Redox-switchable breathing behavior in tetrathiafulvalene-based metal-organic frameworks

Metal-organic frameworks (MOFs) that respond to external stimuli such as guest molecules, temperature, or redox conditions are highly desirable. Herein, we coupled redox-switchable properties with breathing behavior induced by guest molecules in a single framework. Guided by topology, two flexible isomeric MOFs, compounds 1 and 2, with a formula of In(Me₂NH₂)(TTFTB), were constructed via a combination of [In(COO)₄]^- metal nodes and tetratopic tetrathiafulvalene-based linkers (TTFTB). The two compounds show different breathing behaviors upon the introduction of N₂. Single-crystal X-ray diffraction, accompanied by molecular simulations, reveals that the breathing mechanism of 1 involves the bending of metal-ligand bonds and the sliding of interpenetrated frameworks, while 2 undergoes simple distortion of linkers. Reversible oxidation and reduction of TTF moieties changes the linker flexibility, which in turn switches the breathing behavior of 2. The redox-switchable breathing behavior can potentially be applied to the design of stimuli-responsive MOFs.