Mn/C/MCM-41 nanoreactors: Ozone oversolubility, pollutant enrichment and confined catalysis for efficient non-radical oxidation of emerging contaminants

Active MnO x location (inside MCM-41 pores vs. external surface) was precisely regulated. • Remarkable ozone oversolubility phenomenon within nanoconfined water was discovered. • Nanoconfinement effect triggered intrinsic inversion of reaction mechanism. • MnO x /C/MCM-41 nanoreactors perform excellently for complex wastewater treatment. Catalytic ozonation is promising for emerging contaminants (ECs) abatement but hindered by intrinsic bottlenecks: low O 3 solubility and catalytic efficiency. Herein, a series of xMn/C/M41 nanoreactors were fabricated via a two-step ligand-adsorption and metal-anchoring strategy. After pyrolysis, the optimized 3.3Mn/C/M41 nanoreactors confined ultra-small (~2 nm) mixed-valent MnO x nanoclusters and carbon within the mesopores of MCM-41, while s-3.3Mn/C/M41 (simultaneous ligand-metal complex adsorption) has 5–10 nm Mn 3 O 4 nanoparticles on the surface. 3.3Mn/C/M41 showed a 6.1 × 10 −2  min −1 sulfamethoxazole reaction rate (1.9 times that of s-3.3Mn/C/M41), > 93% removal of three other ECs, along with robust pH adaptability (3.5–10.5), matrix resistance and cycling stability. The excellent performance stems from the mesoporous confinement effects: 300-fold ozone oversolubility, rapid contaminant enrichment, and highly active MnO x nanoclusters with numerous undercoordinated Mn, oxygen vacancies, and Mn N motifs. Experimental and theoretical calculations demonstrate that the catalytic mechanism transforms from a hydroxyl radical (for s-3.3Mn/C/M41) to non-radical of electron transfer and 1 O 2 . This work provides a novel strategy to address the intrinsic bottlenecks of catalytic ozonation, and offers a promising platform for efficient remediation of emerging contaminants in complex aquatic environments. Download: Download high-res image (166KB) Download: Download full-size image