Two-fold interpenetrated Mn-based Metal-Organic Frameworks (MOFs) as battery-type electrode materials for charge storage
Two novel interpenetrated 2-fold Mn-based MOFs (SC-7 and SC-8), assembled from rigid ligand H3TATB (4,4',4''-s-triazine-2,4,6-triyl-tribenzoic acid) and Mn ions with the assistance of flexible N-donor linker BIB (bis((1H-imidazol-1-yl)methyl)benzene) or TIPA (tris(4-imidazolylphenyl)amine), have been succefully prepared. The as-obtained MOFs show two distinct topological structures with symbol of 44·62 and (52·6)(53·6·73·82·9) due to the discrepancy of the flexibility of bi-imidazole and tri-imidazole linkers. The electrodes based on the as-prepared bulk Mn-MOFs behave as alkaline batteries in electrochemical cells, and deliver high capacities (279 and 172 mAh g-1 at 1 A g-1 for SC-7 and SC-8, respectively). Theoretical mechanism analyses indcate that surface-controlled (k1v) process can be transformed into diffusion-dominated (k2v1/2) process when charging time exceeds 30 seconds in MOFs-based systems. Our research provides a new strategy to construct much stable and more redox sites in MOFs for the application in battery-capacitor hybrid devices.