Catalytic activity of Cu₂O nanoparticles supported on cellulose beads prepared by emulsion-gelation using...

Nanocatalysts tend to aggregate and are difficult to recycle, limiting their practical applications. In this study, an environmentally friendly method was developed to produce cellulose beads for use as supporting materials for Cu-based nanocatalysts. Cellulose beads were synthesized from a water-in-oil emulsion using cellulose dissolved in an LiBr solution as the water phase and vegetable oil as the oil phase. Upon cooling, the gelation of the cellulose solution produced spherical cellulose beads, which were then oxidized to introduce surface carboxyl groups. These beads (diameter: 95-105 μm; specific surface area: 165-225 m² g^-1) have a three-dimensional network of nanofibers (width: 20-30 nm). Furthermore, the Cu₂O nanoparticles were loaded onto oxidized cellulose beads before testing their catalytic activity in the reduction of 4-nitrophenol using NaBH₄. The apparent reaction rate constant increased with increasing loading of Cu₂O nanoparticles and the conversion efficiency was >90 %. The turnover frequency was 376.2 h^-1 for the oxidized cellulose beads with the lowest Cu₂O loading, indicating a higher catalytic activity compared to those of other Cu-based nanoparticle-loaded materials. In addition to their high catalytic activity, the cellulose beads are reusable and exhibit excellent stability.