Tuning the Hydroxyl Microenvironment of Fe-Zeolite for Selective Oxidation of Benzene by N2O.

The catalytic oxidation of benzene to phenol by nitrous oxide (N2O) offers a green route for valorizing a potent greenhouse gas. Although steam treatment of Fe/ZSM-5 drastically boosts phenol selectivity, the atomic-level origins remain obscured. This study combines spectroscopy characterizations and density functional theory (DFT) calculations to reveal that steam-induced dealumination generates electron-donating silanol nests, which electronically tailor adjacent Fe centers. We identify hydroxylated binuclear Fe sites as the predominant locus for high selectivity. Mechanistically, enhanced metal-to-adsorbate electron back-donation facilitates rate-determining N2O activation and electrophilic attack on benzene. This electronic environment also selectively poisons side reactions, raising the barrier for overoxidation and sterically electronically impeding biphenyl formation. The process induces exothermic phenol desorption, averting coking, whereas mononuclear sites lead to phenolic stagnation. This work provides a unified atom-scale picture of selectivity in the N2O-mediated benzene oxidation, establishing microenvironment engineering as a powerful strategy for zeolite-based catalyst design.