Facet‐regulated local coordination of oxygen species on <scp>MgO</scp> for efficient cycloaddition of <scp>CO₂</scp> with propylene oxide

Abstract Regulating the concentration of low‐coordinated oxygen species on certain exposed crystal facets of oxides still remains a challenge. Herein, we developed a facile facet‐engineering method to construct regulable ratios of (100), (110), and (111) facets on the MgO by modulating the surface curvature. As revealed by in situ CO 2 diffused reflectance infrared Fourier transform spectroscopy and kinetic studies, it is found that MgO with a high density of active facets (i.e., [111] and [110] facets) exhibits ca. two times higher CO 2 adsorption capacity. Based on the results of the density functional theory calculation, the activation of CO 2 by MgO is enhanced with the increase in low‐coordinated oxygen on active facets. Notably, the trapezoidal MgO with high‐density active facets shows an increase in propylene epoxide conversion by ca. 33% without halogens, while maintaining a high propylene carbonate selectivity of 97.9%. This work will pave the way for the rational design of high‐performance oxide catalysts by the facet‐regulating strategy.