Reconstruction of cobalt atoms in ZIF-67 and in-situ growth of carbon nanotubes at low temperature for High-Performance strain sensors

Carbon nanotubes (CNTs) with unique physical and chemical properties, show greatly potential applications in various fields, but often suffer from harsh and complex synthetic conditions. Taking advantage of the atom-level uniform distribution of metal (e.g., cobalt) atom in zeolitic imidazolate framework (ZIF, e.g., ZIF-67), we here develop a facile approach using ZIF-67 as the precursor of catalyst to grow CNTs by chemical vapor deposition (CVD) at a low temperature of 500 °C, much lower than traditional condition (> 700 °C). During temperature increasing process, Co atoms in ZIF-67 are in-situ reconstructed to form Co nanoparticles with proper diameters, and pyrolysis of ZIF-67 also occurs to form a graphite layer on Co nanoparticles at the same time, promoting following CVD growth of CNTs. The catalyst precursor ZIF-67 can be easily loaded in/on any substrate through solution process instead of using traditional complex high-energy consumption techniques, which makes it possible to synthesize CNTs on various low-cost substrates in large scale for wide applications. Finally, the low-temperature grown CNTs-based strain sensor with excellent sensitivity and long-term stability even under ultralow strain of 0.4 % is demonstrated.