Structure of Zinc Oxide Particles Inserted in Nanopores of Microporous Material

Abstract
The insertion of nanoparticles in the cages of microporous materials raised up a large interest, due to the applications of such systems in the field of catalysis and microelectronics, but the atomic structure of such particles, their location inside the cages and their interaction with the microporous framework is subject to controversies. EXAFS can bring accurate information so far the study of the coordination shells around the central atom can be extended beyond the first one. In zinc exchanged aluminosilicate sodalites, whose cubic structure contains one type of nanopores (6 Å in diameter), it was suggested previously that some zinc oxide particles can be located in the centre of the sodalite cages. The carefull EXAFS analysis at Zn K-edge, including ab-initio calculations using the FEFF code, reveals the presence of Al neighbours belonging to the framework at less than 3 Å from zinc cations as well as an elongation of the Zn-Zn distance with respect to crystalline ZnO. The coordination radii and numbers are consistent with the model of three zinc cations, each of them being located almost in the plane of the 6-oxygen ring of the wall shared by two joined cages.