Detection of nanodefects in the framework of NaY zeolite originating from the in situ synthesis of metal-free phthalocyanine

Abstract

In order to obtain a suitable model system for investigating the formation of nanodefects in a zeolite framework during the in situ synthesis of phthalocyanines, metal-free phthalocyanine was encapsulated within the pores of a NaY zeolite by in situ cyclotetramerization of adsorbed 1,2-dicyanobenzene. Such defects will be regarded as nanodefects, which are created by removal of only a few atoms or ions from framework positions. In contrast to scanning electron microscopy, powder X-ray diffraction, nitrogen adsorption, 27Al, and 29Si MAS NMR, all showing no significant changes, the occurrence of an absorption at λ≈280 nm in the diffuse reflectance UV spectrum was found to be characteristic for nanodefects in the zeolite framework. This absorption occurs due to the change of the coordination of a small percentage of framework aluminum centers from tetrahedral to octahedral.