K. Hadjiivanov et H. Knozinger, FTIR study of low-temperature CO adsorption on Cu-ZSM-5: Evidence of the formation of Cu2+(CO)(2) species, J CATALYSIS, 191(2), 2000, pp. 480-485
CO adsorption at ambient temperature leads to formation of the well-known C
u+-CO species (2158 cm(-1)) and Cu+(CO)(2) dicarbonyls (2177 and 2150 cm(-1
)). In addition, Cu2+-CO complexes (2179 cm(-1)) appear under equilibrium C
O pressure and are very easily destroyed by evacuation. The CO stretching f
requency almost coincides in position with v(s) of the Cu+(CO)(2) species.
Lowering the temperature in the presence of gas-phase CO leads to formation
of Cu2+(CO)(2) geminal dicarbonyls (2170 cm(-1)) and a small amount of Cu(CO)(3) tricarbonyls (evidenced by a band at 2191 cm(-1)). The results demo
nstrate the high coordinative unsaturation of both Cu+ and Cu2+ ions in Cu-
ZSM-5. (C) 2000 Academic Press.