Hydroxylic functionalization of graphene oxides with iridium N-heterocyclic carbenes for catalytic applications

摘要

The functionalization of graphene oxides (GO) has become an uprising research field which leads to an improvement of the electrochemical, biological or catalytic properties of these materials. Plenty of strategies are described in the literature to achieve that. Most of them employ the carboxylic groups which decorate the edges of the GO sheets or its sp2 carbon lattice. However, few of them use the surface hydroxylic groups for the same purposes. In this work, graphene oxide is covalently modified through its surface OH groups to develop active catalysts based on supported iridium N-heterocyclic carbene (NHC) complexes. [1] Thus GO obtained by modified Hummers method, was covalently functionalized with an appropriate hydroxyl-ending imidazolium salt via the formation of a labile organic carbonate as intermediate. Thermally reduced graphene oxide at 400 °C (GO-TR400) in which the acid groups were eliminated was also used for comparison purposes. [2] The covalent linkage of the ligand to the GO was determined by RMN. The amount of ligand attached (quantified by TGA and XPS) was, in both samples, the expected according to the amount of OH groups in each sample. The presence of free acid groups in GO also confirmed the selectivity of the reaction proposed.