Pyrazine‐Embedded 2D Conjugated Metal–Organic Framework with Quasi‐Honeycomb Lattice for High‐Capacitance Lithium‐Ion Storage

Abstract

Abstract As a unique class of framework electronic materials, 2D conjugated metal–organic frameworks (2D c ‐MOFs) exhibit intrinsic porosity, superior electrical conductivity, and abundant active sites. These properties endow them with great potential in electrochemical lithium‐ion storage. However, the development of 2D c ‐MOF‐based capacitors has encountered a bottleneck in enhancing Li‐ion storage capacitance, and the design of high‐capacitance MOF electrode materials has remained a challenge. Herein, we synthesize a Cu‐OHDDQP (octahydroxy‐dibenzo[ a , c ]dibenzo[5,6:7,8]quinoxalino[2,3‐ i ]phenazine) 2D c ‐MOF with a quasi‐honeycomb lattice by employing a nonplanar D 2 ‐symmetric conjugated ligand embedding redox‐active pyrazine moieties. The quasi‐honeycomb lattice features a dual‐porous tessellation of C 6 ‐symmetric and C 3 ‐symmetric pores. Notably, when utilized as active material for electrochemical lithium storage, Cu‐OHDDQP achieves a record‐high gravimetric specific capacitance among reported 2D c ‐MOFs of 452 F g −1 in aqueous lithium electrolyte, along with a decent cycling stability of 90% after 1000 cycles. Such high capacitance is attributed to both the quasi‐honeycomb lattice leading to higher surface area and the redox‐active pyrazine moieties offering extra lithium‐adsorption sites and associated pseudocapacitance. This work demonstrates that rational ligand design enables high‐capacitance MOF electrodes materials, highlighting the potential of conductive MOFs for electrochemical energy technologies.