A microwave-assisted hydrothermal synthesis produces ZnFe2O4 containing Na residue as a precursor to a CO2 hydrogenation catalyst that displays high CO2 conversion and high selectivity to 

liquid hydrocarbon products in the gasoline and diesel range with high olefin-to-paraffin ratios. Compared to reference catalysts derived from Fe2O3 and a ZnO–Fe2O3 physical mixture, 

the ZnFe2O4-derived catalyst contains well-dispersed iron particles with Zn serving as a structural promoter. A profound effect of the residual Na as an electronic promoter is also observed, which improves the selectivity for C5+ hydrocarbons and olefins. The ZnFe2O4-derived catalyst exhibits excellent performance in the CO2 Fischer–Tropsch reaction as it forms the active Hägg iron carbide (χ-Fe5C2) phase readily through the in situ carburization of iron.