Tuning Water Sorption in Highly Stable Zr(IV)-Metal-Organic Frameworks through Local Functionalization of Metal Clusters.

Water adsorption of metal-organic frameworks (MOFs) is attracting intense interest because of their potential applications in atmospheric water harvesting, dehumidification, and adsorption-based heating and cooling. In this work, through using a hexacarboxylate ligand, four new isostructural Zr(IV)-MOFs (BUT-46F, -46A, -46W, and -46B) with rare low-symmetric 9-connected Zr6 clusters were synthesized and structurally characterized. These MOFs are highly stable in water, HCl aqueous solution (pH = 1), and NaOH aqueous solution (pH = 10) at room temperature, as well as in boiling water. Interestingly, the rational modification of the metal clusters in these MOFs with different functional groups (HCOO-, CH3COO-, H2O/OH, and PhCOO-) enables the precise tuning of their water adsorption properties, which is quite important for given application. Furthermore, all four MOFs show excellent regenerability under mild conditions and good cyclic performance in water adsorption.