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Ionic liquid consists of an organic cation and generally an inorganic anion. The properties of liquids can be modulated by changing the anion or the cation or both. Two ionic liquids derived from the anion [FSI] were synthesized and characterized: (N-n-butyl-N-methylpyrrolidinium bis-(fluorosulfonyl imide), [BMPYR][FSI]) and triethyl-n-pentylphosphonium bis(fluorosulfonyl)imide), [P 2225 ][FSI]). We also report the comparison with [TFSI] based ionic liquids, namely: (N-n-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide), [BMPYR][TFSI]), (N-n-butyl-N-methylpiperidinium bis(trifluoromethylsulfonyl)imide), [BMP][TFSI]), triethyl-npentylphosphonium bis(trifluoromethylsulfonyl)imide), [P 2225 ][TFSI]) and (triethyl(2-methoxyethyl) phosphonium bis(trifluoromethylsulfonyl imide), [P 222201 ][TFSI]. Thermophysical properties, such as viscosity (298.15−373.15 K), density (298.15−373.15 K), conductivity (298.15−361.15 K), electrochemical (cutoff density current within 150 μA•cm −2 ), and thermal stability (303.15−973.15 K) were experimentally determined. The results showed that [FSI] derivatives exhibit better transport properties and lower thermal and electrochemical stability when compared with their [TFSI] counterparts.

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Among their potential applications, metal–organic frameworks (MOFs) emerge as promising alternative electrode materials to overcome the disadvantages of low energy density supercapacitors. Although the potential of MOFs lies in their adjustable pore structure and high surface areas, they possess poor conductivity. In this context, composites with conductive matrices, including organic conductive polymers, have proved to enhance the electrochemical properties of MOFs and their structural stability in the long-term cycling process compared to the pristine MOF. In this study, we have chosen defective zirconium MOF-808 (d-MOF-808) as a porous material because of its resistance to strong acidic media in a postsynthetic modification process. As a conductive agent, polyaniline (PANI) was selected due to its high stability and facile synthesis. The obtained composites of d-MOF-808@PANI at d-MOF/PANI ratios of 15:1, 30:1, and 60:1 increase the charge transport properties compared to the pristine d-MOF-808 and PANI. Electrochemical evaluation of the new hybrid electrode materials was made to demonstrate the capacitance retention. Among the series of materials prepared, the 60:1 composite shows the highest capacitance (188 F/g at 30 mV s–1) in 1 M KOH and a notable capacitance retention of 99.8% for up to 10,000 cycles with 99.7% coulombic efficiency.