Computational mechanistic insights into hafnium catalyzed CO₂ activation and reduction

Abstract

In this study, we present the reaction mechanisms for CO₂ activation and reduction reactions using hafnium complex as a frustrated Lewis pair catalyst investigated using density functional theory (DFT) calculations. CO₂ activation reactions with different oxidation states of the catalyst were explored. The energy barriers for CO₂ activation with oxidised, single-electron reduced and two-electron reduced catalyst were calculated to be 17.18, 14.46 and 15.73 kcal/mol, respectively. The mechanisms of CO₂ reduction to CO and HCOO^- upon addition of HCl as a proton source were also studied. The activation energies to release CO and HCOO^- from the hafnium complex were calculated to be 9.05 and 75.34 kcal/mol, respectively. The results indicated that formate formation is unlikely. The overall analysis of the reaction mechanisms shows that the studied Hf complex effectively activates CO₂ and can also potentially reduce the activated CO₂ to CO.

GRAPHICAL ABSTRACT

Keywords:

• CO₂ activation
• CO₂ reduction
• density functional theory
• hafnium catalysis

Acknowledgements

The authors acknowledge the Departments of Chemistry of Addis Ababa University and the University of Botswana for the research facilities. Computational resources were supplied by the project ‘e-Infrastruktura CZ’ (e-INFRA CZ ID:90140) supported by the Ministry of Education, Youth and Sports of the Czech Republic.

Disclosure statement

No potential conflict of interest was reported by the authors.