Graphene oxide grafted with polyoxazoline as thermoresponsive support for facile catalyst recycling by reversible thermal switching between dispersion and sedimentation

Grafting polyoxazolines exhibiting a cloud point temperature (T-cp) in the reaction medium onto graphene oxide (TRGO) prepared by thermal reduction of graphite oxide affords thermoresponsive catalyst supports and enables catalyst recycling by thermal switching between dispersion and sedimentation. In a facile grafting-to process the functional groups of the TRGO react with the cationic oxazolinium end groups, obtained by living cationic ringopening polymerization of 2-ethyl-2-oxazoline, and covalently attach PEtOx having an average molar mass > 10 000 g.mol(-1) and a T-cp of 65 degrees C in polar solvents like water. Below the T-cp at 25-30 degrees C stable dispersions of palladium supported on TRGO-g-PEtOx (Pd@TRGO-g-PEtOx) are obtained. As compared to the Pd@TRGO benchmark in the absence of PEtOx, Pd@TRGO-g-PEtOx exhibits higher catalyst activity in Suzuki-Miyauracoupling reactions. Opposite to Pd@TRGO, Pd@TRGO-g-PEtOx readily agglomerates above T-cp at 65 degrees C and enables easy and complete recovery of the catalyst by filtration and repeated catalyst reuse without encountering neither filtration problems nor drastic losses of catalyst activity.