Polymorph Selection in Zeolite Synthesis Occurs after Nucleation

Bertolazzo, Andressa A.; Dhabal, Debdas; Molinero, Valeria

doi:10.1021/acs.jpclett.2c00033

Cited by 16 publications

(23 citation statements)

References 68 publications

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“…The non-classical mechanism of crystallization through an intermediate mesophase (in systems that have such phases with stability between amorphous and crystal) requires that the rate of crystal formation is controlled by the nucleation barriers. Our analysis here and in ref indicates that the nucleation barriers for the amorphous to crystal transition are negligible for most zeolites at the high crystallization driving forces typical of hydrothermal synthesis. Under these conditions, the crystallization proceeds through a spinodal-like decomposition from the amorphous parent phase, with the rate of the amorphous to zeolite transition controlled by the characteristic time scale of restructuring of the silica network τ t .…”

Section: Discussionsupporting

confidence: 56%

“…Our analysis here and in ref indicates that the nucleation barriers for the amorphous to crystal transition are negligible for most zeolites at the high crystallization driving forces typical of hydrothermal synthesis. Under these conditions, the crystallization proceeds through a spinodal-like decomposition from the amorphous parent phase, with the rate of the amorphous to zeolite transition controlled by the characteristic time scale of restructuring of the silica network τ t . We conclude that mesophases would not influence the nucleation rate of most zeolites.…”

Section: Discussionsupporting

confidence: 56%

“…39,66,72,73 Under these conditions, the rate of crystallization is not controlled by the nucleation barriers but by the time scale τ t of reorganization of the glassy silica network. 74 We predict that mesophases would not be part of the nucleation pathway of the most stable silica zeolites under conditions of hydrothermal synthesis.…”

Section: Resultsmentioning

confidence: 91%

“…The temperatures of hydrothermal synthesis of zeolites are 350–450 K, which are around 50% of the crystal to amorphous temperatures of most zeolites. ,,, Under these conditions, the rate of crystallization is not controlled by the nucleation barriers but by the time scale τ t of reorganization of the glassy silica network . We predict that mesophases would not be part of the nucleation pathway of the most stable silica zeolites under conditions of hydrothermal synthesis.…”

Section: Results and Discussionmentioning

confidence: 92%

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Unstable and Metastable Mesophases Can Assist in the Nucleation of Porous Crystals

et al. 2022

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Porous crystalsincluding zeolites, metal–organic frameworks, and clathratesare widely used as catalysts and molecular sieves and in energy applications. These materials are synthesized from solution through an intermediate amorphous phase. However, the structural gap between the amorphous and porous crystal phases can lead to large nucleation barriers and difficulties in the control of crystal polymorphs. Previous reports indicate that porous mesophases can facilitate the amorphous to porous crystal transformation, directing the crystallization toward specific crystal structures. To date, it is not known how mesophase stability and synthesis temperature impact the facilitation. Here, we use molecular simulations and nucleation theory to investigate the crystallization of a zeolite in a family of models with tunable mesophase stability. We find that the nucleation mechanism evolves from non-classical to classical as the mesophase stability approaches that of the crystal. The simulations reveal that even an unstable mesophase can facilitate porous crystal nucleation through the formation of a transient fluctuation within which the crystal is originated. We conclude that tapping into the medium-range order of mesophases that have ordered pores without crystalline tiling is promising to increase the crystallization rates of porous crystals while directing the synthesis toward specific polymorphs.

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Section: Discussionsupporting

confidence: 56%

Section: Discussionsupporting

confidence: 56%

Section: Resultsmentioning

confidence: 91%

Section: Results and Discussionmentioning

confidence: 92%

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Unstable and Metastable Mesophases Can Assist in the Nucleation of Porous Crystals

et al. 2022

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“…Molecular simulations have the right spatial resolution. However, in the synthesis mixture, the zeolite crystallites and the surrounding amorphous matrix have very similar local and medium-range orders 69 . Fig.…”

Section: Dynamical Classification Of Structures With Thermal Noisementioning

confidence: 99%

CEGAN: Crystal Edge Graph Attention Network for multiscale classification of materials environment

Sankaranarayanan

Banik

Dhabal

et al. 2022

Preprint

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Machine learning models and applications in materials design and discovery typically involve the use of feature representations or “descriptors” followed by a learning algorithm that maps it to a user-desired property of interest. Most popular mathematical formulation-based descriptors are not unique across the atomic environments or suffer from transferability issues across different application domains and/or material classes. In this work, we introduce the Crystal Edge Graph Attention Network (CEGAN) workflow that uses graph attention-based architecture to learn unique feature representations and perform classification of materials across multiple scales (from atomic to mesoscale) and diverse classes ranging from metals, oxides, non-metals and even hierarchical materials such as zeolites. We first demonstrate a case study where the classification is based on a global, structure-level representation such as space group and structural dimensionality (e.g., bulk, clusters, 2D, etc.). Using representative materials such as polycrystals and zeolites, we next demonstrate the transferability of our network in successfully performing local atom level classification tasks, such as grain boundary identification and other heterointerfaces. Finally, we demonstrate classification in (thermal) noisy dynamical environments using a representative example of crystal nucleation and growth of a zeolite polymorph from an amorphous synthesis mixture. Overall, our approach is agnostic to the material type and allows for multiscale classification of features ranging from atomic-scale crystal structures to heterointerfaces to microscale grain boundaries.

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Full‐scale modeling of chemical experiments

Wang,

2023

Smart Molecules

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Computational chemistry methods are playing an increasingly pivotal role in chemical experiments. From quantum chemistry simulations to finite element simulations, researchers can always find an appropriate simulation method to elucidate the specific mechanisms at a certain resolution scale. However, in organic or inorganic synthesis, the synthesis mechanisms span multiple spatial and temporal scales of chemical experiments. Furthermore, the intricate nature of these mechanisms renders it impossible for any single simulation method to provide a comprehensive depiction of the entire process. In this perspective, using zeolite and polymer synthesis simulations as examples, we stress the significance of full‐scale modeling techniques for chemical experiments and urge the corresponding sophisticated simulation platform.

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Polymorph Selection in Zeolite Synthesis Occurs after Nucleation

Cited by 16 publications

References 68 publications

Unstable and Metastable Mesophases Can Assist in the Nucleation of Porous Crystals

Unstable and Metastable Mesophases Can Assist in the Nucleation of Porous Crystals

CEGAN: Crystal Edge Graph Attention Network for multiscale classification of materials environment

Full‐scale modeling of chemical experiments

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