Metal oxide hollow heterojunctions derived from bimetal-organic frameworks for efficient urea photosynthesis.

As urea is an important chemical in agriculture, the green synthesis of urea has attracted widespread attention. However, developing simple and green strategies for urea synthesis remains challenging. In this study, we developed a novel metal oxide hollow heterojunction for efficient photocatalytic urea synthesis. By calcining a bimetallic MUV-10 MOF precursor in an air atmosphere, the TiO2/Mn2O3 (denoted as TMO) metal oxide hollow heterojunction was successfully prepared, while the octahedral structure was well preserved. Among these catalysts, the bimetallic oxide TMO-8 exhibits the highest light-harvesting capability and photogenerated carrier separation efficiency, enabling efficient photocatalytic urea synthesis from CO2 and NH3. Under visible light irradiation, the TMO-8 hollow heterojunction achieved a high urea production rate of 93 µmol g-1 h-1, which surpasses those of the state-of-the-art photocatalysts. This study provides a new strategy for designing efficient heterojunction photocatalysts and offers an efficient pathway for artificial photosynthetic urea synthesis under mild conditions.