Flexible long-chain-linker constructed Ni-based metal-organic frameworks with 1D helical channel and their pseudo-capacitor behavior studies

Two novel and isostructural Ni-based MOFs with topological symbol of 422·54·62, namely [Ni2(TATB)2(L)2(H2O)], have successfully synthesized, where L is the flexibly N-donor bid (1,10-bisimidazoledecane) or btd (1,10-bistriazoledecane) linker and TATB is the deprotonation mode from 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic acid (H3TATB). Two types of left- and right-handed helical channels with mean diameter of 11 Å results in large void space in 3D network. When directly use as electrode materials, the as-synthesized Ni-MOFs single-crystal electrodes behave as pseudo-capacitor and deliver high gravimetric capacitance with superior energy deliverable ability and cycling stability. For example, the maximum gravimetric capacitance is 705 F g−1 with the energy density of 29.6 Wh kg−1 at a current density of 1 A g−1. Even after 5000 continuous cycles, the capacitance retention maintains at 92.1%. The good electrochemical performance should be ascribed to the 1D helical channels facilitating the diffusion of OH−. Furthermore, the low bulk solution (0.46 and 0.50 Ω) and charge-transfer resistances accelerate the contact between OH− and active species in the electrode, and consequently result in efficiency Faradaic reaction. This work opens a new way for the directly application of 3D topological MOFs single-crystal with novel interior structures especially porous and channel-like architectures in electronic energy storage field.