Warp-Weft Stack Strategy for Weaving 2D Porphyrin-Based COFs from 1D Chains toward CO₂ Photoreduction

The development of efficient photocatalysts for converting carbon dioxide into valuable chemicals is crucial for sustainable energy. Porphyrin-based covalent organic frameworks (COFs) represent a promising class of materials for photocatalytic CO₂ reduction. In this work, a novel synthetic strategy termed "warp-weft stack" is presented and utilized to design and synthesize a series of 2D porphyrin-based COFs from 1D chain precursors. The strategy employs low-symmetry (C₂) porphyrin and dialdehyde monomers, which first form 1D chains via imine bonds and are then woven into 2D frameworks through axial metal coordination. Comprehensive characterization confirms that the cobalt-porphyrin-based COFs exhibit a partially ordered layered structure with moderate crystallinity, suggesting that the metal center plays a key role in directing the dimensional evolution from chains to sheets. In contrast, the metal-free analog forms an amorphous aggregate. In a photocatalytic system with [Ru(bpy)₃]Cl₂ and ascorbic acid, the cobalt-porphyrin COF demonstrates markedly enhanced activity and selectivity for CO₂ reduction. This study not only provides a novel pathway for the bottom-up construction of dimensionally controlled porous materials but also underscores the importance of integrated metal sites in directing framework assembly and optimizing catalytic function for sustainable chemical synthesis.