Mild and Efficient Catalytic Nitration of Benzene with NO 2 to Nitrobenzene Promoted by Molecular Oxygen over Inorganic Bonded (FeCl 2 ) 2 -SiO 3

A new stable inorganic bonded Lewis acid catalyst ((FeCl 2 ) 2 -SiO 3 ) was synthesized and applied for the liquid-phase catalytic nitration of benzene with NO 2 to nitrobenzene in the presence of molecular oxygen. The results demonstrate that the inorganic bonded 10% (FeCl 2 ) 2 -SiO 3 catalyst showed excellent catalytic performance with 98.5% benzene conversion and 99.6% selectivity to nitrobenzene at 50 °C. Moreover, the catalyst maintained a high nitrobenzene yield after five cycles of reuse without significant deactivation. Characterization by XRD, XPS, UV–vis, FT-IR, and SEM consistently confirmed the successful bonding of FeCl 3 onto the silica support. Theoretical calculations further confirm that the Si–O–FeCl 2 sites in (FeCl 2 ) 2 -SiO 3 serve as the active catalytic sites in the nitration. A possible reaction mechanism for the nitration process was proposed. Oxygen promotes the activation of NO 2, while the Lewis acid sites contribute to the stabilization of NO 3 – . This synergy facilitates the formation of a stable electrophilic reagent, thereby significantly enhancing the reaction efficiency. This work provides a mild, efficient, safe, and eco-friendly approach for highly selective preparation of nitrobenzene with promising potential for industrial application.