Al-TUD-1: Introducing tetrahedral aluminium

Tetrahedral aluminium was synthesized inside the TUD-1 structure with a low Si/Al ratio. The Al ion in its tetrahedral structure was stabilized by sodium as a counter cation. However, the tetrahedral aluminium species in the TUD-1 structure reverted to a mixture of hexa-, penta- and tetrahedral coordination sites after the exchange of sodium cations with protons. The Al-TUD-1 materials were found to be catalytically active for the acetal protection of benzaldehyde.

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► Aluminium was introduced in purely tetrahedral form into the mesoporous silicate TUD-1.
► A sodium counter ion proved to be essential for stability while catalytic activity was only observed when the material was ion exchanged.
► Among the catalysts tested for the acetal protection of benzaldehyde, H-Al-TUD-0.7-IE gave maximum 53% yield of 2-phenyl-1,3-dioxolane.
► Na-Al-TUD-1 are catalytically virtually inactive, corresponding to their weak acidity.