Interrogating the missing links in tandem CO hydrogenation: role of intermediate transport, active site proximity, and ion exchange in zeolites.

The tandem hydrogenation of CO to fuels and chemicals using bifunctional oxide/zeolite catalysts offers a promising strategy for reducing anthropogenic CO emissions while generating sustainable alternatives to fossil fuels. Despite significant advancements in this field, fundamental gaps remain in understanding the inflence of active site-proximity, intermediate transport rates, and the metal oxide migration and their ion-exchange with zeolitic Brønsted acid sites (BAS) on the reaction rates and hydrocarbon (HC) product selectivities. Challenges also include high CO selectivity and understanding the complexities of hydrocarbon pool (HCP) propagation in zeolite pore channels. This perspective integrates insights from analogous bifunctional catalytic systems, such as alkane hydrocracking and isomerization, to refine our understanding of site-proximity and transport artifacts on reaction rates and product selectivities. We examine diffusion-reaction formalisms for elucidating site-proximity effects on rates and HC selectivity, discuss methods to suppress CO selectivity using surface organometallic chemistry (SOMC) approaches, and explore strategies for suppressing ion-exchange and tuning HCP dynamics. By addressing these challenges, we outline a conceptual roadmap for advancing tandem CO hydrogenation chemistry, providing potential strategies to enhance catalytic efficiency of bifunctional oxide/zeolite systems.