Structural and thermal properties of the two isostructural lanthanide metal-organic frameworks: [Er-2(pdc)(3)(dmf)(2)]center dot dmf (1) and [Tm-2(pdc)(3)(dmf)(2)]center dot dmf (2) where pdc = C5H3N(COO)(2)(2) and dmf = N,N'-dimethylformamide, have been investigated. They are characterized by the BET surface area of 302 and 101 m(2)/g for 1 and 2, respectively. This paper deals with the influence of activation conditions on sorption properties of the investigated complexes. Thermal investigations of as-made and activated complexes point to their entirely different thermal decompositions. (C) 2010 Elsevier B.V. All rights reserved.