Early-stage silanol condensation, defect healing and temporary reservoirs drive the development of the framework and porous system in silicalite-1 synthesized at 180 0C

Abstract

Hydrothermal synthesis is a well-established and scalable route for producing well-ordered zeolites that underpin industrial catalysis, separation, and adsorption. However, the concurrent chemical condensation and structural reorganization occurring at elevated temperatures make it difficult to elucidate how framework order and connectivity emerge from amorphous precursors, hindering the rational design of zeolites with tailored structural and catalytic properties. Here, we employ a time-resolved, multimodal approach to track the crystallization of Silicalite-1 (MFI) at 180 °C over shortened synthesis durations (1–5 h). The results reveal a sequential evolution from short-range ordering to partially organized pre-channels and pre-intersections that gradually link into a continuous microporous framework. Unexpectedly, transient mesopores act as temporary reservoirs for bound water, silanol groups, and template species, mediating condensation and defect healing that drive the assembly of pre-channels and their consolidation into stable intersections. This cooperative interplay between mesopores and framework growth clarifies how hierarchical order develops in the early stages of crystallization. Upon calcination, extended treatment removes residual species, opens pore network, and enhances accessibility, consolidating the matured MFI lattice. The resulting holistic, time-resolved mechanism offers mechanistic insight into framework evolution and provides a foundation for designing more time- and energy-efficient hydrothermal synthesis routes of zeolites. Show more