Advances in covalent organic frameworks for photocatalytic CO₂ reduction: Strategies and future perspectives

The rapid depletion of fossil fuels and increasing emissions of greenhouse gases, particularly CO₂, have amplified global energy and environmental challenges. Converting CO₂ into valuable fuels through photocatalytic processes offers a sustainable solution to these issues, especially by utilizing solar energy to drive CO₂ reduction into energy-dense compounds. Covalent organic frameworks (COFs), a unique class of crystalline and porous organic polymers, have emerged as promising photocatalysts due to their structural stability, tunable porosity, and adaptable functionality. These properties enable COFs to support various catalytic sites, both metallic and non-metallic, facilitating selective and efficient CO₂ reduction. This review systematically examines the intrinsic properties of COFs, the synthetic methods used to optimize their structures, and the functional modifications that enhance their photocatalytic capabilities. We explore how COFs with metal and non-metal active sites, as well as hybrid COF catalysts, advance photocatalytic CO₂ reduction and analyze the driving forces behind CO₂ reduction reaction (CO₂RR). Finally, we summarize recent breakthroughs and offer perspectives on future research directions in COF material synthesis, functional modifications, and mechanistic studies to further improve CO₂ reduction efficiency and sustainability.