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.