Anionic Property Is Crucial for the High Activities of Metalloligand Catalysts

Abstract

Metalloligand catalysts represent a significant class of catalysts, but the factors influencing the catalytic activity remain poorly understood, which presents a major challenge for their continued advancement. Herein, a comparative theoretical study is performed to investigate the CO₂ hydrogenation facilitated by metalloligand catalysts. The anionic Co–Ga and Ni–Ga catalysts are predicted to exhibit very strong bond-activation abilities with low energy barriers, whereas their neutral Co–Ga and Ni–Ga congeners exhibit significantly weaker bond-activation capabilities and higher energy barriers to CO₂ hydrogenations. The Lewis acidic character of the metalloligand is identified as a key factor contributing to the high energy barriers observed in neutral metalloligand catalysts. Moreover, the anionic nature of the catalysts can counteract the Lewis acidity of metalloligands, enhancing dπ basicity and promoting the catalytic activity of metalloligand catalysts. Guided by these insights, the anionic Rh–Ga catalyst RhGa1 is designed to facilitate CO₂ hydrogenation with an energy span of 11.5 kcal/mol, representing a potential for high catalytic activity. The computational results suggest that the anionic nature is the determining factor for the low formate–metal binding free energies (ΔG_bind) in anionic metalloligand catalysts.