Stimuli‐Responsive of Flexible Silver–Organic Framework Film with Molecular Rotors Based on Methylene Rotation

Environmental stimuli‐responsive materials exhibit immense potential in various applications. Herein, three stable silver‐based organic frameworks (MOF‐Ag‐1, MOF‐Ag‐2, and MOF‐Ag‐3) are constructed connecting by the same [Ag2(CN4)2] secondary building blocks. The MOF‐Ag‐3 shows controllable molecular rotation driven by water vapor due to the flexible framework and methylene molecular rotor. Meanwhile, the soft materials (MOF‐Ag‐3@PVDF film, PVDF = polyvinylidene fluoride) that enable visible shape transformation have been prepared by integrating deformable MOF‐Ag‐3 crystals into polymer films. Moreover, the vertical distribution of MOF‐Ag‐3 crystals is adjusted by acid etching to prepare a double‐layer structure actuator, containing alternant moving layer and fixed layer. The smart actuator presents bending deformation in the water vapor (folding angle φ = 451°, RH = 80%), performing “pull‐ups” and “sit‐ups” stimuli‐responsive behaviors as the “arms” or “waist” part. In addition, the MOF‐Ag‐3@PVDF film not only produces distortion under a CH3SH vapor but also shows fluorescence quenching to the CH3SH/water mixture vapor (0.5% CH3SH) with a low detection limit of 0.48 μm. This work indicates the molecular‐level construction of stimuli‐responsive materials for pollutant monitoring.