A Sustainable Approach for Graphene Oxide‐supported Metal N‐Heterocyclic Carbenes Catalysts

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. Heterogeneous catalysts are proved to have better functional groups tolerance; however, catalysts support largely influences the active catalyst sites to affect catalyst efficiency and selectivity. Thus 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 π-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 metalÀ NHC synthesis on GO/rGO support and synthetic strategies to graft MÀ NHC onto GO/ rGO surface, catalytic efficiency, for the catalytic transformation are critically reviewed. Furthermore, a plausible mechanism for non-covalent grafting methodology is summarized to direct readers to give a better understanding of MÀ NHC@rGO complexes. This would also allow the designing of engineered catalysts for unexplored catalytic applications.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

“…GO and RGO can be modified with 1,3-dipolar cycloadditions, ,, diazonium radical additions, ,− carbene and nitrene additions, [3,3] sigmatropic rearrangements, alkylations, and halogenations, − among other chemical inclusions. ,, Additional covalent modifications can occur on the newly installed oxygen-containing groups. Utilizing the carboxylic acids, many groups have performed amide couplings with amines on small molecules, − biomolecules, polymers − and other compounds of interest. ,− This approach has also been used to help further solubilize and passivate through attachment of polyethylene glycol (PEG)-amines ,, or poly- l -lysine. , In a similar manner, esters, ,− ethers, and silanes − have been attached as well.…”