Investigating the mechanism of propylene epoxidation over halogen (X = F, Cl, Br, I) modified Cu₂O(110) surfaces: a theoretical study

The direct epoxidation of propylene using molecular oxygen to synthesize propylene oxide (PO) is a process of significant industrial and environmental interest. In this study, we employed density functional theory to explore the influence of halogen doping (specifically F, Cl, Br, and I) on the Cu2O(110) surface. The computational investigation revealed that replacing a surface lattice oxygen with a halogen atom would enhance the electron density of adjacent Cu sites, leading to more effective formation of the O-2(-) species. Our results indicated that the selectivity for PO production on these halogen-modified catalysts adheres to the sequence Cl > Br > F > I. Further structural analysis indicated that halogen integration adjusts the twist angle of the pivotal oxametallacycle propylene intermediate, effectively suppressing the competitive alpha-H abstraction side reaction and thereby elevating PO selectivity. These insights into the electronic and structural effects induced by halogens presented a compelling strategy for the development of more efficient catalysts for propylene epoxidation.