Dual‐Redox Sites Guarantee High‐Capacity Sodium Storage in Two‐Dimension Conjugated Metal–Organic Frameworks

Abstract 2D π‐d conjugated metal–organic frameworks ( c ‐MOFs) are promising anode candidates for sodium‐ion batteries (SIBs) due to their high intrinsic conductivity and stability in organic electrolytes. However, the development of c ‐MOFs with multi‐redox sites to improve the overall performance of SIBs is highly desired but remains a great challenge. Herein, this work reports the electrochemically active hexaazatrinaphthylene‐based 2D π‐d c ‐MOFs (HATN‐XCu, X = O or S) as advanced anode materials with dual‐redox sites for SIBs. The ordered porous and layer‐stacked structure can provide fast transmission and diffusion channels for ions along the stacking directions. Ex situ Fourier transformed infrared spectra together with X‐ray photoelectron spectroscopy reveal the dual‐redox site storage mechanism of HATN‐XCu, namely, the continuous multi‐electron reactions occurring on the redox‐active CN group and [CuX 4 ] unit, respectively. Based on the synergistic effect of dual‐redox sites, HATN‐OCu anode exhibits impressive reversible capacity (500 mAh g −1 at 0.1 A g −1 ) and high‐rate performance (151 mAh g −1 at 5 A g −1 ). Significantly, a sodium‐ion full battery assembled using a HATN‐OCu anode and Na 3 V 2 (PO 4 ) 2 O 2 F cathode also displays high‐rate performance (117 mAh g −1 at 5 A g −1 ) and stable long‐cycle life (the capacity retention of 80% after 500 cycles at 2 A g −1 ).