Abstract:　A　new　organic–inorganic　hybrid　polyoxometalate　H2[Cu(en)2(H2O)]2[Cu(en)2]{[Cu(en)2]3　(CuSiW11O39)2}·6H2O　(1)　(en = ethylenediamine)　have　been　hydrothermally　synthesized　and　characterized　by　IR　spectrum,　thermogravimetric　analysis,　power　X-ray　diffraction　and　single-crystal　X-ray　diffraction.　Crystal　data　for　1:　monoclinic,　P21/c,　a = 18.8077(3) Å,　b = 23.0703(5) Å,　c = 26.0723(6) Å,　β = 96.438(2)°,　Z = 4.　Single-crystal　X-ray　diffraction　analysis　revealed　that　1　exhibits　a　2-dimensional　network　constructed　from　mono-Cu-substituted　[CuSiW11O39]n　6n−　chains　and　[Cu(en)2]2+　bridges.　Graphical　Abstract:　A　new　organic–inorganic　hybrid　polyoxometalate　H2[Cu(en)2(H2O)]2[Cu(en)2]{[Cu(en)2]3(CuSiW11O39)2}·6H2O　(1)　(en = ethylenediamine)　have　been　hydrothermally　synthesized　and　characterized,　which　exhibits　a　2-dimensional　network　constructed　from　mono-Cu-substituted　[CuSiW11O39]n　6n−　chains　and　[Cu(en)2]2+　bridges.[Figure　not　available:　see　fulltext.]　©　2016,　Springer　Science+Business　Media　New　York.