Spatially Engineering the Internal Microstructure of a Single Crystal via Nanoparticle Occlusion

Abstract Single crystals are characterized by their continuous, highly ordered atomic lattices. Therefore, introducing impurities or structural defects into their matrices presents a major challenge, particularly in a spatially‐controlled manner. Herein, we demonstrate a nanoparticle occlusion approach that enables the microstructure of cuprous oxide (Cu 2 O) single crystals to be engineered in a tunable way. This is achieved by directly incorporating poly(glycerol monomethacrylate) 51 ‐ block ‐poly(benzyl methacrylate) 100 [G 51 ‐B 100 ] diblock copolymer nanoparticles into growing Cu 2 O crystals, leading to the formation of G 51 ‐B 100 @Cu 2 O composite crystals with structural defects localized at the G 51 ‐B 100 /Cu 2 O interfaces. The spatial distribution of these defects can be systematically engineered, ranging from the surface region to the entire crystal. Remarkably, the G 51 ‐B 100 occlusion endows the resulting composite crystals with excellent catalytic performance in dye degradation under dark conditions, with activity correlated to the extent of nanoparticle occlusion. This study offers a unique strategy to create interfacial defects in single crystals, imparting emerging functionalities to the resulting composites.