Artificial photosynthetic system for diluted CO 2 reduction in gas-solid phase.

Rational design of robust photocatalytic systems to direct capture and in-situ convert diluted CO ₂ from flue gas is a promising but challenging way to achieve carbon neutrality. Here, we report a new type of host-guest photocatalysts by integrating CO ₂ -enriching ionic liquids and photoactive metal-organic frameworks PCN-250-Fe ₂ M (M = Fe, Co, Ni, Zn, Mn) for artificial photosynthetic diluted CO ₂ reduction in gas-solid phase. As a result, [Emim]BF ₄ (39.3 wt%)@PCN-250-Fe ₂ Co exhibits a record high CO ₂ -to-CO reduction rate of 313.34 μmol g ^-1 h ^-1 under pure CO ₂ atmosphere and 153.42 μmol g ^-1 h ^-1 under diluted CO ₂ (15%) with about 100% selectivity. In scaled-up experiments with 1.0 g catalyst and natural sunlight irradiation, the concentration of pure and diluted CO ₂ (15%) could be significantly decreased to below 85% and 10%, respectively, indicating its industrial application potential. Further experiments and theoretical calculations reveal that ionic liquids not only benefit CO ₂ enrichment, but also form synergistic effect with Co ²⁺ sites in PCN-250-Fe ₂ Co, resulting in a significant reduction in Gibbs energy barrier during the rate-determining step of CO ₂ -to-CO conversion.
(© 2024. The Author(s).)