Study On The Synthesis And Electrochemical Properties Of Metal Organic Frameworks And Their Derivatives

Metal organic frameworks?MOFs?is a new kind functional material with two-dimensional layered or three-dimensional network,composed of organic ligands and central metal ions through coordination bonds such as coordination bonds,?-? bonds or hydrogen bonds.It has charming topology structure and permanent porosity,specific surface area,controllable structure,functional diversification,which contributes to the potential application in the catalytic,molecular recognition,gas storage,magnetic and other fields.In addition,metal oxide materials that derived from MOFs are widely used as electrode materials for lithium ion batteries and exhibit excellent electrochemical properties.However,with the rapid development of high-power electric devices,the cycle stability,rate capability and safety of the current commercial lithium-ion battery need to be further improved,so the exploration of excellent electrode materials is of great significance.In this dissertation,carboxylic acid ligands of 3,3',5,5'-azobenzenetetracarboxylic acid?H₄ABTC?and 4-benzimidazole-1-benzoic acid?HCPBm?were used to coordinate with Co²⁺,Ni²⁺,La³⁺,Eu³⁺,Tb³⁺,Gd³⁺ through solvothermal synthesis and 7 novel MOFs have been obtained: {[Eu?HABTC??H₂O?₂]·2H₂O}_n?1?,{[Tb?HABTC??H₂O?₂]·2H₂O}_n?2?,{[Gd?HABTC??H₂O?₂]·2H₂O}_n?3?,{[La₂?ABTC??H₂O?₆] · 2H₂O}_n?4?,{[Ni₂?ABTC??H₂O?₃?DMF?] · 2H₂O}n?5?,[Co?CPBm?₂]n?6?and [Ni?CPBm?₂]_n?7?.1-3 have the same coordination mode,1-4 are all two-dimensional layered structure,5 has a three-dimensional network structure,both 6 and 7 are two-dimensional layered structure with one-dimensional chenal.After carefully analyzing the structure characteristics of the MOFs,the Co₃O₄ and Ni O for electrode materials of lithium ion battery derived from 6 and 7 were successfully prepared after pyrolysis,and the morphology of Co₃O₄ and Ni O electrodes were characterized by SEM,TEM and HRTEM after different cycles.It showed that the block-like morphology of Co₃O₄ and Ni O electrodes have been well retained,and the Co₃O₄ and Ni O electrodes can maintain 98.0% and 96.2% high coulomb efficiency after 50 cycles at 2000 m A/g high current density,respectively.In addition,the Co₃O₄ electrode can maintain a high specific capacity of 569.9 m Ah/g after 50 cycles at 2000 m A/g,exhibitting a better cyclic stability.