Solar-Driven CO 2 -to-CH 4 Conversion Enabled by Fe Tetrahedra in Cs 3 FeCl 5

Lead halide perovskites have demonstrated significant potential for CO2 photoreduction, yet achieving efficient conversion to value-added hydrocarbons (e.g., CH4) remains a challenge. This study proposes an iron-based halide photocatalyst, Cs3FeCl5 nanocrystals (NCs), which achieves a photocatalytic CO2-to-CH4 yield of 2.88 mmol g–1 h–1 with a selectivity nearing 100%. This performance surpasses that of most reported single-component photocatalysts for CO2 methanation. Experimental and theoretical studies reveal that Cs3FeCl5 NCs exhibit intrinsic spin polarization to enhance charge separation, and that their tetracoordinated Fe2+ centers strongly hybridize with CO2 via d–p orbital interaction, thus lowering the activation energy and stabilizing the *COOH intermediate for CH4 production. Under natural sunlight, Cs3FeCl5 NCs maintain an impressive photocatalytic performance, highlighting their significant potential for scalable CO2 conversion. This work underscores the critical role of strong CO2 activation in driving hydrocarbon conversion and provides new design principles for cost-effective solar-to-fuel photocatalysts.