Application Of Metal-Organic Frameworks In Cs(I) Separation And Supercapacitors

With the energy crisis and environmental problems,countries around the world have begun to vigorously develop clean energy such as nuclear,wind,solar and tidal energy.However,the nuclear waste generated after nuclear power generation contains a large amount of highly radionuclides.Among them,137 Cs is a high heat release radionuclide.Due to its similar chemical properties to potassium,it is easy to be absorbed and enriched by plants once it is leaked into the environment,which is not conducive to environmental and ecological health.In addition,wind,solar and tidal energy are intermittent energy sources that need to be converted into stable energy output through energy storage devices.Supercapacitors are considered good candidates because of the long cycle life,high power density,and short charge/discharge times.Metal-organic frameworks(MOFs)have the advantages of large specific surface area,adjustable porosity and structure,and functional modification,which can not only be used for the separation of metal ions,but also be used as electrode materials for supercapacitors.Therefore,the MXene/Cu HCF composite was prepared by loading copper hexacyanoferrate(Cu HCF)on the surface of MXene by in-situ growth method to remove cesium ions from radioactive wastewater and seawater.Meanwhile,a bimetallic Ni Co-MOFs with unique morphology were prepared and used to assemble asymmetric supercapacitor devices.The main research contents are summarized as follows:(1)Here,the MXene/Cu HCF-2 with spongy porous structure was prepared by in-situ growth of Cu HCF for achieving Cs(I)adsorption from wastewater and seawater.The in-situ growth method can avoid the stacking and agglomeration of Cu HCF,thus improving the effective utilization rate of Cu HCF.MXene/Cu HCF-2can reach the adsorption equilibrium of Cs(I)within 20 min with the maximum adsorption capacity(qmax)of 326.80 mg/g,because the porous and loose structure of MXene/Cu HCF-2 is conducive to the diffusion and adsorption of Cs(I).Additionally,the removal rate of Cs(I)by MXene/Cu HCF-2 can reach up to 90% even in 0.5 mol/L HNO3 solution and Cs(I)spiked seawater containing various competitive cations.More importantly,MXene/Cu HCF-2 can efficiently and selectively adsorb Cs(I)ions with excellent reusability.(2)Herein,a simple,mild,and one-step solvothermal process was used to fabricate Ni-MOF crystals,which was a template for preparing flower-like Ni Co-MOF-2 by in-situ etching methods.Interestingly,the “petals” of Ni Co-MOF-2 are formed by stacking multiple nanowires,which can enhance richer active sites to promote charge transfer owing to the larger contact area between the electrolyte and the electrode material.Consequently,the Ni Co-MOF-2 exhibits a larger specific capacity of 108.5 m Ah g-1 at a current density of 0.5 A g-1 and the assembled asymmetric supercapacitor(Ni Co-MOF-2//AC)delivers a stack energy density of 45.7 Wh kg-1 at a power density of 450.6 W kg-1 with excellent life span of84.3% capacity retention after 6500 cycles.