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Direct CO2 hydrogenation to higher hydrocarbons, that is, CO2 Fischer–Tropsch (CO2-FT) synthesis, is an attractive way to mitigate anthropogenic CO2 emissions and to produce fuels alternatively to oil- or natural-gas-based processes. One of the major shortcomings of typically applied Fe-based catalysts in CO2-FT is high selectivity to methane. Herein, we provide descriptors relevant for purposeful preparation of unpromoted Fe2O3 with the suppressed formation of this undesired product. This was possible owing to the combination of controlled material synthesis, sophisticated catalyst characterization (including along the catalyst bed) by state-of-the-art techniques with spatially resolved steady-state, and transient kinetic analyses. The defectiveness of in situ formed Fe5C2, that reflects the deviation from the stoichiometric composition and expressed as the ratio of C/Fe, affects the ability to adsorb CO2 and CO as well as to activate H2. CH4 formation is hindered over less-defective iron carbides, which are characterized by strong adsorption of CO and CO2 but low adsorption of H2. Thus, the catalyst efficiency in terms of C2+-hydrocarbon formation is improved. The imperfection of Fe5C2 can be controlled through the morphology of iron(II) oxalate dihydrate used as a precursor for preparation of Fe2O3. In addition to the defectiveness, the size of crystallites of α-Fe2O3 and the ratio of α-Fe2O3 to γ-Fe2O3 in fresh samples are two indirect descriptors affecting the ability of in situ formed Fe5C2 to directly hydrogenate CO2 to CH4. These structural characteristics depend on temperature, at which Fe2O3 materials were prepared. The lowest achieved CH4 selectivity is 0.05 at CO2 conversion of about 0.2. The ratio of olefins to paraffins among C2–C4-hydrocarbons is about 6.