Synthesis, Characterization, And Properties Of Main Group Metal (Pb~Ⅱand In~Ⅲ) Organic Frameworks

Metal-Organic Frameworks （MOFs） as a member of the porous materials, integrating the advantages of inorganic porous materials and organic porous materials. MOFs process large specific surface area, tunable pore size, functionalized channel surface and other characteristics, currently attracting noteworthy attention for their applications in gas storage, purification, molecular sensing, photoluminescence, and catalysis et al. They are one of the most promptly rising fields in chemical and material sciences. In practical applications, the stability of MOFs is one of the essential factors. Hence, the search for robust MOFs with high stability is urgent.Currently, the study of MOFs is focused on the synthesis, characterization and application of complexes based on transition metal and rare earth. While, the investigation of main group MOFs is relative few. Secondary electronic shell of the main group metal is full and there are no empty d orbitals. The main group metal coordinates with ligand by covalent bonds. So that the formation of MOFs may be possess high stability. Therefore, the design and synthesis of robust and excellent properties of main group MOFs and research of their catalysis, adsorption, ion-exchange, et al is very meaningful. With those parameters in mind, we choose main group metals （PbⅡ and InⅢ） and multi-acid organic ligand, five functional MOFs materials have been obtained by solvent thermal synthesis method. The structures of the five compounds were characterized and analyzed by X-ray diffraction, elemental analysis, IR and TG-DSC analysis. In addition, the thermal stability, chemical stability, adsorption, catalytic properties, post-synthesis and fluorescence properties of the compounds have been investigated. The main results of this thesis are as follows:1. Upon adjustment of the synthetic procedure, a series of novel robust molecular bowl-based Metal-Organic Frameworks were solvothermally isolated by employing 5-tert-butylisophthalic acid (H₂C₁₂H₁₂O₄) as ligand, [Pb₄(C₁₂H₁₂O₄)4（DMF）4]·_0.5H₂O （1） and [Pb₄(C₁₂H₁₂O₄)4（H₂O）4]·2DMA·4H₂O （2）.Both of 1 and 2 prosess open Lewis acid sites, which could act as Lewis acid catalysts to cyanosilylation reaction. The cyanosilylation reaction was catalyzed by the open metal sites both on the surface and inside the channels of the catalyst. Interestingly, through slight changes in the the reaction conditions, the micro-（1a） and nanosized（1b） forms of 1 were isolated. Due to the size of catalyst is reduced, a large number of active sites exposed. Thus, the catalytic activity is no longer limited by the catalyst pore size, larger sizes of the substrates also exhibits excellent catalytic activity. The present study will demonstrate that the catalytic activity of the as-prepared molecular-bowl based MOFs could increase by modulating of the catalysts size.2. An exceptionally robust metal-organic framework, with ID nanotubular open channels, In2（OH）（btc）（Hbtc）0.4 （L）0.6·3H₂0 （3）, has been synthesized via an in situ ligand reaction by employing main group metal In（NO₃）₃,1,2,4-H₃btc and piperazine, in which 1,2,4-Hsbtc is partially transformed into the L ligand.Compound 3 exhibits highly selective sorption of CO₂ over N2. Both Lewis acid sites and Br（?）nsted acid sites are involved in compound 3. As a result, as a heterogeneousLewis acid and Br（?）nsted acid bifunctional catalyst,3 possesses excellent activity and recyclability for chemical fixation of CO₂ coupling with epoxides into cyclic carbonates under mild conditions.3. A new anionic porous MOF with SrAl₂ topology has been solvothermally isolated by employing main group metal InIII and tetracarboxylic acid ligand （H₄L 2,3’,5,5’-biphenyl tetracarboxylic acid） as precursors, [（CH₃）2NH₂] [In（L）]·CH₃CH₂OH（4）.Compound 4 could act as an excellent host for encapsulation and sensitization of Ln³⁺ and highly selective absorption and separation of cationic dyes via ion-exchange processes. The results showed that the compound 4 could serve as an antenna to sensitize Ln³⁺ cations, especially suitable for Tb³⁺ and Eu³⁺ ions. The possible sensitization mechanism has been studied by surface photovoltage spectroscopy for the first time. In addition, the compound 4 could also applied in the selectively absorption of cationic dyes, which features good reversibility. It can be used as an ion chromatographic stationary phase for the selective separation of cationic organic dyes.4. A new bearing free carboxylic acids MOF with PtS topology has been solvothermally isolated by employing main group metal InⅣ and polycarboxylic acid ligand （H₆L= 2,3’,5,5’-biphenyl tetracarboxylic acid）, [（CH₃）2NH₂] [In（H₂L）]-CH₃CN-2DMF （5）.In compound 5, two carboxyl of the ligand did not take part in coordinating with InⅢ ions. Therefore, we have successful encapsulatied chiral amino acids L-and D-proline which process Br（?）nsted base site into the channel of compound 5 by post-synthesis modification. Meanwhile, the chirality of the amino acids has been transfered into the framework and the facile strategy could offer homochiral MOFs materials.