Identification of Signals from Individual Crystallographic T-Sites of HBEA Zeolite Framework in 27Al MAS NMR Spectra

Abstract

Based on quantum-chemical computation, a solution with periodic boundary conditions (PBC) was employed within density functional theory (DFT) simulations in order to assign the chemical shifts in the ²⁷Al MAS NMR spectra of Al-BEA (HBEA) zeolite (Si/Al = 31) to the individual crystallographic T-sites calculated for polymorph B of an identical zeolite. The results were compared both to relevant published reports (Si/Al = 71 and 75) and to the experimental data previously obtained by the authors for a mixture of polymorphs (Si/Al = 25). Deconvolution of the ²⁷Al MAS NMR spectrum into Al signals at different T-sites of polymorph B was compared to a similar deconvolution for polymorph A.