Unveiling the Transformation Pathway from ε-Al₁₃ to δ-Al₁₃

The atomic-scale investigation of aluminum polyoxocation transformation pathways is crucial for the precise regulation of alumina precursor chemistry and the rational design of advanced aluminum-based materials. In particular, the Baker-Figgis-Keggin (Keggin) series of [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺ (Al₁₃) clusters exhibit unique electronic structures and remarkable chemical properties, serving as key intermediates in the hydroxide precipitation process, whereas their structural transformation mechanisms remain poorly understood. Herein, the isomerization details from ε-Al₁₃ to δ-Al₁₃ are first captured by experimental techniques, and we employ biased ab initio molecular dynamics simulations to further elucidate the underlying mechanism of this transformation, which reveal a solvent-mediated dissociation-reorganization pathway. Additionally, we demonstrate that the ionic environment precisely governs the dissociation kinetics through two synergistic mechanisms: counterion charge transfer modulates the electrostatic stabilization of the polynuclear framework, while specific cation coordination facilitates electron density redistribution at critical Al-O-Al junctions. These findings provide a fundamental mechanistic framework for controlling polyoxocation reactivity, with direct implications for optimizing aluminum-based catalytic systems and the design of functional materials.