Catalytic Applications of Graphene Oxide and Reduced Graphene Oxide Supported Metal-N-Heterocyclic Carbenes: Recent Advances and Future Prospects Φ

Abstract

Sustainable noble metal-N-heterocyclic carbenes (NHC’s) are a topic of arising concern in both the chemical industry and the academic community due to a growing consciousness of environmental pollution and scarcity. Recovering and reusing homogeneous catalysts from the reaction mixture requires a tremendous amount of capital investment in the chemical manufacturing industry. Heterogenous catalysts are proved to have better functional groups tolerance, however, catalysts support largely influences the active catalyst sites to affect catalyst efficiency and selectivity. The choice of catalyst supports plays an almost decisive role in this emerging area of catalysis research. Graphene oxide (GO)/ reduced graphene oxide (rGO) support has a potential growth in heterogeneous catalysis owing to their commercial availability, considerably larger surface area, inert towards chemical transformations, and easy surface functionalization to attached metal complexes via covalent and non-covalent aromatic p-conjugates. To take advantage of two independently well-established research areas of noble metal-N-heterocyclic carbenes and GO/rGO support via covalent or non-covalent interactions approach would offer novel heterogeneous complexes with improved catalytic efficiency without sacrificing product selectivity. This unique concept of marrying metal-N-heterocyclic carbenes with GO/rGO support has potential growth in the chemical and pharmaceutical industry, however, limited examples are reported in the literature. In this perspective, a comprehensive summary of metal-NHC synthesis on GO/rGO support and synthetic strategies to graft M-NHC onto GO/rGO surface, catalytic efficiency, and plausible mechanism for the catalytic transformation are critically reviewed. Furthermore, a summary of these robust heterogeneous catalysts, oxidation state, catalyst loading, and applications towards chemical transformation is summarized to direct readers to give a better understanding of M-NHC@rGO complexes. This would also allow designing engineered catalysts for unexplored catalytic applications.

Keywords: Graphene Oxide, Reduced Graphene Oxide, Carbene, transition metals, heterogeneous catalysts