CO2 Enrichment Boosts Highly Selective Infrared‐Light‐Driven CO2 Conversion to CH4 by UiO‐66/Co9S8 Photocatalyst

Abstract 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 .