Coordinative-Guest-Triggered Dimensional Crossover in a Metal-Organic Framework With Rigid Metal-Oxo Rods.

Structural phase transitions of metal-organic frameworks (MOFs) induced by guest-molecule exchange within their pores have attracted considerable attention not only from the viewpoint of structural chemistry but also for the modulation of their functional properties. Herein, we report a reversible structural phase transition triggered by the exchange of coordinative guest molecules in a Pb-based MOF composed of Pb2+ ions and 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ), formulated as [Pb(DHBQ)(DMF)(H2O)] (DMF = N,N-dimethylformamide). This compound forms a 3D framework structure in which 1D Pb-O rods, constructed from Pb2+ ions and oxygen atoms of bridging DHBQ2- ligands, serve as secondary building units (SBUs). The framework contains 1D pores accommodating coordinative DMF and H2O molecules. Exchange of these guest molecules induces a reversible structural phase transition accompanied by significant changes in both the Pb-O rod structure and the overall dimensionality of the framework. To the best of our knowledge, this represents the first example of a MOF composed of rigid SBUs that exhibits a reversible structural phase transition involving a change in framework dimensionality driven by guest-molecule exchange. These findings provide new insight into dynamic structural transformations in MOFs and highlight a strategy for controlling framework topology and properties through guest coordination.