Epitaxy Of Core-shell Hetero-structured Coordination Polymers

Developing hetero-structure coordination polymer is an effective way to propel the functional materials.As we know,due to its flexible framework,the misfit of the crystal lattice will induce different properties or change its framework.Here,in this dissertation,we focused on the hetero-structure coordination polymer.We adopt epitaxial growth method to synthesis hetero-crystal.Scanning electron microscope and X-ray powder diffraction were used to characterize the structure.The valence state of ion were showed by mossbauer spectrum results.At the same time,we also use electrochemistry method to clarify how the interface between core and shell crystals affect Na+ ion storage capacity.Results show that the crystallization rate was slower because of the addition of sodium citrate.Owing to the chelation effect.In this way,core-shell crystal grow via a ion by ion way.The characterization by scanning electron microscope showed that 10 nanometer and 25 nanometer thick shell was deposited on a single nano-cubic core Prussian blue crystal.In the primary stage,the core structure dominated the whole particle,which was cubic framework.But with the shell was thicker and thicker,the stress between core and shell structure is stronger and stronger.When the shell was up to 25 nanometer in thickness,new equilibrium was established.The particle structure was dominant by the shell structure.Regarding to the electrochemical performance,the shell structure could filtrate the external ions.In our work,the shell crystal was induced,the Na+ ion storage capacity of the shell crystal was of the pure core crystal.So that,the Na+ ion storage capacity of the core crystal became half,too.Similarly,there was only one voltage platform when shell crystal existed.The electrochemical performance depended on the shell crystal.On the basis of core-shell Prussian blue,we also explored the MIL88 series.We tried to deposit rigid MIL88 crystal on soft MIL88 crystal.When the solvent was wiped off.The lattice of the soft MIL88 got shrinking,while the rigid one kept its initial framework.In this way,huge internal stress led to tearing of the interface.