Department of Physical and Macromolecular Chemistry

Zeolites are widely employed in adsorption and catalysis due to the combination of their porous structure, confinement effects, and surface chemistry. Among their different functionalities, hydroxyl groups play a central role in determining molecular interactions and catalytic reactivity. Understanding their nature, local environment, accessibility, and evolution under working conditions is therefore essential for establishing molecular-level structure–activity relationships. In this lecture, in situ and operando FTIR spectroscopy will be used to illustrate three complementary approaches to the study of hydroxyl groups in zeolites: i) understanding their molecular environment, ii) controlling their properties through catalyst engineering strategies, and iii) monitoring their evolution under reaction conditions.
Particular attention will be devoted to silanol groups in MFI zeolites, where FTIR spectroscopy combined with probe molecules reveals distinct hydroxyl environments and hydrogen-bonding networks. Their concentration and distribution can be rationally modified through controlled post-synthesis treatments, providing a strategy for tuning molecular adsorption and catalytic behavior. Operando studies of methanol conversion further demonstrate that silanols should not simply be regarded as structural defects, but can directly participate in catalytic processes, with their local environment determining their reactivity.

The discussion will then be extended to other zeolitic systems to illustrate how FTIR spectroscopy can follow active sites, adsorbed species, and structural responses directly under working conditions. Examples involving Brønsted acidity in SAPO-34, Ge-containing MFI zeolites, and flexible RHO nanozeolites will highlight the versatility of this approach for connecting surface chemistry with adsorption properties, catalytic pathways, and material dynamics. Overall, the lecture will show how FTIR spectroscopy provides a bridge between the molecular identification of active sites, their rational modification, and their direct observation during adsorption and catalysis.