Solvent-Directed Phase Control in Disulfide-Linked Metal–Organic Frameworks Revealed by Microcrystal Electron Diffraction

High Resolution Image Download MS PowerPoint Slide Precise control over phase, topology, and reactivity in metal–organic frameworks (MOFs) is critical for translating chemical responsiveness into predictable function. Disulfide-linked coordination networks are attractive flexible materials, yet their strong sensitivity to synthesis conditions has hindered mechanistic understanding of how the structure governs reactivity. Here, we achieve phase control in a zinc disulfide MOF system by tuning solvent coordination and water activity, enabling access to a microcrystalline open-pore structure (Zn-MOF-α) and a dense, topologically distinct isomer (Zn-MOF-β) from the same disulfide linker. Microcrystal electron diffraction (MicroED) studies determined both structures directly from micro- and nanocrystalline particles, revealing distinct secondary building units (SBUs), connectivity, and pore architecture. Systematic solvent studies identify water as a driver of α → β transformation, while the reverse transformation (β → α) is accessible in solutions of N, N -dimethylformamide in water (DMF/H 2 O). Time-resolved experiments reveal a clear time and solvent dependence between the α- and β-phases, supporting distinct assembly pathways. By correlating topology, morphology, Brunauer–Emmett–Teller (BET), thermal gravimetric analysis (TGA), and spectroscopic signatures including electron paramagnetic resonance (EPR), we show that the open α-framework provides higher sulfur-centered radical populations and lower thermal robustness relative to the dense β-phase. Together, these results provide design rules for predictable phase outcomes and topology-dependent disulfide activation in flexible MOFs, enabling rational control of structure–function relationships in responsive porous materials.