CO 2 Enrichment Boosts Highly Selective Infrared-Light-Driven CO 2 Conversion to CH 4 by UiO-66/Co 9 S 8 Photocatalyst.

Photocatalytic CO 2 reduction to high-value chemicals is an attractive approach to mitigate climate change, but it remains a great challenge to produce a specific product selectively by IR light. Hence, UiO-66/Co 9 S 8 composite is designed to couple the advantages of metallic photocatalysts and porous CO 2 adsorbers for IR-light-driven CO 2 -to-CH 4 conversion. The metallic nature of Co 9 S 8 endows UiO-66/Co 9 S 8 with exceptional IR light absorption, while UiO-66 dramatically enhances its local CO 2 concentration, revealed by finite-element method simulations. As a result, Co 9 S 8 or UiO-66 alone does not show observable IR-light photocatalytic activity, whereas UiO-66/Co 9 S 8 exhibits exceptional activity. The CH 4 evolution rate over UiO-66/Co 9 S 8 reaches 25.7 µmol g -1 h -1 with ca.100% selectivity under IR light irradiation, outperforming most reported catalysts under similar reaction conditions. The X-ray absorption fine structure spectroscopy spectra verify the presence of two distinct Co sites and confirm the existence of metallic Co─Co bond in Co 9 S 8 . Energy diagrams analysis and transient absorption spectra manifest that CO 2 reduction mainly occurs on Co 9 S 8 for UiO-66/Co 9 S 8 , while density functional theory calculations demonstrate that high-electron-density Co1 sites are the key active sites, possessing lower energy barriers for further protonation of *CO, leading to the ultra-high selectivity toward CH 4 .