Photosynthesis of Urea from N2 and Co2 Using Dual Active Sites Polyoxometalates at Room Temperature

The synthesis of urea from N2 and CO2 has enormous economic and environmental benefits. In this study, the photocatalyst SiW6Mo6@MIL-101(Cr) was synthesized employing a dual active site regulation strategy, reaching 1148 μg·h-1·g-1cat and 100% selectivity for urea under the optimal experimental condition. Both performance tests and DFT calculations unequivocally establish that polyoxometalates SiW6Mo6 serves as a bifunctional photocatalyst, offering dual active sites for the proficient adsorption and activation of N2 and CO2. Specifically, the W site is attributed to the activation of nitrogen, whereas the Mo site is ascribed to the activation of CO2. The urea synthesis reaction's rate-limiting step involves the interaction of *CO and *N2, forming the tower-like intermediate *NCON*, where the dual active sites play a crucial role in reducing the reaction barrier. Moreover, MIL-101(Cr) immobilizes SiW6Mo6, enhances dispersion and gas adsorption capacity, and supplies additional electrons through light absorption for the reduction reactions.