Defect-engineered metal-organic frameworks for volumetrically and kinetically co-enhanced atmospheric water harvesting

Atmospheric water harvesting emerges as a promising technological solution to address water scarcity in arid and desolate regions. The spatiotemporal water collection efficiency of this new technology is crucial for its practical deployment, which mainly relies on both the volumetric water uptake capacity and the kinetic water adsorption rate of sorbent materials. Metal-organic frameworks are an emerging class of hygroscopic sorbents for atmospheric water harvesting due to their large specific surface area and pore volume, programmable water binding sites, and definite porous crystalline structure. However, achieving both high volumetric adsorption capacity and fast adsorption kinetics in MOF crystals remains challenging. To address this problem, we herein adopted a facile defect engineering strategy to tune the water binding sites and the pore structure in an industrially viable Al-fumarate MOF. The defective MOF shows a hierarchical porous structure with abundant exposed water binding sites, which simultaneously reduce the diffusion resistance of water molecules and increase the water binding affinity, leading to a higher water adsorption capacity and a faster adsorption rate even in a low humidity environment. Our work demonstrates a facile and green approach for enhancing the water collection capability of MOFs for atmospheric water harvesting.