Covalent organic frameworks enable efficient atmospheric water harvesting in arid climates

Abstract

Atmospheric water harvesting (AWH) may present a sustainable solution to global water scarcity, particularly in arid regions where conventional water resources are limited. Sorption-based AWH (SAWH) using covalent organic frameworks (COFs) has emerged as a promising technology for low-humidity conditions (<40% RH), yet challenges in adsorption capacity, energy efficiency, and material stability persist. This review comprehensively analyzes the unique advantages of COFs for low-humidity SAWH, emphasizing their tunable pore structures, hydrophilic engineering, and exceptional cycling stability. We systematically compare COFs with conventional sorbents (e.g., hydrogels, salt composites) and demonstrate their superior performance, such as COF-ok (ortho-ketoenamine)'s working capacity of 0.4 g g⁻¹ at 30% RH and solar-driven regeneration at 45 °C. By elucidating water adsorption mechanisms (surface adsorption, micropore filling, capillary condensation) through isotherm analysis and molecular simulations, we establish design principles for optimizing COFs. Furthermore, we discuss innovative strategies, including topological design, composite systems, and post-synthetic modifications, to enhance low-humidity performance. Finally, we outline future directions, such as computational screening and device engineering, to bridge laboratory-scale achievements with practical applications. This work provides a foundational guide for advancing next-generation SAWH materials to address water scarcity in the most challenging climates.