Recent advances on CO2-assisted synthesis of metal nanoparticles for the upgrading of biomass-derived compounds

Nanostructured catalysts have attracted increasing attention for biomass conversion into high-valued chemicals due to the rapid depletion of fossil resources and severe environmental issues. In this review, the basic properties of supercritical carbon dioxide (scCO2) and the roles of scCO2 in the fabrication of metal nanoparticles (including metal oxide nanoparticles) via supercritical fluid deposition method were assessed in detailed. The structure modulation strategy of the metal nanoparticles based on preparation conditions such as reaction temperature and pressure, types of metal precursors, and deposition time are summarized systematically. Besides, compared to the metal catalysts using the conventional methods, the catalysts obtained using scCO2 exhibited excellent catalytic performance on biomass conversion reactions, mainly focusing 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. © 2024