THE RELATIONSHIP BETWEEN THE LOCAL-STRUCTURE OF COPPER(I) IONS ON CU+ZEOLITE CATALYSTS AND THEIR PHOTOCATALYTIC REACTIVITIES FOR THE DECOMPOSITION OF NOX INTO N-2 AND O-2 AT 275 K/

Cu+/zeolite catalysts were prepared by a combination of ion-exchange a nd thermovacuum treatments. In situ characterization of these catalyst s and their photocatalytic reactivities for the decomposition of NOx ( NO and N2O) have been investigated by means of in situ photoluminescen ce, XAFS, ESR, UV, and FT-IR techniques along with an analysis of the reaction products. It was found that Cu(I) ions included within the na nopores of ZSM-5 and mordenite zeolites exist as isolated Cu(I) monome rs with planar three-coordinate or two-coordinate geometry, while in t he Y-zeolite cavities they exist as the [Cu(I)-Cu(I)] dimer species as well as the isolated Cu(I) monomer species. UV irradiation of these C u+/zeolite catalysts in the presence of NOx led to the photocatalytic decomposition of NOx into N-2 and O-2 at temperatures as low as 275 K. A local charge separation involving an electron transfer from the ele ctronically excited state of a Cu(I) ion (3d(9)4s(1) state) to the ant i-pi-bonding orbital of an NO molecule was found to play a vital role in initiating the photocatalytic decomposition of NO,. Furthermore, th e photocatalytic reactivity of these Cu+/zeolite catalysts was found t o be strongly affected by the local structure of the Cu(I) ions which could easily be modified by changing the type of zeolites and loading of the copper ion. Special attention has, therefore, been focused an t he relationship between the local structure of copper ions on the cata lysts and their photocatalytic reactivities. (C) 1998 Elsevier Science S.A.