Switchable Magnetic Properties in a Hydrogen-Bonded Cobalt(II)-Organosulfonate Framework via Reversible Dehydration–Hydration

Dynamic modulation of magnetic properties through single-crystal-to-single-crystal (SC–SC) transformations has always been difficult. In this study, we present a hydrogen-bonded cobalt(II)-organosulfonate framework exhibiting reversible dehydration–hydration switching of magnetic properties, accompanied by SC–SC transformation. Notably, a subtle structural transformation induced by dehydration–hydration triggers three key modifications: (1) significant geometric distortion at the Co2+ center, (2) rotational reorientation of bridging ligands, and (3) reorganization of the hydrogen-bonding network. These structural changes manifest in remarkable macroscopic property modulations, including a naked-eye-detectable color transition from yellow to pink, switching between weak antiferromagnetic coupling states, and on–off switching of the single-ion magnet (SIM) property. Our findings establish an effective strategy for modulating SIM property in coordination polymers through controlled structural reorganization within a 3D hydrogen-bonded organosulfonate framework.