A Spontaneous Galvanic Process-Induced SC–SC Transformation for Synergistic Br2 Capture in a Water-Stable MOF

Abstract We report a water-stable, framework-anion-induced, redox-active Zn(II)-metal–organic framework (MOF) that captures and reduces molecular bromine (Br2) through an unusual framework-SBU-mediated redox-activation pathway without involving conventional metal- or ligand-centered redox chemistry. Upon exposure to Br2, the parent 2D Zn(II)-MOF [MOF(1)] reduces Br2 to Br– through a single-crystal-to-single-crystal (SC–SC) transformation, resulting in a 2D → 1D structural transition accompanied by the loss of a cyclic six-membered metal–oxo secondary building unit (SBU) and the evolution of O2. The exclusive appearance of O2 upon interaction of Br2–water with MOF(1) under rigorously anaerobic conditions provides direct evidence for a spontaneous galvanic mechanism involving cleavage of Zn–O–Zn linkages and lattice water, as confirmed by experimentally (gas chromatography analysis) and theoretically. The generated Br– ions subsequently coordinate to the metal centers in MOF(2), confirming efficient Br2 capture. Cyclic voltammetry reveals the redox-active sites upon Br– coordination, supporting a multistep reduction pathway, while kinetic analysis indicates that ∼89% of Br2 is reduced and sequestered within MOF(2) within 50 min. This study establishes a unique mechanism for synergistic halogen redox capture and framework reorganization, providing new insights into chemically responsive transformations in redox-active MOFs.