Perovskites for CO2 Conversion: Active-Phase Identity, Reconstruction, and the Evidence Behind Mechanistic Claims.

Converting CO2 into fuels and chemicals is a central challenge in sustainable chemistry. Perovskites offer compositional flexibility, tunable band structures, redox-active B-site cations, controllable defect chemistry, and a propensity for exsolution and surface reconstruction under operating conditions. This review critically synthesizes perovskite-based CO2 conversion across halide and lead-free halide perovskites; Cu- and Fe-substituted systems; oxynitrides and oxyfluorides; and thermochemical, chemical-looping, solid oxide electrolysis, and methanation oxides. Using an evidence hierarchy that prioritizes 13CO2 isotope labeling, operando spectroscopy, local structure probes, and postreaction characterization, the analysis distinguishes established active-site claims from activity correlations, identifies systems whose working catalyst is a reconstructed phase rather than the as-synthesized perovskite, and outlines the standards needed for mechanism-guided catalyst design.