Spectroscopic Characterization of Heteroatom‐Containing Zeolites

Heteroatom-containing zeolites have attracted increasing research interest in the field of heterogeneous catalysis because of their distinct properties compared with conventional aluminosilicate zeolites in terms of activity, bifunctionality, and stability. A precise design of heteroatom sites in zeolites from the aspects of content, types, and locations is critical to obtain high catalytic performance, which necessitates the characterization of heteroatom species in zeolites, particularly during their preparation, pre-treatment, and application processes. In this chapter, various spectroscopic techniques for the characterization of heteroatom-containing zeolites are briefly summarized. X-ray-based techniques are discussed in Section 8.1 as powerful tools to provide structural information about zeolite frameworks and the coordination and valence states of heteroatoms. Ultraviolet–visible–near infrared spectroscopy is introduced in Section 8.2, which is a convenient and sensitive method to probe the incorporation and location of heteroatoms in zeolites. Section 8.3 addresses Raman spectroscopy for the investigation of the synthesis mechanism and assembly of heteroatoms in zeolites. Solid-state nuclear magnetic resonance (NMR) spectroscopy is presented in Section 8.4, focusing on double-resonance and two-dimensional correlation NMR methods for the atomic-level understanding of the nature of heteroatom sites and their host–guest interactions with zeolites. The information obtained by these spectroscopic techniques plays a key role in the elucidation of structure–property relationships of heteroatom-containing zeolites, which is highly relevant to their technological applications in heterogeneous catalysis.