Construction of Co₃O₄ three-dimensional mesoporous framework structures from zeolitic imidazolate framework-67 with...

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.