Rational engineering and synthesis of pyrene and thiazolo[5,4-d]thiazole-functionalized conjugated microporous polymers for efficient supercapacitor energy storage

Abstract

The exceptional characteristics of supercapacitors (SCs) render them highly suitable for addressing the escalating demand for high-energy storage devices, thereby offering a potential resolution to the prevailing energy challenges. Conjugated microporous polymers (CMPs) present diverse structures, with customizable architectures and functionalities. Their inherent porosity, which can be meticulously controlled, and remarkable stability, positions CMPs as cost-effective materials for energy storage applications. In this study, the Schiff-base reaction between dithiooxamide and pyrene aldehyde derivatives [Py-Ph-4CHO and Py-Th-4CHO] was employed to synthesize two CMPs, designated as Py-Ph-TzTz and Py-Th-TzTz CMPs. Thermal stability investigations, conducted via thermogravimetric analysis (TGA), revealed T_d10 values of 502 °C for Py-Ph-TzTz CMP and 352 °C for Py-Th-TzTz CMP, with significant carbon residues of up to 67 wt% and 63 wt% at 800 °C, respectively. Galvanostatic charge–discharge (GCD) and cyclic voltammetry (CV) techniques were used to assess the electrochemical performance of these TzTz-CMPs in SCs. The specific capacitance for the three-electrode system was determined to be 652 and 464 F g⁻¹ for Py-Th-TzTz CMP and Py-Ph-TzTz CMP, respectively as measured by GCD at 1 A g⁻¹. Furthermore, symmetric devices were fabricated for each CMP to facilitate a more accurate and practical assessment. The specific capacitances of the Py-Ph-TzTz and Py-Th-TzTz CMPs, determined using GCD curves, were found to be 108 and 226 F g⁻¹, respectively. The high capacitances exhibited by the synthesized TzTz-CMPs in this study, comparable to those reported for other porous CMPs, can be attributed to the incorporation of electronegative moieties such as thiazolo[5,4-d]thiazole (TzTz). These groups enhance the electron density distribution, improve conductivity, and fortify electrostatic interactions.