Iron-Based Catalysts for Direct CO₂ Hydrogenation to Hydrocarbons: A Systematic Review and Descriptive Quantitative Synthesis of Conversion, Selectivity and Stability (2017–2026)

Iron-based catalysts for direct CO₂ hydrogenation to hydrocarbons (CO₂-FTS) have attracted rapidly growing research interest as a Power-to-X route, yet we did not identify a prior systematic review with descriptive quantitative synthesis focused specifically on this catalyst class. To the best of the authors’ knowledge, this work provides a systematic descriptive quantitative synthesis, covering 60 coded reports published between January 2017 and July 2026 and identified by structured searches of Scopus, Web of Science Core Collection, and ScienceDirect. After PRISMA-adapted eligibility reconciliation, 49 primary studies were included; 42 reported extractable numerical CO₂ conversion data and contributed to the descriptive quantitative synthesis, while seven were retained for qualitative analysis only. Median CO₂ conversion across the 42 quantitative studies was 38.3% (range 8.5–69.9%; SD = 15.3%), providing a dataset-specific reference for the reviewed literature. Across the predefined subgroups, mean CO₂ conversion varied from 31.6% to 47.1%, with substantial differences in operating conditions and small subgroup sizes limiting direct attribution to catalyst composition. The highest absolute conversion, 69.9%, was achieved by two-stage reactor engineering with interstage H₂O removal, not catalyst reformulation, identifying product-water inhibition as an important single-stage conversion constraint. The highest recorded product selectivities across the dataset were 64.3% to C₅⁺ (Na-FeMgMnOx), 82.6% to light olefins (Y₂O₃/Fe–Co/SAPO-34), and 75.6% to aromatics (ZnFeOx-Na/HZSM-5); maximum demonstrated stability was 205 h (3K/6Cu-Fe₂O₃/C nanosheets). Analysis of the full conversion–selectivity dataset reveals that only approximately 14% of studied systems simultaneously exceeded the conversion median and a 44% target-selectivity threshold. The synthesis further identifies that key physicochemical descriptors (BET surface area, post-reaction Mössbauer phase composition, CO₂-TPD basicity, ASF α, space-time yield normalised to iron mass, and stability data) are absent from 60–85% of primary reports, and proposes recommended reporting elements to facilitate future quantitative synthesis. Because study-level variances and standardised controls were unavailable, no weighted effect-size meta-analysis was performed; the results should be interpreted as a descriptive quantitative synthesis. The review was not prospectively registered.