Two novel 2-D organic–inorganic hybrid silicotungstates [H2en][Cu(en)2(H2O)]2{[Cu(en)2]3[Cu(en)(ox)]2[Ln2(ox)(α-SiW11O39)2]}·nH2O (Ln=ErIII, n=10 for 1, Ln=SmIII, n=8 for 2) with mixed organic ligands of ox and en (ox=oxalate, en=ethylenediamine) have been hydrothermally synthesized and characterized by IR spectrum, thermogravimetric analysis (TGA), power X-ray diffraction (PXRD) and X-ray single-crystal diffraction, respectively. Notably, 1 and 2 are isomorphic and exhibit the first novel 2D organic–inorganic hybrid silicotungstates assembled by {Cu2Ln2(ox)(SiW11)2} dimers and [Cu(en)(ox)]/[Cu(en)2] linkers. Furthermore, the TG curve of 1 and 2 display three steps of weight loss in the range of 25–1000°C.