Metal-decorated methylene-bridged cycloparaphenylene nanotubes for high-capacity hydrogen storage

Efficient hydrogen storage is critical for advancing a sustainable hydrogen economy. This study introduces a novel class of nanotubes constructed from methylene-bridged cycloparaphenylenes (MCPPs) as high-capacity hydrogen storage materials. These nanotubes feature pentagonal rings that act as active sites for binding 3d transition metal atoms, avoiding structural deformation or metal clustering. Metal decoration induces tunable magnetic and electronic properties, such as ferromagnetism and band gap reduction, enhancing reactivity and adsorption behavior. Among the studied metals, vanadium, nickel, and copper demonstrate favorable hydrogen adsorption. Copper-decorated MCPP nanotubes achieve a gravimetric hydrogen capacity of 8.45 wt% and an optimal adsorption energy of −0.20 eV, enabling room-temperature storage (∼280 K) without cryogenic cooling. Molecular dynamics simulations confirm thermal stability up to 500 K, ensuring durability and reusability. These findings underscore the potential of metal-decorated MCPP nanotubes as promising candidates for next-generation hydrogen storage, combining high capacity, thermal resilience, and practical reusability.