Preparation Of Zinc-Based Bimetallic Organic Framework Materials And Application Of Their Derivatives In Lithium Batteries

Metal organic frameworks（MOFs）are composed of inorganic metals as central nodes and organic ligands as linkers,and self-assemble to form a class of hybrid compounds with a periodic network structure.The derivatives obtained by calcining them at high temperatures have perfect structural controllability and high porosity,and can be well used as anode materials for lithium-ion batteries.In this paper,three different bimetallic MOFs were synthesised by using hydrothermal synthesis with different ligands or metals.A new bimetallic organic framework（MOF）{CoZn[（4,4′-BDA）（Phen）]₂}_nwith a purplish-red rod-like crystal structure was synthesized by hydrothermal method using 4,4′-biphenyldicarboxylic acid（4,4′-H₂BDA）as the ligand,1,10-phenanthroline（Phen）as the auxiliary ligand,and Co²⁺and Zn²⁺as the metal sources.Then,the new precursor CoZn-MOF-B@C was obtained by adding surfactant and activated carbon with NaOH to adjust the pH.Its derivative ZnO/CoO@C was used as an anode material for lithium-ion batteries and showed good lithium storage performance.The initial discharge specific capacity of ZnO/CoO@C was 1437.9 mAh g^-1at a current density of 0.2 A g^-1and was maintained at 741.8 mAh g^-1after 100 cycles.The CoZn-BTC@NC precursor was synthesized by hydrothermal method using trimesic acid（H₃BTC）as ligand and Co²⁺and Zn²⁺as metal sources,and a urea solution with a concentration of 0.5 mol/L was added in situ,which was then calcined at 450℃ under an argon atmosphere to synthesize the nitrogen-containing bimetallic oxide electrode material CoO-ZnO@NC-450.The initial discharge specific capacity of CoO-ZnO@NC was 975.2 mAh g^-1at a current density of 0.2 A g^-1and was maintained at 796.2 mAh g^-1after 100 cycles.The nano-MnZn-BTC precursors were synthesized by hydrothermal method using trimesic acid（H₃BTC）as ligand and Mn²⁺and Zn²⁺as metal sources,followed by the addition of surfactant CTAB.The precursors were calcined at different temperatures under an argon atmosphere and among the derivatives obtained,Mn₃O₄/ZnO@C-500 showed excellent electrochemical properties with an initial discharge specific capacity of 1185.6m Ah g^-1at a current density of 0.2 A g^-1,which was maintained at 790.5 mAh g^-1after 100cycles.