Speciation of copper in micropores

Speciation of copper in the micropores of zeolites and a contaminated soil was studied by extended X-ray absorption fine structural (EXAFS) spectroscopy. The Fourier transformed EXAFS data showed that copper oxide in zeolites ZSM-5 and ZSM-48 possessed a Cu-O bond distance of 1.95 Å with coordination numbers (CNs) of 1-2. Since ZSM-5 and ZSM-48 possessed channel openings of 5-6 Å, the possible sizes of the linear-type copper oxides in these confined pores were 2.93-2.95 Å. However, in the supercages (∼13 Å) and channels (7.4 Å) of zeolite Y, a three dimensional structure of CuO was observed. Interestingly, we found that CuO in the Cu-contaminated soil had a similar structure to that in ZSM-5 or ZSM-48. Nevertheless, the EXAFS data indicated that the CNs of Cu-O and Cu-O-Cu were 0.4 and 0.3, respectively, suggesting a highly perturbed copper oxide in the irregular micropores of the contaminated soil.