Syntheses, Structures And Properties Of Metal-organic Frameworks Based On Nitrogen-rich Ligands

Metal–organic frameworks (MOFs) synthesized by assemblingmetal ions with organic ligands have recently emerged as new classof crystalline porous materials. For example, the amenability todesign fine-tunable and uniform pore structures makes thempromising materials for a variety of applications. For example, usingporous MOF materials to capture CO2, using MOFs as photocatalystsfor degradation of organic dyes or water splitting. In addition, someMOFs with reversible structure transformation can response towardexternal stimuli, which are vitally important for applications insensing, molecular capture, switching, and so on. This dissertationmainly focuses on the hydro(solvo)-thermal syntheses, structuresand properties of series of coordination complexes based on4-(1H-1,2,4-triazol-1-yl) benzoic acid (Htzbc) and bis(1H-tetrazol-5-yl)methane (H2btm). The thesis is divided into four chapters. The maincontents are summarized as below：In the first chapter, we introduce the research progress of the nitrogen-rich metallic organic compounds briefly. We alsosummarize and highlight the recent development of the singlecrystal-to-single crystal (SCSC) transformation, the carbon captureand sequestration (CCS) performance of MOFs and photoactivity ofMOFs on organic dyes. In addition, the aims and experimentalresults of this work are also outlined.In the second chapter, firstly, we use4-(1H-1,2,4-triazol-1-yl)benzoic acid (Htzbc) as ligand and copper nitrate as metal source toget a mononuclear complex [Cu(tzbc)2(H2O)4](1), which canreversibly transform into an4-fold interpenetrated diamondoid MOF[Cu(tzbc)2] EtOH DMF(2) soaking in mixed DMF/EtOH solvent.Interestingly, despite4-fold interpenetration, desolvated2with1Dchannels and rich N-groups shows exclusive CO2adsorption up to12.5wt%and CO2/N2adsorption ratio of36at room temperatureand low pressure, indicating potential application in the separationof industrial and automobile exhaust. Next, two coordinationcomplexes with slightly different3D framework: Mn(tzbc)(CH3COO)(3) and Mn3(CH3COO)2(C6H8O4)(tzbc)2(4) have been tuned by additionof isonicotinic acid and butane dicarboxylic acid respectively. Theframework of compounds3and4are both based on-Mn1-O-Mn2-chain. Due to the coordination of ancillary butane dicarboxylic acidinvoleld in compound4, the3D frameworks between3and4is slightly different, which leading to their different adsorptionperformance.In chapter3, three coordination complexes: Zn5(OH)2(btm)2(SO4)2(5), Zn2(btm)(OH)2(6) and Mn(phen)(btm)(7) have beenachieved by hydrothermal synthesis from bis(1H-tetrazol-5-yl)methane and different metal salts. Luminescent studies showthat excitation at353nm leads to strong blue fluorescent emissionbands at429and467nm for compound5, which can probably beassigned to intraligand (π-π*) fluorescent emission. UV visdiffuse-reflecance spectrometry indicate that compound7ispotential semiconductor materials, and the performance on thephotocatalytic degradation of organic dyes upon UV-lightirradiation reveals that compound7is highly efficientphotocatalysts.In the last chapter, a concise conclusion was drawn and anoutlook of this work is given.