Metal-organic frameworks for atmospheric water harvesting: A review of structural and environmental influences

Metal-organic frameworks for atmospheric water harvesting

Abstract

Freshwater scarcity is an escalating global challenge, affecting billions of people despite the Earth's vast water resources. Conventional solutions like desalination and conservation, while useful, are often limited by geographic, economic, or technical constraints. Atmospheric Water Harvesting (AWH) has emerged as a promising alternative to supplement existing water sources, especially in arid and remote regions. Among various materials used for AWH, Metal-Organic Frameworks (MOFs) have attracted significant attention due to their high surface area, tunable porosity, and excellent water adsorption capacity. This review explores the factors that significantly affect water adsorption in MOFs, like pore size, structural defects, hydrophobicity or hydrophilicity, metal center composition, and environmental condition factors such as temperature, pressure and humidity. For instance, larger pore volumes and hydrophilic surfaces tend to enhance water adsorption, and smaller pores result in limited uptake. Similarly, increase in pressure improves the water adsorption in the framework whereas temperature rise cause the water molecules to gain KE which results in lower adsorption and water molecules inside a humid MOF favors further adsorption by increasing its affinity for water molecules. The design and selection of effective materials for atmospheric water harvesting and related applications can be guided by an understanding of how these aspects impact MOF performance.