Ni@onion-like carbon and Co@amorphous carbon: Control of carbon structures by metal ion species in MOFs

We first report the facile synthesis of metal–carbon composites consisting of metal nanoparticles (NPs) and different types of carbon species: onion-like and amorphous carbon, Ni@onion-like carbon and Co@amorphous carbon. By simply changing the metal species in an isostructural metal–organic framework, thermal decompositions of MOF-74 directly afforded different types of metal NPs and carbon composites, which exhibited good electrical conductivity. In particular, the Ni@onion-like carbon, having a well-ordered carbon structure, had high electrical conductivitiy (σ = 5.3 Ω–1 cm–1 at 295 K), explained by a modified model of the Efros–Shklovskii variable range hopping.