Simultaneous Enhancement of Adsorption Kinetics and Capacity in MOFs for Arid-Environment Atmospheric Water Harvesting via Ordered Mesopore Engineering

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.