The　title　compound,　{[Zn4(C8H4O4)3(OH)2(C12H6N2O2)2]·2H2O}n　,　has　been　prepared　hydrothermally　by　the　reaction　of　Zn(NO3)2·6H2O　with　benzene-1,4-dicarboxylic　acid　(H2bdc)　and　1,10-phenanthroline-5,6-dione　(pdon)　in　H2O.　In　the　crystal　structure,　a　tetranuclear　Zn4(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　μ3-OH　group.　The　pdon　ligand　chelates　to　zinc　through　its　two　N　atoms　to　form　part　of　the　[ZnN2O4]　octahedron.　The　two　crystallographically　independent　bdc2-　ligands　are　fully　deprotonated　and　adopt　μ3-κO:κO＇:κO＇＇　and　μ4-κO:κO＇:κO＇＇:κO＇＇＇　coordination　modes,　bridging　three　or　four　ZnII　cations,　respectively,　from　two　Zn4(OH)2　units.　The　Zn4(OH)2　fragment　connects　six　neighbouring　tetranuclear　units　through　four　μ3-bdc2-　and　two　μ4-bdc2-　ligands,　forming　a　three-dimensional　framework　with　uninodal　6-connected　α-Po　topology,　in　which　the　tetranuclear　Zn4(OH)2　units　are　considered　as　6-connected　nodes　and　the　bdc2-　ligands　act　as　linkers.　The　uncoordinated　water　molecules　are　located　on　opposite　sides　of　the　Zn4(OH)2　unit　and　are　connected　to　it　through　hydrogen-bonding　interactions　involving　hydroxide　and　carboxylate　groups.　The　structure　is　further　stabilized　by　extensive　π-π　interactions　between　the　pdon　and　μ4-bdc2-　ligands.　©　2015　International　Union　of　Crystallography.