Fudan Xu Yuxi research group: preparation of ultra-small metal organic framework nanocrystals and their high-efficiency electrochemical energy storage

Metal organic frame (MOF) materials are widely used in many fields, such as energy and environment, because of its high specific surface area, pore volume, pore size and structure easy to adjust Especially when MOF materials are reduced to nanometer size, their physical and chemical properties will change dramatically Therefore, it is of great significance to prepare ultra-small MOF materials and apply them to energy storage to solve today's energy problems However, the current methods for the preparation of ultra-small nanoparticles, such as laser, electrochemistry, Joule heat, atomic / molecular deposition and so on, are not suitable for MOF materials due to their extreme reaction conditions or the requirements for the internal structure of molecules Therefore, it is very important to find a simple, environmental friendly and universal method to prepare ultra-small MOF materials Xu Yuxi, a team of researchers from the Department of polymer science, Fudan University, developed a simple "thermal assisted space limited pulverization" method to successfully prepare sub-5 nm ultra-small MOF nanocrystals Firstly, MOF particles with uniform size distribution (~ 100 nm) were grown on the surface of graphene oxide (go) by electrostatic and complexation; then conducting polymer materials (PPy) were coated on its surface by in-situ polymerization; the resultant go / CO MOFs / PPy (GCP) composite was calcined in 350 ° C air 2 h The ultra-small MOF nanocrystals (gcp350) coated with ultra-thin nitrogen doped carbon / graphene (NC / g) layer can be obtained The unique structure of the composite has the following advantages: (1) the ultra-small nanocrystalline has a large specific surface area, which can significantly improve the contact area between the electrolyte and the active material, effectively reduce the lithium ion and electronic transmission distance; (2) the ultra-small nanocrystalline can provide more active sites, effectively improve the utilization rate of the active material; (3) The gap between the ultra-small nanocrystals and the NC / g coated on the surface can effectively alleviate the volume change during the charging and discharging process of lithium-ion battery, and improve its cycle stability; (4) the interconnected conductive porous NC / g framework can promote the high-speed transmission of electrons / ions in the whole composite Based on the above advantages, the composite as the self-supporting anode of lithium-ion battery shows excellent electrochemical performance: at the current density of 0.1 a · g-1, the reversible specific capacity is up to 1301 MAH · g-1; when the current density is increased to 40 a · g-1, the specific capacity is still up to 494 MAH · g-1, showing excellent rate performance; at 10 a · g-1 At the current density of 2000 cycles, the capacity retention rate is 98.6%, and the specific capacity attenuation rate of each cycle is only 0.0007% The electrochemical properties of the ultra-small MOF nanocomposites are much better than that of other reported MOF lithium anode materials In this work, a simple and convenient method for preparing ultra-small MOF nanocrystals is proposed By choosing suitable coating and calcination temperature, the method can be applied to other MOF materials with good universality, which provides a new way for the preparation of ultra-small functional MOF materials and their application in high-efficiency energy storage and conversion This work is another progress made by Xu Yuxi's team in graphene / MOF functional complex The paper was recently published in ACS Nano (DOI: 10.1021 / acsnano 8b01488) About the author: researcher Xu Yuxi