High field ENDOR as a characterization tool for functional sites in microporous materials

Area of Science:

• Materials Chemistry
• Spectroscopy
• Solid-State Physics

Background:

• Understanding functional sites in materials and biology requires detailed spatial and electronic structure determination.
• Paramagnetic sites are amenable to characterization using electron paramagnetic resonance (EPR) spectroscopy.
• High field (HF) EPR and HF electron nuclear double resonance (ENDOR) have expanded the capabilities for analyzing these sites.

Purpose of the Study:

• To provide an overview of recent applications of pulsed HF ENDOR spectroscopy to microporous materials.
• To present the new opportunities offered by HF ENDOR for characterizing zeotype materials.
• To discuss the theoretical basis, techniques, instrumentation, and applications of pulsed HF ENDOR.

Main Methods:

• Pulsed high field electron nuclear double resonance (HF ENDOR) spectroscopy.
• Analysis of HF ENDOR spectra.
• Signal assignment techniques.
• Description of instrumentation for pulsed HF ENDOR.

Main Results:

• Detailed characterization of transition metal ions and complexes in zeolite cages.
• Analysis of transition metal substitution in zeolite frameworks, aluminophosphate molecular sieves, and mesoporous materials.
• Investigation of NO interaction with Lewis sites and trapped S atoms in zeolites.

Conclusions:

• Pulsed HF ENDOR spectroscopy is a powerful tool for characterizing paramagnetic centers in microporous materials.
• The technique offers significant advantages for understanding the structure-function relationships in zeotype materials.
• Further development and application of HF ENDOR will continue to advance materials science and related fields.