Iron salicylaldehydate conjugated metal–organic framework for quasi solid-state supercapacitor
Abdul Khayum Mohammed, Ajmal Pandikassala, Pilar Pena Sánchez, Safa Gaber, Stefano Canossa, Maria Kurian, Gigi Xavier, Yao He, Felipe Gándara, Sreekumar Kurungot, Dinesh Shetty
Abstract
Conjugated metal–organic frameworks (c-MOFs) are potential candidates for excellent electro and photochemical activities such as energy storage and catalysis. However, the poor chemical stability of c-MOFs obstructs them from the practical utilities in acid or base-functioned energy storage devices. Herein, we have introduced a novel iron-based salicylaldehydate 3D-c-MOF (Fe-Tp) with high chemical stability in strong acid environments. The robust coordination bond between iron and C3 symmetric salicylaldehyde organic pockets results in a doubly interpenetrated 3D framework with ultra-high chemical stability. The biphasic doubly interpenetrated structure of Fe-Tp was elucidated using theoretical modeling with the assistance of single-crystal electron diffraction analysis. The Fe-Tp showed chemical stability even in 10 M H2SO4 for 24 h. Moreover, we have investigated the dynamic charge storages in Fe-Tp in varying concentrations of acid electrolyte (122 F g−1 at 0.1 M H2SO4 to 400 F g−1 at 5 M H2SO4 at 0.1 A/g). The Fe-Tp-based flexible quasi-solid-state supercapacitor was fabricated using proton-loaded PVA electrolyte gel. It showed an excellent electrode capacitance of 106.25 mF cm−2 (at 0.25 mA cm−2) with remarkable cyclic stability (36,000 cycles with 80 % capacitance retention at 5 mA cm−2).