Tailoring Mn d-band center and valence cycling for high-efficiency catalytic ozonation of ibuprofen in pharmaceutical wastewater treatment.

Residual drugs, as emerging contaminants, pose particular challenges to treating pharmaceutical wastewater, requiring advanced oxidation technologies. Catalytic ozonation (CO) is a promising process for degrading emerging contaminants by generating various reactive oxygen species (ROS). However, catalyst design still largely relies on a trial-and-error approach. This approach lacks mechanistic support, particularly at the atomic and orbital levels, which hinders the development of efficient catalysts. This study proposes a universal strategy for raising the d-band center of manganese oxides (MnOx), which enhances their ability for ozone adsorption and activation. Three modulation strategies, including redox-inert metal doping, redox-active metal lattice doping, and redox-active metal heterojunction doping, are studied and compared to reveal their ability to change the orbital hybridization and electron structure of MnOx. Redox-active metal lattice doping is identified as a reliable approach to improve the catalytic activity of MnOx, due to its superior ability to accelerate electronic transport and Mn valence cycling. Micro-interface analysis and DFT calculations revealed that orbital hybridization between Mn and doped metal raises the d-band center of Mn. This electronic structure optimization promotes the formation of strong acid sites, which serve as the key active site for O3 adsorption and decomposition. Moreover, the electron derived from MnOx activates the adsorbed ozone to yield •OH, which is the key ROS for degrading ibuprofen (IBP), a typical residual pharmaceutical. This work provides a universal electronic-structure engineering strategy to design highly active MnOx used in CO for more sustainable water purification applications.