Metallic engineering in metal-porphyrin frameworks for highly efficient CO2 photoreduction

CO2 photoreduction is an environmentally friendly technique to reduce carbon emissions and produce valueadded products, but the poor efficiency and low selectivity restricted its applications. Here we proposed a one-stone-two-birds strategy, metallic engineering, to boost CO2 photoreduction performance, in which the improved reduction ability and the regulated CO2 reduction kinetics can be simultaneously achieved. The electronic configurations of 3d5, 3d7, and 3d8 with S = 1/2, 1/2, and 0 spin ground states were successfully constructed via metal engineering on metal-porphyrin frameworks (SNNU-600-M). Among SNNU-600-M catalysts, SNNU-600-Ni (S = 0) exhibites ultrahigh CO yield (21697.6 mu mol g- 1 h- 1 ) with high selectivity. The 3d8 electronic configuration of Ni(II) on the one hand signficantly improve the reduction ability. On the other hand, due to the instinctive unstable feature of 3d9 for Ni(I) after photoexcitation, the photoinduced electron enables the proton adsorption on the neighbor N site, regulates the kinetics and facilitates the generation of key intermediate *COOH, leading to efficient CO production. This work provides a new insight into the electronic configuration regulation for efficient photocatalysis.