A Hydrolytically Stable Cu(II)-Based Metal−Organic Framework with Easily Accessible Ligands for Water Harvesting
2021
Wang, Lu | Wang, Kecheng | An, Hao-Tian | Huang, Hongliang | Xie, Lin-Hua | Li, Jian Rong
Water scarcity is a critical issue in desert and arid regions, and atmospheric water harvesting is a potential solution. The challenge is lacking ideal adsorbents that can efficiently capture water from low-humidity air and be regenerated readily. Herein, we report a hydrolytically stable metal–organic framework (MOF), [Cu₂(AD)₂(SA)] (Cu-AD-SA), with excellent performance in water harvesting. More importantly, this material can be facilely prepared from two easily accessible ligands adenine (HAD) and succinic acid (H₂SA). Cu-AD-SA has a three-dimensional (3D) framework structure with the crs topology and intersecting channels of ∼5 Å in diameter. The channel surface is decorated by uncoordinated aromatic N atoms, amine groups, and alkyl moieties. Interestingly, Cu-AD-SA shows a high water adsorption capacity of 0.16 g g–¹ at low pressure of 0.2 P/P₀ and 25 °C. Furthermore, dynamic water adsorption–desorption cycling experiments demonstrated a stable working capacity of 0.13 g g–¹ for uptaking water from a low-humidity air (water partial pressure: 0.85 kPa, 20% RH at 30 °C, 5.3% RH at 55 °C) at 30 °C and desorption at 55 °C. The water adsorption mechanism was also studied by analyzing its single-crystal structure after water loading. The results indicated the existence of strong H-bonding interactions between water molecules and uncoordinated N atoms and amine groups on the framework, which should play an important role in the high adsorption at low pressure. All the above features suggest great potential of Cu-AD-SA for water harvesting in arid regions.
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