The identity of the metal–organic framework formed by Mn(II) and 4,4′-dicarboxy-2,2′-bipyridine (H₂dcbp) depends upon the predominant solvent employed in the synthesis and yields the robust network isomers {[Mn(dcbp)]·½DMF}_n, 1, and {[Mn(dcbp)]·2H₂O}_n, 2, which possess vastly different physical properties: 1 irretrievably binds DMF, whereas 2 reversibly binds water whilst retaining crystallinity.