Composite Si-O-metal network catalysts with uneven electron distribution: Enhanced activity and electron transfer for catalytic ozonation of carbamazepine

Electron-rich center and electron-poor center were formed around Si and metal atom linked via Si-O-metal bonding bridge in the Co-Ce doping mesoporous molecular sieves MCM-48 for catalytic ozonation of carbamazepine (CBZ). The density functional theory (DFT) calculations of Co-Ce-MCM-48 concluded that unique Co-O-Si-O-Si-O-Ce had a much lower energy gap than those of Si-O-Si-O-Si-O-Si, Co-O-Si-O-Si-O-Ce and Co-O-Si-O-Si-O-Ce. The successful immobilization of Co-Ce was verified by X-ray absorption fine-structure (XAFS), Raman and 29Si MAS-NMR spectrum. Co-Ce-MCM-48/O3 process achieved 75.6% mineralization of CBZ at 60 min by generation of reactive oxygen species (ROSs) and enhanced redox behaviors of Ce(Ⅲ)/Ce(Ⅳ) and Co(Ⅱ)/Co(Ⅲ). Two new intermediates (P13 and P14) of CBZ in Co-Ce-MCM-48/O3 were observed by DFT and LCMS/MS results. This study opened a new insight by employing an integration of theoretical and experimental techniques to elucidate the synergistic effect of uneven electrons distribution at Co-O-Si-O-Si-O-Ce and catalytic reaction pathway of CBZ.