INTERACTIONS OF COPPER AND ZINC IN MCM-41

Speciation of copper and zinc (1:1) in MCM-41 has been studied by X-ray absorption near edge structural (XANES) and X-ray absorption fine structural (EXAFS) spectroscopies in the present work. The least-square fitted XANES spectra show that Cu(II) and Zn(II) are the major copper and zinc species, respectively in the channels of MCM-41 during calcination at 573–1173 K. The EXAFS data indicate that copper in MCM-41 possesses a Cu–O bond distance of 1.97 A with a coordination number (CN) of 3.4. During calcination at 573–1173 K, about 3.8–4.2 nearest oxygen atoms are bonded to the central copper atoms with Cu–O bond distances of 1.95–1.96 A in MCM-41. A small amount of Cu–Zn alloy may be formed during calcination. Existence of Zn–O)–Si (3.05–3.11 A) with CNs of 1.7–2.3 is also observed by EXAFS, suggesting an interaction between zinc and the framework SiO2 of MCM-41 during calcination.