| Metal-organic frameworks(MOFs)are mainly composed of two components: metal(metal clusters)and organic ligands,so the flexible combinations make them "the evergreen tree" in the nanomaterial world.Zeolite imidazole framework material(ZIF),as a typical MOF material,has many excellent physical and chemical properties,such as extremely high specific surface area and porosity,good thermal stability and chemical stability,etc,and it had shown a good application prospect in many fields such as adsorption,gas separation,energy storage materials,catalysis and so on.In this paper,the heteroatom-doped MOF matrix composites and bimetallic MOF-derived Zn/Co porous carbon frameworks were synthesized by transition metal doping and calcination of ZIF-67 and ZIF-8,and their performances as electrochemical modified materials were investigated respectively.Firstly,the alkali-mediated hydrothermal method was used to introduce transition metal elements such as iron,cobalt,and nickel into ZIF-67 to synthesize transition metaldoped ZIF-67 nanocomposites with different proportions.The morphology and chemical composition of the nanocomposites were characterized by XRD,SEM,TEM,FTIR,and XPS;the electrochemical performance of the material was studied by cyclic voltammetry(CV)and electrochemical impedance(EIS).The electrochemical Hg(II)sensing interfaces were constructed based on the as-synthesized materials,and the detection conditions were optimized with the anodic stripping voltammetry(SWASV)method.The results show that the best electroanalytical response is obtained as the Fe/Co ratio of 1:1,with a sensitivity of 41.5μA/μM,which is 260% higher than that of pure ZIF-67 modified electrode,the lowest detection limit is only 40% of the pure ZIF-67 modified electrode.The experiment proves that the transition metal-doped ZIF-67 nanocomposites have good stability,good reproducibility,and high anti-interference ability.Secondly,the bimetal MOF precursor Zn/Co-ZIF was prepared via the one-pot method,and porous ZnCo-contained carbon framework nanocomposites were synthesized by pyrolyzing the precursor.Its morphology and chemical composition were characterized by XRD,SEM,TEM,and XPS,and its applications as the electrochemical sensing materials were studied.On one hand,the bimetal-node ZIF(Zn/Co-ZIF)showed better conductivity than the single metal-node ZIF,such as ZIF-67 and ZIF-8.On the other hand,the calcined N-doped porous carbon skeleton has more active sites for Hg(Ⅱ)adsorption.These synergistic effects enhanced the electrochemical response towards Hg(Ⅱ).The detection sensitivity and minimum detection limit of the as-prepared nanocomposites modified electrode are 33.49μA/μM and 7.21 n M,respectively.And also,the Zn/Co-ZIF modified electrode shows good stability(RSD=1.67%)and reproducibility(RSD=1.81%),and high anti-interference ability. |
