Graphydiene: A new mixed sp/sp2 2D carbon allotrope for optimal hydrogen storage

A new two-dimensional carbon allotrope, graphydiene (GPYD), is proposed and studied by DFT simulations. GPYD consists of Dewar-anthracene fragments bridged by acetylenic bonds, generated by an ordered 4–6–8–22 carbon ring network. Phonon spectra free of imaginary modes and ab initio molecular dynamics (AIMD) simulations at 300 K confirm dynamical and thermal stability, while elastic constants satisfy the Born-Huang criteria. Optical calculations reveal strong in-plane infrared absorptivity with moderate dichroism, suggesting applications in flexible IR photodetectors. Na-decorated GPYD (Na@GPYD) accommodates up to 32 H 2 molecules (8.25 wt%) with average binding energies from –0.30 up to –0.20 eV, entirely within the reversible physisorption window. Charge analysis shows negligible charge transfer to H 2 ( − 0 . 01 | e | /H 2 ), indicating an induced dipole van der Waals interaction mechanism. These results establish Na@GPYD as a high-capacity candidate for solid-state hydrogen storage and related energy applications. • Graphydiene features Dewar-anthracene fragments and acetylenic bonds. • Phonon spectra lack imaginary modes, and AIMD simulations confirm stability. • Elastic constants meet Born–Huang criteria, demonstrating mechanical integrity. • Strong infrared absorption and moderate in-plane dichroism. • Na@GPYD adsorbs 32 H 2 molecules (8.25 wt%) with optimal reversible binding energies.