Catalytic Cycle Network: Boosting CO2 Hydrogenation to Propane

The utilization of CO2 hydrogenation to manufacture high-value chemicals is a viable strategy for achieving carbon neutrality. However, the reaction mechanisms still need to be further developed to improve catalytic efficiency. In this context, we report a bifunctional ZnZrOx/SSZ-13 catalyst, the conversion of CO2 reached 44.7%, while the selectivity for CO was maintained at 16.7%, and remarkably, the selectivity and yield for propane increased to 70.3% and 26.1%, respectively. A "catalytic cycle network" that involve H2O generated in situ by tandem reaction is suggested, and its mechanism confirmed through in situ DRIFTS spectroscopy, density functional theory (DFT) calculations, studies on water diffusion, and empirical evidence. This innovative mechanism, which departs from traditional tandem catalysis, signals a paradigm shift in the field of catalytic chemistry. At low space velocities, water generated during the reaction contributes by mass transfer diffusion to promote the tandem reactions. This phenomenon establishes a positive feedback loop in which "reaction-produced H2O promotes the reaction" and integrates with tandem reactions to form a "catalytic cycle network". Such complex, multi-level interactions significantly improve the hydrogenation of CO2. Subsequent studies of the structure-activity relationship between zeolite properties and bifunctional catalyst performance reveal a synergistic effect of zeolite acidity and hydrophobicity on reaction performance, which together determine the efficiency of the reaction. These findings provide a solid foundation for the design of effective catalysts for CO2 hydrogenation and have the potential to transform the field, thereby making a significant contribution to sustainable chemical synthesis.