Characterization of Li Cations in Zeolite LiX by Solid-State NMR Spectroscopy and Neutron Diffraction

Lithium cations in the dehydrated zeolites LiX-1.0 [(SiAlO 4 ) 96 Li 96 ] and LiX-1.25 [(Si 106 Al 86 O 384 )Li 86 ] are characterized by a combination of neutron diffraction and magic-angle spinning (MAS) NMR spectroscopy. Both samples show in the 6 Li and the 7 Li MAS NMR spectra three lines assigned to Li cations in three different crystallographic sites (SI‘, SII, and SIII‘). The low-field component in 6 Li and 7 Li MAS NMR spectra recorded at a temperature of 295 K belongs to mobile Li cations, as proven by variable-temperature 7 Li MAS NMR spectra. Variable-temperature neutron diffraction experiments show a phase transition in the temperature range T = 220−230 K in case of LiX-1.0. Neutron diffraction data recorded at 296 K were refined in the cubic space group Fd and data obtained at 20 K were refined in the orthorhombic space group Fddd . No phase transitions were observed in the refinement of the neutron diffraction data of zeolite LiX-1.25 ( Fd ) recorded at 10 K.