Organic cation conformational flexibility governs mechanical response in organic–inorganic hybrid materials

(2, Hmpi = 2-hydroxymethyl-piperidinium). Compound 1 exhibits a moderate reversible deformation of 5% with pronounced shape-locking. In contrast, compound 2 shows a large reversible deformation up to 17%. Structural and variable-temperature Raman analyses establish the adaptability of organic cations as the governing factor for ferroelastic strain modulation, operating through controlled ring dynamics and lattice slippage mechanisms. These results establish a clear structure-mechanics relationship: conformational rigidity promotes shape-locking, while enhanced conformational flexibility enables greater actuation freedom. Decoding the structural code behind mechanical response offers a rational basis for designing adaptive crystals with shape memory function.