Unlocking the Chemical and Structural Complexity of Aluminum Hydroxy Acetates: from Commodity Chemicals to Porous Materials

Aluminum acetates have been in use for more than a century, but despite their widespread commercial applications, essential scientific knowledge of their synthesis-structure-property relationships is lacking. High-throughput screening, followed by fine tuning and extensive optimization of reaction conditions using Al³⁺, OH^- and CH₃COO^- ions, has unraveled their complex synthetic chemistry, yielding for the first time the four phase pure products Al(OH)(O₂CCH₃)₂ ⋅ x H₂O (x=0, 2) (1A and CAU-65, 1B), Al₃O(HO₂CCH₃)(O₂CCH₃)₇ (2), and the porous aluminum salt [Al₂₄(OH)₅₆(CH₃COO)₁₂](OH)₄ (CAU-55-OH, 3). Structure determination by electron and X-ray diffraction was carried out and the data suggested porosity for 1B and 3, which was confirmed by physisorption experiments. Even the scale-up to the 10 L scale was accomplished for 1A, 1B and 3 with yields of up to 1.1 kg (99 %). This study of a seemingly simple chemical system provides important information on both fundamental inorganic chemistry and porous materials.