Halide perovskites as disposable epitaxial templates for the phase-selective synthesis of lead sulfochloride nanocrystals.

Colloidal chemistry grants access to a wealth of materials through simple and mild reactions. However, even few elements can combine in a variety of stoichiometries and structures, potentially resulting in impurities or even wrong products. Similar issues have been long addressed in organic chemistry by using reaction-directing groups, that are added to a substrate to promote a specific product and are later removed. Inspired by such approach, we demonstrate the use of CsPbCl perovskite nanocrystals to drive the phase-selective synthesis of two yet unexplored lead sulfochlorides: PbSCl and PbSCl. When homogeneously nucleated in solution, lead sulfochlorides form PbSCl nanocrystals. Conversely, the presence of CsPbCl triggers the formation of PbSCl/CsPbCl epitaxial heterostructures. The phase selectivity is guaranteed by the continuity of the cationic subnetwork across the interface, a condition not met in a hypothetical PbSCl/CsPbCl heterostructure. The perovskite domain is then etched, delivering phase-pure PbSCl nanocrystals that could not be synthesized directly.