A conductive anionic Co-MOF cage with zeolite framework for supercapacitors

Abstract

Conductive MOFs could exhibit full potential as integrated electrode materials for supercapacitors without interference from additional conductive additives. Here we report an anionic Co-MOF cage with zeolite framework, which was balanced by the redox-active guest [Co(H2O)6]2+ and protonated [(CH3)2NH2]2+ ions. Benefit from the unique ion skeleton structure, Co-MOF exhibits a conductivity higher than most of reported MOFs with the value of 1.42 × 10-3 S/cm, which can be directly fabricated as electrode for supercapacitors. A maximum specific capacitance of 236.2 F/g can be achieved at a current density of 1 A/g of Co-MOF. Additionally, the electric performance and morphology of this Co-MOF can be modified by cetyltrimethylammonium bromide (CTAB) and the maximum specific capacitance could increase up to 334 F/g at 1 A/g when the ratio of ligand and CTAB is 1:6 (Co-MOF-6). Furthermore, the specific capacitance can retain at 64.04% and 77.92% of the initial value after 3000 cycles of Co-MOF and Co-CTAB-6, respectively. Obviously, the addition of CTAB further improves both capacitance and cycle stability.