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 CO 2 photoreduction, yet achieving efficient conversion to value-added hydrocarbons (e.g., CH 4 ) remains a challenge. This study proposes an iron-based halide photocatalyst, Cs 3 FeCl 5 nanocrystals (NCs), which achieves a photocatalytic CO 2 -to-CH 4 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 CO 2 methanation. Experimental and theoretical studies reveal that Cs 3 FeCl 5 NCs exhibit intrinsic spin polarization to enhance charge separation, and that their tetracoordinated Fe 2+ centers strongly hybridize with CO 2 via d–p orbital interaction, thus lowering the activation energy and stabilizing the *COOH intermediate for CH 4 production. Under natural sunlight, Cs 3 FeCl 5 NCs maintain an impressive photocatalytic performance, highlighting their significant potential for scalable CO 2 conversion. This work underscores the critical role of strong CO 2 activation in driving hydrocarbon conversion and provides new design principles for cost-effective solar-to-fuel photocatalysts.