Ultrahigh Selectivity of 95.78% for Visible Photocatalytic CO₂-to-CH₄ Conversion on Cu-Modulated Cs₄CdBi₂Cl₁₂ Microcrystals

The conversion of CO 2 to CH 4 by using solar energy represents a promising carbon-neutral process. Nonetheless, some critical issues, including the inherent stability of CO 2, the presence of erratic intermediates, and intricate electron transfer processes, pose significant challenges to the photocatalytic conversion of CO 2 to CH 4 . Therefore, how to introduce specific active metals as an innovative site has been recognized as one effective approach to improve the photocatalytic performance of catalysts. Here, we designed and incorporated Cu sites into Cs 4 CdBi 2 Cl 12 microcrystals for the first time, aiming to produce CH 4 with high selectivity by adjusting the CO 2 reduction pathway. Among the synthesized microcrystals, the Cs 4 Cd 0.8 Cu 0.2 Bi 2 Cl 12 exhibited superior visible photocatalytic performance, achieving CO and CH 4 yields of 1.54 and 8.78 μmol/g, respectively, with CH 4 electron selectivity as high as 95.78%. Additionally, we utilized in situ Fourier transform spectroscopy to elucidate the mechanism underlying the photoreduction of CO 2 to CH 4 . By introducing a novel active site, this study opens up a new avenue for the development of photocatalysts featuring highly selective reduction of CO 2 to CH 4 .