,and the theoretical enantioselective adsorption ratio ra was about 1.4 and 1.7.Further adsorption kinetics studies show that the adsorption of R/S-phenylethanamine or R/Sphenylethanol by Eu-HMOF can reach saturation within 24 hours,and that the maximum adsorption rates for R-phenylethanamine,S-phenylethanamine,R-phenylethanol and S-phenylethanol are about 2.6%,4.2%,3.7%and 5.7%,respectively.The adsorption of R-or S-phenylethanol by Cu-HMOF-1 can reach saturation within 5 hours,and the maximum adsorption rates for R-and S-phenylethanol are about 7.9%and 4.5%,respectively.The adsorption of R-and S-phenylethanol by Cu-HMOF-2 can reach saturation within 7 hours,and the maximum adsorption rates for and S-phenylethanol were about 16.3%and 11.8%,respectively.These results indicate that the three HMOFs have certain ability of enantioseparation for the racemic mixture of 1-phenylethylamine and 1-phenylethanol.In particular,Cu-HMOF-2 shows excellent adsorption capacity and higher enantioselectivity for R-phenylethanol,and has excellent enantioselective adsorption performance.The performance of Cu-HMOF-2 for the enantioseparation of racemic 1-phenylethanol was further studied by HPLC with chiral column.The results show that Cu-HMOF-2 has good enantioseparation for the racemic mixture 1-phenylethanol,and the enantiomeric excess(ee)is about 19.8%.