Vacancy-rich Ti3C2Ox (MXene)-anchored Co nanocluster catalyst enhances the selective hydrogenation of cinnamaldehyde

Abstract

The efficiently selective hydrogenation of carbonyls in unsaturated aldehydes by nonnoble metal catalysts is still a severe challenge. Herein, an Co nanocluster catalyst anchored on vacancy-rich Ti3C2Ox (TCOs) was designed and prepared by a simple chemical reduction method for selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The Co/TCOs-H2 catalyst showed a superior catalytic activity with a TOF of 23.6 h-1, and reached a cinnamaldehyde conversion of 96.7% and a cinnamyl alcohol selectivity of 65.5% at low cobalt loading. Further, the characterizations demonstrated that Co nanoclusters were successfully anchored on TCOs, where the exist of surface oxygen vacancies (VOs) promote their vertical adsorption properties for cinnamaldehyde. Importantly, density functional theory calculation revealed that VOs enhanced selective adsorption of C=O on Co nanocluster by modifying the outside charge density of Co atoms, resulting an increase of the adsorption energy difference for conjugated double bonds and a lower energy barrier for H2 dissociation on Co nanocluster sites. This work develops a feasible strategy for constructing highly active metal nanocluster sites on two-dimensional MXenes and provides insight into the role of VOs on MXene in metal nanocluster during hydrogenation reactions.