Unveiling the Power of Proximity of Prevalent Fe-Based Tandem Catalysts in CO ₂ Hydrogenation via Modified Fischer–Tropsch: Crucial Relations toward Industrialization

CO₂ reduction using renewable H₂ represents an emerging approach for minimizing dependency on fossil fuels and reducing the carbon footprint while providing chemicals and fuels. In this context, CO₂ hydrogenation using Fe-based oxide, which exhibits outstanding capabilities in both reverse water gas shift (RWGS) and Fischer-Tropsch synthesis (FTS) reactions, integrated with zeolite has been a promising method for heavy hydrocarbon (C₅₊) production. This review investigates the critical roles of promoter, zeolite topology and acidity, and synthesis methods in optimizing product distribution and their contributions to active site proximity. It has been found that the catalyst integration manner and the interaction between the basic sites of Fe-based oxide and the acidic sites of zeolites significantly influence catalytic performance. In addition, the proximity of active sites, a crucial factor in tandem catalysis, can be controlled via different catalyst synthesis methods, dispersion on mesoporous supports, or using encapsulated structures that can provide the confinement effect while guiding the reaction sequence. Furthermore, the choice of alkali promoters (Na vs K) is very important since each can alter electronic properties, reduction behavior, and hydrocarbon distribution due to different electronegativity and ionic radii. While Na could hamper all reduction steps and diffuses into bulk iron oxide, K remains mainly on the surface, increasing electron density and facilitating iron carbide formation. Besides, integrating spectroscopic imaging techniques with proximity metrics will enhance the understanding of active site spatial distribution. To bridge the gap between lab-scale results and industrial applications, advanced computational methods coupled with artificial intelligence (AI) and machine learning (ML) techniques are required to monitor and analyze catalyst behavior and optimize large-scale production. The findings of this study provide a comprehensive understanding of catalyst design principles with emphasis on the importance of the proximity of active sites, offering insights for the next generation of efficient CO₂ hydrogenation catalysts for industrial-scale fuel production.