Interpenetrated nano-MOFs for ultrahigh-performance supercapacitors and excellent dye adsorption performance

Abstract

Designing and preparing kinetically stable metal–organic frameworks through ligand functionalization can effectively improve their supercapacitive performances. Herein, we have successfully synthesized a novel polythreaded Co-based MOF by choosing a flexible N-donor ligand and a rigid multicarboxylate linker, [Co(HTATB)(dib)]·2H₂O (1), where dib is the flexible N-donor 1,4-di(1H-imidazol-1-yl)butane linker and HTATB is the deprotonation mode from 4,4′,4′′-s-triazine-2,4,6-triyl-tribenzoic acid. The bulk Co-MOFs crystals and the corresponding nanorod powders have been evaluated as electrode materials for supercapacitors. The maximum gravimetric capacitance of the nanorod electrode is 2405 F g⁻¹ at 0.75 A g⁻¹ in 4 M KOH, which is higher than 1 M and 6 M KOH solution and seven times larger than that of the bulk-crystal electrode. Furthermore, the nanorod electrode also exhibits excellent Coulombic efficiency (92.2%), rate capability (53.5% after 20 times increase) and good cycling performance (93.5% after 3000 continuous cycles). The excellent electrochemical property may be ascribed to the 3D networks constructed from 2D entangled layered structures facilitating electron transport, sufficient interlayer spaces available for the storage and diffusion of OH⁻ ions, and the small-size effect of the nanorods. Further, the dye adsorption performance of crystalline 1 for methyl orange and Congo red has also been investigated.