Ferrocene Dicarboxylic Acid Ligand-Exchanged Hollow MIL-101(Cr) Nanospheres for Solar-Driven Atmospheric Water Harvesting

Developing efficient water adsorbents for solar-driven atmospheric water harvesting (AWH) still remains a challenge due to the poor photothermal heating ability and slow sorption kinetics of most adsorbents. Postsynthetic ligand exchange (LE) provides an alternative strategy to prepare metal–organic framework (MOF) materials with varied structures and functions. In this work, multifunctional hollow MIL-101(Cr) with ferrocene dicarboxylic acid (Fc(COOH)2) ligand exchanged (HMF) nanospheres are prepared and utilized for efficient AWH. The resulted HMF nanospheres present great visible light absorption (>80%) and photothermal conversion ability (61.6%) due to the introduced Fc(COOH)2 ligand. The water adsorption and desorption rates of the HMF nanosorbent are 2.3 times and 4.5 times that of MIL-101(Cr). The fast water capture and solar-driven release kinetics of HMF nanosorbents indicate its great potential for actual water harvesting. The outdoor water collection experiment demonstrates that the areal water harvesting capacity of the HMF nanosorbent is 1720 g m–2 per cycle with packed thickness of 8 mm. HMF nanosorbents also demonstrate good antibacterial activity (91.4%), which is beneficial to the collection of healthy and safe water. This work provides a facile and practical method to design multifunctional MOFs from the molecular level by LE and to achieve solar-driven AWH and other fields.