Liquid Coordination Polymers with Anhydrous Proton Conductivity

Abstract Liquid states in coordination polymers (CPs) and metal‐organic frameworks (MOFs) are typically considered transient intermediates in the crystal‐to‐glass transformations of organic–inorganic hybrid materials. However, their potential as functional materials has remained largely unexplored. Inspired by the unique properties of ionic liquids, organic liquids, and liquid metals, we explore liquid CPs as a platform for novel functionalities distinct from those of their crystalline and glass counterparts. Here, we present a strategy to achieve functional liquid CPs near ambient conditions by introducing H 3 PO 4 as a network modifier, shifting compositions away from stoichiometric ratios. This process disrupts extended coordination networks during melting, producing a stable liquid state. By tuning the ratio of network modifiers, we achieve control over liquid properties, including anhydrous proton conductivity up to 27 mS cm −1 at 353 K and viscosities ranging from 18.8 to 10 5.9 Pa·s at 303 K. These findings demonstrate the transformative potential of liquid CPs, introducing them as a new platform for designing liquid conductors.