Advances in covalent organic frameworks for photocatalytic CO 2 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.