Recent Developments in Metal-free Materials for Photocatalytic and Electrocatalytic Carbon Dioxide Conversion into Value Added Products

Rising atmospheric CO2 levels due to human activities require immediate action to mitigate their climate impact. Converting CO2 into value-added chemicals offers a promising approach for sustainable development. This conversion process, however, needs efficient catalysts to reduce activation energy, enhance product selectivity, increase reaction rates, and improve overall productivity. Conventional metal-based catalysts, though effective, present challenges such as scarcity, high costs, and toxicity. As an alternative, metal-free catalysts emerge as a viable solution, offering comparable activity, abundance, reusability, and reactivity profiles. Despite the growing interest in metal-free catalysts for CO2 reduction, a comprehensive understanding of their application and recent advancements remains limited. This review aims to bridge this gap by exploring the use of metal-free catalysts in converting CO2 into value-added products. It provides an in-depth discussion of available metal-free catalysts and the corresponding challenges in their application in photochemical and electrochemical CO2 conversion. The review begins with recent developments in organic, carbon-based, and polymer-based metal-free catalysts, highlighting key performance metrics. It then addresses major challenges, such as enhancing faradaic efficiency to compete with metal-based catalysts and improving stability. Strategies like compositing, codoping, innovative reactor design, and real-time catalyst analysis are examined in detail. Finally, future perspectives and recommendations for the synthesis and performance assessment of these catalysts are offered to guide sustainable advancements in this field.