The synthesis of metal-organic coordination frameworks is of great attention for their potential to exhibit useful bulk properties and due to their intriguing variety of architectures and topologies [1]. The selection of multifunctional ligands and metal ions are important in the construction of specific supramolecular architectures with multi-nodal topological nets [2]. The present work has been dedicated to the preparation of 3d-4f mixed metal extended structure of complex [Co(2,3-pdc)]3La(H2O)3 (1) using 2,3-pyridine-dicarboxylic acid (2,3-H2pdc ) as ligand. The structure of complex 1 was determined by single crystal X-ray diffraction. The complex 1 (trigonal, space group P3) has been synthesized using metalloligand approach at ambient conditions, that is isostructural with the reported Co,Gd mixed metal complex [3], synthesized by hydrothermal method. The structure comprises a network of LaO9 and CoO3N3 units connected through pyridine-2,3-dicarboxylate anions where the La+3 ions adopt a tricapped trigonal prismatic coordination arrangement (by contribution of three coordinated water molecules and carboxylate oxygens from three 2,3-pdc ligands) and the Co3+ ions are octahedrally coordinated by three oxygen and three nitrogen atoms from 2,3-pdc ligands. Both polyhedral units and dicarboxylate anions are connected and give rise to a 2D-layered structure running parallel to the plane ab (figure 1). The supramolecular architecture is built by stacking of layers that generates a 3D network with pores extending along the c axis (aperture ca. 7 Ȧ). The complex was investigated by thermogravimetric analysis. The thermal behaviour of complex shows a several decomposition stages. In the first stage, endothermic removal of the three water molecules occurs up to 200oC. The anhydrous complex is thermally stable up to about 300oC. The last stages in the temperature range of 300-560oC are related to the decomposition of 2,3-pdc ligands are by 2-3 superposed exothermic effects. The residue after decomposition constitute ~ 35%. The assembly of coordination polymer is of perspectives to use for the application in gas storage and ceramic material.scheme