Conformation-Adaptive Transformations of Flexible Frameworks: From Controlled Stimuli-Responsiveness to Regulated...

Synthesizing enzyme-like porous materials that can regulate responsiveness through conformations remains a challenge. Here, two flexible framework conformers (FJI-H29 and FJI-H41) were prepared from a semirigid ligand. They not only exhibit different responses to the same stimuli, but their responsive behaviors can also be regulated precisely. FJI-H29 is thermosensitive, it can undergo continuous thermal-driven transformations, from reversible deformations to irreversible reconstruction, and the reconstruction barrier can be further tuned. While FJI-H41 is sensitive to the kinetic energy generated by solvent removal; when the solvents escape vigorously, it in situ shrinks to a more stable conformer (FJI-H43); when the solvents escape slowly, it first forms a shape maintaining metastable state (FJI-H41'), then spontaneously transforms into FJI-H43. Structural analysis shows the FJI-H29 is mechanically stable, while its ligands undergo more severe distortion with increasing temperature, enabling it to undergo thermal-driven reconstruction. Whereas FJI-H41 is mechanically unstable, so it is prone to undergo desolvent-driven deformations. FJI-H43 not only exhibits a temperature-dependent gate-open effect for the adsorption of C₂H₂ and CO₂ but can also be used for one-step C₂H₄ purification from C₂H₂/C₂H₄/CO₂ mixture; but FJI-H29 does not work. This provides a new strategy for preparing enzyme-like porous materials.