A Quinoidal Two-Dimensional Metal-Organic Framework for High-Performance Micro-Supercapacitors and Solid-State...

Two-dimensional (2D) metal-organic frameworks (MOFs) integrating redox-active linkers enable dense charge sites and open ion pathways for microscale energy storage. We report a quinoidal dicarboxylate ligand, AQM-H₂L, derived from p-azaquinodimethane, forming crystalline frameworks with Cu²⁺ and Zn²⁺ nodes. The Cu-based MOF (AQM-AQM-H₂L-Cu) exhibits layered sheets (>14 Å spacing) constructed from dinuclear Cu-carboxylate units and conjugated AQM linkers, which narrow the bandgap and introduce Cu²⁺/Cu⁺ pseudocapacitance. Exfoliated nanosheets (∼5 nm) retain crystallinity and excellent processability. Integrated into graphene films, they deliver areal and volumetric capacitances of 29.6 mF cm^-2 and 18.1 F cm^-3, achieving 2.6 mWh cm^-3 energy density at 160 mW cm^-3. As ionic fillers (1 wt%) in PEO solid polymer electrolytes, the nanosheets markedly enhance LiFePO₄ cell performance, affording 169.8 mAh g^-1 at 0.2 C and 93% retention after 400 cycles. This work establishes quinoidal linkers as a compact and robust design motif for ionically active 2D frameworks toward high-performance miniature and solid-state energy devices.