The bioderived chitosan was modified by carbon dioxide (CO

2

) and utilized to prepare hydrogel beads loaded with silver nanoparticles (AgNPs). The reaction intermediate between CO

2

and the amine group of chitosan

carbamic acid group

was proven effective in increasing the coordination site of chitosan for silver. The conductivity and viscosity changes of the solution confirmed the occurrence of the reaction and that the largest amount of carbamic acids was formed at 30 min. The scanning electron microscopy (SEM)

X-ray diffraction (XRD)

X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared resonance (ATR-FTIR) results confirmed that the silver loading capacity of chitosan after modification with CO

2

was doubled. The silver content was the largest and the AgNPs size was the smallest when the reaction time was 30 min. The results also showed that the Ag atoms were coordinated with the N and O atoms of chitosan. The prepared silver-loaded chitosan (CS-Ag) hydrogel beads were applied to catalyze the methylene blue reduction reaction. The reaction rate catalyzed by CO

2

-modified CS-Ag beads were greater than that catalyzed by unmodified beads under the same conditions

and the beads modified for 30 min performed the best. Also

the reactions catalyzed by CO

2

-modified CS-Ag beads were more sensitive to temperature

and with the increase of reaction temperature

the difference of reaction rate became larger

up to about three times of the original one.