| Coordination polymers (CPs) based on phosphonate ligands are reported to show very good thermal and chemical stabilities. However, the phosphonate-based CPs tend to form dense structure due to the three oxygen atoms chelating bonds to metals. A strategy of attaching organic groups such as hydroxyl, amine, and carboxylate groups to the phosphonate has proven to be efficient way to obtain porous phosphonate-based CPs. Since azolate ligands have the advantage of strong and directional coordination ability in bridging metal ions, attaching azolate groups to the phosphonate may generate excellent multi-functional ligands, make it easier to synthesize highly stable CPs. With this consideration in mind, atriazole modified phosphonate ligand was synthesized in our lab, namely4-(1,2,4-triazol-4-yl)phenylphosphonic acid (H2ptz). We then synthesized more than20new coordination polymers by using this ligand, and all structures were characterizedby single-crystal X-ray diffraction. In addition, the adsorption, magnetism and catalysis properties of those compounds have also been investigated.In chapter2, we explored the synthesis and structures of isostructural metal-phosphonate frameworks. We obtained four groups of2-D layered metal phosphonate isostructures [M(ptz)-H2O](where M=Fe(Ⅱ)(Feptz-1), Co(Ⅱ)(Coptz-1), Cu(Ⅱ)(Cuptz-1));[M(Hptz)(μ-Cl)]·2H2O (where M=Co(Ⅱ)(Coptz-2), Ni(Ⅱ)(Niptz-1));[M5(Hptz)2(ptz)4](where M=Mn(Ⅱ)(Mnptz-1), Co(Ⅱ)(Coptz-3));[M3(Hptz)2(ptz)2(4H2O)]·6H2O (where M=Fe(Ⅱ)(Feptz-2), Ni(Ⅱ)(Niptz-2)), by using the paramagnetic transition-metal ions (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, et. al) with H2ptz under hydrothermal conditions.Among them, the first two groups of isostructures contain similar one-dimensional metal phosphonate chains. However, the first two groups exhibit different magnetic behavior, magnetic measurements reveal antiferromagnetic behavior for [M(ptz)-H2O], ferromagnetic for [M(Hptz)(Cl)]·2H2O. The magnetism studies over the temperature showed pronounced antiferromagnetic interactions between the combined oxo-and diazo-bridged metal centers in both [M5(Hptz)2(ptz)4] and [M3(Hptz)2(ptz)2(4H2O)]·6H2O.In chapter3, we explored the crystal-to-crystal transformations between metalphosphonates. There are several types of structural transformations that are primarily influenced by the expansion of coordination number, thermal association, condensation, rearrangement of bonds orthe removal/exchange of solvents. We found three kinds of crystal-to-crystal transformations by controlling these factors. Crystal-to-crystal transformations between the following three metalphosphonates:[Cd5(ptz)3(SO4)2(5H2O)]·6H2O (Cdptz-1),[Cd3(ptz)2(Cl)2(4H2O)]·2H2O (Cdptz-2) and [Cd4(ptz)2(SO4)(Cl)(OH)H2O]·H2O (Cdptz-3). Crystal-to-crystal transformation from [Co(Hptz)(Cl)]·2H2O (Coptz-2) to [Co(ptz)·H2O](Coptz-1). Crystal-to-crystal transformation from a0-D trinuclear metal phosphonate [Ni3(Hptz)6·6H2O]·9H2O (Niptz-3) to a2D phosphonate-based MOF [Ni(Hptz)2]·7H2O (Niptz-4). Studies of thermal and chemical stability show that Niptz-4remains its crystallinity up to300℃, and has remarkable chemical resistance to boiling water and organic solvents. Niptz-4also exhibits very high adsorption for CO2and separation capacity for CO2/N2.In chapter4, we explored the potential applications of porous metal phosphonates in gas storage, separation and heterogeneous catalysis. We obtained three PCPs with the same topology [Ni3(Hptz)3(HPO4)(M,3-O)·3H2O](H3O)-·9H2O (Niptz-6),[Ni3(ptz)3(μ3-O)·3H2O]·(2H3O)·10H2O (Niptz-5),[Co4(ptz)3(μ3-O)·3H2O]·9H2O (Coptz-5), by using Co2+, Ni2+with H2ptz under hydrothermal conditions. Coptz-5, Niptz-5, and Niptz-6have remarkable chemical resistance to boiling water and acidic solution. In addition, they also exhibit very high adsorption for CO2and separation capacity for CO2/N2. Coptz-5, Niptz-5and Niptz-6are also efficient heterogeneous catalyst in the ring opening of styreneoxide with alcohols due to the presence of protonated water molecules in the channels. |
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