Largely Pseudocapacitive Two-Dimensional Conjugated Metal-Organic Framework Anodes with Lowest Unoccupied Molecular Orbital Localized in Nickel-bis(dithiolene) Linkages.

Although two-dimensional conjugated metal-organic frameworks (2D -MOFs) provide an ideal platform for precise tailoring of capacitive electrode materials, high-capacitance 2D -MOFs for non-aqueous supercapacitors remain to be further explored. Herein, we report a novel phthalocyanine-based nickel-bis(dithiolene) (NiS)-linked 2D -MOF (denoted as Ni[CuPcS]) with outstanding pseudocapacitive properties in 1 M TEABF/acetonitrile. Each NiS linkage is disclosed to reversibly accommodate two electrons, conferring the Ni[CuPcS] electrode a two-step Faradic reaction with a record-high specific capacitance among the reported 2D -MOFs in non-aqueous electrolytes (312 F g) and remarkable cycling stability (93.5% after 10,000 cycles). Multiple analyses unveil that the unique electron-storage capability of Ni[CuPcS] originates from its localized lowest unoccupied molecular orbital (LUMO) over the nickel-bis(dithiolene) linkage, which allows the efficient delocalization of the injected electrons throughout the conjugated linkage units without inducing apparent bonding stress. The Ni[CuPcS] anode is used to demonstrate an asymmetric supercapacitor device that delivers a high operating voltage of 2.3 V, a maximum energy density of 57.4 Wh kg, and ultralong stability over 5000 cycles.