Carbon Dioxide Fixation and Sulfate Sequestration by a Supramolecular Trigonal Bipyramid

The subcomponent self‐assembly of a bent dialdehyde ligand and different cationic and anionic templates led to the formation of two new metallosupramolecular architectures: a Fe II 4 L 6 molecular rectangle was isolated following reaction of the ligand with iron(II) tetrafluoroborate, and a M 5 L 6 trigonal bipyramidal structure was constructed from either zinc(II) tetrafluoroborate or cadmium(II) trifluoromethanesulfonate. The spatially constrained arrangement of the three equatorial metal ions in the M 5 L 6 structures was found to induce small‐molecule transformations. Atmospheric carbon dioxide was fixed as carbonate and bound to the equatorial metal centers in both the Zn 5 L 6 and Cd 5 L 6 assemblies, and sulfur dioxide was hydrated and bound as the sulfite dianion in the Zn 5 L 6 structure. Subsequent in situ oxidation of the sulfite dianion resulted in a sulfate dianion bound within the supramolecular pocket.