Long-Cycle Stable Zn²⁺ Storage in 2D Conductive Metal–Organic Frameworks via Exclusive Ligand Redox Mechanism

2D conductive metal–organic frameworks (2D c-MOFs) have emerged as novel cathode materials in the development of rechargeable aqueous zinc-ion batteries (ZIBs) because of its integrated multiple redox-active moieties. However, the redox of the metal nodes usually leads to the collapse of the c-MOF structure during Zn²⁺ insertion/extraction process, thereby curtailing its cycling lifespan. Herein, a triphenylene-catecholate-based 2D c-MOF (Zn-HHTP) is fabricated by chelating the inactive Zn nodes, endowing the structural stability during charge and discharge processes only through ligand redox. The 1D open channel of Zn-HHTP facilitates rapid insertion and extraction of zinc ions, thus enabling stable working of ZIBs at high rates. Impressively, Zn-HHTP as cathode in ZIBs exhibits an ultra-long cycling stability with capacity retention of 86.6% after 4000 cycles at the current density of 4 A g⁻¹, exceeding the other MOF-based cathodes ever reported. Density functional theory (DFT) calculations combined with ex situ X-ray photo-electron spectroscopy (XPS) further elucidate the redox mechanism between catechol and benzene ring of HHTP during the successive insertion/extraction of Zn²⁺, due to their comparatively negative electrostatic potentials. This work provides a new strategy to prolong the cycling capability of ZIBs by utilizing the highly active non-metallic redox moieties in 2D c-MOFs.