Controlled synthesis of highly stable zeolitic imidazolate framework-67 dodecahedra and their use towards the templated formation of a hollow Co3O4 catalyst for CO oxidation

In this work, dodecahedral microcrystals of zeolitic imidazolate framework-67 (ZIF-67) with good uniformity and exceptional stability have been synthesized by simply controlling the mole ratio of reactants at room temperature. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) characterization indicates that the as-synthesized ZIF-67 microcrystals are highly uniform and have perfect rhombic dodecahedral morphology with 12 exposed {110} faces. The X-ray diffraction (XRD) and thermogravimetry analysis (TGA) investigations demonstrate that they display high thermal stability up to ∼350 °C in air and ∼425 °C in vacuum, as well as remarkable chemical resistance to boiling organic solvents and room-temperature water. Through a two-step oxidative thermolysis process, these ZIF-67 dodecahedra can be further converted into hollow Co3O4 architectures consisting of nanosized building blocks. Owing to their large specific surface area and unique structure, the hollow Co3O4 catalyst obtained at the calcination temperature of 425 °C exhibits high catalytic activity and stability for gas-phase CO oxidation.