Systematic review of covalent organic frameworks for photocatalytic/electrocatalytic CO₂ reduction: From structural engineering to mechanistic insights

The rapid increase in atmospheric CO₂ levels driven by fossil fuel combustion has exacerbated environmental crises worldwide. Efficient CO₂ capture and conversion have therefore become indispensable toward achieving carbon neutrality. Photocatalytic/electrocatalytic CO₂ reduction reactions (peCO₂RR) powered by renewable energy is a promising strategy for converting CO₂ into high-value chemicals and fuels. However, this process is hindered by the intrinsic limitations of traditional catalysts. As emerging crystalline porous polymers, covalent organic frameworks (COFs) offer distinct advantages for the peCO₂RR, including tunable topological structures, atomically precise active site design, large specific surface areas, and excellent chemical stabilities, which address the inherent limitations of conventional catalytic materials. This review systematically summarizes recent advances in COF-based peCO₂RR by exploring the intrinsic correlation between structural engineering and catalytic performance. Herein, we discuss the precise design of two-dimensional (2D)/three-dimensional (3D) crystalline pore structures, green synthetic strategies, and diverse functionalization routes. A comprehensive analysis of multimodal catalytic mechanisms, including photocatalysis, electrocatalysis, and their synergistic effects, is provided. Furthermore, we focus on the orientation of synthesis towards C1 and C2 products and clarify the core structural factors responsible for governing the product selectivity. The critical roles of theoretical simulations and in-situ/operando characterization techniques in uncovering catalytic pathways and the evolution of intermediates are also highlighted. Finally, we discuss the key challenges presented by COF-based systems in terms of their structural robustness, catalytic selectivity, scalable preparation, and device integration and propose targeted prospects for rational design and practical applications. By moving beyond traditional laboratory metrics, this review aims to establish a comprehensive structure–property–performance roadmap that offers fundamental design principles to bridge the gap between molecular-level engineering and industrial-scale applications, thereby accelerating the deployment of COF-based technologies in the drive toward global carbon neutrality.