Boosting hydrogen storage performance in COF-108 by single-walled carbon nanotube insertion, boron substitution, and lithium doping at room temperature

A novel hybrid material based on covalent organic frameworks (COFs) was proposed for highly efficient hydrogen (H2) storage at room temperature. Single-walled carbon nanotubes (SWNTs) were inserted into COF-108, and additional lithium (Li) atoms were doped into the boron-substituted structures. Density functional theory calculations were used to determine the optimized hybrid structures and the reasonable force field parameters between the hydrogen in H2 and the elements in the sorbent. In addition, H2 adsorption simulations via the grand canonical Monte Carlo approach revealed that SWNT insertion and Li doping substantially elevated the room-temperature H2 storage performance. A detailed analysis was provided on the impact of the number of doped Li atoms and the specific surface area on H2 uptake. The highest excess gravimetric and volumetric H2 uptake values were 5.08 wt% and 31.65 g/L, respectively, for Li-doped B-substituted SWNT(15,0)@COF-108 and SWNT(9,9)@COF-108 at 298 K and 100 bar. Surprisingly, the total H2 uptake of Li-doped B-substituted SWNT(9,9)@COF-108 not only met but also surpassed the 2020 target of the U.S. Department of Energy (DOE) within the temperature and pressure limits of the DOE. This study presents a theoretically grounded, multiple modification strategy for the design of porous materials with exceptional H2 storage capabilities, offering a promising avenue for the development of advanced H2 storage solutions.