Accelerated Catalytic Ozonation in a Mesoporous Carbon-Supported Atomic Fe–N₄ Sites Nanoreactor: Confinement Effect and Resistance to Poisoning

Abstract

The design of a micro-/nanoreactor is of great significance for catalytic ozonation, which can achieve effective mass transfer and expose powerful reaction species. Herein, the mesoporous carbon with atomic Fe-N₄ sites embedded in the ordered carbon nanochannels (Fe-N₄/CMK-3) was synthesized by the hard-template method. Fe-N₄/CMK-3 can be employed as nanoreactors with preferred electronic and geometric catalytic microenvironments for the internal catalytic ozonation of CH₃SH. During the CH₃SH oxidation process, the mass transfer coefficient of the Fe-N₄/CMK-3 confined system with sufficient O₃ transfer featured a level of at least 1.87 × 10^-5, which is 34.6 times that of the Fe-N₄/C-Si unconfined system. Detailed experimental studies and theoretical calculations demonstrated that the anchored atomic Fe-N₄ sites and nanoconfinement effects regulated the local electronic structure of the catalyst and promoted the activation of O₃ molecules to produce atomic oxygen species (AOS) and reactive oxygen species (ROS), eventually achieving efficient oxidation of CH₃SH into CO₂/SO₄^2-. Benefiting from the high diffusion rate and the augmentation of AOS/ROS, Fe-N₄/CMK-3 exhibited an excellent poisoning tolerance, along with high catalytic durability. This contribution provides the proof-of-concept strategy for accelerating catalytic ozonation of sulfur-containing volatile organic compounds (VOCs) by combining confined catalysis and atomic catalysts and can be extended to the purification of other gaseous pollutants.