Design of cobalt catalysed carbon nanotubes in bimetallic zeolitic imidazolate frameworks.

[Display omitted] • Three types of bimetallic ZIFs with different zinc (Zn) to cobalt (Co) ratio were synthesized and carbonized. • Co nanocatalyst induced graphitization during pyrolysis. • The size of Co nanocatalyst affected the carbon nanotube growth. • Carbon nanotube dramatically improved the electrical conductivity. Carbon nanotubes are the most effective way to enhance electrical conductivity between particles, although the growth mechanism in zeolitic imidazolate frameworks still remains elusive. According to our density functional theory calculations and experimental studies, the role of cobalt nanoparticles as catalysts was proved to induce graphitization during pyrolysis. In particular, the sizes and exposed facets of the Co particles play an important role in triggering a hierarchical carbon nanotubes. This work paves the way to control the growth of carbon nanotubes toward various applications. [ABSTRACT FROM AUTHOR]