Growth Environment-Driven Structural Adaptability Enabling Chirality in a Spin-Crossover Framework

Controllable induction of chiral and achiral topological isomers in metal–organic frameworks (MOFs) from achiral tectons remains a challenge. This study demonstrates the tunable growth of an achiral two-dimensional (2D) spin-crossover MOF (SCO-MOF) and a chiral three-dimensional (3D) SCO-MOF by systematically modifying the growth environment. In the C2Cl4–CH3OH system, planar C2Cl4 molecules template the formation of the achiral 2D SCO-MOF. Replacing C2Cl4 with CHCl3 in the CHCl3–CH3OH system induces the sequential growth of achiral 2D and chiral 3D SCO-MOFs, while reducing the CHCl3 proportion suppresses the achiral 2D framework, yielding pure chiral 3D SCO-MOF. In the H2O–CH3OH system, devoid of bulky solvents, chiral 3D samples are rapidly and selectively synthesized at 363 K. Enantiopure agents ((S)-(−)-PET and (R)-(+)-PET) further control the chiral orientation of the 3D samples. Single-crystal X-ray diffraction (SC-XRD) data reveal that the chiral 3D structure features oppositely handed large and small double helices in an ABAB packing mode, homologous to the ABAB-stacked supramolecular structure of its achiral 2d isomer. The denser 3D framework enhances thermal and chemical stability and exhibits pressure-induced and guest-loss abolition of SCO properties.