Optimizing Hygroscopic Metal-Organic Frameworks via EDTA-Mediated Structural Reinforcement and Photothermal Modification

Hygroscopic metal-organic frameworks (MOFs) are considered as superior moisture sorbents due to their highly adjustable and desired water adsorption/release performance, enabling effective atmospheric water harvesting (AWH) in arid regions. However, the water adsorption capacity, recycling stability, and functionality of current MOFs should be further improved to meet the requirements of practical AWH systems. Here the hydrophilicity at low relative humidity (RH) and cycling stability of MOF-808 are simultaneously enhanced through the ethylenediaminetetraacetic acid (EDTA)-mediated post-modification. Based on the structural reinforcement, EDTA-modified MOF-808 (E-MOF-808) delivers a stable water uptake capacity of 0.39 g g-1 at 25% RH even after 50 water adsorption-desorption cycles, more than five times that of pristine MOF-808. In addition, bridging by EDTA with the strong chelating ability, the E-MOF-808 can spontaneously capture Cu2+ for further functional improvement. Accordingly, light-absorbing CuS nanoparticles can be in situ decorated on E-MOF-808 for facilitating solar-driven water release. It is envisioned that this EDTA-mediated function enhancement should provide valuable insights into the all-in-one design of versatile MOFs sorbents.