At room temperature, gaseous Fi extracts tetrahedrally coordinated aluminum from the lattice of an acid, near-faujasite HY zeolite (Si/Al approximate to 13) and forms fluoro-hydroxy-aluminum complexes of the type Al2F(OH)(n)((5-n)+) in which Al is octahedrally coordinated. Moreover, the crystallinity of the zeolite is almost unchanged by the fluorination process. The HY dehydrated at 200 degreesC under vacuum and treated under a F-2 pressure of 300 mbar at room temperature is practically totally dealuminated. At lower pressure the transformation is partial. The coordination shell of the complex becomes unstable at about 500 degreesC. Upon losing ligands, octahedral Al reverts partially to the tetrahedral coordination and is partially reinserted into the lattice. At a higher temperature an amorphous alumina phase is formed. Al-27 and F-19 high-resolution solid-state NMR, FT-IR, X-ray diffraction, and temperature-programmed desorption (TPD) are the main tools used in this work.