Two　new　3-D　porous　bismuth　coordination　polymers,　(C5NH6)2[Bi2(H2O)2(C2O4)4]·2H2O　1　and　(NH4)[Bi(C2O4)2]·3H2O　2,　have　been　hydrothermally　synthesized　and　characterized　by　single-crystal　X-ray　diffraction.　Compound　1　crystallizes　in　the　monoclinic　symmetry,　P21/c　space　group　with　a=10.378(2)　Å,　b=17.285(3)　Å,　c=16.563(5)　Å,　α=90°,　β=119.66(2)°,　γ=90°,　V=2581.8(10)　Å3,　Z=4,　R1=0.0355　and　wR2=0.0658　for　unique　4713　reflections　I　>2σ(I).　Compound　2　crystallizes　in　the　tetragonal　symmetry,　I41/amd　space　group　with　a=11.7026(17)　Å,　b=11.7026(17)　Å,　c=9.2233(18)　Å,　α=90°,　β=90°,　γ=90°,　V=1263.1(4)　Å3,　Z=32,　R1=0.0208　and　wR2=0.0518　for　unique　359　reflections　I>　2σ(I).　Compounds　1　and　2　are　3-D　open-framework　structures　with　a　66　uniform　net,　which　consist　of　honeycomb-like　layers　connected　to　each　other　by　oxalate　units.　While　different　guest　molecules　fill　in　their　cavities　of　honeycomb-like　layers,　study　of　ultrasonic　treatment　on　2　indicates　the　replacement　of　NH4+　by　K+　on　potassium　ion　exchange.　Thermogravimetric　analysis　indicates　that　the　open-channel　frameworks　are　thermally　stable　up　to　200　°C,　and　other　characterizations　are　also　described　by　elemental　analysis,　IR　and　ultraviolet-visible　diffuse　reflectionintegral　spectrum　(UV-Vis　DRIS).　©　2008　Elsevier　Inc.　All　rights　reserved.