Covalent-Organic Frameworks with Dual-Metallic Sites for Enhanced Photocatalytic H ₂ Production

Photocatalytic hydrogen (H 2 ) production represents a highly promising pathway for future H 2 supply, yet efficient photocatalysts for water splitting remain scarce. This study synthesized two covalent organic framework (COF) materials (PorBpy-COF and ZnPorBpy-COF) via the Knoevenagel condensation reaction. These COFs feature a donor−acceptor structure and incorporate highly polar cyano groups, thus enhancing their electron−hole separation efficiency and photocatalytic activity for superior photocatalytic H 2 production. Furthermore, Ni 2+ was coordinated to the bipyridine sites of ZnPorBpy-COF, yielding n wt %Ni@ZnPorBpy-COF ( n = 1, 3, and 5) and 3 wt %Ni@ZnPorBpy-COF exhibited a H 2 production rate as high as 13.40 mmol g −1 h −1, surpassing some previously reported COF-based catalysts, while demonstrating excellent stability over 20 h. This enhancement is attributed to the postconstructed “porphyrin-Zn 2+ -bipyridine-Ni 2+ ” dual-metallic synergistic system, which improves the charge-carrier dynamics. This work elucidates the structure−function relationship of COF-based photocatalysts, providing insights for next-generation hybrid COF systems.