Computational Prediction of the Complete Adsorption–Regeneration Cycle of Functionalized Metal–Organic Frameworks for Atmospheric Water Harvesting

This work presents a comprehensive multiscale computational investigation of the complete adsorption-regeneration cycle of functionalized adsorbents for atmospheric water harvesting (AWH) under low-humidity conditions. The target system is copper-docked MOF-303, a nanoporous framework with well-defined nanoscale channels and adsorption sites, functionalized with Amino and Nitro clusters, selected to tailor host-guest interactions and optimize water uptake and release. The simulations capture key molecular-level phenomena including host-guest interactions, water mobility, adsorption kinetics, and regeneration temperatures, providing a detailed picture of performance under varying environmental conditions. Cu-NH₂@MOF-303 showed the highest water capacity, reaching a ∼38% increase over the pristine structure, while Cu-NO₂@MOF-303 achieves an improvement of ∼25%. The kinetics follow a similar trend: the pristine framework saturates in 4 min at 2000 Pa, whereas Cu-NH₂@MOF-303 reaches equilibrium almost instantaneously (∼0.1 min). Cu-NO₂@MOF-303 also accelerates uptake, saturating within <3 min at 2000 Pa. Density functional theory (DFT) results confirm the enhanced affinity, with adsorption energies shifting from -84.77 kJ mol^-1 in pristine MOF-303 to -99.93 kJ mol^-1 (Cu-NH₂) and -90.16 kJ mol^-1 (Cu-NO₂). Despite requiring a modestly higher regeneration temperature (≈25 K above pristine MOF-303), Cu-NH₂@MOF-303 offers a favorable balance between stronger binding and practical desorption, making it suitable for low-to-moderate relative humidity conditions.