Electronic and Geometrical Structure of Zn+Ions Stabilized in the Porous Structure of Zn-Loaded Zeolite H-ZSM-5: A Multifrequency CW and Pulse EPR Study

Electron spin resonance and hyperfine sublevel correlation (HYSCORE) spectroscopy at X- and Q-band frequencies have been employed, in conjunction with X-ray absorption spectroscopy (XAS), to determine the geometric and electronic structure of Zn+ ions in H-ZSM-5 zeolite. Zn+ ions were generated by the direct exposure of dehydrated acid H-ZSM-S to Zn vapors. The number of Zn ions is found to increase substantially upon UV irradiation. A single EPR active species is detected, indicating a single site of adsorption, characterized by the presence of an Al3+ site, as revealed by superhyperfine interactions. The full g (g(x) = 1.9951, g(y) = 1.9984, g(z) = 2.0015) and Al-27 vertical bar Al vertical bar (A(x) = 2.8, A(y) = 2.7, A(z) = 4.6) MHz tensors were resolved, allowing for a detailed description of the geometric and electronic structure of Zn+ ions stabilized in the cages of H-ZSM-5 zeolite. The dispersion and nuclearity of Zn species formed during the sublimation/irradiation process was assessed by means of XAS spectroscopy, which indicates the absence of metal or metal oxide particles in a significant amount.