The calculations of gas adsorption are performed by employing the TPSSh functional and the aug-cc-pVTZ basis sets as implemented in ORCA. The semiempirical Grimme's D3 correction is employed in conjunction with the Becke-Johnson (BJ) damping scheme to account for van der Waals forces which are critically important for the correct description of the adsorption mechanism. For each calculation we place two molecules on each side of the metal atom and perform a full geometrical optimization. The molecules are always bound in end-on configuration except for H2 molecule for which the side-on geometry is considered. For the charge analysis, we employ the Bader method to extract the electrostatic charge associated with the metal cation. For the calculation of the binding energy, a geometrical counterpoise correction is applied to correct for the basis set superposition error arising from the use of localized orbitals.