Self-Assembled Cobalt–Nickel Bimetallic-Organic\nFramework Materials with High Supercapacitor Performance

Abstract

Two\nnew metal–organic frameworks (MOFs), [Co(bcpp)(bbip)]·H₂O (Co-MOF) and [Ni(bcpp)(bbip)]·H₂O (Ni-MOF),\nhave been generated based on a V-type flexible carboxylic ligand 3,5-bis(4-carboxyl\nphenoxy) pyridine (H₂bcpp) and a rigid N-donor ligand 1,1′-(1,4-phenylene)bis(1<i>H</i>-benzimidazole) (bbip) by a solvothermal method. Co-MOF\nand Ni-MOF are isostructural with a 2-fold interpenetrated layered\nstructure. Moreover, a series of bimetallic Co_<i>x</i>Ni_<i>y</i>-MOFs (<i>x</i>/<i>y</i> = 1:1, 2.5:1, 2.75:1, 3:1, 3.25:1, and 3.5:1) were obtained\nby using one-pot synthesis. Owing to their mixed metallic components\nand internal layered structure, the bimetallic Co_<i>x</i>Ni_<i>y</i>-MOFs possess a remarkable electrochemical\nstorage property. Significantly, the Co_2.75Ni₁-MOF has high specific capacitance (699 F g^–1)\nat 0.5 A g^–1 and good cycling durability (retained\n72.7% over 3100 turns). Additionally, an asymmetrical ultra-capacitor\nbased on Co_2.75Ni₁-MOF and activated carbon\n(AC) delivers a maximum energy density of 20.44 Wh kg^–1 at 387.49 W kg^–1 and a high cycle-to-cycle stability\nwith 85.4% of the primary capacitance over 15,000 turns.