Abstract

Abstract Selective photocatalytic reduction of CO 2 to value‐added fuels, such as CH 4 , is highly desirable due to its high mass‐energy density. Nevertheless, achieving selective CH 4 with higher production yield on p ‐block materials is hindered by non‐ideal adsorption of *CHO key intermediate and an unclear structure‐function relationship. Herein, we unlock the key reaction steps of CO 2 and found a volcano‐type structure‐function relationship for photocatalytic CO 2 ‐to‐CH 4 conversion by gradual reduction of the p‐ band center of the p ‐block Bi element leading to formation of Bi‐oxygen vacancy heterosites. The selectivity of CH 4 is also positive correlation with adsorption energy of *CHO. The Bi‐oxygen vacancy heterosites with an appropriate filled Bi‐6 p orbital electrons and p band center (−0.64) enhance the coupling between C‐2 p of *CHO and Bi‐6 p orbitals, thereby resulting in high selectivity (95.2 %) and productivity (17.4 μmol g −1 h −1 ) towards CH 4 . Further studies indicate that the synergistic effect between Bi‐oxygen vacancy heterosites reduces Gibbs free energy for *CO‐*CHO process, activates the C−H and C=O bonds of *CHO, and facilitates the enrichment of photoexcited electrons at active sites for multielectron photocatalytic CO 2 ‐to‐CH 4 conversion. This work provides a new perspective on developing p ‐block elements for selective photocatalytic CO 2 conversion.