Semiconducting Polyaromatic Covalent Organic Frameworks Constructed through Self-Aldol Condensation

The construction of semiconducting covalent organic frameworks (COFs) via single-component self-polymerization is of broad interest in reticular chemistry. Herein, two semiconducting polyaromatic COFs with all-fused-ring conjugation structures were synthesized through the self-aldol condensation of indanone-based building blocks. The resulting COFs exhibit n-type semiconducting properties and exceptional stability under harsh acidic and alkaline conditions. The electrical conductivity and charge carrier mobility of the polyaromatic COFs reached up to 5.5 × 10^-3 S cm^-1 and 0.62 cm² V^-1 s^-1, which ranked as the highest values among n-type semiconducting COFs. The high crystallinity, intrinsic porosity, excellent conductivity, and abundant five-membered rings as active sites render these COFs as effective metal-free electrocatalysts toward oxygen reduction reaction (ORR). Notably, one of these COFs shows a half-wave potential of up to 0.77 V under alkaline conditions, which constitutes one of the highest values among the reported metal-free ORR electrocatalysts. In addition, owing to the strong robustness of the polyaromatic COFs, they also exhibit long-term catalytic durability. This study not only expands the diversity of semiconducting COFs but also establishes new paradigms for the development of high-performance metal-free electrocatalysts toward the ORR process.