Two-Dimensional Cr(III)-Based Metal–Organic Framework with Ultrahigh Stability and Superprotonic Conductivity Enabled by Sulfonate Stereochemistry

Proton-conducting two-dimensional metal–organic frameworks (2D MOFs) are attractive solid electrolytes for electrochemical technologies, yet simultaneously achieving superprotonic conductivity and robustness remains highly challenging. Here, we report TGU-80(Cr), a 2D Cr(III)-MOF synthesized via a solvent-free route enabled by a stereochemistry-guided sulfonate-linker design. Three-dimensional electron diffraction reveals a bidentate sulfonate coordination motif that preserves one noncoordinating O atom on every sulfonate, furnishing O-dense nanochannels that favor hydration and hydrogen-bonding networks. These channels support fast proton transport, delivering a conductivity up to 5.61 × 10 –2 S cm –1 at 90 °C and 100% RH, which, to the best of our knowledge, is among the highest reported for additive-free proton-conducting 2D MOFs. Owing to inert Cr–O bonds and extensive interlayer hydrogen bonding, TGU-80(Cr) also exhibits exceptional chemical stability from strongly acidic media to 1 M NaOH. This work not only establishes an unprecedented 2D Cr-MOF that combines ultrahigh stability with superprotonic conductivity but also expands the design and synthesis strategies for low-dimensional reticular materials via the green solvent-free route.