Emerging applications of N-heterocyclic carbenes and related materials in environmental decontamination

The increasingly environmental pollution have drawn global attentions to the development of new techniques that can effectively deal with the pollutants. With the unique set of electronic properties and structural diversities, N-heterocyclic carbenes (NHCs) and related materials are emerging as potential adsorbing materials for adsorptive decontamination of various pollutant-containing mediums. Recent investigations have revealed the feasibility of molecular and heterogeneous NHCs for adsorptive separation of harmful gases including CO₂, CO, NO_x, SO₂, etc. Rather than simple gas trapping, NHCs functions as effective catalytic centers that activating and transforming the captured gas molecules. Besides, heterogeneous NHCs and their complexes have been applied to adsorptive removal of various organic pollutants and heavy metal ions from water solution with high efficiencies. These advancements have illustrated the significant potential of NHCs and their related materials in environmental decontamination. Instead of the well-known catalytic applications of NHCs in organic transformations, this review aims to offer an overview of the emerging applications of NHCs in the field of environmental decontamination and provide a comprehensive understanding of the mechanisms behind the N-heterocyclic carbene material-mediated environmental decontamination processes. With this in mind, the structure, synthesis, application, and performance of NHCs and related materials in environmental processes including gas separation and wastewater treatment are summarized, and the structure-activity relationship is discussed. Besides, the current challenge and future development of NHC-mediated environmental treatments are proposed. This review is expected to serve as a preliminary database for the environmental applications of NHC and related materials and offer deep insights into the rational design of novel NHC-based environmental materials for greener and efficient environmental processes.