Engineering Dynamic Proton "Hubs" in Hydrogen-Bonded Frameworks for Superprotonic Conductivity

Mimicking the synergistic proton conduction in biology remains a formidable challenge for synthetic materials. Here, we report a strategic approach by engineering dynamic proton "hubs" within hydrogen-bonded organic frameworks (HOFs). These hubs are supramolecular secondary building units (SSBUs) formed by charge-assisted hydrogen bonds between ammonium and sulfonate groups, which are programmed into the frameworks to direct proton traffic. The resulting ammonium-sulfonate HOF, BPDS_NH₄, exhibits a highly competitive proton conductivity of 0.21 S cm^-1 (90°C, 90% RH). The exceptional performance is governed by the dual function of the proton hubs: their high charge density and hydrophilicity create a highway for vehicular transport of solvated proton clusters (H⁺(H₂O)_n), while the dense, dynamic H-bonded network within each hub serves as a confined arena for ultrafast Grotthuss hopping. These processes are synergistically coupled, as verified by activation energy analysis and H/D isotope effect. This work establishes the construction of supramolecular proton hubs as a versatile blueprint for the rational design of advanced proton-conducting materials.