Abstract
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.