Sulfur‐Modulated Covalent Organic Framework Superstructures With Highly Dense and Fully Accessible Protophilic Sites for High‐Performance All‐Organic Proton Batteries

Abstract

ABSTRACT Covalent organic frameworks (COFs) have emerged as competitive battery materials by solving the solubility and/or kinetics limitations of small molecules and polymers, while offering structure‐function merits over inorganics. However, a tricky trade‐off remains between active‐site density and accessibility. Here we describe a trade‐off‐breaking design of sulfur‐modulated COF superstructures (TD‐COFS) via synergistic geometric‐electronic structure engineering. Flower‐shaped TD‐COFS is constructed by intermolecular H‐bonding and π‐π stacking self‐assembly of tricarbonyl‐benzothiazole motifs, maximizing exposure of well‐organized multi‐protophilic active sites and π‐electron delocalization routes. Electron‐rich S‐heterocyclic benzothiazole (replacing N‐containing bipyridine, TM‐COFS) increases the electronegativity of TD‐COFS and reduces the redox barrier (S < N), enabling synchronous optimization of molecular charge distribution and electronic bandgap (−0.75/1.82 vs. −0.52/2.47 eV of TM‐COFS). Furthermore, sulfur modulation boosts proton‐transfer redox activity with a low activation energy (0.23 eV), and achieves full accessibility of highly dense protophilic sites in TD‐COFS (99.3% vs. 0.34 eV/84.7% of TM‐COFS), liberating high capacity (356 mAh g −1 ) and cycling stability (70 000 cycles). Besides, the assembled soft‐packed all‐organic proton batteries deliver state‐of‐the‐art capacity (161 mAh g −1 ), energy density (81 Wh kg −1 cell ), and life (3000 cycles). This work broadens the design philosophy of structured‐tailored COFs with highly dense and accessible protophilic sites for better proton batteries.