Synthesis of Al-MOFs: From Discovery to Pilot-Scale

Scientific and technological progress is closely linked to the availability of materials with defined properties that are optimized for the application. While it is often possible to improve material properties step by step, major advances are achieved through the discovery of new compounds, which cannot be planned. In this context, fundamental research plays an important role by allowing exploratory investigations of chemical parameter spaces to discover new compounds and subsequently determine their properties.

This presentation describes the application of high-throughput (HT) methods for the systematic study of aluminum MOFs. Aluminum, the third most abundant element in the Earth’s crust, forms a variety of complex species in aqueous solution, including polyoxocations such as the Al₁₃ Keggin ion and Al₃₀ clusters. Al- containing metal-organic frameworks (Al-MOFs) have attracted considerable interest due to their structural flexibility, stability, and unique sorption properties.[1,2] Archetypal Al-MOFs such as MIL-53, MIL-100, CAU-1,CAU-10-X, and MOF-303 are typically synthesized with aryl-based polycarboxylic acids, but frameworks incorporating (poly)phosphonic acids and formic acid ([Al(HCOO)₃]) have also been explored.[3] HT studies in our group led to the discovery of the porous compounds CAU-10, an aluminum hydroxy isophthalate, and CAU- 55,[4] a recently discovered porous salt containing Al₂₄ clusters. Using CAU-10 as an example, it is shown how its serendipitous discovery led to numerous further studies on the synthesis and application of aluminum carboxylates in water adsorption for cooling and water harvesting. However, further detailed studies are required for application. This includes the development of water-based "green" syntheses under the mildest possible reaction conditions and with high yields. These are easily scalable while maintaining the properties.[5] Other aspects such as separation and purification of CAU-10, shaping, cycle stability and possible future work will also be discussed.

1. Loiseau, et al. Comptes Rendus Chim. 18 (2015) 1350.
2. Schilling et al., Synthesis, Structure and Selected Properties of Aluminium, Gallium, and Indium-Based Metal-Organic Frameworks. In The Chemistry of Metal Organic Frameworks, Wiley-VCH pp 105-135 (2016).
3. Evans et al. Sci. Adv. 8 (2022) eade1473.
4. Achenbach et al. Angew. Chem. Int. Ed. 62 (2023) e202218679.
5. Mertin, manuscript in preparation.