Intramolecular Dual Donor-Acceptor Featured Covalent Organic Frameworks Enabled by Gating Effects for Ultra-Stable...

Sodium metal batteries (SMBs) face severe challenges of uncontrolled sodium dendrite growth and interfacial instability. Herein, guided by theoretical predictions, a distinct locally polarized covalent organic framework (TB-Br-COF) was synthesized and employed as a Na⁺ transport accelerator to promote uniform Na deposition. TB-Br-COF excited the gating effect (a high gating ratio of 23.1) through electronic response to accomplish the separation of Na⁺ from the electrolyte solvent via the sodiophilic sites (-O-C═C units, C═N linkages, C─Br bonds, and aromatic rings). Simultaneously, it synergistically induced two electron migration routes based on the dual donor-acceptor (linkages and linkers) structures, thereby enhancing both electron separation efficiency and Na⁺ cations' transport. Benefiting from that, the TB-Br-COF-based symmetric battery achieved an ultra-stable operating time of 1000 h at 1 mA cm^-2 with 1 mAh cm^-2. Moreover, the full battery based on the modified Na@TB-Br-COF electrode and the carbon-coated Na₃V₂(PO₄)₃/C (NVP/C) demonstrated high compatibility and good cycling stability. Theoretical calculation and in situ spectra measurements have jointly proved the molecular stability and mechanical robustness. Therefore, this investigation unveils an unconventional method for creating COF-based protective layers for the practical SMBs.