An asymmetric supercapacitor based on a non-calcined 3D pillared cobalt(II) metal-organic framework with Long cyclic stability

In this work, a new 3D metal–organic framework (MOF) {[Co₃(μ₄-tpa)₃(μ-dapz)(DMF)₂]·2DMF}ₙ (Co(II)-TMU-63; H₂tpa = terephthalic acid, dapz = pyrazine-2,5-diamine, DMF = dimethylformamide) containing low-cost and readily available ligands was generated, fully characterized, and used as an electrode material in supercapacitors without the need for a calcination process. Thus, the synthesis of this material represents an economical and cost-effective method in the energy field. The crystal structure of Co(II)-TMU-63 is assembled from two types of organic building blocks (μ₄-tpa ²⁻ and μ-dapz ligands), which arrange the cobalt nodes into a complex layer-pillared net with an unreported 4,4,4,6T14 topology. The presence of open sites in this MOF is promising for studying electrochemical activity and other types of applications. In fact, Co(II)-TMU-63 as a novel electrode material when comparing with pristine MOFs shows great cycling stability, large capacity, and high energy density and so acts as an excellent supercapacitor (384 F g⁻¹ at 6 A g⁻¹). In addition, there was a stable cycling performance (90% capacitance) following 6000 cycles at 12 A g⁻¹ current density. Also, the Co(II)-TMU-63//activated carbon (AC) asymmetric supercapacitor acted in a broad potential window of 1.7 V (0–1.7 V), exhibiting a high performance with 4.42 kW kg⁻¹ power density (PD) and 24.13 Whkg⁻¹ energy density (ED). These results show that the pristine MOFs have great potential toward improving different high-performance electrochemical energy storage devices, without requiring the pyrolysis or calcination stages. Hence, such materials are very promising for future advancement of the energy field