An asymmetric supercapacitor with an interpenetrating crystalline Fe-MOF as the positive electrode and its congenetic derivative as the negative electrode

Herein, a novel Fe-based MOF Fe(TATB)(Tipa)(H2O) (FeSC) with 3D interpenetrated topology has been successfully prepared through the reaction of a tribasic aromatic carboxylic acid 4,4 ',4 ''-(1,3,5-triazine-2,4,6-triyl)tribenzoic acid (H₃TATB), Fe(SO₄)₂·7H₂O, and a flexible nitrogen-containing pro-ligand tris(4-(1H-imidazol-l-yl)phenyl)amine (Tipa) under hydrothermal conditions. After high-temperature annealing of FeSC, another three-component composite Fe₂O₃/Fe₃N/Fe₃C (denoted as FeSC^#) is obtained. The physicochemical properties of both congenetic materials are explored through X-ray single-crystal diffraction, PXRD, FTIR, XPS, TGA, and SEM. Moreover, cyclic voltammetry, constant current charge-discharge, and electrochemical impedance spectroscopy techniques were applied to conduct electrochemical studies on the two electrode materials in alkaline electrolytes. Crystalline FeSC and annealed FeSC^# showed high specific capacities of 409.2 and 415.2 C g^-1 at a current density of 1 A g^-1, respectively. Furthermore, FeSC and FeSC^# have been employed as positive and negative electrode materials to assemble an asymmetric supercapacitor (namely Fe-ASC), where this device displays excellent characteristics of high capacitance and low impedance, providing an energy density of 49.85 W h kg^-1 with 90.6% capacitance retention after 6000 charge-discharge cycles. These results suggest that the crystalline FeSC and the corresponding three-component congenetic composite FeSC^# are promising electrode materials to construct full energy-storage cells.