The present paper aims to investigate the role of open metal site metal-organic frameworks (MOFs) on hydrogen adsorptivity using periodic boundary condition (PBC) density functional theory (DFT). Hence, MIL-47-M (M = V and Fe) were selected and one hydrogen molecule adsorptivity was calculated in different orientations on them. Four different chemical sites were identified in every cluster section of these MOFs, and molecular hydrogen adsorption was studied in these sites. In these MOFs, V has fewer electrons than Fe in its valence layer. Results demonstrated that when dihedral angle of M-O-H-H is 0, the binding energy of hydrogen adsorption is higher than that in other orientations in both MILs (-26.16 and -19
