Polyoxometalate-constructed 2D irregular porous inorganic framework with single-crystal superprotonic conductivity

This study presents a novel polyoxometalate (POM) constructed crystalline inorganic framework, featuring a 2D layered architecture with irregular porosity and inherent proton sources. This unique configuration establishes an intrinsic hydrogen bonding network that facilitates proton hopping (Grotthuss mechanism), achieving a [100] directional proton conductivity of 1.75×10−3 S cm−1 under a low relative humidity (RH) of 35% at 298 K. Notably, under elevated conditions (338 K, 95% RH), it attains a superprotonic conductivity of 1.61 S cm−1, representing one of the highest values recorded for framework materials to date. Analysis of the molecular structure, pore geometry characteristics and topological connectivity, and water vapor adsorption experiment (offering proton diffusion coefficient), indicates that the exceptional water-mediated proton dynamics stem from the interlayer S-shaped irregular pore channels, which probably induce a siphon-like effect to significantly enhance the transport of hydrated protons under the vehicle mechanism. This work not only proposes a POM strategy for constructing 2D inorganic frameworks but also reveals the irregular pore channel-enhanced proton dynamics, providing new insights into the optimization of proton conductors.