Multi‐Step Nucleation of a Crystalline Silicate Framework via a Structurally Precise Prenucleation Cluster

• Published in: Angewandte Chemie Vol. 135; no. 28
• Main Authors: Jin, Biao, Chen, Ying, Tao, Jinhui, Lachowski, Kacper J., Bowden, Mark E., Zhang, Zihao, Pozzo, Lilo D., Washton, Nancy M., Mueller, Karl T., De Yoreo, James J.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 10.07.2023
• Subjects: Atomic force microscopy; Chemistry; Clathrates; Crystallization; Crystals; Cyclosilicate Hydrate; Hydrogen bonding; Hydrogen bonds; Metal-organic frameworks; Monomers; Multi-Step Nucleation; NMR; Nuclear magnetic resonance; Nucleation; Polyanions; Polyelectrolytes; Prenucleation Clusters; Reaction mechanisms; Resonance scattering; Self-Assembly; Zeolites
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202303770

Hierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of zeolites and metal–organic frameworks, pre‐organized multi‐ion “secondary building units” (SBUs) have been proposed as fundamental building blocks. However, detailing the progress of multi‐step reaction mechanisms from monomeric species to stable crystals and defining the structures of the SBUs remains an unmet challenge. Combining in situ nuclear magnetic resonance, small‐angle X‐ray scattering, and atomic force microscopy, we show that crystallization of the framework silicate, cyclosilicate hydrate, occurs through an assembly of cubic octameric Q38 polyanions formed through cross‐linking and polymerization of smaller silicate monomers and other oligomers. These Q38 are stabilized by hydrogen bonds with surrounding H2O and tetramethylammonium ions (TMA+). When Q38 levels reach a threshold of ≈32 % of the total silicate species, nucleation occurs. Further growth proceeds through the incorporation of [(TMA)x(Q38)⋅n H2O](x−8) clathrate complexes into step edges on the crystals. In situ characterizations reveal a multi‐step crystallization pathway for cyclosilicate hydrate crystals that starts with the formation of structurally precise prenucleation clusters, which comprise the secondary building units of this framework lattice.