Facile Synthesis of Hierarchical MFI Zeolite Nanosheets for Enhanced Dye Adsorption Performance

Hierarchical zeolites have garnered significant attention for their applications in industrial adsorption, separation, and catalysis. However, the facile synthesis of high-quality hierarchical zeolites poses a considerable challenge. In this study, we present a facile and low-cost strategy for constructing hierarchical MFI zeolite nanosheets (HNSs) using a seed-assisted and amino acid-assisted cross-cutting approach. Successful synthesis was achieved through careful control of the addition of the seeds (nucleated amorphous silicon precursors, NASPs) and amino acids. The HNSs exhibit a substantial micropore volume (0.17–0.20 cm³ g^–1), indicating the high crystallinity of MFI-type zeolites. TEM and AFM investigations into the growth mechanism reveal that the formation of the hierarchical zeolite nanosheets follows the nonclassical growth mechanism, characterized by crystal epitaxial growth and a self-assembly pathway. Importantly, the cross-cutting strategy can be extended to the synergistic interaction between the NASPs and NH₄⁺ or even pH to synthesize HNSs. Furthermore, treatment with NH₄F aqueous solution enhances the dye adsorption performance of the fluorine-modified HNSs (adsorption capacity: 116.53 mg g^–1), attributed to the presence of abundant F heteroatom sites. This work offers an efficient, industrially viable method for synthesizing hierarchical zeolite nanosheets, presenting promising prospects for adsorption applications.