Enhancing Water Harvesting Efficiency in a Phosphonate Metal–Organic Framework through Controlled Defect Generation

Abstract

Global access to drinking water shrinks yearly, yet the atmosphere─our largest sustainable water source─remains largely untapped. Metal–organic frameworks (MOFs), a tunable class of crystalline porous materials, are promising candidates for atmospheric water harvesting. The channel-pore MOF STA-16(Co) stands out due to its robust phosphonate-based structure, which provides high stability and excellent water uptake. However, STA-16(Co) suffers from slow water uptake kinetics. To address this limitation, we introduced defects into STA-16(Co) by selectively removing linkers through treatment with nitrilotriacetic acid, significantly improving water diffusion kinetics. The defective MOFs demonstrate markedly faster water saturation rates─delivering ∼50% more water in a 40 min cycle─while maintaining the same uptake capacity and isothermal behavior as pristine STA-16(Co). Solid-state nuclear magnetic resonance analysis confirms that localized defects enhance efficiency without altering the overall pore geometry. This study presents a straightforward and generalizable strategy to optimize water sorption in channel-based MOFs.