A　3-D　metal-organic　framework　(MOF)　{Zn-4(mu(3)-OH)(2)(bdc)(3)(pad)(2)}center　dot　2H(2)O　(1,　H(2)bdc　=　1,4-benzenedicarboxylic　acid,　pad　=　1,10-phenanthroline-5,6-dione)　with　unusual　Zn-4(mu(3)-OH)(2)(COO)(6)(N-2)(2)　secondary　building　units　(SBUs)　has　been　hydrothermally　synthesized　and　characterized　by　single　crystal　X-ray　diffraction,　powder　X-ray　diffraction,　thermogravimetric　analysis,　elemental　analysis,　and　infrared　spectroscopy.　The　tetranuclear　Zn-4　SBU　was　formed　through　two　dinuclear　Zn-2　clusters　by　sharing　two　mu(3)-OH　bridges.　Considering　this　Zn-4　SBU　as　a　six-connected　node,　the　overall　framework　of　1　has　a　pcu　topology.　This　tetranuclear　Zn-4　SBU　can　be　used　as　a　node　in　construction　of　MOFs.