The thermal behavior of double complex compounds (DCC) [Cr(ur)6][Co(CN)6]·4H2O (I), [Cr(ur)6][Co(C2O4)3]·3.5H2O (II), [Cr(ur)6][Fe(CN)6]·4H2O (III), [Cr(ur)6][Fe(C2O4)3]·2H2O (IV) and urea (ur) was studied (ur = urea, H2NCONH2). Thermal decomposition was carried out by the TG-MS method and method of static experiments in the reducing atmosphere at a 1-h exposure. The final thermolysis products are characterized by elemental analysis, XDR, IR spectrometry, SEM, the specific surface area (SBET) of the samples. The porous structure of the samples was determined. Cr2O3 + Co0 are formed as a result of thermal reduction of I, II, Cr2O3 + Fe0 + Fe2O3 for III, FeCr2O4 + Fe0 for IV. The replacement of CN− ligands by C2O4 2− ligands leads to an increase in the specific surface by a factor of ~ 2. Catalytically activity of Co-containing degradation products is demonstrated in the model catalytic decomposition of H2O2. The relationship between SBET and the obtained values of the rate constants of the reaction is not observed. Fe-containing samples are not catalytically active.