Solid-State 91Zr NMR Characterization of Layered and Three-Dimensional Framework Zirconium Phosphates

Layered and open framework zirconium phosphates (ZrPs) have many current and potential applications in the areas of catalysis, sorption, protonic conductors, solar energy storage, crystal engineering, and ion exchange. Characterization of ZrP-based materials is important because understanding the relationship between the properties of these materials and their structures is crucial for developing new uses and for improving their performances in current applications. However, local Zr environments in many ZrPs have not been characterized directly by Zr-91 solid-state NMR (SSNMR). This is because Zn-91 (I = 5/2) is an unreceptive nucleus with many NMR unfavorable characteristics, leading to low sensitivity. In this work, the local environments of the zirconium centers in several ion-exchanged derivatives of layered alpha-ZrP (K+, Li+-, Co(NH3)(6)(3+)-ZrP) have been probed directly using Zr-91 MAS, static quadrupolar echo, and/or quadrupolar Carr- Purcell-Meiboom-Gill NMR Several layered and three-dimensional framework zirconium phosphates (ZrPO4-DES8, ZrPO4-DESI, ZrPO4-DES2, ZrPOF-pyr, ZrPOF-Q1, ZrPOF-EA, and ZrPOF-DEA) with novel structures were also examined. Theoretical calculations using the CASTEP and Gaussian model cluster approaches were also performed in order to provide insights into the observed spectra. In addition to Zr-91 SSNMR, P-31, C-13, and F-19 SSNMR spectroscopy was also utilized to characterize the above-mentioned materials.