Synergistic Modulation of Band Gap and Porosity in Conjugated Microporous Polymers for High-Rate Lithium-Ion Storage

Conjugated microporous polymers (CMPs) have emerged as promising organic anode materials for lithium-ion batteries (LIBs), owing to their tunable chemical structures, robust physicochemical stability, and well-developed porosity. In this study, three anthraquinone-based CMPs were synthesized via Buchwald–Hartwig coupling by strategically modulating the core structures with triphenylamine (PAQTA), triphenylbenzene (PAQTB), and triphenyltriazine units (PAQTT), respectively. The physicochemical properties were systematically characterized by using a comprehensive set of techniques, including Fourier-transform infrared spectroscopy (FT-IR) in conjunction with X-ray photoelectron spectroscopy (XPS), and solid-state 13C nuclear magnetic resonance spectroscopy. Among these CMPs, PAQTA shows a polyaniline-like chemical structure with the narrowest band gap (2.17 eV) and the biggest mesoporous volume. Electrochemical study results demonstrate that the PAQTA electrode exhibits a facilitated charge transport kinetic and the highest diffusion coefficient. It, therefore, achieves a high reversible capacity of 800 mAh g–1 at 0.05 A g–1 and a high-rate performance (305 mAh g–1 at 2 A g–1), significantly outperforming PAQTB and PAQTT at the same current density. Mechanistic studies via ex situ XPS, FT-IR, and density functional theory calculations elucidate the lithium-ion storage mechanism of PAQTA, which involves synergistic redox reactions at the carbonyl groups and conjugated benzene moieties. This work provides valuable insights for designing high-rate and stable organic anode materials via molecular orbital and porosity modulation strategies.