InO Nanocrystals for CO Fixation: Atomic-Level Insight into the Role of Grain Boundaries.

N-functionalization of amines with CO and H is one of the most important processes to make use of CO. Although noble metal-based catalysts with remarkable performance have been widely used in this process, developing efficient non-noble-metal-based catalysts remains a grand challenge. Herein, we report InO nanocrystals with high density of grain boundaries (HGB-InO), which show excellent activity toward methylation of amines. Impressively, HGB-InO achieved the optimal yield of 82.7% for N,N-dimethylaniline with a mass activity of 21.2 mmol·gh in methylation of N-methylaniline, comparable to noble-metal-based catalysts. As a bonus, HGB-InO held noticeable stability, remarkable selectivity, and comprehensive applicability. Further mechanistic studies revealed that the presence of high density of grain boundaries not only facilitated the adsorption and activation of CO to generate CHOH as the intermediate but also enhanced the activation of N-H bond in amines, contributing to the attractive activity of HGB-InO toward methylation of amines.