For the bare MOF, peak D is a combination of seven vibrational modes (400.0, 400.3, 400.4, 400.4, 400.9, 403.6 and 405.0 cm -1 ). Two of these, at 403.6 and 405.0 cm -1 , dominate the intensity of the S(ω) and are associated with a torsion of the pyrazines. With CO, they undergo a red-shift by 18.4 and 8.7 cm -1 , giving rise to peak D ′ at 385.1 cm -1 and peak D ′′ at 396.3 cm -1 , respectively. For CO2 the associated red-shift is smaller (7.0 and 6.4 cm -1 ) and gives rise to peak D ′′′ (two modes at 396.6 and 398.6 cm -1 ). This result differs from the case of SO2 adsorption where the two modes are almost unchanged. The intensity of the other five modes under peak D is a factor of two lower and only two of them (400.0 and 400.3 cm -1 ) undergo a noticeable shift upon gas adsorption. These involve large displacements of the two Fe atoms and result in tilting and distortion of the octahedra together with an in-plane movement of the Pt atoms. Upon CO (CO2) adsorption, the first blue-shifts by 7.5 (8.6) cm -1 from 400.0 to 407.5 (408.5) cm -1 and falls under peak D ′′ (D ′′′ ). The second one red-shifts by 13.6 (12.3) cm -1 from 400. and between 362 and 425 cm -1 (right panel). The spectra of the empty Fe(pz)[Pt(CN) 4 ] (black) and after CO (red) and CO 2 (green) adsorption are reported. The computed S(ω) is reported in the middle (for bare and CO) and lower panels (bare and CO 2 ). For a better visualization, the vertical lines represent the normal mode frequencies ω with intensity S(ω) and no convolution with the Gaussian function.