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

Rational design of robust photocatalytic systems to direct capture and in-situ convert diluted CO 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-enriching ionic liquids and photoactive metal-organic frameworks PCN-250-FeM (M = Fe, Co, Ni, Zn, Mn) for artificial photosynthetic diluted CO reduction in gas-solid phase. As a result, [Emim]BF(39.3 wt%)@PCN-250-FeCo exhibits a record high CO-to-CO reduction rate of 313.34 μmol g h under pure CO atmosphere and 153.42 μmol g h under diluted CO (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 (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 enrichment, but also form synergistic effect with Co sites in PCN-250-FeCo, resulting in a significant reduction in Gibbs energy barrier during the rate-determining step of CO-to-CO conversion.