Design,Syntheses And Properties Of Metal-Organic Frameworks Based On Zwitterionic Ligands

Metal-organic frameworks (MOFs) are a class of emerging porous materials developed on the basis of coordination chemistry and zeolite chemistry, which exhibit intriguing framework structures and interesting properties for applications in the fields of gas sorption, magnetism, luminescence and catalysis by merging the functions of inorganic and organic moieties.The heterogeneously catalytic application of MOFs was one of the earliest realized properties, and remains the hot research topic. MOFs are self-assembled by connection of metal ions and organic linkers via coordination bonds under suitable conditions. The structures and properties of MOFs can be systematically tuned by selecting the metal ions and tailoring the functionalities of organic ligands, such as introducing different catalytic-active moieties to modify the catalytic properties of MOFs.Fourteen new MOFs have been synthesized through self-assembly of imidazole zwitterionic ligands as linkers, including (3,3’-methylenebis(1-(4-carboxy phenyl)-1H-imidazol-3-ium)chloride(H2bmpcCl2), 1,3-bis(3,5-dicarboxyben-zyl)-1H-imidazol-3-iumchloride(H4dcbimCl),4,7-bis(3,5-dicarboxyphenyl)-1,3-diethyl-lH-b-enzo-imidazol-3-iumchloride (H4tcimCl),3,3’-methylenebis (1-(4-carboxy-2-methy-lphenyl)-1H-imidazol-3-ium) chloride(H2mmpcCl2)), and metal ions as connecting nodes, including PbⅡ, CoⅡ, CdⅡ, CuⅡ and ZnⅡ, and polyoxometalates and metalloporphyrins as additive moieties to tune the functionalities of MOFs. These MOFs have been characterized by single crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared spectroscopy, Thermogravimetric analysis and Elemental analysis. According to their structural characters and the properties of metal nods, the fluorescence properties of these MOFs were selectively studied. Moreover, the catalytic properties of some MOFs were investigated. Compounds 2-5, containing polyoxometalate functional moieties, are highly efficient in selective adsorption of different dye molecules and highly active in selective photocatalytic degradation of different dyes. Compound 12, is highly active in Cross-Dehydrogenative Coupling reaction catalyzed by the unsaturated metal sites. In addition, Compound 13, containing pyridyl-metalloporphyrin moieties, is photoactived in selective photooxidation of thioethers.