Cluster–oxalate frameworks with extra-large channels: solvent-free synthesis, chemical stability, and proton conduction

Abstract

Two cluster–oxalate frameworks (denoted as SCU-62 and SCU-65) were prepared under solvent-free conditions. They contain extra-large 16-ring channels constructed from regular Mn₆(SO₄)₆ double six-ring units (D6Rs) and lacunary In₅(HPO₄)₆ D6Rs, respectively. Notably, SCU-65 remains stable in both boiling water and aqueous solutions with a pH range of 3–12. It has a proton conductivity of 5.5 × 10⁻⁵ S cm⁻¹ at 85 °C under 95% relative humidity.