Thianthrene- and Thianthrene Tetraoxide-Functionalized Conjugated Microporous Polymers for Efficient Energy Storage

Abstract

Supercapacitors (SCs), with their exceptional properties, present a promising solution to the ongoing energy crisis by meeting the increasing demand for high-energy storage devices. Conjugated microporous polymers (CMPs) offer a range of sizes, precisely controlled porosities, impressive intrinsic porosity, remarkable stability, and customizable structures and functionalities. These attributes collectively make CMPs cost-effective materials for energy storage applications. In this research, we effectively created three organic electrodes based on CMPs for energy storage via the Suzuki coupling reaction of 1,3,6,8-tetrakis(4-bromophenyl)pyrene (PyPh-Br₄) and benzene-1,4-diboronic acid (BZ-2B(OH)₂) with 2,8-dibromothianthrene (Th-Br₂) or 3,7-dibromodibenzothiophene S, S-dioxide (SU-Br₂) or 2,8-dibromothianthrene-5,5′,10,10′-tetraoxide (DSU-Br₂) to produce PyPh-BZ-Th, PyPh-BZ-SU, and PyPh-BZ-DSU CMP, respectively. Their thermal stability was examined using TGA measurements, and both PyPh-BZ-Th CMP and PyPh-BZ-SU CMP displayed T_d10 of 540 and 467 °C with high carbon reside up to 70 wt % at 800 °C. Electrochemical performance for these materials was evaluated using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). Within a three-electrode setup, specific capacitances of 617, 538, and 596 F g^–1 for PyPh-BZ-Th, PyPh-BZ-SU, and PyPh-BZ-DSU CMPs were recorded by GCD at 0.5 A g^–1. To obtain a more practical and accurate evaluation, we further constructed symmetric devices for each CMP. Using GCD curves, the specific capacitances were found to be 187, 63, and 105 F g^–1, respectively, for PyPh-BZ-Th, PyPh-BZ-SU, and PyPh-BZ-DSU CMPs. The high capacitances of the synthesized CMPs in this study, comparable to those of other reported porous CMPs, can be attributed to electronegative moieties, such as sulfur (S) and sulfone (SO₂) groups. These groups enhance electrostatic interactions and improve the wettability of the electrodes. This study demonstrates that using the Suzuki coupling reaction technique, CMPs incorporating Py, Th, and DSU moieties can be effectively produced for energy storage applications.