A Quinoidal Two‐Dimensional Metal–Organic Framework for High‐Performance Micro‐Supercapacitors and Solid‐State Lithium Batteries

Abstract

ABSTRACT 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‐H 2 L, derived from p ‐azaquinodimethane, forming crystalline frameworks with Cu 2+ and Zn 2+ nodes. The Cu‐based MOF (AQM‐AQM‐H 2 L‐Cu) exhibits layered sheets (>14 Å spacing) constructed from dinuclear Cu‐carboxylate units and conjugated AQM linkers, which narrow the bandgap and introduce Cu 2+ /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 LiFePO 4 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.