Dual-extended-polyhedral metal–organic frameworks for atmosphere water harvesting

A series of dual-extended-polyhedral metal–organic frameworks (MOFs) was constructed based on the 14-coordinated Cu₂₄-MOP-1 (MOP = metal–organic polyhedron) supermolecular building blocks (SBBs) with enhanced stability and tunable functionality for high water uptake efficiency and capacity. Exceptional water stability was demonstrated by the retention of chemical integrity and crystallinity of USC-CP-5 (where USC-CP stands for University of South China coordination polymer) after exposure to boiling water for 24 h. Functionalization with –Cl, –OCH₃, –OH, and –NH₂ groups of USC-CP-5 resulted in water uptake capacities of 450, 460, 490, and 590 cm³∙g⁻¹ at relative pressure (P/P₀) = 0.9, respectively. This performance is ascribed to both the increased hydrophilicity of the ligands and stronger hydrogen bonding. Intriguingly, high-temperature activated USC-5–NH₂ exhibits a significant water uptake of 38.5 wt.% at P/P₀ = 0.3 and releases 0.44 L∙kg⁻¹ water between 25 and 65 °C. This water release process is reversible for at least 100 cycles with minimal weight loss of only 1.6 wt.%. Consequently, USC-5–NH₂ holds considerable potential for harvesting and releasing atmospheric water in arid desert regions, powered by solar energy.