Li Doping in Two-Dimensional Holey Biphenylene Framework for Efficient Molecular Hydrogen Storage: A First-Principles Insight

Hydrogen holds strong potential for renewable energy systems, though storage challenges limit its practical deployment. In this study, using dispersion-corrected density functional calculations, the hydrogen storage capacity of a Li-doped novel two-dimensional holey biphenylene (hBP) framework is explored. Phonon dispersion curve and molecular dynamics simulations collectively reveal the structural stability of the hBP framework. Pristine hBP adsorbs H2 weakly, with an adsorption energy of −0.12 eV/H2, lies outside the optimal window (−0.2 to −0.7 eV/H2) necessary for effective hydrogen storage. Li doping of the hBP framework significantly improves the adsorption energy and thus the storage capacity of hBP. Upon Li doping, strong local polarization and electron transfer enhance H2 interaction, increasing the adsorption energy range from −0.25 to −0.41 eV/H2. Each Li dopant enables the adsorption of up to six H2 molecules, contributing to a maximum hydrogen storage capacity of 13.3 wt %. A desorption temperature of 319 K at 1 atm, obtained for the H2-saturated Li-doped hBP framework, indicates hydrogen release occurs above its critical temperature, suggesting that the material can store hydrogen safely and with high energy efficiency. The combination of high gravimetric capacity, optimal binding strength, and structural robustness highlights Li-doped hBP as a promising material for next-generation hydrogen storage systems.