Preparation And Properties Of Metal Organic Frameworks Based On V-shape Nitrogen Heterocyclic Ligands

Metal organic frameworks（MOFs）are one-dimensional,two-dimensional and three-dimensional network structures which were constructed by metal ions and organic ligands through coordination bonds.MOFs materials are widely used in gas adsorption and separation,catalysis,energy storage and conversion,sensing,magnetism and other fields.Therefore,the design and preparation of MOFs materials with unique properties and diverse structures have attracted the interest of researchers.As reported,v-shape nitrogen ligand 3,5-di（pyridin-4-yl）-4H-1,2,4-triazol-4-amine（4-abpt）is more likely to form complex compounds and the nitrogen atoms can form stable coordination bonds with metal ions.In addition,carboxylic acid ligands（1R,3S）-1,2,2-trimethylcyclopentane-1,3-dicarboxylic acid（（+）Dcam）and 4,4’,4"-nitrilotribenzoic acid（H₃NTB）can construct MOFs with diverse structures as they have strong coordination ability and a variety of coordination modes.Inspired by the above thoughts,three new MOFs were designed and synthesized by using these ligands and different metal salts in this work.The catalytic,electrochemical,fluorescence and magnetic properties of the compounds were investigated.This paper mainly includes the following two works:（1）A 2D layered Co-MOF[Co（Dcam）（H2O）]（1）was successfully prepared by the reaction of（+）Dcam carboxylic acid ligand and 4-abpt nitrogen-containing ligand with cobalt nitrate hexahydrate under solvothermal condition.The Co-MOF was used as a precursor to calcine at high temperature under air condition to prepare layered porous Co₃O₄（NL-Co₃O₄）.The monolayer thickness of NL-Co₃O₄ is approximately 70 nm.The unique structure of layered porous of NL-Co₃O₄ derived from Co-MOF plays an important role in improving electrochemical and electro-catalysis properties.As lithium ion battery anode material,NL-Co₃O₄ shows out-bound cycling performance and rate capacity,which has an unprecedented high reversible capacity of 1120.5 mA h g^-1 at 200 mA g^-1 after 300 cycles and well rate capacities of 579.4 mA h g^-1 under the current density of 6.4 A g^-1.NL-Co₃O₄ still exhibits capacity of 576 mA h g^-1 after 200 cycles at high current densities of 4 A g^-1,respectively.Moreover,NL-Co₃O₄ has efficient oxygen evolution reduction（OER）catalytic performance（overpotential,ca.420 mV）,comparable with commercial RuO2.During the process of continuous catalysis of OER,NL-Co₃O₄ shows good durability for about 15 h.（2）Two compounds[Zn₃（H₃NTB）（4-abpt）]（2）and[Co3（H₃NTB）2（4-abpt）（DMF）2]（3）were successfully prepared by the reaction of 4-abpt nitrogen-containing ligands and H₃NTB carboxylic acid ligands with different metal salts under solvothermal conditions.Both 2 and 3 show a three-dimensional network structure.The fluorescence measurements demonstrate that compound 2 can detect Al³⁺ by turn-on fluorescence with high sensitivity,which was not affected by the co-existing metal ions.Magnetic studies show that compound 3 exhibits antiferromagnetic interactions.