We synthesized a new porous coordination polymer {La-1.75(OH)(1.25)[RU(dcbpy)(3)]center dot 16H(2)O} (La-7-[4Ru](4); H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) composed of a luminescent ruthenium(II) metalloligand [Ru(4,4'-dcbpy)(3)](4-) and La3+ cations. X-ray analysis for La-7-[4Ru](4) revealed that the La3+ cations and [4Ru] metalloligands are crystallized in a molar ratio of 7:4 with OH- counteranions and a void fraction of similar to 25.5%. Interestingly, La-7-[4Ru](4) shows a reversible structural transition triggered by water ad/desorption, which affects not only the triplet metal-to-ligand charge-transfer ((MLCT)-M-3) emission energy but also the ion conductivity in the solid state. This correlation suggests that La-7-[4Ru](4) is an interesting material that enables visualization of the ion conductivity via the 3MLCT emission energy.