(Figure Presented) A change for the meta: On dehydration, a 3D homometallic porous organic-inorganic framework constructed from {Co₃(OH) ₂} chains (see structure, pink Co, red O, blue N, gray C) undergoes a transition from being a single-chain magnet into a metamagnet. Apart from the loss of solvent water molecules, the dehydration leaves the framework structure largely unchanged. Keywords: cobalt magnetic properties metal-organic frameworks nanoporous materials.