Screening the activity of Lewis pairs for hydrogenation of CO₂

Abstract

CO₂ capture coupled with CO₂ conversion to hydrocarbon fuels could reduce the overall anthropogenic carbon footprint but requires an efficient catalytic pathway for CO₂ hydrogenation. In this work, we examine functional groups that can be integrated within nanoporous materials, such as metal organic frameworks, that could lead to the development of materials that can selectively adsorb CO₂ from flue gas and convert it into a useful fuel. We focus on the use of Lewis pair (LP) moieties as catalytic functional groups because of their activity for heterolytic dissociation of H₂ and subsequent hydrogenation of CO₂. However, most LP functional groups also strongly bind CO₂, such that the catalytic site can be poisoned if the binding energy of CO₂ is much stronger than that of H₂. In this work, we screen a variety of LP moieties using density functional theory to compute the adsorption energies of H₂ and CO₂. We consider five classes of LP functional groups, with each class designed to explore modifying the binding energies in different ways. We have developed a mathematical model for predicting the H₂ adsorption energies on various Lewis pairs as a function of geometric and energetic properties of the functional moieties.

Keywords:

• Lewis pairs screening
• density functional theory
• H₂ adsorption
• CO₂ adsorption
• CO₂ hydrogenation