The nanostructure of β-gallium oxide crystals influences the conversion to carbamates; specifically, for the synthesis of alkyl carbamates (like propyl N-octylcarbamate) from CO₂ and n-propanol in the absence of phosgene. The nanostructures with variable aspect ratios (length (L)/width (D); from 2 to 18) were prepared by the controlled addition of neutral and cationic surfactants during gallium oxide synthesis. These catalysts displayed selectivities to the corresponding carbamates as high as ~70%, superior to non-nanostructured Ga₂O₃ catalysts. The conversion was found to be inversely proportional to the square of the relative crystallinity. The catalysts retained their structure and catalytic performance upon recycling.