Chromium Environment within Cr-Doped Silico-Aluminophosphate Molecular Sieves from Spin Density Studies

High Resolution Image Download MS PowerPoint Slide X-/Q-band electron paramagnetic resonance (EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopies have been employed, in conjunction with density functional theory (DFT) modeling, to determine the location of Cr 5+ ions in SAPO-5 zeotype materials. The interaction of the unpaired electron of the paramagnetic Cr 5+ species with 27 Al could be resolved, allowing for the first detailed structural analysis of Cr 5+ paramagnetic ions in SAPO materials. The interpretation of the experimental results is corroborated by DFT modeling, which affords a microscopic description of the system investigated. The EPR-active species is found to be consistent with isolated Cr 5+ species isomorphously substituted in the framework at P 5+ sites.