Amorphous CuxO nano flakes with a thickness of 10 to 50 nm were synthesized through the dye-assisted transformation of rhombic dodecahedral Cu2O nanocrystals using facile solution process. The morphology evolution observed by electron microscopy is highly dependent on the reaction between the surface and the dye. The crystal grain shrinks during the process until the formation of a purely amorphous nano flake. The amorphous CuxO nano flake consists of a combination of Cu(I) and Cu(II) with a ratio close to 1:1. It shows enhanced photocatalytic reactivity towards the degradation of methyl orange as compared to rhombic dodecahedral Cu2O nanocrystals with all active (110):Cu facets. The chemical composition and architecture remain the same after repeating degradation tests. The high surface-to-volume ratio contributes to its superior photocatalytic performance while its low surface energy, confirmed by density functional theory simulations, explains its improved stability. The nano flakes also shows the ability to degrade nitrobenzene effectively, thus demonstrating great promise as a highly stable and active photocatalyst for environmental applications.