Green One-Step Synthesis of Catalytically Active Palladium Nanoparticles Supported on Cellulose Nanocrystals.

Palladium nanoparticles (PdNPs) supported on cellulose nanocrystals (CNXL) were synthesized in a single step from Pd(hexafluoroacetylacetonate)2 (Pd(hfac)2) in subcrit. and supercrit. carbon dioxide. CNXLs acted as both the reducing agent and support material for the obtained nanoparticles. Dry Pd nanoparticles supported on the cellulose nanocrystals (PdNP@CNXL) were obtained by simply venting the CO2 and were characterized by FT-IR, XPS, powder X-ray diffraction (XRD), thermogravimetric anal. (TGA), and transmission electron microscopy (TEM). The results show that the Pd nanoparticle diams. varied between 6 and 13 nm with varying pressure (240-2200 psi), reaction time (2-17 h), and wt. ratio of the precursor Pd(hfac)2 to CNXL (1-4% wt./wt.). Particles with diams. above 13 nm appeared not to remain attached to the CNXL surface. Reaction conditions also affected the Pd loading in the final PdNP@CNXL composite. Finally, the PdNP@CNXL composites were shown to be effective catalysts for carbon-carbon bond formation in the Mizoroki-Heck cross-coupling reaction, in line with other reports. [on SciFinder(R)]