Phosphorus-Functionalized Organic Linkers Promote Polysulfide Retention in MOF-Based Li–S Batteries

Metal–organic frameworks (MOFs) have been an area of intense research for their high porosity and synthetic tunability, which afford them controllable physical and chemical properties for various applications. In this study, we demonstrate that functionalized MOFs can be used to mitigate the so-called polysulfide shuttle effect in lithium–sulfur batteries, a promising next-generation energy storage device. UiO-66-OH, a zirconium-based MOF with 2-hydroxyterephthalic acid, was functionalized with a phosphorus chloride species that was subsequently used to tether polysulfides. In addition, a molecular chlorophosphorane was synthesized as a model system to elucidate the chemical reactivity of the phosphorus moiety. The functionalized MOFs were then used as a cathode additive in coin cell batteries to inhibit the dissolution of polysulfides in solution. Through this work, we show that the functionalization of MOF with phosphorus enhances polysulfide redox and thereby capacity retention in Li–S batteries. While demonstrated here for polysulfide tethering in batteries, we envision this linker functionalization strategy could be more broadly utilized in separations, sensing, or catalysis applications.