Twins in polyhedral 26-facet Cu7S4 cages: Synthesis, characterization and their enhancing photochemical activitiesElectronic supplementary information (ESI) available: Additional XRD patterns, SEM, TEM, HRTEM images, SAED patterns and absorption spectra (Fig. S1S7). See DOI: 10.1039/c2dt12091g

Unusual polyhedral 26-facet Cu 7 S 4 cages wholly exposed with amazingly unique nanotwinned structures as building blocks were successfully synthesized via a facile ethanol-assisted sacrificial Cu 2 O templates approach. Furthermore, a solvent-controlled fabrication of polyhedral copper sulfides (Cu 7 S 4 and CuS) with different stoichiometries and microstructures can be artificially achieved, which is determined by the intrinsic difference of the surface states of Cu 2 O templates. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). Stoichiometric-dependent characteristics were demonstrated in the UVvis absorption investigations. The as-prepared Cu 7 S 4 microcages exhibit higher photocatalytic activity for enhancing degradation of methylene blue, which might be attributed to their special nanotwinned building blocks. This study is of great importance in bottom-up assembly of unusual ordering hollow copper sulfides superstructures, but also offers a good opportunity to understand the fundamental significance of nanotwinned structures for their potential applications. Unusual polyhedral 26-facet Cu 7 S 4 microcages wholly composed of nanotwinned building blocks were successfully synthesized via a facile ethanol-assisted sacrificial Cu 2 O templates approach.