N-heterocyclic carbene-ligated metal complexes and clusters for photocatalytic CO2 reduction

Abstract

Photocatalytic reduction of CO₂ to high value-added products is a green and sustainable approach to reducing excessive CO₂ emissions. N-heterocyclic carbenes (NHCs) are a class of structurally versatile ligands due to their strong σ-donor properties, forming covalent bonds with many metal centers, and ability to activate CO₂ molecules. The resulting NHC-ligated metal centers and clusters have high stability, tunable π-conjugation and unique reactivity, making them excellent candidates for CO₂ photoreduction. Herein, this frontier article provides a comprehensive review of the literatures on active NHC-stabilized metal complexes and clusters for photocatalytic CO₂ reduction. We discuss the synthetic strategies of NHC-ligated metal species, including their incorporation into porous matrices such as metal–organic frameworks (MOFs). We also summarize their photocatalytic applications in CO₂ reduction, providing guidance for the rational design and development of NHC-based MOF photocatalysts for efficient and sustainable CO₂ photoreduction.