Redox-Active Two-Dimensional Tetrathiafulvalene-Copper Metal–Organic Framework with Boosted Electrochemical Performances for Supercapatteries

Abstract

Metal–organic frameworks (MOFs) have attracted noticeable attention as promising candidates for electrochemical energy storage. However, the lack of electrical conductivity and the weak stability of most MOFs result in poor electrochemical performances. Here, a tetrathiafulvalene (TTF)-based complex, formulated as [(CuCN)2(TTF(py)4)] (1) (TTF-(py)4 = tetra(4-pyridyl)-TTF), is assembled by in situ generation of coordinated CN– from a nontoxic source. Single-crystal X-ray diffraction analysis reveals that compound 1 possesses a two-dimensional layered planar structure, which is further stacked in parallel to form a three-dimensional supramolecular framework. The planar coordination environment of 1 is the first example of a TTF-based MOF. Attributed to the unique structure and redox TTF ligand, the electrical conductivity of 1 is significantly increased by 5 orders of magnitude upon iodine treatment. The iodine-treated 1 (1-ox) electrode displays typical battery-type behavior through electrochemical characterizations. The supercapattery based on the 1-ox positrode and AC negatrode presents a high specific capacity of 266.5 C g–1 at a specific current of 1 A g–1 with a remarkable specific energy of 62.9 Wh kg–1 at a specific power of 1.1 kW kg–1. The excellent electrochemical performance of 1-ox is one of the best among those reported supercapatteries, demonstrating a new strategy for developing MOF-based electrode materials.

A two-dimensional semiconducting Cu(i)-MOF for binder and conductive additive-free supercapattery

“…47 Recently, Zhu et al have reported a CuCN-based MOF as an electrode material for a supercapattery with a specic capacity of 677.5 C g −1 at 1 A g −1 current density. 48 In the continuation of research involving the design and synthesis of these interesting MOFs, herein, we report on the synthesis of a new 2D copper(I) cyanide-based semiconductive MOF using a 1H-1,2,4-triazole substituted pyridine ligand as a linker. The superior conductivity and the presence of Cu(I) redox-active centers in its 2D structure, which eventually transform into an interesting 3D-framework with suitable channel structure due to p-p stacking, encouraged us to investigate it as a binder and conducting additive-free electrode material in energy storage devices.…”

“…47 Recently, Zhu et al have reported a CuCN-based MOF as an electrode material for a supercapattery with a specific capacity of 677.5 C g −1 at 1 A g −1 current density. 48…”