Construction of Co3O4 three-dimensional mesoporous framework structures from zeolitic imidazolate framework-67 with enhanced lithium storage properties.

ABSTRACT

High-porosity mesoporous framework structures are attractive for electrochemical energy storage and other applications. Herein we demonstrate a novel synthesis strategy to make zeolitic imidazolate framework-67 oxidize to a Co3O4 three-dimensional mesoporous framework structure. This strategy relies on the oxygen-limitation effect of the closed nanocage and the affinity effect of polyvinylpyrrolidone towards zeolitic imidazolate framework-67. Several TiO2 nanospheres, as the unique structure junctions, are uniformly embedded within the Co3O4 framework to enhance the framework strength. The TiO2/hydrous titania polyhedron nanocage, as the protecting shell, further encapsulates the Co3O4 framework, forming a perfect capsule-type hybrid. As anode materials for lithium-ion batteries, TiO2@Co3O4 framework capsules show superior lithium storage performance with high reversible capacity, stable cycling life and good rate capability. A reversible capacity of 1042 mAh g-1 can be delivered after 200 cycles at a current density of 300 mA g-1. The average discharge capacity over 200 cycles reaches 926 mAh g-1. This demonstrates the superiority of this material structure and its great potential as an anode for high-performance lithium-ion batteries. This work indicates a new strategy to take advantage of metal-organic frameworks to synthesize their mesoporous framework derivatives.