Water-Induced Dynamic Structural Adaptivity of Zr-MOF for Holistic Metrics Optimization in Atmospheric Water...

Adsorption-based atmospheric water harvesting (AWH) is a new water supply technology to address water scarcity in decentralized arid regions. Advanced hygroscopic metal-organic frameworks (MOFs) have been designed to enhance water harvesting capability, but current structural design strategies often face tradeoffs among key performance metrics. Enhancing one performance aspect often results in compromises in others, significantly limiting the overall water production efficiency. Herein, we report a water-induced structural adaptivity in a Zr-MOF, fb-Zr-MOF-1, during the water adsorption process to balance and co-optimize all performance metrics. At low humidity levels, the rotational swing of flexible pyrazole ring enables the synergy between Lewis basic N-site and Zr₆ node, favoring competitive water adsorption and desorption rates. At high humidity level, the pore expansion accommodates more water to increase the adsorption capacity. Meanwhile, the moderate water binding energy (Q_st = 49.6 kJ mol^-1) facilitates energy-efficient regeneration. Based on holistic metrics optimization, fb-Zr-MOF-1 showed a high water uptake of 0.41 g g^-1 at P/P₀ = 30% with an average of ∼14 adsorption-desorption cycles per day and a mild desorption temperature of 318 K, achieving higher daily water production capacity compared to most prevailing MOFs. This study provides insights into a new structural adaptive design strategy for hydroscopic MOF for highly efficient and energy-efficient atmospheric water harvesting in an arid environment.