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

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.