Sulfonic Acid-Based Covalent Organic Frameworks with Efficient Zn²⁺ Transport and Storage for Aqueous Zinc-Ion Batteries

Covalent organic frameworks (COFs) with well-ordered nanopores and numerous accessible redox sites exhibit significant promise in aqueous zinc-ion batteries (AZIBs). However, challenges such as complex synthesis, limited capacity, and poor cycling stability still persist. In this study, we present a Zn²⁺ preintercalation strategy enabling the one-pot synthesis of long-range interconnected COFs functionalized with -SO₃^- groups (COFs-Zn). The COFs-Zn shows a robust precoordination structure between Zn²⁺ and building blocks, establishing a stable ionic reservoir for efficient Zn²⁺ (de)intercalation during cycling. Thus, COFs-Zn deliver a high reversible capacity of 166 mAh g^-1 at 0.5 A g^-1, excellent rate capability, and cycling stability. In situ and ex situ characterizations combined with density functional theory calculations reveal a reversible Zn²⁺ intercalation mechanism, while enhanced reaction kinetics are attributed to their porous network structure and strong polar adsorption sites from -SO₃^- groups. This work offers a promising route for designing COF-based materials for high-performance AZIBs.