Abstract:

Ammonium fluoride (NH₄F) etching is an effective method for constructing hierarchical zeolites, yet its impact on the detailed structure and acidity remains unclear. This study employs probe molecule-assisted solid-state NMR technique to systematically investigate the evolution of acid site structures and properties during NH₄F etching of ZSM-5 zeolites. The results reveal that the degree of NH₄F etching significantly manipulates the amount, strength, type, and spatial accessibility of acid sites, and it is also directly associated with the development of hierarchical pore structures. This work elucidates the influence mechanism of NH₄F etching on zeolite structure and acidic property at the atomic level, providing a theoretical basis for the rational design and optimization of efficient hierarchical zeolites.

Key words: Solid-state NMR, Acidic property, Probe molecule, NH4F etching, Hierarchical zeolites