Thin cupric oxide (Cu₂O) nanobelts with width of few tens of nanometers to few hundreds of nanometers were fabricated in anhydrous ethanol on nanoporous copper templates that was prepared via dealloying amorphous Ti₄₀Cu₆₀ ribbons in hydrofluoric acid solutions at 348 K. The Cu₂O octahedral particles preferentially form in the water, and nanobelts readily undergo the growth along the lengthwise and widthwise in the anhydrous ethanol. The ethanol molecules serve as stabilizing or capping reagents, and play a key role of the formation of two-dimensional Cu₂O nanobelts. Cu atoms at weak sites (i.e., twin boundary) on the nanoporous Cu ligaments are ionized to form Cu²⁺ cations, and then react with OH⁻ to form Cu₂O and H₂O. The two-dimensional growth of Cu₂O nanostructure is preferred in anhydrous ethanol due to the suppression of random growth of Cu₂O nanoarchitectures by ethanol. Cu₂O nanobelts have superior photodegradation performance of methyl orange, three times higher than nanoporous Cu.