Simultaneous introduction of K+ and Rb+ into OMS-2 tunnels as an available strategy for substantially increasing the catalytic activity for benzene elimination

Abstract

OMS-2 is one of the most promising catalysts for carcinogenic benzene elimination, and single-type alkali metals are typically introduced into the OMS-2 tunnels to modify its catalytic activity. Here, we reported a novel approach for significantly increasing the catalytic activity of OMS-2 via the simultaneous introduction of K+ and Rb+ into the tunnels. The catalytic results demonstrated that K+ and Rb+ codoped OMS-2 showed catalytic activity for benzene oxidation that exceeded those of K+ and Rb+ single-doped OMS-2, as evidenced by enormous decreases (△T50 = 106 °C and △T90 > 132 °C) in catalytic temperatures T50 and T90 (which correspond to benzene conversion percentages of 50% and 90%, respectively). The origin of the effect of K+ and Rb+ codoping on the catalytic activity of OMS-2 was experimentally and theoretically investigated via 18O2 isotope labeling, CO temperature-programmed reduction, and density functional theory calculation. The higher catalytic activity of K+ and Rb+ codoped OMS-2 was attributed to its higher lattice oxygen activity as well as its higher oxygen vacancy defect concentrations compared to the single-doped OMS-2 cases.