Theoretical study of hydrogen storage in a truncated tetrahedron hydrocarbon

A hydrocarbon molecule, having a truncated tetrahedron shape with a suitable size for the storage of a hydrogen molecule, is designed using quantum chemical methods. The molecule consists of four benzene rings bridged by six vinylene groups at the 1, 3, and 5 carbon positions of each ring, and has a stoichiometry of C 36 H 24 . The molecular geometry optimized under T d symmetry by the B3LYP/cc-pVTZ method shows no imaginary frequencies. The size of the molecular cavity, measured by the distance between opposite vinylene groups, is 8.0 Å. The cavity has four openings along each tetrahedron face. The radius of the opening is approximately 2 Å. The system interacting with a hydrogen molecule is optimized by the MP2/cc-pVTZ method. The interaction energy is evaluated by an extrapolation method through increasing the basis set size of the hydrogen molecule from the cc-pVTZ to the cc-pV6Z with counterpoise corrections. The hydrogen molecule enters the opening by overcoming an energy barrier of +730 meV and locates at the center of the cavity with a binding energy of −140 meV. The high barrier arises from the small size of the opening. The binding energy is three times larger than that of a graphite surface and may allow hydrogen storage at milder temperatures and pressures than those required with graphite.