Green One-Step Synthesis of Catalytically Active Palladium\nNanoparticles Supported on Cellulose Nanocrystals

Abstract

Palladium nanoparticles (PdNPs) supported\non cellulose nanocrystals\n(CNXL) were synthesized in a single step from Pd­(hexafluoroacetylacetonate)₂ (Pd­(hfac)₂) in subcritical and supercritical carbon\ndioxide. CNXLs acted as both the reducing agent and support material\nfor the obtained nanoparticles. Dry Pd nanoparticles supported on\nthe cellulose nanocrystals (PdNP@CNXL) were obtained by simply venting\nthe CO₂ and were characterized by FT-IR, X-ray photoelectron\nspectroscopy (XPS), powder X-ray diffraction (XRD), thermogravimetric\nanalysis (TGA), and transmission electron microscopy (TEM). The results\nshow that the Pd nanoparticle diameters varied between 6 and 13 nm\nwith varying pressure (240–2200 psi), reaction time (2–17\nh), and weight ratio of the precursor Pd­(hfac)₂ to CNXL\n(1–4% w/w). Particles with diameters above 13 nm appeared not\nto remain attached to the CNXL surface. Reaction conditions also affected\nthe Pd loading in the final PdNP@CNXL composite. Finally, the PdNP@CNXL\ncomposites were shown to be effective catalysts for carbon–carbon\nbond formation in the Mizoroki–Heck cross-coupling reaction,\nin line with other reports.