Fabrication of a Co–Mo-Based Metal–Organic Framework for Growth of Double-Walled Carbon Nanotubes

Double-walled carbon nanotubes (DWCNTs) make up a unique class of carbon nanotubes (CNTs) that are particularly intriguing for scientific research and are promising candidates for technological applications. A more precise level of control and greater yields can be achieved via catalytic chemical vapor deposition (CCVD), which involves the breakdown of a carbonaceous gas over nanoparticles. The addition of molybdenum to the system can increase the selectivity with regard to the number of walls that exist in the obtained CNTs. As reported herein, we have designed and synthesized a novel Co-Mo-MOF, [Co(3-bpta)_1.5(MoO₄)]·H₂O (where 3-bpta = N,N'-bis(3-pyridyl)terephthalamide), and employed the Co-Mo-MOF as a bimetallic catalyst precursor for the CCVD approach to prepare high-quality DWCNTs. The Co-Mo-MOF was employed after being calcined in N₂ and H₂ at 1100 °C and decomposing into CoO, CoMoO₄, and MoO₃. Existing CoMoO₄ is unaltered after reduction in H₂ at 1100 °C, while CoO and MoO₃ are converted into Co⁰ and MoO₂, and more CoMoO₄ is created at the expense of Co⁰ and MoO₂ without clearly defining agglomeration. Finally, the interaction between metallic Co particles and C₂H₄ is what initiates the formation of DWCNTs. In-depth discussion is provided in this paper regarding the mechanism underlying the high selectivity and activity of Co-Mo catalysts in regulating the development and structure of DWCNTs. The DWCNTs also offer excellence performance when they are used as water purification agents and as selective sorbents. This work opens a feasible way to use MOFs as a way to produce MWCNTs, thus blazing a new trail in the field of MOF-derived carbon-based materials.