STRUCTURE OF ZINC-OXIDE PARTICLES INSERTED IN NANOPORES OF MICROPOROUS MATERIAL

The insertion of nanoparticles in the cages of microporous materials r aised 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 interacti on with the microporous framework is subject to controversies. EXAFS c an bring accurate information so far the study of the coordination she lls around the central atom can be extended beyond the first one. In z inc exchanged aluminosilicate sodalites, whose cubic structure contain s one type of nanopores (6 Angstrom in diameter), it was suggested pre viously that some zinc oxide particles can be located in the centre of the sodalite cages. The carefull EXAFS analysis at Zn K-edge, includi ng ab-initio calculations using the FEFF code, reveals the presence of Al neighbours belonging to the framework at less than 3 Angstrom from zinc cations as well as an elongation of the Zn-Zn distance with resp ect to crystalline ZnO. The coordination radii and numbers are consist ent with the model of three zinc cations, each of them being located a lmost in the plane of the 6-oxygen ring of the wall shared by two join ed cages.