<p>Given their reactivity, excellent catalytic properties and affinity to heavy metal, Cu_xS particles were introduced into the matrix of carboxylic cation exchangers (CCEs) to obtain novel hybrid ion exchangers (HIXs). The study focused on the synthesis and thermal behaviour of HIXs in which commercially available, gel-type (G) and macroreticular (M) structure CCEs were used as supports for dispersed Cu_xS particles. Using CCEs in the Cu²⁺ form and a Na₂S solution, under mild conditions, HIXs containing 21.3 (G) and 17.6 (M) mass% of inorganic deposits composed of copper and sulphur with a molar Cu/S ratio of 1.29 and 1.38 were prepared. Four HIXs, G/Na#Cu_xS and M/Na#Cu_xS (carboxylic groups in the Na⁺ form), and also G/H#Cu_xS and M/H#Cu_xS (carboxylic groups in the H⁺ form), were subjected to thermal analysis under air and under N₂. The results were discussed on the basis of the TG/DTG curves, FTIR spectra and XRD patterns of the solid residues. HIXs with –COONa groups and –COOH groups had differing thermal stability—up to 450 °C <i>vs</i> up to 200 °C. A noteworthy phenomenon occurred during pyrolysis of G/H#Cu_xS and M/H#Cu_xS, when Cu_xS was converted to copper oxides under air-free conditions in the reaction with CO₂ produced by decarboxylation of acrylic acid-divinylbenzene copolymer. The composite materials obtained have great potential for development in the area of catalysis, water and wastewater purification, and as unconventional biocidal agents.</p>