Tailored Metalloporphyrin-Based Three-Dimensional Covalent Organic Frameworks for Enhanced Photocatalytic CO ₂ Reduction

The development of efficient photocatalysts for CO₂ reduction is essential for addressing climate and energy issues. Three-dimensional covalent organic frameworks (3D COFs) have emerged as potential candidates; however, challenges in their synthesis and structural analysis have hindered the rational design of high-performance photocatalysts. Here, we report the design and synthesis of a series of highly crystalline metalloporphyrin-based 3D COFs (3D-MPor-COF, M = Co, Ni, Pt) featuring 5-fold <b>pts</b> topology. Photocatalytic experiments reveal that the metal center significantly affects their activity, with 3D-CoPor-COF achieving a CO production rate of ∼11.3 mmol g^-1 h^-1 and 91.9% selectivity. Further optimization through pore enlargement yields isoreticular 3D-CoPor-Ph-COF, which exhibits a substantially enhanced rate of ∼20.7 mmol g^-1 h^-1 and 95.4% selectivity. These results highlight the critical role of tailoring pore environments─including both catalytic site identity and pore size─to optimize 3D COFs for photocatalytic CO₂ reduction, offering molecular-level insights for the development of COF-based photocatalysts in sustainable energy applications.