Dual Proton–Electron Conductivity in 2D Azaborine Metal–Organic Frameworks

Dual proton-electron conductors are highly sought after for applications in electronics and energy storage. Whereas two-dimensional metal-organic frameworks (MOFs) (2D MOFs) with high electrical conductivity are now numerous, introducing conduits for ion transport in these is challenging. Herein, we report the synthesis of two new mixed electron-proton conductors, M₃TABC₂ (M = Cu, Zn; TABC = hexahydroxy-1,5,9-triaza-2,6,10-trihydroxyboracoronene), made from a new conjugated azaborine ligand with mobile protons. Cu₃TABC₂ and Zn₃TABC₂ show high electronic conductivities of 6.0 × 10^-2 S/cm and 2.2 × 10^-4 S/cm, and ionic conductivities of 1.6 ± 0.1 × 10^-5 S/cm and 1.9 ± 0.4 × 10^-5 S/cm, respectively. Overall, this work demonstrates the incorporation of mobile protons into aromatic ligands as a strategy for enabling mixed conductivity in 2D MOFs.