  Nanostructured catalysts have attracted the increased attention for biomass
conversion into high-valued chemicals due to the rapid depletion of fossil
resources and increasingly severe environmental issues. Supercritical carbon
dioxide (scCO2) fluid is an attractive medium for synthesizing nanostructured
materials due to its favorable properties. In this review, the properties of
scCO2 and the roles of scCO2 in the fabrication of metal nanoparticles were
assessed in detailed. A general overview of the synthesis of different types of
metal nanoparticles (including metal oxide nanoparticles) using scCO2 and the
relationship between the structure of the obtained metal nanoparticles and the
preparation conditions such as reaction temperature and pressure, types of
metal precursors, and deposition time are system summarized and compared in
tables. Besides, compared to the meatal catalysts using the conventional
methods, the catalysts obtained using scCO2 exhibited excellent catalytic
performance on biomass conversion reactions, mainly focused on oxidation,
hydrogenation reactions. Finally, opportunities and challenges of metal
nanoparticle preparation using scCO2 for biomass valorization to chemicals and
liquid fuels are highlighted. This review could be helpful for the rational
design of more efficient metal catalysts for the selective synthesis of fine
chemicals and fuels from biomass-derived chemicals.
