Homonuclear Dual‐Atom Cobalt Sites for Enhanced Selective Hydrogenation

Abstract

ABSTRACT Single‐atom catalysts based on non‐noble metals have demonstrated remarkable selectivity in selective hydrogenation. However, their electron‐deficient metal sites and the absence of adjacent metal sites often limit their hydrogenation activity. In this study, a homonuclear dual‐atom cobalt site catalyst (Co‐DAC) containing Co─Co bonds was synthesized by adsorbing a Co 2 ‐complex onto ZIF‐8 through a simple impregnation–pyrolysis process. The intrinsic activity of Co‐DAC in selective hydrogenation, including nitroarene hydrogenation to arylamines and alkyne semi‐hydrogenation to alkenes, was then investigated. The turnover frequency of Co‐DAC was 431 h − 1 in nitrobenzene hydrogenation and 1665 h − 1 in phenylacetylene semi‐hydrogenation. These values were 6.8‐fold and 17.5‐fold higher than those of the single‐atom catalyst, respectively. Moreover, it demonstrated broad substrate scope in these two reactions. Mechanistic studies revealed that the Co─Co dual‐atomic sites enhanced the adsorption capacity for nitro groups. Simultaneously, due to the electron coupling between Co─Co atom pairs, the electron density on the Co atoms increased. This facilitated the activation of H 2 and the desorption of aniline from the Co sites. Furthermore, the Co─Co sites enabled the homolytic cleavage of H 2 with a lower activation energy barrier. Therefore, Co‐DAC exhibited significantly improved catalytic performance in selective hydrogenation.