A review on the advancements in covalent organic frameworks for photocatalytic reduction of carbon dioxide

Carbon dioxide (CO2) emissions from human activities have raised atmospheric CO2 levels to unsafe highs, necessitating the development of technologies to capture and utilize this greenhouse gas. Photocatalytic conversion of CO2 into value-added chemicals and fuels using solar energy has attracted significant research interest as a carbon capture and utilization approach. However, existing photocatalysts suffer from limitations such as low efficiency, instability, and poor selectivity. Covalent organic frameworks (COFs) are an emerging class of organic porous materials that show promise for photocatalytic CO2 reduction applications due to their tuneable properties, high surface areas, and photochemical stability. This review provides an overview of recent advances in the development of COF-based photocatalysts for improving the efficiency of solar-driven CO2 reduction. Key strategies investigated include functional group incorporation, metal doping, and integration of cocatalyst nanoparticles. Introducing polar functional groups and metal ions via doping has been demonstrated to enhance CO2 binding affinity and adsorption capacity within COF structures. The incorporation of noble metal cocatalysts promotes efficient charge separation and transfer, improving photocatalytic activity. Experimental and computational studies have provided insights into structure-activity relationships, linking photocatalytic performance to factors such as pore size, crystallinity, functional group polarity, and electronic structure. Further optimization of COF compositions, morphologies, and interfaces holds promise for realizing highly efficient and durable photocatalytic systems for CO2 reduction. Realizing the full potential of COFs will require the development of robust structure-property correlations to guide rational material design. With continued advances, COFs may enable economically viable and sustainable technologies for converting CO2 emissions into valuable chemicals and fuels using only sunlight as an energy input.