Cyclodextrin-Based Supramolecular Crosslinking Polymers With Multiple Ruthenium Centers for Highly Efficient...

Possessing multiple catalytic sites, supramolecular polymers have received attention due to their desirable electrocatalytic activity for ammonia synthesis from NO₃ ^¯. Herein, a covalently cross-linked supramolecular catalytic system (Ru@POP-CD) was synthesized by nucleophilic substitution reaction between ruthenium-coordinated phenanthroline cyclodextrin and tetrafluoroterephthalonitrile, which is not only efficiently electrocatalytic for ammonia synthesis from nitrate but also provides an effective way to combat environmental pollution. Different from noncovalently cross-linked supramolecular polymers, Ru@POP-CD could be kept on the electrode for cycle use and inhibit the hydrogen evolution reaction (HER), achieving a Faradaic efficiency (FE_NH3) of 78.5% at -0.8 V versus RHE in 0.1 M KNO₃/0.1 M KOH solution, with a NH₃ yield rate of 8.72 mg h^-1 cm^-2. This superior electrocatalytic performance is attributed to the unique cyclic structure with rich hydroxyl groups of the cyclodextrin, effective affinity for anionic nitrate through hydrogen bonding and the synergistic interaction of Ru tunable d-orbitals, facilitating the electroreduction of nitrate at the electrode. Meanwhile, in neutral electrolyte (0.1 M KNO₃/0.05 M K₂SO₄), Ru@POP-CD still possesses highly efficient catalytic performance, with the NH₃ yield rate of 7.45 mg h^-1 cm^-2 and FE_NH3 of 83.8% at -0.9 V versus RHE, showing great potential in electrochemical energy supply systems.