Solvent-Directed Structural Divergence in Hybrid Organic–Inorganic Perovskites with Identical Composition

Hybrid organic–inorganic perovskites (HOIPs) exhibit rich structural diversity that is highly sensitive to synthetic conditions. However, the structure-directing role of solvent remains insufficiently understood. In this work, we demonstrate a solvent-controlled strategy to modulate crystal structures in a TMP–Cd–Cl system (TMP = thiomorpholine), yielding two compounds with identical chemical composition but distinct structural dimensionalities. Specifically, (TMP) 2 CdCl 4 crystallizes as a zero-dimensional structure under concentrated HCl conditions, whereas (TMP)CdCl 3 forms a one-dimensional chain structure when deionized water is used as the solvent. Both compounds exhibit reversible thermally induced phase transitions (395 and 422 K, respectively) and distinct dielectric switching behaviors. This work highlights the critical role of solvent in directing coordination modes and structural dimensionality in HOIPs, and provides a simple yet effective approach for the rational design of structure–property relationships in hybrid perovskite materials.