Metal–Organic Framework Flexibility Boosting Atmospheric Water Harvesting by a Zinc-Based Glycine–Glyoxime–Histidine Framework

Structural flexibility of metal–organic frameworks (MOFs) is both a challenge and an opportunity, depending on the MOF’s properties and the proposed applications. Here, we focus on ZnGGH, a peptide-based flexible MOF that switches from its “gate-closed” ZnGGH-9 conformer to “gate-open” ZnGGH-4 upon water adsorption. We use periodic density functional theory (DFT), semiempirical self-consistent charge density functional tight binding third order (DFTB3) and neural network-based MACE-MP simulations to understand the ZnGGH’s behavior and assess its potential for atmospheric water harvesting (AWH). Our results show that ZnGGH selectively adsorbs water over CO 2, O 2, and N 2 . As water loading increases, water-linker interactions trigger the gate opening and affect temperature-dependent water diffusion within the pores. Based on our analyses and comparison with benchmark AWH MOFs (MOF-303, MOF-333 and MOF-808), the gate opening facilitates AWH by weakening of the water interactions during water adsorption/desorption cycles while maintaining water selectivity. The MOF is thermally and hydrolytically stable under AWH conditions. To enable grid-scale applications, future work should focus on reducing synthesis costs to improve its economic viability.