Polyvinyl pyrrolidone-coordinated ultrathin bismuth oxybromide nanosheets for boosting photoreduction of carbon dioxide via ligand-to-metal charge transfer

Photoreduction of CO2 to useful ingredients remains a great challenge due to the high energy barrier of CO2 activation and poor product selectivity. Herein, Polyvinyl pyrrolidone (PVP) coordinated BiOBr was synthesized by a facile chemical precipitation method at room temperature. The CO2 photoreduction behaviors of PVP coordinated BiOBr were evaluated with H2O without sacrificial agent under the simulated sunlight. The evolution rates of CO and CH4 are 263.2 µmol g-1h-1 and 3.3 µmol g-1h-1, which are 8 times and 2 times higher than those of pure BiOBr respectively. Furthermore, the coordination of PVP on BiOBr surface enhances greatly the selectivity of product CO, which is close to 100%. Loading PVP onto BiOBr could not only induce and stabilize the oxygen vacancy, but also increase the charge density of BiOBr via the ligand to metal charge transfer (LMCT), which could be beneficial to the adsorption and activation of CO2 molecule. The photoreduction mechanism of CO2 for PVP coordinated BiOBr was proposed based on the improved charge density of BiOBr by the experimental results and Density functional theory (DFT) calculations. This finding provides a new pathway to boost the conversion efficiency and selectivity for the activation of CO2 photoreduction and new molecule insights into the role of PVP in photocatalysis.