Crystallographic and Spectroscopic Snapshots of Multi‐Stimuli‐Responsive Dinuclear Cobalt Metal−Organic Frameworks

Abstract Investigating the reversible structural transformation of stimuli‐responsive metal–organic frameworks (MOFs) through single‐crystal diffraction and establishing a structure–property relationship pose a significant challenge. Herein, the controllable synthesis of Co‐MOF‐1 and Co‐MOF‐2 by incorporating water into the solvothermal synthesis process is presented. In comparison to the trinuclear [Co₃(COO)₈]²⁻ clusters found in Co‐MOF‐1, Co‐MOF‐2 presents a variable dinuclear [Co₂(COO)₄(H₂O)₅] cluster. Single crystal diffraction studies, utilizing synchrotron radiation, confirm the reversible two‐step transformation. The presence of various organic solvents induces the single‐crystal‐to‐single‐crystal (SC‐to‐SC) transformation of Co‐MOF‐2. This transformation is initiated by the cleavage of three coordinated water molecules and subsequent coordination of carboxylates in the ligand, resulting in solvatochromic behavior. Further, the reversible stimuli‐responsive behavior can also be rapidly induced under the stimuli of heat, vacuum, and X‐rays. This study successfully demonstrates the crystallographic and spectroscopic snapshots of dynamic coordination bonds in MOFs and contributes to a deeper understanding of the structure–property relationship.