Cobalt-containing covalent organic frameworks for visible light-driven hydrogen evolution

Covalent organic frameworks (COFs) have recently emerged as a new class of photocatalysts. However, integrated design is crucial to maximizing the performance of COF-incorporating photocatalytic systems. Herein, we compare two strategies of installing earth-abundant metal-based catalytic centers into the matrice of a 2D COF named NUS-55. Compared to NUS-55(Co) prepared from the post-synthetic metalation of coordination sites within the COF, the molecular co-catalyst impregnated NUS-55/[Co(bpy)₃]Cl₂ achieves a seven-fold improvement in visible light-driven H₂ evolution rate to 2,480 µmol g⁻¹ h⁻¹, with an apparent quantum efficiency (AQE) of 1.55% at 450 nm. Our results show that the rational design of molecular anchoring sites in COFs for the introduction of catalytic metal sites can be a viable strategy for the development of highly efficient photocatalysts with enhanced stability and photocatalytic activities.