Cobalt- and calcium-based metal–organic frameworks (MOFs) as an advanced electrode material for supercapacitors

Cobalt- and calcium-based metal–organic frameworks (Co-MOF and Ca-MOF) [Co (tpa) (Mi) and Ca (tpa)] (tpa = terephthalic acid and Mi = methyl imidazole) were synthesised through solvothermal method. Structural characterisation revealed that metal centres are equally occupied by Co2+ and Ca2+ ions. Supercapacitive behaviour of synthesised Co-MOF and Ca-MOF was evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) measurements in 6 M KOH as electrolyte. The Co- and Ca-MOFs exhibited outstanding specific capacitance of 1726 and 185 Fg−1 at a discharge current density of 1 Ag−1, good rate capability, and 97.4% capacitance retention after 3000 cycles. To the best of our knowledge, Co-MOFs and Ca-MOFs are used in supercapacitor, and their encouraging properties indicate that Co-/Ca-MOF can be a promising candidate as an advanced electrode material for supercapacitors.