| Metal-Organic Frameworks(MOFs)are composed of metal ions(ion clusters)and organic ligands through chemical bonds.Due to the adjustable structure and function,MOFs have been widely studied by researchers in recent years.MOFs based materials have bright application prospects in the fields of gas storage,catalytis,magnetism,fluoresecence detection,and so on.In our dissertion,two isostructural phenoxy-containing polycarboxylic acid ligands were selected as organic building units to react with rare earth and transition metal salts through solvothermal method.The structures,luminescence sensing and magnetic properties of these MOFs were investigated in details.The main work of this thesis includes the following three aspects:1.Four Ln-MOFs,namely,[La(L1)(DMF)2]n(1),{[La(L2)(H2O)3]?H2O}n(2),[Gd(L1)(DMF)2]n(3)and[Dy(L1)(DMF)2]n(4),were synthesized by the reaction of3,5-bis[(2-carboxyphenyl)oxy]benzoicacid(H3L1)and3,5-bis[(3-carboxyphenyl)oxy]benzoic acid(H3L2)with rare earth metal salts.Complexes1,3 and 4 are isostructural and all display one-dimensional chain structures,in which two adjacent Ln3+ions are bridged by carboxylic acid ligands to form Ln2(COO)4 binuclear units and each L13-anion is linked to four adjacent Ln3+ions by(?2-?1)-(?1-?1)-?4coordination.Complex 2 demonstrates special two-dimensional structure.The L23-ligands are in(?1-?1)-(?1-?1)-(?1-?1)–?6 coordination mode and M-type configuration.In the layered structure,each La3+ion is bridged by six carboxylic acid groups,forming a macrocycle with La6(CO2)12 as its components.Topologically,the flexible ligand and La centers could be viewed as 6-connected nodes,and the whole 2D net was represented as a novel binodal(6,6)-connected net with Schlafli symbol of(415)2.Luminescence measurements reveal that two complexes exhibit blue emission at 351 nm in the solid state and demonstrate excellent fluorescence sensing properties in DMF.These two complexes have specific recognition and fast response toward Fe3+,Cr2O72-and benzothiazole organic compounds.Theoretical analysis on the UV-vis spectra of the ligand H3L1 and the low-temperature fluorescence spectra of its Gd complex(complex 3)indidate that this aromatic carboxylate ligand may exhibit antenna effect through possible effective energy transfer from the ligand to Eu3+or Tb3+ions.Magetic measurements indicate antiferromagnetic interactions may be present between Gd3+or Dy3+ions in complexes 3and 4,respectively.2.Two Ln-MOFs,[Eu(L1)(DMF)2]n(5)and[Tb(L1)(DMF)2]n(6),were synthesized from 3,5-bis[(2-carboxyphenyl)oxy]benzoic acid(H3L1).Complexes 5 and 6 are isomorphous complexes with complex 1,which possess one-dimensional chain structures and characteristic red and green emissions of Eu3+and Tb3+at solid state.The two complexes are stable in common organic solvents.Interestingly,reversible crystal-to-crystal transformation was observed in H2O and DMF.Also,the transformed phases exhibit stronger luminescence intensity in H2O.The two complexes have excellent fluorescence sensing properties toward Fe3+,Cr2O72-and Cr O42-in both DMF and H2O.The detection limits of Cr2O72-are lower in the latter.Additionally,two complexes possess fluorescence quenching effect for benzothiazole organic compounds in H2O and the distinguishment of AMOE and BEM could be realized by complex 6 whilst not by complex 5,althouth they are isostructural.A series of bimental and trimental doped complexes were constructed by tuing the stiohiometric ratio of different Ln3+ions.The bidoped EuxTb1-x complexes exhibit emissions range from red to yellow and green by doping Eu(NO3)3 and Tb(NO3)3 in the ratio of 9:1 to 1:9.ICP measurements show that the actual proportion of metal ions in the doped complexes is consistent with the theoretical proportion.White light material was obtained by doping Eu(NO3)3,Tb(NO3)3 and La(NO3)3 with combined red,green and blue emssions.The trimetal coped complex Eu0.5093Tb0.2323La0.2584 can detect C2O42-in H2O through the change of characteristic emission color from white to blue,which is one of the rare complexes that were explored for detection of C2O42-.Thus,the emission and sensing activities could be tuned and improved by mixed-lanthanide complexes.3.Seven transition metal MOFs,namely,[Cd3(L1)2(4,4-bpy)]n(7),{[Cd3(L1)2(bpea)3(H2O)4]?2H2O?4DMF}n(8),[Cd3(L1)2(DMF)4]n(9),[Co3(L1)2(DMF)4]n(10),[Mn3(L1)2(DMF)4]n(11),[Mn3(L2)2(H2O)4]n(12)and{[Zn(L2)(bpe)]?2H2O}n(13),were synthesized by the reaction of 3,5-bis[(2-carboxyphenyl)oxy]benzoic acid(H3L1)and3,5-bis[(3-carboxyphenyl)oxy]benzoic acid(H3L2).In Complex 7,the L13-ligand adopts(?2-?2)-(?2-?1)-(?1-?1)–?6 coordination mode,connecting Cd2+ions to form one-dimensional metal-carboxylate chains,which are linked further by 4,4-bpy to form three-dimensional framework.The L13-ligand in complex 8 is coordinated in(?1-?0)-(?1-?1)-(?1-?1)–?3 mode.The Cd2+ions are connected form a two-dimensional layer structure.Complexes 9-11 are isostructural layers,in which L13-ligands in(?2-?1)-(?1-?1)-(?1-?1)–?6 coordination mode connect the two metal ions to form binuclear structural units.In complex 12,the L23-ligand adopt(?2-?1)-(?2-?1)-(?1-?1)–?6 mode,connecting Mn2+ions to form a three-dimensional framework.Complex 13 also displays two-dimensional layer structure.Luminescence measurements reveal that complexes 7-9exhibit excellent selectivity and sensitivity toward Fe3+and Cr2O72-in DMF.Magnetic results indicate the metal centers within complexes 10-12 exhibit ferromagnetic or antiferromagnetic interactions. |
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