Simultaneous Enhancement of Adsorption Kinetics and Capacity in MOFs for Arid-Environment Atmospheric Water...

Metal-organic frameworks (MOFs) are promising adsorbents for atmospheric water harvesting (AWH), particularly in arid climates. However, the inherently narrow pores (typically with sizes < 2 nm) of conventional MOFs limit both water diffusion and adsorption capacity, thereby constraining the practical daily water yield of MOF-based AWH systems. Herein, ordered mesopore engineering is applied to a typical hygroscopic MOF, UiO-66-NH₂, to construct channels with larger pores, thereby overcoming these limitations. The resulting material with uniform 11 nm 2D hexagonal mesopores, denoted OM-UiO-66-NH₂, exhibits a 3.7-fold faster water adsorption rate and nearly an order-of-magnitude higher effective water diffusivity than the pristine UiO-66-NH₂ at 30% relative humidity (RH). Moreover, OM-UiO-66-NH₂ achieves a 12% increase in water uptake capacity (0.43 g g^-1 at 30% RH) and maintains stable performance over 500 adsorption-desorption cycles. When integrated into a modular harvester, OM-UiO-66-NH₂ exhibits ultrafast adsorption (92% saturation within 5 min) and high condensation efficiency (94%), achieving a daily water yield of 27.8 L kg^-1 day^-1 at 30% RH. This study demonstrates that ordered mesopore engineering effectively overcomes diffusion limitations in MOFs, advancing the design of high-performance materials for efficient AWH in arid environments.