Boosting the Transfer Hydrogenation of Nitrobenzene to Azobenzene from Glycerol by Tuning the Oxygen-Vacancy Defects over Iron-Based Catalysts

Catalytic transfer hydrogenation (CTH) of nitrobenzene (NB) to value-added azobenzene has been a long-standing challenge. Here, we report that constructing magnetic iron-based catalysts enriched with oxygen-vacancy defects and appropriate Fe0 can enhance the catalytic activity and selectivity for the CTH of NB to azobenzene. The concentrations of oxygen-vacancy defects and Fe0 can be precisely tuned by altering the reduction temperature of iron-based catalysts. FeOx-600 catalyst with the richest oxygen-vacancy defects and appropriate Fe0 sites shows full conversion of NB with 98.6% azobenzene selectivity in 12 h at 80 °C. Glycerol is used as the hydrogen donor, and lactic acid is selectively obtained (91.6%) during the CTH of NB. FeOx-600 shows catalytic performance comparable to that of the state-of-art Au-based catalysts for the direct production of azobenzene from NB. FeOx-600 also shows good stability during the 6 catalytic recycles. This is the first report of an iron-based catalytic system that can selectively convert NB to azobenzene from glycerol; in this regard, it is an exciting discovery that has the potential for large-scale industrial applications.