Cyclodextrin-Based Polymer-Assisted Ru Nanoparticles for the Aqueous Hydrogenation of Biomass-Derived Platform Molecules

A green water-soluble cyclodextrin polymer has been prepared through cross-linking of -cyclodextrin (-CD) and polyethylene glycol diglycidyl ether (PEGDE). The as-synthesized co-polymer (PEG-CD) showed an excellent ability to stabilize and constrain the size of Ru-Nanoparticles in aqueous phase, as compared with other polymer stabilizer used in this work such as polyvinyl pyrrolidone (PVP-K30) and polyethylene glycol diglycidyl ether (PEGDE). The co-ploymer PEG-CD-stabilizied Ru NPs have been found to be a highly efficient catalyst in the aqueous hydrogenation of levulinic acid into -valerolactone under mild reaction condition. This catalyst system can be easily extended to the selective hydrogenation of other lignocellulose-derived platform molecule including 5-hydroxymethylfurfural, furfural, phenol, 2-methoxy-4-methyl phenol and 2-methoxy-4-ethyl phenol, etc. The further characterization analysis indicated that the small-sized and highly dispersed Ru NPs (1.2-2.0nm) embedded in co-ploymer PEG-CD matrix were highly stable for the consecutive catalytic recycles. Additionally, the inclusion interaction of substrate molecules and -CD units within polymer matrix played a crucial role in the enhancement of catalytic performance.