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

Abstract

The 2157 cm−1 (strong) and 2108 cm−1 (very weak) ν(CO) IR bands due to Cu+–CO in ZSM-5 zeolite with 12C and 13C 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 [νasint(TOT)(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)n aqua complexes and secondary (solvent-like) effects were considered to explain the results.