Effects of water and ion-exchanged counterion on the FTIR spectra of ZSM-5. II. (Cu+-CO)-ZSM-5: coordination of Cu+-CO complex by H2O and changes in skeletal T-O-T vibrations

The 2157 cm(-1) (strong) and 2108 cm(-1) (very weak) v(CO) IR bands due to Cu+-CO in ZSM-5 zeolite with C-12 and C-13 isotopes, respectively, are reversibly red-shifted by subsequent adsorption of H2O at 293 K. On the contrary. the locally perturbed internal (T-O-T) asymmetric stretching framework vibration [v(as)(int)(TCFT)(Cu+-CO) = 965 cm(-1)] is reversibly blue-shifted. The courses of the band shifts revealed notable features. Charge transfers from water to Cu+ ions, changes in coordination spheres of Cu+(CO)(H2O), aqua complexes and secondary (solvent-like) effects were considered to explain the results.