A hydrophilic o-phenanthroline-based covalent organic polymer with a reversible tautomeric structure for boosting photocatalytic hydrogen peroxide production†

Photocatalytic production of hydrogen peroxide (H₂O₂) from solar energy, oxygen and water is an environmentally friendly and sustainable approach. However, the efficiency is highly restricted by the limited light absorption, charge separation and oxygen capture of the active centers. In this study, a novel hydrophilic o-phenanthroline-based covalent organic polymer (COP) with a reversible iminol-to-ketoenamine tautomeric structure was successfully prepared through the Schiff base reaction. The highly conjugated structure significantly enhances its visible light absorption and accelerates the separation and migration of photogenerated charges. Furthermore, the o-phenanthroline linker facilitates the adsorption and activation of oxygen molecules, and the hydrophilicity is highly advantageous for the rapid photocatalytic reactions. Therefore, the as-prepared COP exhibits excellent photocatalytic H₂O₂ production performance (814 μmol g⁻¹ h⁻¹) without the addition of any cocatalysts or sacrificial agents. This work provides a new example for the design of photocatalysts based on covalent organic polymers towards H₂O₂ production.