Structural Evolution of Amorphous Precursors toward Crystalline Zeolites Visualized by an in Situ X-ray Pair Distribution Function Approach

Zeolites are microporous aluminosilicate materials that have been used as industrial catalysts and adsorbents. The mechanism of formation of crystalline structures during the synthesis and the possible intermediate structures are not completely understood because the structural analysis of amorphous intermediates is significantly difficult. Here we observe the structural evolution of zeolite precursors to form crystalline zeolites using in situ X-ray pair distribution function (PDF) analysis. In situ X-ray PDFs showed the local ordering behavior of the aluminosilicate species at the atomic level. Furthermore, the in situ relative PDF analysis allowed the study of the structural evolution of the amorphous precursors before the crystallization started (the crystallization induction period). These results provide a direct and clear visualization of the structural evolution during the crystallization of zeolites, which has not been achieved with other techniques, and may lead to the creation of advanced zeolites and zeolite-based materials.