Dual role of graphene as support of ligand-stabilized palladium nanoparticles and carbocatalyst for (de)hydrogenation of N-heterocycles

Abstract

The hybrid material composed of palladium nanoparticles (PdNPs) functionalized with N-heterocyclic carbene ligands (NHCs) immobilized onto the surface of reduced graphene oxide (rGO) results in an efficient catalytic material towards hydrogenation and dehydrogenation of N-heterocycles. The rGO plays a dual role by acting as a carbocatalyst in acceptorless dehydrogenation of N-heterocycles and as a support for the palladium nanoparticles facilitating its interaction with molecular hydrogen turning this hybrid material into an effective hydrogenation catalyst. Hot filtration experiments support the heterogeneous nature of the process underlining the strong interaction of palladium nanoparticles with the graphene enabled by π-interactions of the ligand with the support. The mild conditions used in both transformations of this system without requiring any additives facilitates its potential application in hydrogen storage technologies in the form of liquid organic hydrogen carriers (LOHCs). At the same time, the hybrid material is a robust and efficient catalytic platform that can be recovered and reused up to eight runs in both transformations without significant deactivation. The use of a single solid catalysts that is recyclable in hydrogen conversion and reconversion through (de)hydrogenation of N-heterocycles paves the way for the development of efficient hydrogen storage materials.