| This thesis is devoted to the study on structures and properties of metal-organic frameworks (MOV) constructed from aromatic acid and hetercyclic bidentate bridging ligands on the basis of crystal engineering.In chapter 1, the basic conception, the progress of related MOF, and the significance of related study were summarized.In chapter 2, three new MOFs, [Cd3(5-NO2-bdc)2 (5- NO2-bdcH)2(bpyo)2]n (MOF 1), [Mn(5-NO2-bdc)(bbim)]n (MOF 2) and {[Gd(5-NO2- bdc)(5-NO2-bdcH)(H2O)2] (bpyo)0.5}n (MOF 3) (5-NO2-bdcH2 = 5-nitro-1,3- benzenedicarboxylic acid; bpyo = 4,4'-bipyridine-N,N'-dioxide;bbim=1,1'-(1,4-butanediyl)bis(benzimidazole)) were obtained under hydrothermal conditions and characterized structurally. The networks exhibit a variety of topologies and coordination modes at the metal centers. MOF 1 exhibits NaCl-type topology and contains the centrosymmetric trinuclear cluster SBU [Cd3(COO)4O2]. MOF 2 adopts CsCl-type topology based on bimetallic cores and is the first example of compounds containing cis bbim bridges. Moreover, MOF 3 possesses a 3D supramolecularframework by stronger contacts between 2D layers and non-rigid bpyo bridges. The thermal stabilities for MOF 1-3 was also examined. The photoluminescence properties for MOF 1 were also studied. Excitation at 340 nm leads to stronger fluorescent emission at 410 and 429 nm, which can probably be assigned to the intraligand (π-π*) fluorescent emission because similar emissions are observed for the free bpyo at 457 nm. Herein, we selected an anionic organic dye X3B, as a model pollutant in aqueous media to evaluate the photocatalytic effectiveness of MOF 3. The rate constant for 3 under UV-light irradiation was found to be 0.1022 h-1, whereas the rate constant for 3 under visible-light irradiation was 0.0138 h-1, when pseudo-first-order kinetics was fitted with the experimental data. Then the·OH radicals could cleave X3B to complete the photocatalytic process. The stability of MOF 3 was monitored using PXRD during the course of photocatalytic reactions, and its stability towards photocatalysis is good. MOF 3 represents the rare example of coordination polymers with 4f metal ion that exhibit good photocatalytic activity for dye degradation under UV light.In chapter 3, six MOFs, [Cu(bdc)(bimb)]n (H2bdc = 1,4-benzenedicarboxylate; bimb = 4,4'-bis(1-Imidazolyl)biphenyl) (MOF 4), [M3(btc)2(bimb)2·(H2O)x]n (M=Cu, x=3 (MOF 5),; M=Mn(MOF 6),Co (MOF 7),Cd (MOF 8), x=4),[Cd(btcH)(bimb)]n (MOF 9) [Cu3(btc)2(bimb)2·(H2O)3]n (H3btc = 1,3,5-benzenetricarboxylate) (MOF 5), [M3(btc)2(bimb)2·(H2O)4]n (M = Mn for MOF 6, Co for MOF 7, Cd for MOF 8) and [Cd(btcH)(bimb)]n (MOF 9) have been obtained under hydrothermal conditions and characterized structurally. The networks exhibit a variety of topologies: MOF 4 exhibits a triply interpenetrating 3D framework with distorted primitive cubic (a-Po) single net; MOF 5-8 are isomorphic, which possess trinodal 4-connected 3D framework; MOF 9 has a 2D (3,4)-connected framework. In addition, the thermal stabilities for MOF 1-9, the photoluminescence properties for MOF 8 and 9 were examined. Remarkably, an anionic organic dye X3B was selected as a model pollutant in aqueous media to evaluate the photocatalytic effectiveness of isostructural compounds MOF 6 and 7, and the results indicated MOF 6 and 7 represent the rare examples of coordination polymers that exhibit high photocatalytic activity for dye degradation under UV light and shows good stability towards photocatalysis. For MOF 6, the rate constant under UV-light irradiation was found to be 0.1084 h-1 and the rate constant under visible-light irradiation was 0.0727 h-1; For MOF 7, the rate constant under UV-light and visible-light irradiation was 0.2644 and 0.1348 h-1, respectively. The values of the band gap obtained from corresponding LMCT transitions are 4.04 and 3.72 eV for 6 and 7, respectively. Clearly, the band gaps of 6 and 7 follow the order 7 < 6 and the degradation rate of X3B follow the reverse order. The difference in catalytic activity between MOF 6 and 7 arises from the discrepancy in central metal ions of the two compounds. MOF 6 and 7 exhibit high photoeatalytic activity for dye degradation under UV light.In chapter 4, conclusions, features of innovation and prospects are presented about this work. |
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