Structure of Homoleptic Cu(I)(CO)(3) Cations in Cu(I)-Exchanged ZSM-5 Zeolite: An X-ray Absorption Study This project was supported by MURST (Cofin 98, Area 03). XAFS measurements were performed at ESRF (European Synchrotron Radiation Facitity) within the public user program. BM8 GILDA beamline is supported by INFN, INFM and CNR. The European Community is gratefully acknowledged for a TMR grant to G.T.P. We are indebted to F. Danca for skilful technical support and to M. Benfatto for critical discussion.