Stable Tetravalent Metal-Organic Frameworks for Electrocatalysis and Aqueous Electrochemical Energy Storage.

Owing to their chemical stability in water, relatively high specific surface area, and high tunability in both pore structures and chemical functionality in their pores, metal-organic frameworks (MOFs) constructed from tetravalent metal-based nodes, including zirconium-based MOFs, titanium-based MOFs, hafnium-based MOFs, cerium(IV)-based MOFs and thorium-based MOFs, have been widely explored for various applications requiring humid or aqueous environments. In particular, over the past ten years, these MOFs have been widely employed in various aqueous electrochemical applications, including water splitting, oxygen reduction, carbon dioxide reduction, ammonia production, electrocatalytic sensing, aqueous supercapacitors, zinc-ion batteries, and vanadium flow batteries. Classified by the type of applications and the role that MOFs could play, progress in this research field is overviewed. Limitations and opportunities in this field for future studies are discussed.