The　title　compound,　{[Zn-4(C8H4O4)(3)(OH)(2)(C12H6N2O2)(2)]center　dot-2H(2)O}(n),　has　been　prepared　hydrothermally　by　the　reaction　of　Zn(NO3)(2)center　dot　6H(2)O　with　benzene-1,4-dicarboxylic　acid　(H(2)bdc)　and　1,10-phenanthroline-5,6-dione　(pdon)　in　H2O.　In　the　crystal　structure,　a　tetranuclear　Zn-4(OH)(2)　fragment　is　located　on　a　crystallographic　inversion　centre　which　relates　two　subunits,　each　containing　a　[ZnN2O4]　octahedron　and　a　[ZnO4]　tetrahedron　bridged　by　a　mu(3)-OH　group.　The　pdon　ligand　chelates　to　zinc　through　its　two　N　atoms　to　form　part　of　the　[ZnN2O4]　octahedron.　The　two　crystallographically　independent　bdc(2-)　ligands　are　fully　deprotonated　and　adopt　mu(3)-kappa　O:kappa　O＇:kappa　O　＇＇　and　mu(4)-kappa　O:kappa　O＇:kappa　O　＇＇:　kappa　O　＇＇＇　coordination　modes,　bridging　three　or　four　Zn-II　cations,　respectively,　from　two　Zn-4(OH)(2)　units.　The　Zn-4(OH)(2)　fragment　connects　six　neighbouring　tetranuclear　units　through　four　mu(3)-bdc(2-)　and　two　mu(4)-bdc(2-)　ligands,　forming　a　three-dimensional　framework　with　uninodal　6-connected　alpha-Po　topology,　in　which　the　tetranuclear　Zn-4(OH)(2)　units　are　considered　as　6-connected　nodes　and　the　bdc(2-)　ligands　act　as　linkers.　The　uncoordinated　water　molecules　are　located　on　opposite　sides　of　the　Zn-4(OH)(2)　unit　and　are　connected　to　it　through　hydrogen-bonding　interactions　involving　hydroxide　and　carboxylate　groups.　The　structure　is　further　stabilized　by　extensive　pi-pi　interactions　between　the　pdon　and　mu(4)-bdc(2-)　ligands.