Modulating the Mn–O strength of OMS-2 by alkali metal doping for the catalytic oxidation of N, N-dimethylformamide

Abstract

Promoting catalytic activity by engineering oxygen mobility and reactivity is an intriguing approach to heterogeneous catalysis. Through the cation-exchange method, alkali metals were introduced into the OMS-2 catalyst, resulting in a weakening of internal Mn–O bonds and an increase in surface oxygen vacancies. Alkali metal doping significantly enhanced the catalytic activity of OMS-2 in the catalytic oxidation of N, N-dimethylformamide (DMF). Specifically, Rb-OMS-2, obtained by doping of Rb into OMS-2, displayed the highest oxygen vacancy, oxygen mobility and reactive lattice oxygen. The Rb-OMS-2 catalyst displayed better catalytic performance with 100 % CO2 yield, lowest N2O concentration and excellent water resistance, and stabilized at 220 °C for more than 120 h. In situ DRIFTS revealed that DMF molecules reacted with three kinds of oxygen species, then breakage of the C–N bond occurred, finally the remaining C-containing groups were subsequently oxidized to CO2, and intermediates of –NH2 and –NO+ reacted to form N2.