Jahn-Teller distortion assisted interstitial nitrogen engineering: Enhanced oxygen dehydrogenation activity of N-doped Mn_xCo_3-xO₄ hierarchical micro-nano particles

Rational design of earth-abundant transition metal oxides catalysts is highly desirable for developing sustainable chemical processes. Herein, we demonstrate a prospective interstitial nitrogen engineering for fabricating oxygen vacancies (OVs)-rich nitrogen-doped-Mn_xCo_3-xO₄ (N-Mn_xCo_3-xO₄) oxide catalyst, in which the ratio of OVs concentration of N-Mn_xCo_3-xO₄ to Mn species is as high as 1:1, according to the characterizations of X-ray absorption (XAS) and X-ray photoelectron (XPS) spectroscopies. The promising strategy of interstitial nitrogen engineering through lattice distortion caused by the Jahn-Teller effect can significantly increase the amount of interstitial nitrogen. The resulting catalyst enables an additive-free aerobic dehydrogenation coupling of aromatic amine to afford azo compounds with > 99% yield and > 99% selectivity at 60 °C. We observed the superb catalytic activity is promoted by the enhanced oxygen mobility in OVs, which were created by the interstitial nitrogen in the catalyst matrix. The presence of interstitial nitrogen in transition metal oxides in this study shows how the manipulation of catalyst matrix can increase the OV sites to promote aerobic oxidation reaction.