In-situ organic cation evolution driven sequential crystal transformation in hybrid metal halides

The properties of organic-inorganic hybrid metal halides (OIHMHs) strongly hinge on their crystal structures. However, structural diversity regulation based on organic-cation design or external stimuli is hindered by the limited diversity of available cations and the random structural changes. Here, we utilize in-situ sequentially generated organic cations from a stepwise reaction between DMSO and acetone to drive a continuous and unidirectional single-crystal-to-single-crystal transformation in OIHMHs, enabling well-defined and predictable structural evolution. The intermediate dimethyl(2-oxopropyl)sulfonium and product trimethylsulfonium cations are sequentially generated and incorporated into the crystal lattice, giving rise to three types of structurally correlated OIHMHs in both Bi- and Sb-based systems. The resulting OIHMH materials preserve the inorganic photoactive unit while exhibiting systematic changes in their physicochemical properties, revealing a dynamic cooperative mechanism between evolving organic cations and the adaptive inorganic octahedral framework. This work demonstrates the feasibility of intermediate cations generated by organic reactions to serve as an underutilized A-site organic cation resource. Such an organic reaction-driven and inorganic framework-mediated strategy establishes a dynamic paradigm for structural evolution, opening a promising avenue toward precise structural modulations and diversified functionalities of OIHMH materials.