Understanding the roles of ionic liquids in photocatalytic CO2 reduction

Abstract

Artificial photosynthesis for the production of value-added chemicals from CO₂ feedstock represents a promising approach toward achieving carbon neutrality. Nevertheless, the initial challenge lies in the capture and activation of CO₂, which is crucial for facilitating highly efficient conversion. Ionic liquids (ILs) are emerging as potential platforms for CO₂ capture and activation due to their diverse ion pairs, which assist in the synthesis and morphological control of photocatalysts, thereby exposing more active sites. Their tunable hydrophilicity and hydrophobicity create a confined environment around the catalyst, enabling selective control over the diffusion of reactants, intermediates, and products to the active sites. Additionally, the electronic structure of the photocatalyst can be adjusted through the careful selection of IL cations and anions, effectively reducing the activation energy barrier for CO₂ or optimizing the reaction pathway. Thus, three key roles of ionic liquids are thoroughly examined in this review. Furthermore, the underlying mechanism is also elucidated to facilitate a profound understanding of the photocatalytic CO₂ reduction process.