Incorporating Redox-Active Hexaazatrinaphthylene into a 2D Conductive Metal-Organic Framework for Robust Sodium-Ion...

Two-dimensional (2D) conductive metal-organic frameworks (cMOFs) hold tremendous promise as anode materials for sodium-ion batteries (SIBs), owing to their electrical conductivity, porosity, appropriate interlayer spacing that facilitates ion intercalation, and stability in organic electrolytes. Yet, creating cMOFs hosting multiple redox-active sites remains challenging. This paper reports a hexaazatrinaphthylene (HATN)-based 2D cMOF, HATN-O-Zn, assembled by coordinating redox-inactive Zn²⁺ through bis(dioxolene) linkages. HATN-O-Zn forms hexagonal rod-like crystals with electrical conductivity that promote rapid Na⁺ diffusion and storage. As an anode, this material delivers a high reversible capacity of 319 mAh g^-1 at 0.1 A g^-1 and retains a capacity of 86 mAh g^-1 after 5000 cycles at 1 A g^-1, demonstrating outstanding cycling stability at room temperature. Notably, HATN-O-Zn sustains performance at -20 °C, showing an initial capacity of 117 mAh g^-1 and 84.4% retention after 200 cycles at 0.1 A g^-1, underscoring stability under harsh conditions. This stability is attributed to the structural robustness provided by redox-inactive Zn²⁺. Spectroscopic and theoretical analyses reveal that dual redox-active sites in the HATN moiety and Zn-bis(dioxolene) linkages facilitate multiple electron transfer. This work highlights the design potential of combining redox-active ligands with redox-inactive metal nodes in 2D cMOFs for durable SIB anodes.