Calcination of a samarium-O-phenylene-S-nickel-S-phenylene-O hybrid copolymer under an argon atmosphere gave Sm2O3-carbon cluster-Ni3S4 composite material. ESR spectral examinations of the calcined materials revealed the possibility of a two-step electron transfer in the process Of Sm2O3 -> carbon cluster -> Ni3S4 with an oxidation site at Sm2O3 particles and a reduction site at Ni3S4 particles. The calcined material was found to reduce methylene blue under visible light irradiation. (C) 2007 Elsevier B.V. All rights reserved.